Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
  • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
  • G01N21/64—Fluorescence; Phosphorescence
  • G01N21/645—Specially adapted constructive features of fluorimeters
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
  • G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
  • G01N21/7703—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator using reagent-clad optical fibres or optical waveguides

Definitions

• the invention relates to a device for supporting chromophoric elements, this device being of the type of those commonly called “biochips”.
• These devices comprise a support formed by a generally multilayer substrate, one face of which carries chromophoric elements which are chemical or biological molecules, or dyes added or grafted to chemical or biological molecules, or semiconductor nanostructures such as wires or quantum dots made integral with these molecules, these chromophoric elements emitting a fluorescence, the wavelength of which depends on their nature, when they are excited by appropriate light, the detection of this fluorescence making it possible to identify and to identify on the support the molecules which have reacted to given treatments.
• Dichroic filters have a high rejection rate of excitation light, of the order of 50 to 90 dB, that is to say 1: 10 "5 to 1: 10 " 9 .
• the intensity of the fluorescence emitted is low, and is 10 5 to 10 9 times weaker than that of the excitation light, the reflection of the excitation light by the support constitutes an important background which comes interfere with the detection of weak signals and does not allow a high signal-to-noise ratio to be obtained.
• the reflection by an air / glass diopter is typically 4% for incidences of up to about 20 degrees relative to normal. Beyond that, it increases or decreases depending on the angle and polarization of the light.
• the reflection of the excitation light by the face of the blade opposite to that carrying the chromophoric elements is of comparative intensity (4% of 96% or 3.84%) and is also bothersome.
• the two reflected intensities are added and the reflection reaches approximately 8%, which is far from being negligible.
• the support it is advantageous for the support to be reflective at the wavelength of the fluorescence emitted, because this makes it possible to multiply by approximately 2 (in geometric optics) or by approximately 4 (in wave optics) the intensity of the fluorescence emitted .
• the object of the invention is in particular to provide a simple, effective and economical solution to this problem, making it possible to cancel or at least reduce the reflection of the excitation light by the support while retaining the advantage resulting from the reflection of the fluorescence emitted.
• chromophoric elements these elements being intended to be illuminated by an excitation light to emit a fluorescence of wavelength different from that of the excitation light
• this support being characterized in that that it comprises at least one internal layer of material reflecting the fluorescence emitted by the chromophoric elements and at least one means of canceling or at least substantially reducing the reflection of the excitation light, this means being chosen from the group including: a layer of material absorbing excitation light, this layer having a thickness such that the product of this thickness by its absorption coefficient ⁇ e at the excitation wavelength is much greater than 1 or has a known value and controlled between 0.1 and 10 approximately,
• At least one layer of transparent and anti-reflecting material at the excitation wavelength formed on at least one face of the support and having a refractive index n 'close to the square root of the refractive index of support and a thickness equal to an odd multiple of ⁇ e / 4n'cos ⁇ , ⁇ e being the excitation wavelength and ⁇ the angle of the excitation rays in said anti-reflective layer,
• the reflection of the excitation light in the direction of the means for collecting the fluorescence of the chromophoric elements is greatly reduced, or even canceled, and the intensity of the fluorescence is increased, which greatly facilitates detection. and measuring this fluorescence.
• the above-mentioned absorbent layer and at least one anti-reflective layer are formed on the face of the support opposite to that carrying the chromophoric elements.
• the absorbent layer and at least one aforementioned anti-reflective layer are formed on the face of the support intended to receive the chromophoric elements.
• the support is made of material transparent to the excitation wavelength, the reflection of this wavelength is canceled by the face of the support which carries the chromophoric elements.
• the absorbent layer is formed on the upper face of the support, and the anti-reflective layer is formed on the absorbent layer.
• the internal layer of material reflecting the fluorescence emitted by the chromophoric elements is located at a distance d from the face of the support carrying the chromophoric elements which is much greater than the quantity ⁇ f.n / 2NA 2 , ⁇ f being the wavelength of the emitted fluorescence, n being the refractive index of the support, NA being the digital aperture of the optical means for collecting the emitted fluorescence, and the above-mentioned anti-reflective layer is formed on the face of the support intended to receive the chromophoric elements.
• an absorbent layer of the aforementioned type can be formed in the support between the anti-reflecting layer and the internal layer reflecting the emitted fluorescence.
• the internal reflecting layer can be formed by a plurality of dielectric layers and is formed to have a substantially zero reflection at the excitation wavelength for the angle of incidence of light. of excitement on the support.
• the internal reflective layer can be formed by a stack of layers having an optical thickness equal to a quarter of the excitation wavelength and refractive indices which are alternately high and low, with a central layer of thickness. double or different. This stack of layers forms a symmetrical Fabry-Perot cavity also called a micro-cavity.
• the wavelength of the minimum of reflection, the angle and the polarization used are determined by the thickness of the layer forming the cavity.
• an absorbent layer of the aforementioned type is advantageously formed in the support between the internal reflecting layer and the face of the support opposite to that intended to carry the chromophoric elements.
• the internal layer of material reflecting the emitted fluorescence is located at a distance from the face of the support carrying the chromophoric elements which is less than the quantity ⁇ f.n / 2NA 2 , and a layer Above-mentioned absorbent is formed between this reflecting internal layer and the face of the support intended to carry the chromophoric elements.
• the inner layer of reflective material can be a metallic or dielectric layer or a plurality of dielectric layers.
• the support comprises two layers of material reflecting the emitted fluorescence, these two layers forming an asymmetrical Fabry-Perot cavity and being located at a distance from the face of the support intended to carry the elements chromophores which is less than the quantity ⁇ f.n / 2NA 2 , and the abovementioned absorbent layer is located between these two reflecting layers and the support face opposite to that intended to carry the chromophoric elements.
• the chromophoric elements can be carried by one of the layers of reflective material, outside the Fabry-Perot cavity.
• the support comprises a first layer of material reflecting the emitted fluorescence situated at a distance from the face of the support intended to carry the chromophoric elements which is less than the quantity ⁇ f.n / 2NA 2 , a second layer of reflective material covering the support face intended to carry the chromophoric elements and situated at a distance from the first reflecting layer less than the quantity ⁇ f.n / NA 2 , and an abovementioned absorbing layer situated between the first layer of reflecting material and the support face opposite to that intended for carry the chromophoric elements.
• the chromophoric elements are between the two layers of reflective material and can be inserted between these two layers by known means, for example by passage, through porous materials or by means of microchannels opening into empty planar cavities formed by sacrificial etching of a stack of layers provided for this purpose.
• the invention is also applicable to the case where the support is intended to carry chromophoric elements of different types which emit fluorescence on different wavelengths when they are excited by appropriate different wavelengths.
• the abovementioned absorbent layer then has different absorption bands corresponding to the excitation wavelengths and can be formed for this purpose either from a single suitable component, or from a mixture of components having different absorption bands. .
• the above-mentioned anti-reflective layer may be formed of a stack of layers having a low reflection for the different excitation wavelengths.
• the invention makes it possible to appreciably increase the signal / noise ratio and to minimize the background signal in optical sensors for detecting and measuring the fluorescence emitted by chromophoric elements in a device of the biochip type.
• FIGS. 1 to 3 are schematic sectional views, on a large scale, of various embodiments of a support according to the invention
• FIG. 4 is a graph showing the variation of the reflection of light as a function of the wavelength in the case of the support of Figure 3;
• the reference 10 generally designates a support according to the invention, which in this embodiment consists essentially of a blade of a material having a refractive index n, the upper face of which is intended to support elements chromophores 12 which are for example chemical or biological molecules as indicated above and which are fixed in a network on the upper face of the support 10.
• chromophoric elements 12 are illuminated by an excitation light 14, generally monochromatic or of small spectral width, possibly polarized (case of lasers), the incidence of which is defined with precision and is often substantially perpendicular to the surface of the support 10 , and they emit in response a fluorescence 16 on a wavelength which depends on the nature of the chromophoric elements 12 and which is greater than the wavelength of the excitation light 14.
• excitation light 14 generally monochromatic or of small spectral width, possibly polarized (case of lasers)
• the intensity of the fluorescence emitted by chromophoric elements are illuminated by an excitation light 14, generally monochromatic or of small spectral width, possibly polarized (case of lasers), the incidence of which is defined with precision and is often substantially perpendicular to the surface of the support 10 , and they emit in response a fluorescence 16 on a wavelength which depends on the nature of the chromophoric elements 12 and which is greater than the wavelength of the excitation light 14.
• the present invention therefore proposes to reduce and as far as possible cancel the reflection of the excitation light 14 by the support 10 to prevent this reflected light being added to the fluorescence emitted 16 in the light signal picked up by the detection means. and measurement, the percentage of the intensity of the excitation light reflected by the support 10 for substantially normal incidences being of the order of 4% for each diopter when the support 10 is made of glass having a refractive index of 1, 5 or around 25% for each diopter when the support 10 is made of silicon having a refractive index of 3.5 (the index of the medium above the support being equal to 1).
• the invention proposes adding to the support 10 at least one of the following means:
• an absorbent layer 18 made of a material having a refractive index close to that of the support 10, its thickness d being determined so that the product of this thickness by its absorption coefficient e the wavelength of the light excitation is much greater than 1 or alternatively, has a known and controlled value of between 0.1 and 10 approximately;
• one or more transparent anti-reflective layers 20 for the excitation wavelength that is to say layers 20 made of a material having a refractive index n 'close to the square root of the index of refraction of the support 10 and having a thickness equal to ⁇ e / 4n'cos ⁇ or an odd multiple of this thickness, ⁇ being the angle with the normal excitation rays in the or each layer 20.
• the absorbent layer 18 is inside the support.
• one or more anti-reflective layers 20 can be formed on the upper surface of the support 10, and an absorbent layer 18 on the lower face of the support 10 or in the vicinity thereof, the chromophoric elements 12 being then deposited on the anti-reflective layer or layers 20.
• the support. 10 is made of transparent material, forming on its underside one or more anti-reflective layers and an absorbent layer, to cancel the reflection of the excitation light 14 by the underside of the support.
• magnesium fluoride MgF2 having a refractive index close to 1.38 can be used to form the anti-reflective layer 20. If the wavelength of the excitation light is 532 nm, the thickness of the layer 20 is then approximately
• the absorbent layer 18 can be formed of organic molecules, optionally embedded in a matrix of the sol-gel type or in a polymer matrix or else of inorganic pigments embedded in the 2004/068124
• the support 10 also preferably includes a mirror 22 formed by an internal layer of material reflecting light at the wavelength of the fluorescence emitted by the chromophoric elements 12, this mirror 22 being located at a distance from the chromophoric elements 12 which is much greater than the quantity ⁇ f.n / 2NA 2 , ⁇ f being the wavelength of the fluorescence emitted 16, n being the refractive index of the support 10, NA being the numerical aperture optical means for detecting and measuring the fluorescence emitted.
• the reduction in the reflection of the excitation light 14 is obtained by means of an anti-reflective layer 20 formed on the upper face of the support 10 and an absorbent layer 18 interposed in the support 10 between the anti-reflective layer 20 and the mirror 22.
• the distance between the mirror 22 and the upper face of the support 10 is relatively large, in particular greater than 5 ⁇ m, which makes it possible to install the absorbent layer 18 between the mirror 22 and the antireflective layer 20 without difficulty.
• the reflective layer 22 forming the mirror can be formed of several dielectric layers having a zero reflection for the excitation wavelength at the angle of incidence used which is generally small and less than 10 °.
• a symmetrical Fabry-Perot cavity or micro-cavity can be formed between two mirrors 22 formed by stacks of dielectric layers of the same reflectivity.
• an absorbent layer 18 is in the vicinity of the underside of the support 10 while an anti-reflective layer 20 is formed on the upper face of the support and carries the chromophoric elements 12.
• the reflection of the support 10 is zero for the excitation wavelength ⁇ e and is very high, preferably close to 100% for the wavelength ⁇ f of the fluorescence emitted by the chromophoric elements.
• the reflection of the support 10 is zero for the excitation wavelength ⁇ e and is very high, preferably close to 100% for the wavelength ⁇ f of the fluorescence emitted by the chromophoric elements.
• the support 10 is a strip of material having a refractive index n, which comprises a reflective layer 24 with high reflection which is metallic or formed by a stack of dielectric layers and which is located at a distance d from the upper face of the support carrying the chromophoric elements 12 less than the quantity ⁇ f.n / 2NA 2 where ⁇ f is the wavelength of the fluorescence emitted by the chromophoric elements 12 and NA is the numerical aperture of the optical means for detecting and measuring this fluorescence.
• the cancellation or reduction of the reflection of the excitation light is obtained by forming an absorbent layer 18 of determined thickness between the reflective layer 24 and the chromophoric elements 12, this thickness being less than or equal at the distance between the reflective layer 24 and the chromophoric elements 12.
• the layer 18 makes it possible to absorb as much as necessary the excitation wavelength without absorbing the wavelength of the fluorescence emitted.
• the metallic reflecting layer 24 can be replaced by a non-symmetrical Fabry-Perot cavity formed between two different reflecting layers 22, one of which forms the upper face of the support 10 and carries the chromophoric elements 12 and the other of which is inside the support 10 and located at a distance from the chromophoric elements 12 which is less than the aforementioned quantity ⁇ f.n / 2NA 2 .
• An absorbent layer 18 is then formed on the underside of the support 10 or in the vicinity of this underside, optionally in combination with an aforementioned anti-reflective layer 20.
• Microcavity solutions make it possible to obtain a reflectivity contrast between excitation and emission wavelengths much higher compared to a solution with an anti-reflection layer produced on a reflective support, which reduces the noise associated with the excitation light.
• a Bragg mirror formed by periodic stacks of layers of high index and low index materials, with a relatively narrow band, in order to have a high reflectivity at the wavelength of the fluorescence emitted. and a low reflectivity outside this band, by adding to this Bragg mirror an antireflective layer or an absorbent layer of the aforementioned type, but having a very small thickness to remain in the field of wave optics.
• Two preferred modes of the invention are therefore the following:
• the Bragg mirror is formed to present exactly the amplitude and the phase of the reflectivity at ⁇ e so that the combination of the reflection by the Bragg mirror with the reflection by the upper face of the support 10 cancels the overall reflection of ⁇ e by the support,
• the Bragg mirror is not precisely adjusted in reflectivity and especially in amplitude and has a wide band and it is then an absorbent layer 18 interposed between this mirror and the upper face of the support 10 which allows by an appropriate choice of the product ( ⁇ e.d) as indicated above to cancel the overall reflection of the support at ⁇ e.
• Known optical synthesis methods such as the "flip-flop” method can be used to form the layers of layers of Bragg mirrors.
• the support according to the invention can be associated with lighting means providing a light excitation whose incidence and polarization are defined to reduce parasitic reflection by the support.
• the embodiments of the invention using reflective multilayers also make it possible to ensure that the chromophoric elements are located in the vicinity of a belly of the emission field, as already described in the aforementioned international application of the same inventors.
• the support 10 comprises a blade of material having a refractive index n and two mirrors 26, 28 separated from each other and between which are the chromophoric elements 12. More specifically, the chromophoric elements 12 are carried by a layer 30 of transparent material which covers the lower mirror 28 and the upper mirror 26 covers the layer 30 while being separated from the latter by a spacer layer 32 which is for example etched to form the cavities in which the chromophoric elements 12 are deposited.
• the mirrors 26, 28 operate under the conditions of wave optics, that is to say that the mirror 28 is separated from the chromophoric elements 12 by a distance which is less than the quantity ⁇ f.n / 2NA 2 and that the distance between the two mirrors 26, 28 is less than the quantity ⁇ f.n / NA 2 .
• the characteristics of the mirrors 26, 28 are determined so that the excitation wavelength is transmitted by the lower mirror 28 and that the wavelength of the emitted fluorescence is reflected by the mirror 28 and passes through the upper mirror 26 to be able to be picked up by the detection and measurement means.
• An absorbent layer 18 of the aforementioned type is formed on or in the vicinity of the underside of the support 10 and is optionally associated with an aforementioned anti-reflective layer as already indicated for the previous embodiments.

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• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
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• 2003
  • 2003-01-15 FR FR0300412A patent/FR2849922B1/fr not_active Expired - Fee Related
• 2004
  • 2004-01-15 CN CNA2004800022645A patent/CN1739021A/zh active Pending
  • 2004-01-15 EP EP04702349A patent/EP1597562A1/fr not_active Withdrawn
  • 2004-01-15 WO PCT/FR2004/000076 patent/WO2004068124A1/fr active Application Filing
• 2005
  • 2005-07-07 US US11/176,053 patent/US20060028642A1/en not_active Abandoned

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