IE87077B1

IE87077B1 - Method of correcting signals of surface plasmon resonance sensor

Info

Publication number: IE87077B1
Application number: IE20170056A
Authority: IE
Inventors: Lee Seungki; Jeong Daehong; Lee Hoyoung; Park Jaehyoung; Kim Hyeongmin
Original assignee: Univ Dankook Iacf
Priority date: 2016-12-12
Filing date: 2017-03-07
Publication date: 2019-12-25
Also published as: KR101867187B1

Abstract

Provided is a method of correcting signals of a localized surface plasmon resonance sensor based on a surface plasmon resonance phenomenon of metal nanoparticles. The signal correction method includes defining a default property value of the sensor in which the default property value is an output signal intensity (A) of the sensor with the metal particles immobilized thereon while the metal nanoparticles of the sensor are immersed in a deionized water or a buffer solution. A change (B) in output signal intensity of the sensor due to antibody-antigen binding is obtained. A final measurement value can be then obtained by dividing (B) by (A). According to the correction method, uniform measurement values can be obtained regardless of using sensors with different density, size, and shape of the metal nanoparticles thereon. <Figure 3A>

Description

METHOD OF CORRECTING SIGNALS OF SURFACE PLASMON RESONANCE SENSOR CLAIM FOR PRIORITY This application claims priority to Korean Patent Application No. 2016-0168650 ﬁled on Dec. 12, 2016 in the Korean Intellectual Property Ofﬁce (KIPO), the entire contents of which are hereby incorporated by reference.

BACKGROUND 1. Technical Field Example embodiments of the present invention relate in general to the ﬁeld of surface plasmon resonance sensors and more speciﬁcally to a method of correcting signals of a localized surface plasmon resonance sensor based on a surface plasmon resonance phenomenon of metal nanoparticles. 2. Related Art Surface plasmon resonance is a phenomenon caused by collective vibration of free electrons when incident light reacts with nanoparticles or a metal thin ﬁlm of gold or silver.

Having an advantage of ability to measure reactions among biomaterials in real time without requiring a speciﬁc marker, surface plasmon resonance has been applied for biosensors capable of measuring various bioreactions and protein chip analyses.

When performing biological measurement such as the measuring of speciﬁc binding among proteins using a surface plasmon resonance sensor, the measurement results always come out differently because characteristics of such sensors are not exactly the same.

Such a problem is particularly apparent when using a localized surface plasmon resonance sensor because, in contrast to surface plasmon resonance sensors that have a thin nu1700ﬁlm of gold or silver as the basic structure, localized surface plasmon resonance sensors are based on a nanostructure of gold or silver.

There are many ways to prepare a gold or silver nanostructure for use in the localized surface plasmon resonance sensors. The most commonly used method among them is to prepare a gold or silver colloid solution by adding a reducing agent capable of reducing ions to particles into a solution containing gold or silver ions, and the prepared particles are adsorbed onto a surface of a sensor. The prepared particles are different in size and shape and the ways of adsorption and the patterns of the particles onto the sensors carmot be exactly the same every time and thus each sensor has different characteristics.

Currently commercially available products are surface plasmon resonance sensors based on a gold thin ﬁlm. Due to the sensor uniformity problem and the like, localized surface plasmon resonance sensors based on nanoparticles are not being commercialized despite the possibility of providing relatively higher sensitivity.

To solve the problem of nonuniformity, the sensor manufacturing process needs to be standardized so that sensors of the same characteristics can be manufactured each time.

This, however, is limited because preparing of nanoparticles and immobilization of the nanoparticles onto a surface of a sensor cannot be standardized.

I Conventional Art Documents l [Patent document) (Patent Document 1) Korean Patent Application No. l00067661 SUMMARY Accordingly, example embodiments of the present invention are provided to substantially obviate one or more problems due to limitations and disadvantages of the related art, and provide a method of correcting signals of a localized surface plasmon resonance sensor.

In some example embodiments, a method of correcting signals of a localized surface plasmon resonance sensor based on a surface plasmon resonance phenomenon of metal nanoparticles includes: deﬁning, as a default property value of the localized surface plasmon resonance sensor with the metal nanoparticles, output signal intensity (A) obtained from the localized surface plasmon resonance sensor before any antibody and antigen is bound to the metal nanoparticles; determining a change (B) in output signal intensity of the localized surface plasmon resonance sensor caused by antibody—antigen binding; and dividing the change (B) in output signal intensity by the default property value.

(A) and (B) are derived from output signals of the localized surface plasmon resonance sensor, wherein the output signals are obtained based on light reﬂected from the metal nanoparticles immersed in deionized (DI) water or a buffer solution.

The change (B) is a difference between output signal intensity (C) and (D) wherein (C) is an output signal intensity of the localized surface plasmon resonance sensor with the antibody and material for preventing nonspecific binding on the metal nanoparticles thereof, and (D) is an output signal intensity of the localized surface plasmon resonance sensor with the antibody, the material for preventing nonspecific binding, and antigen binding to the antibody on the metal nanoparticles thereof.

The localized surface plasmon resonance sensor is a ﬁber-optic sensor that contains the metal nanoparticles on a core thereof, wherein (A), (C) and (D) are obtained using a channel unit which has a microﬂuidic channel including a plurality of solution inlets in a body thereof and the localized surface plasmon resonance sensor inserted thereinto, wherein the metal nanoparticles of the localized surface plasmon resonance sensor are contacted in the channel unit with different solutions which are each supplied through different solution inlets.

In other example embodiments, a method of correcting signals of a localized surface plasmon resonance sensor includes: ( I ) defining, as a default property value of the localized surface plasmon resonance sensor, output signal intensity (A) of the localized surface plasmon resonance sensor while metal nanoparticles of the localized surface plasmon resonance sensor are immersed in DI water or a buffer solution; (11) binding an antibody to the metal nanoparticles and then washing the metal nanoparticles with a DI water or a buffer solution; (HI) determining output signal intensity (C) of the localized surface plasmon resonance sensor having the antibody and material for preventing nonspecific binding onto the metal nanoparticles while the metal nanoparticles are immersed in a DI water or a buffer solution; (N) determining output signal intensity (D) of the localized surface plasmon resonance sensor having the antibody, the material for preventing nonspeciﬁc binding, and antigen bounded with the antibody on the metal nanoparticles while the metal nanoparticles are immersed in a DI water or a buffer solution; and (V) calculating B(=D-C) + A.

Example embodiments of the present invention provide a method of correcting signals of a localized surface plasmon resonance sensor. According to example embodiments of the present invention, the sensor measurement values, which would be not uniform for each sensor depending on the size, density, distribution, shape, and the like of metal nanoparticles in the case of conventional surface plasmon resonance sensors, can be made precise through correction. Moreover, when a sensor device including a channel unit having a plurality of solution inlets is used, the attainment of such measurement values can become even more convenient, and more precise measurement values can be obtained.

BRIEF DESCRIPTION OF DRAWINGS Example embodiments of the present invention will become more apparent by describing in detail example embodiments of the present invention with reference to the accompanying drawings, in which: FIG. 1 is a schematic diagram of a ﬁber-optic localized surface plasmon resonance sensor to which a method of correcting signals of a surface plasmon resonance sensor according to an example embodiment of the present invention is applicable; FIGS. 2A and 2B are schematic diagrams of a surface plasmon resonance sensor device to which a method of correcting signals of a surface plasmon resonance sensor according to an example embodiment of the present invention is applicable; FIGS. 3A and 3B are diagrams for illustrating a signal correction process of a surface plasmon resonance sensor according to an example embodiment of the present invention; and FIGS. 4A and 4B are graphs showing measurement values before and after signal correction of a surface plasmon resonance sensor according to an example embodiment of the present invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS Hereinafter, example embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing example embodiments of the present invention, detailed descriptions of related well-known functions or conﬁgurations deemed to unnecessarily obscure the gist of the present invention will be omitted.

First, brieﬂy, example embodiments of the present invention are directed to providing a method of uniformly controlling characteristics of surface plasmon resonance sensors.

Localized surface plasmon resonance sensors based on a resonance phenomenon of metal nanoparticles give out different measurement values depending on the size, density, shape, and the like of the particles. Although it is necessary to carry out a plarmed and precise manufacturing process to solve the above problem, preparing uniform nano-scale particles that can result in uniform measurement values and reproducing such a preparation process repeatedly are not practically possible with current technology. Therefore, in example embodiments of the present invention, the default property value of a sensor is quantitatively measured and the obtained default property value is used as a correction value of itself. The corrected value is a ﬁnal real value for the sensor, which is an accurate result of measurement.

A sensor output is obtained while metal nanoparticles of a localized surface plasmon resonance sensor are immersed in a deionized (DI) water or a buffer solution by irradiating the metal nanoparticles with excitation light and the output is stored as a default (unique) property value of the sensor. The obtained property values may be different for every sensor, but a value of each sensor is a property value for itself. Then, an object of interest is measured with the sensor and the measured value is divided by its default property value. The divided result is an accurate real value that is corrected with its unique characteristics of each sensor. That is, the corrected result is a ﬁnal measurement value that we want to know.

The default property value may be deﬁned as the sensor output value that is generated by the scattering of metal nanoparticles, such as gold adsorbed onto the core of optical ﬁbers, in DI water or a buffer solution which has a refractive index of about 1.33. Such a default property value depends on characteristics of each sensor and may be considered as a unique property value of the sensor.

FIG. 1 is a schematic diagram of a ﬁber-optic localized surface plasmon resonance sensor to which a method of correcting signals of a surface plasmon resonance sensor according to an example embodiment of the present invention is applicable. FIG. 2 is a schematic diagram of a surface plasmon resonance sensor device to which a method of correcting signals of a surface plasmon resonance sensor according to an example embodiment of the present invention is applicable. FIGS. 3A and 3B are diagrams for describing a signal correction process of a surface plasmon resonance sensor according to an example embodiment of the present invention. FIG. 4A and 4B are graphs showing measurement values before and after signal correction of a surface plasmon resonance sensor according to an example embodiment of the present invention.

Referring to the drawings, the method of correcting signals of a surface plasmon resonance sensor according to example embodiments of the present invention is as follows: First, the sensor output signal intensity A generated by the resonance of metal nanoparticles bound to the core of the sensor in a DI water or a buffer solution having a predetermined refractive index is determined, and the signal intensity A is deﬁned as a default property value of the sensor. Then, a change B in output signal intensity caused by antibody-antigen binding is determined using the sensor with antibody bound to the metal nanoparticles. The change (B) in output signal intensity is divided by the default property value A to obtain a ﬁnal measurement value.

In this case, the change (B) in output signal intensity is a difference between C and D, wherein C corresponds to the sensor output signal intensity that is generated by the resonance of metal nanoparticles with antibody and material for preventing nonspeciﬁc binding, and D is the sensor output signal intensity that is generated by the resonance of metal nanoparticles with antibody and antigen speciﬁcally bound to the antibody.

The signal intensity B, C, or D may be determined after washing the metal nanoparticles with a DI water or a buffer solution or removing any abnormal substances bound to the metal nanoparticles.

Preferably, the above correction process is realized through the ﬁber-optic localized surface plasmon resonance sensor device as illustrated in FIGS. 1, 2A, and 2B.

As shown in the drawings, the sensor is a ﬁber-optic localized plasmon resonance sensor that contains metal nanoparticles on the core thereof. Also, the sensor device preferably includes a channel unit 11 including a microﬂuidic charmel 117 having a plurality of solution inlets 113 and a solution outlet 115 in the body thereof so that different solutions are injected through different solution inlets and subsequently contact the metal nanoparticles of the sensor, thereby preventing the mixing of the solutions and resulting in a more precise measurement value.

Example The localized surface plasmon resonance sensor as shown in FIG. 1 is realized by causing gold nanoparticles to be immobilized onto the core of optical ﬁbers. The sensor device of FIGS. 2A and 2B can be manufactured by combining the sensor with a channel unit 11 that includes a microﬂuidic channel 117 having a plurality of solution inlets 113 in the body thereof. The sensor device of FIGS. 2A and 2B can be used for real-time continuous biological measurement.

As described above, the channel unit 11 includes a microﬂuidic charmel 117 in the body, and the microﬂuidic channel 117 includes the solution inlets 113, the solution outlet 115, and a sensor insertion hole 119. A surface plasmon resonance sensor 17 based on optical ﬁbers is inserted into the sensor insertion hole 119 in which a portion of the core 171 with the metal nanoparticles 172 immobilized thereon, is exposed to the microﬂuidic channel 117, which allows the portion of the core 171 to contact a ﬂuid in the channel.

An optical measuring unit 5 is connected to a rear end of the ﬁber-optic surface plasmon resonance sensor 17. The optical measuring unit may include a light source 51 and a detector 51, in which the light source 51 and the detector 52 may be connected to the sensor 17, via a multimode optical ﬁber coupler 53 as illustrated in the drawing.

A solution supply unit 3 may supply different solutions into the microﬂuidic channel 117 of the charmel unit 11 through each of solution inlets 113. The supplied solutions may ﬂow through the microﬂuidic channel 117 of the channel unit 11 and contact with the surface plasmon resonance sensor 17 in a reaction chamber 118. Thereafter, the solutions may be discharged through the solution outlet 115. The unexplained reference numeral 31 denotes a set of tubes, each of which is connected with each of the solution inlets 113 of the channel unit 11, the reference numeral 33 is a shutoff valve for preventing solution backﬂow, and the reference numeral 32 is a syringe pump.

In example embodiments of the present invention, an antibody-antigen reaction of a prostate cancer marker is measured using the above sensor device. A measurement procedure and results are generally indicated by way of a sensorgram, which indicates the magnitude of output signals of the ﬁber-optic sensor over time in a continuous manner.

FIGS. 3A and 3B are drawings that illustrate the process of attaining a desired ﬁnal measurement value using the correction method according to example embodiments of the present invention.

First, a default property value of a surface plasmon resonance sensor 17 that has been installed is measured and stored. For this, a buffer solution is injected through one of the solution inlets 113 designated for a buffer solution so that the front end of the surface plasmon resonance sensor 17 is immersed in the buffer solution in a reaction chamber 118 so that metal nanoparticles 172 is immersed in the buffer solution. The metal nanoparticles 172 are irradiated with light from a light source 51, and light reﬂected from the metal nanoparticles 172 is received the detector to obtain the sensor output signal intensity A. The signal intensity A is then stored. The sensor output signal intensity A may be deﬁned as a default property value of the sensor.

Next, a solution containing an antibody is injected through one of the solution inlets 113 designated for an antibody solution so that the antibody is immobilized onto the metal nanoparticles 172 of the surface plasmon resonance sensor 17. Sensor output signal intensity based on light reﬂected from the antibody-bound metal nanoparticles 172 is also determined, preferably after washing the metal nanoparticles 172 with a DI water or a buffer to remove antibodies involved in abnormal adsorption.

Subsequently, a solution containing material for preventing nonspeciﬁc binding (e.g., a bovine serum albumin (BSA) solution), is injected through one of the solution inlets 113 designated for a BSA solution so that BSA is adsorbed onto the metal nanoparticles 172.

Likewise, sensor output signal intensity C is obtained based on light reﬂected from the metal nanoparticles 172 with the material for preventing nonspeciﬁc binding, and the signal intensity C is stored. The signal intensity C may be obtained after washing the metal nanoparticles 172 by ﬂowing a DI water or a buffer solution through the buffer solution inlet to remove abnormal adsorption material.

Next, a solution containing antigen is injected through one of the solution inlets 113 designated as an antigen solution inlet into a microﬂuidic channel 117 of the channel unit 11 so that antibody-antigen binding based on an antibody-antigen reaction is induced. Sensor output signal intensity D is then obtained light reﬂected from the metal nanoparticles 172 with antibody-antigen binding and the material for preventing nonspeciﬁc binding. The signal intensity D is then stored. Likewise, the signal intensity D may be obtained after the nanoparticles 172 is washed by ﬂowing a DI water or a buffer solution through the buffer solution inlet to remove abnormal adsorption material on the nanoparticles 172.

The above C is subtracted from the above D to determine a change B in sensor output signal intensity. Such a change is generated by antibody-antigen binding based on an antibody-antigen reaction. By dividing B by A, which is the default property value of the sensor, a desired ﬁnal measurement value is obtained.

In the antibody-antigen reaction, the change (B), which is obtained in a buffer solution before and after exposure of the antibody to the antigen solution, is slightly different for each sensor even when the antigen concentration is the same, depending on the conditions of the gold nanoparticles adsorbed onto a sensor surface. Therefore, in example embodiments of the present invention, B is divided by the default property value A of the sensor to attain a ﬁnal measurement value.

In fact, when prostate cancer antibody and antigen according to the above-described process are used and signal intensities are measured with a plurality of manufactured sensors while changing antigen concentration, the values measured at the same antigen concentration become considerably uniform after signal correction as shown in FIGS. 4A and 4B.

While the example embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the scope of the invention.

[Description of Reference Numerals] 3: solution supply unit 1: channel unit 51: light source 53: multimode optical ﬁber coupler 115: solution outlet 7-2: metal nanoparticles : optical measuring unit 17: surface plasmon resonance sensor 52: detector 13: solution inlets 171: core

Claims

WHAT IS CLAIMED IS: . ,1 I

1. l. A method of correcting signals of a localized surface plasmon resonance sensor based on a surface plasmon resonance phenomenon of metal nanoparticles, comprising: deﬁning, as a default property value of the localized surface plasmon resonance sensor with the metal nanoparticles, output signal intensity (A) obtained from the localized surface plasmon resonance sensor before any antibody and antigen is bound to the metal nanoparticles; determining a change (B) in output signal intensity of the localized surface plasmon resonance sensor caused by antibody-antigen binding; and dividing the change (B) in output signal intensity by the default property value.

2. The method of claim 1, wherein (A) and (B) are derived from output signals of the localized surface plasmon resonance sensor, wherein the output signals are obtained based on light reﬂected from the metal nanoparticles immersed in deionized (DI) water or a buffer solution.

3. The method of claim 2, wherein The change (B) is a difference between output signal intensity (C) and (D) wherein (C) is an output signal intensity of the localized surface plasmon resonance sensor with the antibody and material for preventing nonspeciﬁc binding on the metal nanoparticles thereof, and (D) is an output signal intensity of the localized surface plasmon resonance sensor with the antibody, the material for preventing nonspeciﬁc binding, and antigen binding to the antibody on the metal nanoparticles thereof.

4. The method of claim 3, wherein the localized surface plasmon resonance sensor is a ﬁber-optic sensor that contains the metal nanoparticles on a core thereof, wherein (A), (C) and (D) are obtained using a channel unit which has a microﬂuidic channel including a plurality of solution inlets in a body thereof and the localized surface plasmon resonance sensor inserted thereinto, wherein the metal nanoparticles of the localized surface plasmon resonance sensor are contacted in the channel unit with different solutions which are each supplied through different solution inlets.

5. A method of correcting signals of a localized surface plasmon resonance sensor, comprising: ( I ) deﬁning, as a default property value of the localized surface plasmon resonance sensor, output signal intensity (A) of the localized surface plasmon resonance sensor while metal nanoparticles of the localized surface plasmon resonance sensor are immersed in DI water or a buffer solution; (]I) binding an antibody to the metal nanoparticles and then washing the metal nanoparticles with a DI water or a buffer solution; (III) determining output signal intensity (C) of the localized surface plasmon resonance sensor having the antibody and material for preventing nonspeciﬁc binding onto the metal nanoparticles while the metal nanoparticles are immersed in a DI water or a buffer solution; (IV) determining output signal intensity (D) of the localized surface plasmon resonance sensor having the antibody, the material for preventing nonspeciﬁc binding, and antigen bounded with the antibody on the metal nanoparticles while the metal nanoparticles are immersed in a DI water or a buffer solution; and (V) calculating B(=D-C) + A.