WO2009008932A2 - Biodétecteur cmos implantable sans fil - Google Patents

Biodétecteur cmos implantable sans fil Download PDF

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Publication number
WO2009008932A2
WO2009008932A2 PCT/US2008/004731 US2008004731W WO2009008932A2 WO 2009008932 A2 WO2009008932 A2 WO 2009008932A2 US 2008004731 W US2008004731 W US 2008004731W WO 2009008932 A2 WO2009008932 A2 WO 2009008932A2
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Prior art keywords
sensor
light
substance
sample
sensor modules
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PCT/US2008/004731
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English (en)
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WO2009008932A3 (fr
Inventor
M. Mekhail Anwar
Paul Matsudaira
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Whitehead Institute
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Publication of WO2009008932A3 publication Critical patent/WO2009008932A3/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0002—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network
    • A61B5/0031—Implanted circuitry

Definitions

  • biosensors Nearly all forms of biosensors utilize a biological entity (i.e. antibody, protein, DNA, drug, etc) to interface with the target (i.e. ligand: virus, receptor, protein, bacteria, etc).
  • a biological entity i.e. antibody, protein, DNA, drug, etc
  • target i.e. ligand: virus, receptor, protein, bacteria, etc.
  • An instrument is then used to read that reaction, and relay its results to the outside world. This is traditionally accomplished with an external device.
  • These devices read signals such as light (from fluorescently labeled entities), radioactivity, mass, electric charge etc. These devices tend to be large and expensive. Additional approaches to reading microarrays and performing measurements of biological substances in mixtures are needed.
  • the present invention relates to a wireless complementary metal oxide semiconductor (CMOS) imager that is useful for microarray imaging (such as protein and DNA mircroarrays) as well as for implantable sensors.
  • CMOS complementary metal oxide semiconductor
  • a system for identifying a biological sample includes a sensor having at least one photodiode for converting photons obtained from interaction with the sample into electrons and for providing analog electrical output; an analog to digital converter in electrical communication with the photodiode for converting the analog output into a digital signal, wherein at least the photodiode and the analog to digital converter form a CMOS circuit, and a processor for processing the digital signal.
  • a sensor for identifying an interaction in a microarray includes a pixel array of photodiodes wherein a size of each pixel of the pixel array is less than 150 micrometers. In some embodiments, a size of each pixel ranges from less than the size of a spot on the microarray to a maximum of the pitch between spots on the microarray. In some embodiments, the size of each pixel is less than twice the size of a spot on the microarray. In some embodiments, an outer layer substantially surrounds the pixel array, wherein the outer layer provides a fluid barrier between electrical components of said sensor and said biological sample.
  • a sensor comprising at least first and second sensor modules, each sensor module comprising an array of photodetectors, wherein the first and second sensor modules are positionable in a functional relationship with respect to each other and with respect to a sample.
  • a system comprising the afore-mentioned sensor modules, a light source, and a processor.
  • the first and sensor modules are physically attached to one another.
  • the first and sensor modules are components of an implantable device.
  • the first and second sensor modules are positionable around a blood vessel and the sensor modules are configured to obtain measurements of light incident on the blood vessel and light transmitted through the blood vessel and its contents, thereby affording a measurement of light absorbed by the blood vessel and its contents.
  • the method includes providing a wireless CMOS biosensor having a pixel array of photodetectors, which are optionally photodiodes, providing a microarray of the biological sample, wherein the microarray has a one-to-one correspondence with the pixel array, tagging the biological sample with a fluorescent label, placing the biosensor proximal to the microarray, illuminating the biosensor and the biological sample, wherein the illuminating causes the tagged biological sample to emit photons, converting the photons into an electrical signal using the CMOS biosensor, and wirelessly receiving the electrical signal, wherein the electrical signal is representative of an amount of tagged biological sample.
  • FIG. 1 is a block diagram illustration of a system for identifying a sample, in accordance with embodiments of the present invention
  • FIG. 2 is a planar view diagrammatic illustration of biosensor chip from the system of FIG. 1, in accordance with embodiments of the present invention
  • FIG. 3 is a diagrammatic illustration of a pixel from the chip of FIG. 2, in accordance with embodiments of the present invention
  • FIG. 4 is a block diagram illustration showing the various components of a sensor and processor from the system of FIG. 1 ;
  • FIGS. 5A and 5B are circuit diagrams for a sensor photodiode and reference photodiode from the pixel of FIG. 3;
  • FIG. 6 is a circuit diagram illustration of an amplifier for use with the chip of FIG. 2, in accordance with embodiments of the present invention.
  • FIG. 7 is a circuit diagram illustration of an analog to digital converter for use with the chip of FIG. 2, in accordance with embodiments of the present invention
  • FTG. 8 is a graphical illustration of a clock signal that is generated from the sine wave of a wireless interface from the system of FIG. 1 ;
  • FIGS. 9A and 9B are diagrammatic illustrations of a light source in accordance with embodiments of the present invention.
  • FIG. 10 is an illustration of direct UV illumination of a commercial CMOS camera using Qdots
  • FIG. 1 1 is a calibration curve showing the number of photons incident on a sensor of the present invention versus applied voltage;
  • FTG. 12 is a graphical illustration of pixel output from ramping LED voltage
  • FTG. 13A and 13B are graphical illustrations of amplifier output versus incident light
  • FIG. 14 is a graphical illustration of digital values from amplifier output
  • FIG. 15 is a graphical illustration of differential output with noise
  • FIG. 16 is a graphical illustration comparing varying concentrations of GFP using the CMOS sensor of the present invention versus a CCD camera.
  • FIG. 17 is an illustration of an implantable sensor comprising two sensor modules each comprising an array of photodetectors.
  • FIG. 18 is an illustration of another embodiment of an implantable sensor in which two sensor modules each comprising an array of photodetectors are attached and electrically coupled to a substrate.
  • FIG. 19 is a schematic illustration showing powering of the sensor by inductive coupling.
  • FTG. 20 is a schematic illustration of light illuminating and passing through a both sensor modules and a vessel positioned between the sensor modules.
  • FIG. 21 is an illustration of a sensor module comprising multiple photodetectors, each capable of detecting light of a different wavelength.
  • FIG. 22 is a plot showing the characteristic IR absorption of glucose and water between 2 ⁇ m and 2.5 ⁇ m and illustrating the inventive method for eliminating the absorption of water from the glucose measurement.
  • FIG. 23 depicts side and front views of a differential optical sensor assembly, including two optical sensor modules (detectors) wire bonded onto metallized quartz substrates.
  • FIG. 24 shows a schematic diagram of a glucose sensing system of the present invention, including a differential sensor assembly that includes two sensor modules, an infrared light source
  • the sensor assembly is implantable and includes data processing circuitry and transmits data to an external unit.
  • the light source, filters, lens, and interface circuitry would be integrated into an external unit that displays and/or stores the information.
  • FIG. 25 shows implementation details of the optical emission and detection in an exemplary embodiment of the glucose sensor.
  • the LED is modulated at a low frequency, typically between 1 and 100 kHz.
  • the photodiode is incorporated into an integrator circuit with a reset mechanism. The signal at the output of the integrator is captured and processed.
  • FIG. 1 is a block diagram illustration of a system 10 for identifying a sample, in accordance with embodiments of the present invention.
  • System 10 includes a biosensor chip 12 having a sensor 14 and a processor 16, a sample 18 to be analyzed, a light source 20 and a wireless interface 22.
  • Sample 18 is positionable in contact with or in close proximity to biosensor chip 12, both of which may be illuminated by light source 20.
  • the proximity of sample 18 to chip 12 is dependent on the spot size of sample 18 and may be, for example, within a distance which is several times the spot size.
  • Sensor 14 senses and converts photons emitted by sample 18 into electrical current, and processor 16 processes signals associated with the current to provide data output.
  • Most or all of the individual components of processor 16 are positioned on the chip itself and comprise a CMOS circuit.
  • Wireless interface 22 provides power and a clock to chip 12, and receives data output from processor 16.
  • chip 12 is a rectangular chip which is positionable in close proximity to sample 18. In one embodiment, chip 12 is approximately 3 x 3 mm in size. It should be readily apparent, however, the chip 12 may be any size suitable for imaging and sensing microarrays or biological in-vivo interactions.
  • Chip 12 is comprised of an array of pixels 24, and processor components including a voltage rectifier and regulator 28, and an analog to digital converter 30.
  • Chip 12 further includes an antenna which is configured to communicate with an external reader. In one embodiment, the antenna is comprised of inductor coils 26.
  • Inductor coils 26 comprise a wireless interface 22, and operate to generate the power and clock signal from the RF wave and to send received digital data to the external reader. Additional processor components are further included on each pixel, as will be described in greater detail hereinbelow.
  • pixels 24 are designed and sized to directly correspond to a microarray having samples therein for analysis.
  • the size of each pixel is designed to correspond to the size of each sample in a microarray.
  • Each pixel is within a multiple of the size of the sample, where the upper limit is the pitch of the array spots, and the lower limit is the size of the spot itself.
  • the pixel could range from 100-300 micrometers.
  • the pixels are less than 150 micrometers.
  • the pixels are approximately 12O x 120 micrometers in size.
  • the size of each pixel is less than twice the size of a spot on the microarray.
  • the pixel array is a 64-pixel array. It should be readily apparent that other configurations are possible and are included within the scope of the invention.
  • Chip 14 may further include an outer layer providing a fluid barrier between electrical components of chip 14 and sample 18.
  • the outer layer is a biocompatible material, such as a biocompatible polymer.
  • PDMS Sylgard 184, Dow Corning
  • the outer layer is optically transparent to light of wavelengths of interest to be measured. For example, for an implantable sensor, it may be of interest to detect substances that absorb in the infrared region of the spectrum, or a portion thereof.
  • FIG. 3 is a diagrammatic illustration of a pixel 24 in accordance with embodiments of the present invention.
  • Pixel 24 includes a sensor photodiode 44 and a reference photodiode 46, in electrical communication with source followers 40 and hold capacitors 42.
  • Hold capacitors 42 may be any size suitable for pixel 24, and are generally chosen to be the largest capacitors that will fit into the designated space on pixel 24. In one embodiment, hold capacitors 42 are 50 pF poly-poly capacitors.
  • Sensor photodiode 44 is a photodiode typically used in a CMOS circuit, and may be, for example, an N-plus P-sub diode, an N-well P-sub diode, a P-plus N-well P-sub diode, an N- plus P-well diode or any other suitable photodiode.
  • different pixels within the pixel array have different diodes.
  • three rows of pixels are comprised of N-plus P- sub diodes, three rows of pixels are comprised of N-well P-sub diodes, and the remaining two rows of pixels are comprised of P-plus N-well P-sub diodes.
  • Reference photodiode 46 is a photodiode which is covered with a metal to measure the dark current. Sensor photodiode 44 and reference photodiode 46 are placed as far away from each other as possible to avoid carriers from one "leaking" to the other. Outputs from sensor photodiode 44 and reference photodiode 46 are subtracted to eliminate noise from the pixel and in one embodiment are laid out in a common centroid arrangement. This configuration provides for a fully differential pixel architecture which can compensate for the high noise level which may occur due to the wireless interface.
  • photodetectors other than photodiodes.
  • photodetector as used herein should be understood to be replaceable by “photodetector, wherein the photodetector is optionally a photodiode”.
  • FIG. 4 is a block diagram illustration showing the various components of sensor 14 and processor 16, and how they are interrelated.
  • An inductor coil 26, located on chip 12, provides an RF signal to a clock generator 36, which generates a pulse and sends it to a clock and decoder 34, positioned on chip 12.
  • Clock/decoder 34 divides the signal by any chosen number (equaling the number of bits of resolution needed).
  • Clock/decoder activates each pixel 24 serially for readout, and the readout signal is amplified by amplifier 32, and sent to analog/digital converter 30.
  • Analog to digital converter 30 uses clock 34 to derive the digital conversion for the analog signal. Any implementation of an analog to digital converter can be used.
  • the integrating current is set by a switch capacitor circuit whose clock is governed by the clock from the RF signal, thus making the analog to digital converter, which samples the output from amplifier 32 and integrates until a threshold voltage is reached. The time it takes for the threshold to be reached is recorded by latching the value of the clock. This becomes the digital signal.
  • the integrating current is derived from the power supply, and is based off of a switch capacitor circuit, so that the analog to digital converter is frequency independent (ie the higher the frequency, the larger the current, and the shorter the time). The final signal is then sent back to inductor 26.
  • the standard CMOS photosensor design is a traditional three transistor design whereby an NMOS reset transistor charges the photodiode (and associated parasitic capacitance) to V , t- V where
  • Vdd is a power supply voltage
  • Vt is the threshold voltage of the reset transistor.
  • the reset transistor is turned off, and the photodiode converts photons to a current which discharges the parasitic capacitance. Because the depletion region capacitance is a function of the reverse bias, the parasitic capacitor functions as a non-linear gain element.
  • the row/column switch is activated, and the source follower reads out the voltage on the photodiode. This voltage is amplified, and converted to a digital signal.
  • the reset transistor is activated, the photodiode voltage is reset, and the process repeats. Pixels can be selectively read out by using a select transistor.
  • the readout circuitry utilizes correlated double sampling (CDS) to reduce fixed pattern noise, such as amplifier offsets.
  • CDS correlated double sampling
  • the amplifier and A/D can be located at the chip level, row/column level, or even at the pixel level.
  • a slightly modified design is used. Each photodiode is connected to a PMOS reset transistor instead of the traditional NMOS, because the area is not limiting, and the photodiode can be reset to V . .
  • image lag can be reduced by using a PMOS reset transistor.
  • FIGS. 5A and 5B are circuit diagrams for the sensor photodiode and reference photodiode, respectively.
  • sensor photodiode 44 (or reference photodiode 46, as shown in FIG. 5B) is connected to a voltage source via a PMOS device. This allows sensor photodiode 44 to have a rapid and complete reset, eliminating image lag.
  • the photodiode current draws current off of the parasitic capacitance, causing a decrease in voltage in response to light.
  • the output from sensor photodiode 44 is buffered by first source follower 40, which has a switch to eliminate power consumption when not in use.
  • the output is stored on hold capacitor 42 and can be read out at a later time by second source follower 41.
  • Second source follower 41 then reads the stored voltage and transmits it to the analog to digital converter 30. This is a serial operation.
  • the pixel can also operated in a mode where both source followers are activated simultaneously, and there is no sample and hold operation. [0017] Due to the presence of a wireless interface, power must be conserved, while achieving the necessary sensitivity and speed.
  • each pixel must integrate during the same time period (i.e. when the light is on, or the light is off). Therefore, each pixel must have memory so that the value of each pixel can be stored at the end of the cycle, and then serially read out and converted to a digital value.
  • the operation of each pixel 24 is as follows.
  • the illuminating light is turned on for time t .
  • All pixels 24 integrate the current generated by sensor photodiode 44 plus the dark current measured by reference photodiode 46.
  • first source follower 40 samples the photodiode voltage and stores it onto hold capacitor 42. 4. The light is kept off for t. , and the photodiodes continue to integrate dark current. During this time, the values on hold capacitors 42 are serially decoded. Second source follower 41 is turned on, and the voltages on hold capacitor 42 (from both the reference and sensor photodiodes) is transferred to a differential amplifier 32. The amplifier output is then sent to the analog to digital converter 30. The digital output is then stored in a shift-register. If the digital output or amplifier output indicates that the analog to digital converter is reaching its dynamic range limits, a reset signal is sent via reset transistor to pixel 24. Therefore each pixel can operate independently, and only resets when necessary.
  • the process repeats for the next pixel.
  • the previous pixel's digital data is modulated at some amount less than the fclk clock frequency, ⁇ j ⁇ , and sent out via the inductor coil.
  • a calibration routine compensates for the non-linear gain of amplifiers and of the parasitic capacitance of the photodiode.
  • chip 12 is illuminated with a constant light source, wherein the change in voltage as a function of time should be constant. By recording the digital output during this process, data is calibrated off-line to remove non-linearities.
  • one pixel comprises only the reference pixel, and in place of the light sensing pixel a capacitor is used. This pixel will only (differentially) measure the dark current, which is assumed to be constant, as its only dependence is on temperature.
  • a current source can be used instead of the dark current. The output from this constant current input is recorded, and used to calibrate the amplifier and analog to digital converter.
  • Amplifier 32 is positioned on chip 12, and receives output from each of pixels 24. In another embodiment, separate amplifiers are used for each pixel.
  • FIG. 6 is a circuit diagram illustration of amplifier 32, in accordance with embodiments of the present invention. The particular design shown in FIG. 6 was chosen based on its simplicity, linearity and insensitivity to temperature variation. However, it should be readily apparent that many other designs are possible, and that any suitable amplifier may be used.
  • the amplifier is open loop to allow for simplicity of design, and high gain and speed with minimal power consumption.
  • the amplifier uses a resistor at the source of the input transistors to eliminate temperature effects on the gain characteristics, and to linearize the gain. This limits output swing, and reduces the gain.
  • the source resistor is eliminated, and a calibration scheme is employed to adjust the nonlinear gain.
  • the calibration pixel has the photodiode that is exposed to light replaced with a capacitor. The remaining covered photodiode only draws dark current. The dark current is constant (as long as the temperature is stable), and this provides a constant current (equivalent to constant light) input to the amplifier and analog to digital converter.
  • the digital circuitry which typically advances to the next pixel after the current one is finished with the analog to digital conversion, stays on the calibration pixel for a set number of cycles. This allows the input voltage to be ramped (due to the constant current of the dark current) and sweep the amplifier and analog to digital converter. This cycle repeats several times to get a good calibration, and allows for correlation of the output digital value with the amount of charge at the input.
  • the digital circuitry activates the calibration at pre-set intervals to allow recalibration during data acquisition.
  • FIG. 7 is a circuit diagram illustration of an analog to digital converter, in accordance with embodiments of the present invention.
  • the output of the amplifier is sampled onto the input capacitor.
  • a current source then charges the capacitor until the NMOS FET is turned on. This switches the output from 1 to 0, and the inverters buffer the output and clean up the signal.
  • This threshold voltage is set at an integer number of threshold voltages (depending on the number of diode connected transistors).
  • the current source is designed so that it can charge the capacitor to the necessary voltage in the time allotted.
  • the output of the converter switches, and the value of the counter is latched into an array of flip flops.
  • the resolution of the analog to digital converter depends on how many clock bits are saved. In one embodiment, there are
  • all circuits are threshold voltage referenced so as to avoid offset between the amplifier common mode output voltage and the range of the analog to digital converter.
  • the common mode output voltage is then I x Rload, which is Vt x (Rload/Rstartup). Therefore, variations in sheet resistance will cancel out. Furthermore, to allow for varying frequencies (the integration time goes as
  • the current sources is a mirror of a switch capacitor current source, which allows the current to vary linearly with f, so that the integration is independent of f.
  • Wireless interface 22 serves to provide power input and clock generation, and to collect data output.
  • Wireless interface 22 comprises an antenna, such as inductor coil 26 made of any combination of metal or other conductive layers, voltage rectifier, voltage regulator, and clock generator.
  • Inductor coil 26 can be an integrated inductor coil, (for microarray applications), or an external inductor coil (for implantable applications). In cases where inductor coil 26 is an external inductor, it can be bonded to the chip, and may further be embedded in an outer layer. For implantable applications, the external inductor may be in contact with a stent or other implantable device, or the device ⁇ i.e. stent ⁇ itself may act as the inductor.
  • Inductor coil 26 is designed so that its resonant frequency is near the needed clock frequency of the chip.
  • the chip uses a 30 loop, square coil with 4 ⁇ m width, and l ⁇ m spacing.
  • the metal 3 layer is only 2 ⁇ wide to reduce capacitance. It should be readily apparent that the specific parameters may vary with chip size and manufacturing process.
  • Inductor coil 26 connects to a rectifier and is connected between RFP and RFN.
  • the rectifier is diode clamped to ensure that high voltages do not affect circuitry on chip.
  • the series of diode connected FETs are designed to ensure that voltage on the coil does not get too high and destroy the chip.
  • the FETs used may be double gate FETs, which should better shield the circuitry from high voltages.
  • the signal from the rectifier, V ⁇ . ⁇ then feeds into voltage regulator 28.
  • Voltage regulator 28 supplies approximately 200 ⁇ Amps, at 1.5V, and additionally provides several reference voltages.
  • the diode clamps are made with high threshold voltage devices to shield the clamp itself from high voltages.
  • separate power supplies are used: one for the analog and one for the digital circuitry, to avoid noise coupling.
  • Each power supply has its own inductor, rectifier and voltage regulator.
  • all of the components are integrated on the chip.
  • Inductor 26 loops around the chip. In cases where two coils are used, the inductor coils may be concentric. In some embodiments, multiple coils are used, wherein the power contribution from each of the multiple coils can be summed.
  • wireless interface 22 is used to power an external LED for visualization of smaller intracellular features, or optical density measurements.
  • FIG. 8 is a graphical illustration of a clock signal that is generated from the sine wave (RF).
  • a digital block called RESBLK outputs a signal called RESB.
  • This signal is a logic 0 when the chip begins to power up.
  • the CKGEN circuit block generates the clock signal.
  • the RF signal from the coil is passed to a capacitive voltage divider, which then feeds into a series of inverters.
  • the clock signal is at the same frequency of the RF signal.
  • the clock is then divided down by a series of D-flip-flops to provide the counter.
  • the memory elements are a series of flip flops that load data in parallel, and then serially shift it out. Power consumption is large in blocks that contain rapidly switching D-flip-flops (i.e. the counter) because of the momentary path from V nn to GND as the states switch.
  • FIGS. 9A and 9B are diagrammatic illustrations of a light source in accordance with embodiments of the present invention.
  • Light source 20 is configured to provide light to sample 18 and chip 14.
  • One goal of the present invention is to eliminate the need for lenses by placing the sensor adjacent to the sample surface, so that the emitted light cannot spread too far before it intersects the sensor. Therefore a lens is not needed to gather the light.
  • the pixel must be as large or larger than the imaging spot (for maximum signal), and must be on the order of the spot size (for example, if the spot is 100 micrometers, the sensor should be between 0 and several hundred micrometers away from the surface). The maximum pixel size is dictated by the spot size and pitch.
  • the senor may be placed extremely close to the surface, maximizing signal reception.
  • chip 12 is placed in close proximity to sample 18.
  • chip 12 is in contact with sample 18.
  • chip 12 is within a few micrometers of sample 18.
  • the proximity of sample 18 to chip 12 may be dependent on the spot size of sample 18 and may be, for example, within a distance which is several times the spot size.
  • Light detection side of chip 12 faces sample 12. In this embodiment, all bond wires have been eliminated, and a wireless interface is present.
  • bond wires can be avoided by using flip-chip bonding, as shown in FIG. 9B.
  • chip 12 is placed in close proximity to sample 18.
  • chip 12 is in contact with sample 18.
  • chip 12 is within a few micrometers of sample 18.
  • a thin transparent substrate 52 is placed beneath sample 18, and metallic connecting element 54 connects chip 12 to a processor, such as a PC board.
  • substrate 52 is a glass cover slip with microfabricated wire traces.
  • substrate 52 is a flexible polymer.
  • metallic connecting element 54 is gold, and may be a ball or bump.
  • metallic connecting element 54 is a lump of solder.
  • light source 20 is a prism 48 configured to provide evanescent lighting.
  • Traditional imaging systems epi-fluorescent
  • the sample can be illuminated from underneath, allowing for the imaging sensor to be placed close to the surface.
  • Evanescent lighting allows for measurement of binding kinetics, which is important for protein microarrays.
  • sample 18 is patterned on a transparent substrate, such as glass or plastic. The substrate with the sample inside is placed on the top, flat surface of prism 48.
  • Light depicted by arrows 50, is directed into the prism at an angle such that a layer approximately 50 nm (approximately 1/10* of the wavelength) above the surface is illuminated.
  • This light causes sample 18 to be illuminated with an evanescent wave.
  • Light detection side of chip 12 is positioned adjacent to sample 18, and light emitted from sample 18 is transmitted to sensor 14. This configuration allows for samples which are close to the surface to be illuminated, while those greater than a few tens of nm away are not.
  • Quantum dots can be conjugated to DNA or protein, and/or used as a secondary label. Typical fluorophores absorb and reemit light with a Stoke's shift of typically between 15 and 30 nanometers. In order to separate the excitation light from the emitted light, an optical filter is needed. Quantum dots, however, absorb exceedingly well at deep UV wavelengths and emit at a constant visible wavelength, while silicon absorbs UV light poorly. Thus, if a quantum dot is used as a marker instead of a fluorophore, UV light can be used as the excitation light, and no optical filter is needed since the silicon cannot "see" the UV light.
  • Quantum dots will emit a visible wavelength of light, which can be detected by the CMOS sensor.
  • An additional advantage of quantum dots is that they do not bleach, allowing long integration times to see extremely small signals.
  • Quantum dots are available from www.qdots.com, and can be conjugated with a variety of proteins (i.e. streptavidin) or functionalized chemical linkers, (i.e. Nh2 or COOH).
  • FIG. 10 is an illustration of direct UV illumination of a commercial CMOS camera. Results are shown for no illumination (frame 60), illumination with UV light (frame 62), illumination with UV light plus quantum dots (frame 64) and illumination with UV plus quantum dots plus background (frame 66). No optical filters were used.
  • CMOS biosensor Some of the many potential applications for a wireless CMOS biosensor such as the ones described above include applications for microarrays as well as for implantable biosensors.
  • Microarrays may include DNA, RNA, protein and other biological applications.
  • Implantable biosensors may be useful in measuring cellular signals, signals involving viruses, bacteria, or other small molecules.
  • the implantable biosensor may also be a drug delivery device.
  • Genetic diagnostic and screening applications are growing as the relationship between genetics and disease pathology is being elucidated.
  • personalized medicine the emerging field whereby drug treatment is partially determined by a patient's genetic makeup (i.e. Iressa, Herceptin, Bidil, etc.) will rely extensively on large scale genetic analysis.
  • Drug trials are now beginning to include genetic screening, to determine the most effective patient profile.
  • a biosensor such as the ones described herein may be useful for large scale genetic screening and analysis and for small scale genetic/diagnostic applications whereby arrays on the order of 10-100 are assayed.
  • the biosensor of the present invention is useful for both traditional microarray reader applications (e.g. cy3/cy5 labeled DNA), as well as GFP labeled protein. Since GFP labeling requires immersion in solution, a sensor such as the one described herein can be useful for this type of application.
  • RNA binding proteins RNAbp
  • RNAbp can be fused to GFP to allow in-vivo tracking, immunoprecipitation, and also function as a label for microarray applications.
  • the immunoprecipitated complex will be RNA + RNAbp + GFP and can be directly applied to an array, without the need for exogenously labeling with Cy3/Cy5.
  • CMOS sensor such as the ones described herein is to label DNA with Qdots (e.g., biotinylated DNA + streptavidin Qdots), rather than Cy3/Cy5 dyes.
  • Qdots e.g., biotinylated DNA + streptavidin Qdots
  • the quantum dots can be illuminated at any wavelength below their emission wavelength, and still fluoresce at a specific emission wavelength, as described above.
  • Streptavidin labeled Qdots have been used on both protein and DNA microarrays. Applicants have shown that Qdots can be illuminated with UV and this UV light is not readily absorbed by the sensor. The Qdots then emit visible light, which can be detected by the sensor. This eliminates the need for an excitation filter. Protein u-arrays for drug development and basic research
  • DNA ⁇ -arrays provide a wealth of information, proteins are the final effectors of physiological function, and provide the key to the vast majority of in-vitro diagnostics.
  • Large scale protein arrays may enable advances in drug screening and interactions - by panning a drug against every protein in the system, both intended and potential side effects can be visualized and in basic research. Understanding protein-protein interactions helps elucidate key biological pathways and mechanisms of action. Furthermore, by knowing the binding kinetics of specific protein-protein interactions, the binding strength and specificity can be determined. These are characteristics that are relevant to both basic research and determining drug kinetics.
  • proteins must be cloned and purified in a time consuming process.
  • a biosensor such as the one described herein, could be combined with a method for patterning proteome arrays and used for studying binding kinetics.
  • a GFP label sample is introduced.
  • An evanescent wave only illuminates fluorophores within l/lO* of a wavelength from the surface. Therefore, only fluorophores that are bound to the surface are illuminated.
  • protein binding kinetics can be ascertained.
  • GFP labeled proteins or proteins labeled with a fluorophore
  • Kinetics can be visualized as well, since only one binding event is required, and real-time data can be taken in a hydrated environment. Since GFP must be hydrated, a fluid compatible sensor must be used.
  • the biosensor of the present invention includes an outer layer to provide a fluid barrier and as such, can be placed in solution and used for assaying binding kinetics in a high throughput format. Additionally, chemical labeling (such as with FITC, or CY3/Cy5), can be used instead of GFP.
  • Implantable diagnostics/monitoring devices [0036] Traditionally, flow cytometry or microscopy has been used for imaging cellular biosensors (cells with a reporter gene). In order to use these imaging techniques, cells must be placed into an in-vitro environment. The optimal biosensor for some applications would be a highly sensitive, real-time, continuous sensor of an organism, constantly circulating and being exposed to potential targets. For example, a cell could act as a living biosensor.
  • B cell / T cell sensors Cells can be used as living biosensors, since they have highly specific detection machinery in the form of antibodies and transmembrane receptors, internal signal amplification through a variety of signal transduction pathways, and reporting of the event via protein activation (e.g. phosphorylation) or gene activation through transcription factors. All cells can detect specific ligands, and certain cells lend themselves well to being engineered to bind to a specific target.
  • the procedure of generating monoclonal antibodies is one in which cells are selected that bind to a specific target.
  • the B cell hybridomas that produce antibodies also carry the antibodies on their surface.
  • BCR B cell receptors
  • the BCR complex activates an intracellular signaling pathway. This pathway activates an intracellular pathway, resulting in intracellular calcium release, and activation of transcription factors, such as API , NF-AT and NF-KB.
  • T cells work in a similar fashion, although the T cell receptor must have the target presented by an MHC II complex.
  • B cell hybridomas capable of antigen specific binding are engineered with a stable transfection of a reporter gene.
  • Hybridomas are generated by fusing a myeloma cell line (AG8) with a B cell population from an immunized mouse.
  • A8 myeloma cell line
  • cells can be transfected with nucleic acid constructs encoding a receptor or cell surface protein of interest.
  • the biosensor of the present invention is small and wireless, making it a potential candidate for implantable applications.
  • the biosensor can detect and measure a reporter gene that produces GFP when the cell encounters a specific target.
  • cells may be labeled or filled with quantum dots (Qdots).
  • Qdots quantum dots
  • the cells loaded with Qdots can migrate across a CMOS image sensor and be illuminated with light, e.g., UV light, and a picture taken. This can be used to track migration of cells. As pixel size and spacing becomes smaller and smaller, intracellular features may also be visualized.
  • a labeled binding agent such as an antibody or ligand is used for in vitro or in vivo use.
  • the binding agent specifically binds to one or more entities of interest.
  • entity could be an organic or inorganic substance, also referred to as an "analyte” or a cell that expresses a molecule on the cell surface, wherein the binding agent binds to the molecule.
  • the binding agent may be labeled with a fluorescent or luminescent moiety.
  • moieties are well known in the art and include small molecules (e.g., fluorescent dyes), polypeptides, quantum dots, etc. See, e.g., The Handbook — A Guide to Fluorescent Probes and Labeling Technologies (Invitrogen Corp.).
  • Certain embodiments of the invention are particularly suited for in vivo applications such as determining the concentration of an analyte in a body fluid of a mammal though of course they can be used for in vitro applications as well.
  • the uses of the system include applications such as determining whether an analyte of interest is present, determining the identity of an analyte, etc.
  • the output of the system may simply indicate that a substance is present or provide the identity of a substance.
  • the system is described in terms of determining concentration but it is understood that these additional applications are encompassed within that phrase.
  • the system stores spectral information for a plurality of substances, which information is of use to identify a substance.
  • the invention provides a system comprising a light emitting source, a wireless-powered optical sensor that is optionally implantable into the body of a mammalian subject, and a wireless communication and power system.
  • part or all of the system utilizes optical power and communication.
  • the light emitting source is outside the body, and the detection system comprising the sensor is inside the body (implantable).
  • the system further comprises a receiver for receiving a signal from the sensor.
  • the sensor is implantable and contained in a biocompatible, optically transparent material.
  • the receiver is located in a unit external to the body.
  • a wireless subsystem is present on both sensor and the receiver unit allowing communication therebetween.
  • a method of determining the concentration of an analyte in a body fluid comprising providing a sensor located in proximity to a sample comprising the fluid, illuminating the sample, obtaining a signal indicative of the interaction of light with the sample, and analyzing the signal to determine the concentration of the analyte.
  • the system and method can be applied to any analyte which has spectral properties that cause it to differ from its surroundings (i.e. distinct absorption spectra).
  • the system comprises an external unit comprising one or more light emitting sources, power transmission circuitry, and wireless receiver circuitry.
  • the components of the external unit are suitably housed, e.g., in a plastic housing.
  • the external unit is attachable to a garment or wearable around a limb, e.g., around the wrist.
  • the external unit comprises a processor capable of analyzing the signal and outputting results.
  • the external unit comprises a display for the results.
  • the light emitting sources are, e.g., LEDS and /or laser diodes. The light they emit may be modulated so as to distinguish it from background / ambient light as well as to modulate it to place the signal frequency above the low frequency flicker noise present in the sensor circuitry.
  • the LED/laser diode output can be synchronized to the sensor circuitry.
  • the light emitting source can be covered by an optical filter to provide a narrower bandwidth of light.
  • the external unit is a handheld device of a suitable size to fit comfortably in a human hand, e.g., having dimensions up to approximately 15 x 15 x 2.5 cm.
  • Devices such as personal digital assistants (PDAs), Blackberry®, Palm Pilot®, or cell phones are examples of handheld devices having suitable dimensions.
  • the device houses the light emitting source and has an optically transparent "window" through which light of a wavelength suitable for interacting with an analyte of interest can pass. The device is held close to the skin (e.g., directly on the surface of the skin or at a distance up to .1 mm - 5 cm from the skin) at a position where the implantable sensor is known to be located.
  • the device may be waved over the approximate location overlying the sensor.
  • Light from the source passes through the skin and impinges on the sample and sensor as described further below.
  • the sensor detects a signal indicative of the interaction of light with the sample and transmits the signal, optionally after processing) to the external unit which displays the results (optionally after processing).
  • the sensor and/or receiver is either physically or wirelessly connected to an implanted or external device that responds to the signal by delivering a substance to the body (e.g., a medication) or altering the dose of a delivered substance.
  • the sensor and/or receiver may be connected to an insulin pump, a pump that delivers a pain medication, an alarm, etc.
  • portions of the system communicate with one another via optical fiber(s).
  • the senor comprises an implantable platform onto which a plurality of sensor modules are integrated (e.g., they may be fabricated substantially at the same time as the sensor modules) or the sensor modules are fabricated separately and attached to the platform, e.g., by flip chip bonding or wire bonding.
  • the platform comprises a substrate that supports the wireless interface circuitry as well as circuitry to interact with the sensor modules.
  • the implementation is silicon-based CMOS (complementary metal oxide semiconductor).
  • the sensor module comprises an array of optical detectors.
  • the sensor comprises detectors capable of detecting non-optical parameters as described further below.
  • each optical detector measures a specific wavelength or optical property. The intensity of light at each wavelength is used to determine the concentration and/or identity of an analyte of interest as further described below.
  • the sensor processes (e.g., amplifies and/or filters) the sensor output, digitizes the data (e.g., using an analog to digital converter) and transmits the data, e.g., to a receiver unit.
  • the data may be modulated at a frequency different from the carrier RF wave.
  • the data is modulated at Vi the frequency of the carrier wave.
  • the platform wirelessly receives power and data, and includes on chip signal processing and analog to digital conversion.
  • the senor utilizes silicon-based CMOS technology wherein circuitry is fabricated on chip.
  • the circuitry in this instance comprises an on-chip inductor coil, a rectifier, and a voltage regulator. These elements allow power to be transmitted to the chip.
  • Digital circuitry generates a clock, decoder for accessing each pixel, an amplifier to magnify the signal, and an analog to digital converter. The digital data is then modulated and transmitted through the RF coil. Any component mentioned, e.g., coil, sensor, amplifier etc, can be attached to the chip rather than integrated.
  • the sensor comprises CMOS (complementary metal oxide semiconductor) detectors on a silicon substrate.
  • the substrate allows IR light of a desired wavelength or range of wavelengths (e.g., 2-10 ⁇ m) to pass through. For example at least 50%, at least 80%, at least 90% or more of the intensity of the IR light may be transmitted. In some embodiments the substrate does not substantially transmit visible light. For example, the total intensity of visible light may be attenuated by at least 90% by the substrate.
  • the sensor comprises CMOS (complementary metal oxide semiconductor) detectors on a glass substrate. Glass allows both visible and IR light to pass through.
  • CMOS complementary metal oxide semiconductor
  • the sensor and method of the invention measure the concentration of an analyte in a body fluid in vivo by directing light containing a plurality of different IR wavelengths through the body fluid.
  • the light of the plurality of different wavelengths travel in substantially the same direction with respect to each other as they pass through the fluid, e.g., they are directed parallel to one another and have essentially the same optical path.
  • the light of different wavelengths does not have the same optical path.
  • the light is emitted from discrete sources each of which emits within a discrete range of wavelengths. In some embodiments one or more sources emits across a range of wavelengths.
  • a source may emit light comprising a plurality of wavelengths.
  • Some embodiments of the sensor comprise at least two sensor modules, each comprising a plurality of detectors. Light of a given wavelength is sensed by a detector on each of at least two sensor modules. Thus variations in absorption, scattering, or differences in path length may be corrected for, and the desired spectral information extracted. Some of the detectors may be devoted specifically to calibrating and correcting for such differences.
  • the differential detection approach of these embodiments allows robust detection and provides a way to overcome certain limitations associated with prior efforts to reliably detect analyte concentrations in vivo.
  • Calibrating wavelengths may also be measured, for example, to account for factors such as blood volume, vessel wall thickness, tissue or other material between the vessel and the sensor modules, as well as components in the blood such as hemoglobin, albumin, globulins, lipids, etc.
  • the detectors could be, e.g., photodiodes.
  • CMOS photodiode array is used in certain embodiments of the invention.
  • differential detection aspects of the invention and implementation thereof are applicable to a broad range of in vivo and in vitro uses and are in no way limited to implantable sensor applications.
  • such aspects could be used to measure substances present in fluids (e.g., oil, water, gas) flowing in pipes or conduits buried underground, under water, within structures, or otherwise separated from a light source used for such measurement by material that could scatter and/or absorb light.
  • fluids e.g., oil, water, gas
  • the device could be implemented in a variety of technologies including but not limited to CMOS-based technologies.
  • the body fluid is blood located in a blood vessel such as a vein.
  • the body fluid is interstitial fluid located outside a blood vessel, e.g., within a membrane or body structure.
  • the light is emitted and detected within a short period of time, e.g., within a time less than or equal to the average interval between heartbeats of the subject (e.g., within a time less than or equal to 1%, 10%, or 50% of the average time interval between heartbeats, or within less than about 1, 5, 10, 20, 50, or 100 ms.
  • between 5 and 100 different wavelengths are detected.
  • between 5 and 20 or between 10 and 20 different wavelengths are detected.
  • a complete spectrum across a range of wavelengths is gathered.
  • at least some wavelengths are used for purposes of normalization and/or calibration.
  • at least some wavelengths are used to account for baseline offset.
  • the wavelengths may bracket or span the spectral region of interest, i.e., the region containing wavelengths at which the substance or substances of interest characteristically absorbs and/or transmits light and which are of use to detect the substance.
  • the differential detection embodiments of the invention obviate the need for at least some of these corrections.
  • each intensity at each wavelength is measured twice, once before the light enters the sample and once after the unabsorbed light leaves the sample, baseline correction, etc., is not needed.
  • the invention provides an implantable sensor device wherein analytes in the blood or interstitial fluid are measured using an external (i.e., outside the body) light source, without needing to account for scattering and absorption due to tissues located between the light source and the implanted sensor modules.
  • the inventive method focuses on making measurements on the sample itself (e.g., blood) thereby offering increased sensitivity by excluding other components that add significant noise to the measurement (e.g., skin, fat, interstitial fluid, bone).
  • a blood vessel having a diameter between about 0.3-1.0 mm is selected, although vessels having larger or smaller dimensions could be used.
  • the sensor modules are positioned so that the shortest straight line distance between the sensor module and the exterior surface of the vessel is less than 5 mm, e.g., less than 1 mm.
  • the sensor is implanted into the outer wall of the vessel.
  • the sensor modules are positioned so that the shortest straight line distance between the sensor module and the interior surface of the vessel is less than 5 mm, e.g., less than 1 mm.
  • modules may be positioned to have multiple vessels therebetween.
  • wavelengths at which analytes of interest have significant absorption and transmission may be selected empirically and/or using known spectral features of analytes of interest optionally guided by experimental results.
  • the intensity of light detected at each of a plurality of wavelengths is used to determine the concentration and/or identity of an entity of interest using multivariate analysis.
  • the sample e.g., blood
  • the sample may contain other analytes that have a spectrum overlapping with that of the analyte of interest. Furthemore, blood vessel walls, cells, and tissues will absorb.
  • the sensor measures at least several different wavelengths at key points in the spectrum for an analyte of interest and other substances found in the sample. From this information, the amounts of each substance that contribute to each spectra can be determined. It may be assumed that the concentration of different substances contribute to the total measured spectrum in a linear manner. It will be appreciated that components with concentrations significantly below (e.g., two to several orders of magnitude below) that of the analyte(s) of interest may be excluded as they will not significantly affect the measurements. Any of a variety of techniques and algorithms known in the art can be used to ascertain concentrations of individual analyte(s). Examples include partial least squares analysis, principal component analysis, linear regression, neural networks, multivariate analysis, etc.
  • Spectral deconvolution methods are known in the art. See, e.g., K.H. Hazen, et al. Analy ⁇ ca Chimica Acta, Vol. 371, pp. 255-267, 1998; .R. A. Shaw and H. H. Mantsch. Infrared Spectroscopy in Clinical and Diagnostic Analysis. Encyclopedia of Analytical Chemistry.; Y. C. Shen, et al., Phys Med Biol 48 (2003) 2023-2032; H. Heise, et al., Anal. Chem., 61 , 2009-2015 (1989); P. Bhandare, et al., Appl. Spectrosc, 8,1214-1221 (1993); K.J. Ward, D.M.
  • multiple measurements are made within a short period of time, e.g., within a time less than or equal to the average interval between heartbeats of the subject (e.g., within a time less than or equal to 1%, 10%, or 50% of the average time interval between heartbeats, or within less than about 1, 5, 10, 20, 50, or 100 ms. Said multiple measurements may each be made at multiple wavelengths.
  • the sensor comprises two sensor modules that are positionable in a functional relationship to each other and to a sample comprising an entity of interest to be detected.
  • “Positioned in a functional relationship” in this context means that the sensor modules are positioned so that light that passes through a first sensor module will be incident on the sample, and light that is not absorbed or significantly scattered by the sample will be incident on the second sensor module.
  • “Incident on the second sensor module” means that at least some of the detectors will be illuminated by the light that passes through the sample. For example, in some embodiments all of the sensors of the second module are illuminated. In some embodiments at least 25%, 50%, 75% or more of the sensors of the second module are illuminated. In another embodiment, a ring comprising at least two sensor modules is arranged around the sample, such as from any angle, a ray of light passes through two sensor modules.
  • the sensor modules are connected via a series of wires or can wirelessly communicate with each other and/or the receiver.
  • the signals from each photodetector can be analyzed sequentially or differentially (e.g., subtract the signals and amplify).
  • each of two sensor modules comprises a photodetector that detects light having a wavelength "X".
  • the signals from these two photodetectors are subtracted, thereby providing a measurement of the absorption (or transmission) of the sample at that wavelength without interference due, e.g., to absorption (or transmission) from materials outside the sample of interest (e.g., tissues located between the light source and the blood vessel). This arrangement allows only the sample of interest to be measured.
  • FlG. 17 is an illustration of an implantable sensor comprising two sensor modules each comprising an array of photodetectors.
  • the sensor modules are positioned on opposite sides of a blood vessel. They need not be directly opposite one another. The positioning need only be such that light passing through one of the sensor modules will pass through at least a portion of the fluid-filled region of the vessel and light not absorbed or scattered by the contents of the vessel and/or vessel walls will pass through at least a portion of the second array of photodetectors allowing detection to take place.
  • the sensor modules may, but need not be, be physically connected to one another. They may be flexibly connected to allow the sensor to encircle at least a portion of a cross-section of a blood vessel.
  • the connecting material is a biocompatible substance.
  • FIG. 18 is an illustration of another embodiment of an implantable sensor in which two sensor modules each comprising an array of photodetectors are attached to and electrically coupled to a substrate, which is a component of a platform that may house additional components such as processor, transmitter, etc.
  • FIG. 19 is a schematic illustration showing powering of the sensor by inductive coupling.
  • FIG. 20 is a schematic illustration of light illuminating and passing through both sensor modules and a vessel positioned between the sensor modules.
  • FIG. 21 is an illustration of a sensor module comprising multiple photodetectors, each capable of detecting light of a different wavelength.
  • the senor is implantable for use in detecting a substance present in a body fluid of a subject, e.g., a mammalian and, optionally determining the concentration of the component.
  • the body fluid may be, for example, blood, lymph, aqueous humor, or interstitial fluid.
  • the substance may be a metabolite, nutrient, hormone, enzyme, etc. It may be a protein, a small molecule, lipid, or sugar such as glucose.
  • the substance is a toxin.
  • the substance is a pharmaceutical agent, e.g., a drug approved by the U.S. Food & Drug Administration or being studied with a view to such approval.
  • the substance is ethanol.
  • the substance is a biomarker whose presence is indicative that the subject has an illness, e.g., cancer or infection.
  • the substance may be a bacterial product.
  • the substance is hemoglobin or bilirubin.
  • the substance has an absorption spectrum in the infrared (IR) region.
  • the array comprises photodetectors that detect infrared (IR) light.
  • the array comprises photodetectors that detect IR in the near, mid, and/or far IR ranges.
  • wavelengths of interest range between 700 nm and 1 mm.
  • the wavelengths of interest are between 2-5 um, e.g., between 2-2.5 um, and/or between 5-10 um or in some embodiments as low as 1-1.5 um.
  • Infrared detectors may be fabricated by placing an infrared absorbing material, e.g., a thermocouple material with a high coefficient of thermal expansion comprising for example, nickel, silicon, germanium, or another material with an appropriately high coefficient of thermal expansion as known in the art.
  • the detectors are composed at least in part of silicon (Si), germanium (Ge), silicon-germanium (SiGe), or combinations thereof.
  • Silicon as used herein includes polysilicon and such other forms of silicon as known in the art.
  • Other materials known to absorb in the IR region such as InGaAs, lead sulfide (PbS), lead selenide (PbSe), indium arsenide (InAs), etc., could be used.
  • the material changes properties, such as resistance, size, or junction potential in response to absorbing the infrared light.
  • the sensor comprises SiGe detectors grown on a Si substrate.
  • a substance to be detected is glucose.
  • the need for glucose monitoring in diabetic patients is known in the art, and the advantages of an implantable glucose sensor are well recognized. See, e.g., U.S. Pat. No. 6,049,727, which is incorporated herein by reference.
  • the '727 patent extensively reviews prior approaches to noninvasive detection of glucose and the challenges encountered.
  • the present invention allows the monitoring of glucose and/or other substance(s) present in a body fluid such as blood (e.g., urea, cholesterol), without the need to implant a light source in the subject.
  • embodiments of the invention allow such monitoring without the need to implant power source, lens, optical filters, etc., in the subject.
  • One aspect of the invention is a novel method of measuring the concentration of an analyte of interest present in a mixture with one or more additional analytes.
  • the method finds use in a variety of contexts including but not limited to, that of an implantable device of the present invention.
  • the invention may be of particular use when the analyte of interest represents only a small proportion of the total mixture.
  • the most significant component is water, which is four orders of magnitude greater in concentration than glucose. See the table below for approximate concentrations of many components present in blood.
  • the method of measuring the absorption due to a second substance in a sample comprising first and second substances comprises (a) largely or completely eliminating the absorption due to the second substance from a measurement of the absorption due to the second substance by (i) obtaining a first absorption measurement at a first wavelength and a second absorption measurement at a second wavelength, wherein the absorption due to the second substance at the first wavelength is substantially identical to the absorption due to the second substance at the second wavelength and wherein the absorption due to the first substance at the first wavelength is substantially different to the absorption due to the first substance at the second wavelength; and (ii) subtracting the first and second measurements from each other, thereby resulting in a measurement of the absorption due to the first substance.
  • the method involves largely or completely eliminating the absorption of the second substance from the measurement of the absorption of the first substance by making at least first and second measurements around a local minimum or maximum in the spectrum of the second substance, i.e., in a region where the spectrum assumes a parabolic shape.
  • substantially identical absorptions may be within, e.g., 1, 2, 5, 10, or 20% of one another in various embodiments of the invention.
  • substantially different absorptions may differ from one another by, e.g., at least 1.5, 2, 2.5-fold, or more, in various embodiments of the invention.
  • the method is illustrated in FIG. 22 for the case of removing the absorption due to water from a signal so as to accurately measure absorption due to glucose, but it will be understood that the method is applicable to any two substances wherein at least one of the substances (i.e., the substance whose absorption is to be removed from the signal) has a spectrum that assumes a suitable, e.g., approximately parabolic or similar shape in a wavelength range of interest. It will also be understood that the method is applicable to spectra of any type, e.g., transmission, reflectance, scattering, etc., as well as absorption spectra, and is of broad utility to measuring analytes present in mixtures.
  • the method is used to remove absorption due to a solvent from measurement of absorption due to a solute. Furthermore, the method can be used to isolate the signal due to a single analyte present in a complex mixture of substances by making multiple measurements as described herein, wherein measurements are made at two different wavelengths for each substance whose absorption is to be removed from the signal, wherein the absorptions due to that substance at each of the two different wavelengths are approximately equal.
  • Appropriate mathematical techniques and algorithms e.g., partial least squares analysis, principal component analysis, linear regression, neural networks, etc., as known to those of skill in the art, may be employed to process the measurement data and solve for the individual concentrations.
  • the absorption spectrum of water is shown with a dashed line and the absorption spectrum of glucose is shown with a solid line. Measurements are made at two wavelengths ⁇ , and X 1 that will have approximately identical water absorption, but significantly different glucose absorption (e.g., differing by a factor of at least 1.5-2, although smaller fold differences are within the scope of the method. If one subtracts the absorption at A 1 from A 2 , the absorption due to water cancels out, leaving only the absorption due to glucose.
  • the expression using the water and glucose absorption can be written as:
  • FIG. 23 depicts side and front views of a differential optical sensor assembly, including two optical sensor modules (referred to as detectors in the figure) wire bonded onto metallized quartz substrates.
  • the sensor assembly is implantable and includes data processing circuitry and transmits data to an external unit.
  • the host substrate houses data processing and transmission circuitry.
  • FIG. 24 shows a schematic diagram of a glucose sensing system of the present invention, including a differential sensor assembly as in FIG. 23.
  • the external unit houses a light source (e.g., LED), appropriate optical components (e.g., one or more lenses) and appropriate filters to selectively transmit light falling within wavelength ranges of interest.
  • a filter assembly allows automated selection of narrowband (e.g., ⁇ 10nm) optical filters.
  • the external unit may house a power source (e.g., RF power source) that transmits power to the sensor modules.
  • Interface circuitry controls the light source and filter assembly and receives electrical signals from the detectors.
  • FlG. 25 shows implementation details of the optical emission and detection in an exemplary embodiment of the glucose sensor.
  • the LED is modulated at a low frequency, e.g., between 1 and 100 kHz.
  • the detector comprises a structure comprising thermocouple material.
  • Thermocouple materials are in some embodiments materials that are microfabrication compatible and have a high coefficient of thermal expansion. Examples are nickel and copper. Materials such as SiGe can also be used.
  • the detector is in the shape of a beam.
  • the beam may be an elongated structural member having substantially parallel sides and a square or rectangular cross-section. In other embodiments the beam may have a circular cross-section and be shaped as a cylinder. The beam resonates according to its size and effective spring constant.
  • the sensor independently measures the change in resistance and resonant frequency.
  • the sensor output is based on individual parameters, or combination of at least two parameters.
  • the structure is made at least in part of nickel and/or SiGe.
  • the beam is coated with a thin layer of absorbing metal, e.g., gold.
  • the structure is made of a material suitable for microfabrication such as silicon or polysilicon, and coated with a thermocouple material (i.e. material with a high coefficient of thermal expansion)
  • the detector comprises a beam of material that absorbs infrared light that is suspended, increasing thermal isolation by means of etching away a supporting sacrificial layer.
  • the structure is made on a silicon on insulator (SOI) wafer, and the oxide is etched away.
  • SOI silicon on insulator
  • another sacrificial material is used, e.g., polysilicon, photoresist, polimide, silicon nitride, SiO2, MgO.
  • the sensor module is fabricated separately and bonded to the chip.
  • the structure e.g., resonator beam
  • the structure is formed from a structural material that is easily microfabricated, such as silicon, poly silicon, or silicon on oxide, and the beam is then coated with a material that has a high coefficient of thermal expansion, such as nickel or copper.
  • the material absorbs infrared light, increases temperature and expands, causing the resonant frequency of the beam to change. This change in frequency is measured, and correlated to the amount of incident light.
  • the light emitting source (LED/Laser diode) and transmission circuitry operate in a closed loop with a sensor module, wherein the signal from the sensor module is used to guide the output from the light emitting source.
  • the power output from the light emitting source is increased until an adequate signal is detected.
  • a suitable light source commercial LEDs are available that emit light from the UV to near or mid IR.
  • the light source emits at a plurality of discrete wavelengths.
  • the light source emits light having a broad range of wavelengths.
  • an appropriate additional element is added to achieve transmission in the far-IR.
  • the element receives light from a source such as an LED that emits in the UV and in turn emits light of a different wavelength.
  • a layer or "film" of quantum dots that emit at the wavelength of interest is used.
  • the quantum dots can absorb at energies greater than their emission (such as the UV or mid IR emitted by commercial LEDs), but emit at a wavelength determined by their properties such as composition and size. Therefore, quantum dots of the appropriate composition and size to emit in the wavelengths of interest (e.g., near-mid IR 2-5 urn), far IR (e.g., 5-10 um) are fabricated into a layer and placed between the LED (emitting a shorter wavelength) and the sensor module.
  • the layer is included in the implantable portion of the apparatus. For example, it may be patterned on the sensor module. In other embodiments it is positioned on the light emitting source itself or in close proximity thereto and housed within the same housing such that light from the light source passes through the layer.
  • Suitable quantum dots are commercially available. Other elements capable of modifying the spectrum of light emitted from commercially available LEDs or other light sources could also be used. It will be appreciated that LEDs that emit with suitable power (mW) having wavelengths in the far IR would also be of use as would a variety of other light sources that emit in the mid to far IR region. Thus there are a variety of ways to provide light incident on the sample wherein the light comprises wavelengths at which the analyte(s) of interest absorb.
  • mW suitable power
  • the light is filtered before it comes into contact with the detectors.
  • the light can be filtered by an optical interference filter, or by a cavity which only allows certain wavelengths of light to resonate.
  • These filters are optical bandpass or bandstop filters, some of which may be integrated with the detectors (e.g., as part of a sensor module) and some of which may be attached.
  • the photodetectors are coated with a material that serves as an optical filter.
  • the optical filter allows only a narrow wavelength of light to pass through, allowing selective detection of light of different wavelengths by the detectors.
  • the thickness and/or composition of the material can be altered to achieve substantial transmission of only a desired range of wavelengths.
  • the senor comprises an optical filter for a wavelength of interest.
  • the filter is located between the light source and the detectors.
  • the filter is located between the light source and a sensor module.
  • the filter is an interference filter.
  • the filter is made, for example, from a layers of films stacked on top of each other such that only a specific wavelength may pass through.
  • the filter is a cavity sized such that one wavelength is resonant.
  • the cavity is formed by putting the detectors, e.g., a sensor module or one or more detectors, between reflective surfaces. The surfaces reflect the light back and forth. Only light of a wavelength corresponding to the dimensions of the cavity is trapped, thereby filtering the light.
  • the cavity dimensions are adjusted by electrical bias to alter the resonant wavelength.
  • the sensor is positioned between two surfaces that reflect the wavelength of light.
  • the photodetectors are capable of detecting light in the visible range (400 - 700 nm wavelength). In some embodiments the photodetectors are fabricated at least in part of silicon.
  • the senor allows the monitoring of variables that provide information about the physiological status of a subject. Examples include temperature and pressure. Temperature can affect the spectral characteristics of a substance in a body fluid, and in some embodiments the measurements are corrected or normalized to account for changes in temperature. For example, concentration values could be normalized to a subject's normal body temperature, to a temperature of -98 degrees F, etc. In some embodiments, changes in temperature are measured to determine whether the subject is suffering from an infection. Pressure can be an indicator of blood volume and flow rate and thus is a parameter useful for monitoring the physiological status of a subject. Such environmental variables as pressure and temperature affect properties of the detectors such as resistance, size, or junction potential and can thus be measured in an analogous fashion to light.
  • a PTAT circuit is incorporated on chip using, e.g., a CMOS process. This functions as a temperature sensor.
  • a pressure sensor can be made from etching underneath a film, or by bonding a MEMS (micro-electromechanical system) pressure sensor to an area on the chip, which then can interrogate the sensor. MEMS pressure sensors are commercially available.
  • the pressure sensor is attached to, e.g., bonded to, the array of photodetectors.
  • one or more of the sensors detects polarized light.
  • the polarization information may be incorporated into the calibration routine.
  • the polarized light sensor is implemented by either fabricating or bonding a polarized light filter onto the optical sensor module.
  • Glucose is known to polarize light.
  • incorporating a sensor of polarized light can give another data point to determine the concentration of glucose from the environment (e.g., blood or interstitial fluid).
  • FIG. 11 is a calibration curve showing the number of photons incident on the sensor versus applied voltage.
  • the LED emits light at around 2.7V of forward bias. At around 3V, the equivalent number of photons is about 40/um ⁇ 2/2.
  • FIG. 12 is a graphical illustration of pixel output from ramping LED voltage.
  • the LED was taken from 0-4V (indices 0-40), and then ramped down from 4V to 0 V (indices 40-80). This shows a response to light. Additionally, a signal of 40 photons/um ⁇ 2/s can be clearly seen.
  • FIG. 13A and 13B are graphical illustrations of amplifier output versus incident light. The output of the amplifier is shown for different pixel types.
  • FIG. 14 is a graphical illustration of digital values from the amplifier output. Signals as low as 10 photons/um2/s can be detected.
  • 0-40 corresponds to 0-4 V
  • 41 to 80 corresponds to 3.9 V to 0 V.
  • FIG. 16 is a graphical illustration comparing varying concentrations of GFP using the CMOS sensor of the present invention versus a CCD camera. Serial dilutions of GFP were made and imaged with both a CCD and the CMOS sensor. The CCD output is the digital output (1 to 4096), and the wireless CMOS sensor output is the amplifier output (before digital conversion).
  • a system for measuring a biological sample comprising: a sensor which provides an electrical output; an analog to digital converter in electrical communication with said sensor for converting said output into a digital signal, wherein at least said sensor and said analog to digital converter form a CMOS circuit; and a processor for processing said digital signal.
  • the senor comprises a photodiode for converting photons obtained from interaction with the sample into electrons.
  • said wireless interface comprises an integrated antenna, said integrated antenna integrated into a physical structure of said system.
  • said sensor is integrated with an implantable device.
  • said implantable device is a drug delivery device
  • said sensor is integrated with said drug delivery device.
  • said sensor further comprises a flip-chip bonding scheme.
  • said sensor further comprises multiple photodiodes arranged in a pixel array of photodiodes.
  • said pixel array of photodiodes comprises a one-to-one correspondence with an array of the biological sample.
  • each pixel of said pixel array is approximately 120 micrometers x 120 micrometers.
  • said sensor further comprises an outer layer substantially surrounding said pixel array, said outer layer providing a fluid barrier between electrical components of said sensor and the biological sample.
  • the system of claim 2 further comprising an evanescent illumination system said illumination system comprising a prism positioned beneath said sensor for introducing light, wherein said at least one photodiode is configured for receiving photons via said evanescent illumination system.
  • said at least one photodiode is selected from the group consisting of an N-plus P-sub diode, an N-well P-sub diode, a P-plus N-well P-sub diode, and an N-plus P-well diode.
  • each pixel of said pixel array comprises a sensor photodiode and a reference photodiode.
  • said reference photodiode is covered with metal.
  • each pixel of said pixel array further comprises a first source follower, a second source follower, and a hold capacitor, and wherein said first source follower is for applying a sample and hold operation onto said hold capacitor for storage, said second source follower is for transmitting said stored hold operation to said processor.
  • microarray is selected from the group consisting of: a protein array, a DNA array, an RNA array, a cellular array, an array including a virus, an array including a bacteria, and an array including small molecules.
  • optical signals include signals from a biological marker.
  • a sensor for identifying an interaction in a microarray comprising: a pixel array of photodiodes, wherein a size of each pixel of said pixel array corresponds to said microarray; and an outer layer substantially surrounding said pixel array, said outer layer providing a fluid barrier between electrical components of said sensor and said biological sample.
  • a size of each pixel ranges from less than the size of a spot on the microarray to a maximum of the pitch between spots on the microarray.
  • a size of each pixel is less than 150 micrometers.
  • each pixel of said pixel array is approximately 120 micrometers x 120 micrometers in size.
  • said outer layer is a biocompatible material. 38. The sensor of claim 32, wherein said pixel array of photodiodes comprises at least one photodiode selected from the group consisting of an N-plus P-sub diode, an N-well P-sub diode, and a P-plus N-well P-sub diode.
  • each pixel of said pixel array comprises a sensor photodiode and a reference photodiode.
  • the sensor of claim 32 further comprising an analog/digital converter in electrical communication with said photodiodes.
  • each pixel of said pixel array further comprises a first source follower, a second source follower, and a hold capacitor, and wherein said first source follower is for applying a sample and hold operation onto said hold capacitor for storage, said second source follower is for transmitting said stored hold operation to said processor.
  • a method for measuring a sample comprising: providing a wireless CMOS biosensor comprising a pixel array of photodiodes; providing a biological sample; tagging said biological sample with a fluorescent label; placing said biosensor proximal to said biological sample; illuminating said biosensor and said biological sample, wherein said illuminating causes said tagged biological sample to emit photons; converting said photons into an electrical signal using said CMOS biosensor; and wirelessly receiving said electrical signal, said electrical signal being representative of an amount of said tagged biological sample.
  • said sample is a biological sample.
  • placing said biosensor proximal to said biological sample comprises placing said biosensor in solution.
  • placing said biosensor proximal to said biological sample comprises placing said biosensor in contact with said biological sample.
  • placing said biosensor proximal to said biological sample comprises providing said biological sample as a microarray, and placing said biosensor within a distance which is several times a spot size of the microarray.
  • each sensor module comprises a plurality of photodetectors 58.
  • a method of determining the concentration of an analyte comprising directing light at a sensor comprising two or more sensor modules each comprising a plurality of photodetectors positionable with respect to each other and with respect to a sample, so that light that passes through the first sensor module and the sample is incident on the second sensor module.
  • a system comprising (i) an implantable sensor comprising at least two sensor modules each comprising an array of photodetectors; and (ii) an external unit that houses a light source and, optionally at least one item selected from a display, a processor, and a receiver.
  • Claims or descriptions that include "or" between one or more members of a group are considered satisfied if one, more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process unless indicated to the contrary or otherwise evident from the context.
  • the invention includes embodiments in which exactly one member of the group is present in, employed in, or otherwise relevant to a given product or process.
  • the invention also includes embodiments in which more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process.
  • the invention includes an embodiment in which the exact value is recited.
  • the invention includes an embodiment in which the value is prefaced by "about” or “approximately”.
  • “Approximately” or “about” generally includes numbers that fall within a range of 1% or in some embodiments 5% of a number in either direction (greater than or less than the number) unless otherwise stated or otherwise evident from the context (except where such number would impermissibly exceed 100% of a possible value).
  • the invention includes methods of using the apparatus for any purpose contemplated herein, and methods for making the apparatus according to techniques contemplated herein or known in the art, unless clearly indicated to the contrary or evident to one of skill in the art that such apparatus would not be usable for such purpose or such method of making would not be suitable to make such apparatus.

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Abstract

L'invention concerne un système et des procédés pour la détection et la mesure de substances à analyser, par exemple à l'intérieur du corps humain. Le système comprend au moins un module de capteur qui peut être placé dans le corps d'un sujet et est capable de mesurer au moins une substance à analyser présente dans le sang ou le liquide interstitiel. Dans certains modes de réalisation, au moins deux modules de capteur sont placés dans l'immédiate proximité d'un vaisseau sanguin, et la concentration d'une substance à analyser, par exemple du glucose, est mesurée. Dans certains modes de réalisation, le dispositif est un appareil sans fil et l'unité implantable à base de CMOS transmet des signaux à une unité externe hébergeant un affichage, une source lumineuse, et une source d'énergie.
PCT/US2008/004731 2007-04-12 2008-04-11 Biodétecteur cmos implantable sans fil WO2009008932A2 (fr)

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ITMI20100258A1 (it) * 2010-02-19 2011-08-20 Antonio Americo Cannata Dispositivo di controllo glicemico
WO2014071079A1 (fr) * 2012-10-31 2014-05-08 The Board Of Trustees Of The Leland Stanford Junior University Dispositifs de détection implantables sans fil
WO2016085475A1 (fr) * 2014-11-25 2016-06-02 Hewlett Packard Enterprise Development Lp Dispositif implantable de détection d'une lumière corrélée à la perméabilité vasculaire
EP3035053A1 (fr) * 2014-12-18 2016-06-22 IMEC vzw Circuit de capteur cmos intégré miniature
WO2016174303A1 (fr) * 2015-04-28 2016-11-03 Nokia Technologies Oy Capteur de mesure physiologique
US10004913B2 (en) 2014-03-03 2018-06-26 The Board Of Trustees Of The Leland Stanford Junior University Methods and apparatus for power conversion and data transmission in implantable sensors, stimulators, and actuators
US10434329B2 (en) 2014-05-09 2019-10-08 The Board Of Trustees Of The Leland Stanford Junior University Autofocus wireless power transfer to implantable devices in freely moving animals

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITMI20100258A1 (it) * 2010-02-19 2011-08-20 Antonio Americo Cannata Dispositivo di controllo glicemico
WO2014071079A1 (fr) * 2012-10-31 2014-05-08 The Board Of Trustees Of The Leland Stanford Junior University Dispositifs de détection implantables sans fil
US10004913B2 (en) 2014-03-03 2018-06-26 The Board Of Trustees Of The Leland Stanford Junior University Methods and apparatus for power conversion and data transmission in implantable sensors, stimulators, and actuators
US10828502B2 (en) 2014-03-03 2020-11-10 The Board Of Trustees Of The Leland Stanford Junior University Methods and apparatus for power conversion and data transmission in implantable sensors, stimulators, and actuators
US10434329B2 (en) 2014-05-09 2019-10-08 The Board Of Trustees Of The Leland Stanford Junior University Autofocus wireless power transfer to implantable devices in freely moving animals
WO2016085475A1 (fr) * 2014-11-25 2016-06-02 Hewlett Packard Enterprise Development Lp Dispositif implantable de détection d'une lumière corrélée à la perméabilité vasculaire
US11484206B2 (en) 2014-11-25 2022-11-01 Ent. Services Development Corporation Lp Implantable device for detecting light correlating to vessel
EP3035053A1 (fr) * 2014-12-18 2016-06-22 IMEC vzw Circuit de capteur cmos intégré miniature
WO2016174303A1 (fr) * 2015-04-28 2016-11-03 Nokia Technologies Oy Capteur de mesure physiologique
CN107683104A (zh) * 2015-04-28 2018-02-09 诺基亚技术有限公司 生理测量传感器

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