Probe type tilted fiber bragg grating sensor for detecting heparin

Abstract

The invention provides a probe type tilted fiber bragg grating sensor for detecting heparin, the sensor is composed of a broadband light source, a single-mode fiber, a polarization controller, a fiber circulator, a spectrum analyzer, a computer and a sensor, the sensor is composed of a flange head, a single-mode fiber, a steel tube package, a side surface and end surface gold film and a tilted fiber bragg grating; based on the linear relation between the reflection spectrum and the solution refractive index, the TFBG can sense the change of the heparin concentration and transmit a spectrum signal to the spectrum analyzer through the optical fiber circulator to be displayed. After the detection task is completed, the sensor can be removed by adjusting the height of the optical fiber clamp frame; in addition, a flange head is adopted to connect the single-mode fiber and the tilted fiber grating, and the single-mode fiber and the tilted fiber grating are packaged through a steel pipe, so that a probe type structure is formed. The design not only enhances the structural stability of the sensor, but also realizes the plug-and-play convenience, thereby remarkably improving the application value and the practical application convenience of the sensor.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber optic sensing, and particularly relates to a probe-type tilted fiber Bragg grating sensor for detecting heparin. Background Art

[0002] Heparin is a highly sulfated linear polysaccharide composed of glucosamine and glucuronic acid. Initially, researchers applied it to anticoagulant therapy in surgical operations due to its significant high negative charge density. Recent studies have shown that heparin can interact with a variety of bioactive proteins. The medicinal value of heparin is extensive, specifically reflected in its anti-inflammatory effect, anti-tumor effect, lipid-regulating function, and antiviral activity. With the widespread clinical application of heparin, its safety issues have become increasingly prominent, especially the serious bleeding or thrombocytopenia that may be caused by heparin overdose (this phenomenon has been widely recognized). Therefore, it is particularly important to monitor and quantify heparin in serum during treatment. So far, researchers have proposed a variety of heparin detection methods, including electrochemical methods, colorimetric analysis, nuclear magnetic resonance technology, surface-enhanced Raman scattering spectroscopy, and fluorometry. However, these methods have certain limitations in terms of the simplicity, sensitivity, and selectivity of application, or the feasibility of actual operation.

[0003] When light of a specific wavelength irradiates the metal surface, it triggers the resonance of free electrons and light waves, forming the surface plasmon resonance phenomenon. The change in the refractive index of the medium near the metal surface is closely related to surface plasmon resonance (SPR). The aggregation or binding of biological or chemical molecules on the metal surface will change the refractive index of this region, thereby affecting the resonance conditions of surface plasmons. By monitoring the change in resonance light intensity or wavelength, the interaction between biological or chemical molecules can be tracked in real time.

[0004] The tilted fiber Bragg grating (TFBG) has become an ideal platform for SPR biochemical sensing research because it can excite multiple cladding modes and is highly sensitive to the fiber surface environment. When the fiber cladding mode is phase-matched with SPR, the TFBG can excite an evanescent wave on the gold surface, realizing highly sensitive biochemical sensing. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to develop a probe-type tilted fiber grating sensor for detecting heparin. During the preparation of the sensor, first, a cutting knife is used to cut one side of the tilted fiber grating, and then a 200-nanometer-thick gold film is deposited on the cutting end face by magnetron sputtering technology. At the same time, a 50-nanometer-thick gold film is also deposited on the tilted fiber grating area by magnetron sputtering. On this basis, the grating area covered with the gold film is further modified with a sensing film layer, and 11-mercaptoundecanoic acid is introduced into this layer through the self-assembly technology of gold-sulfur bonds. Subsequently, positively charged chitosan is added, and based on the principle of electrostatic self-assembly, chitosan binds to negatively charged 11-mercaptoundecanoic acid to jointly form a probe structure. Finally, through electrostatic self-assembly, positively charged chitosan binds to negatively charged heparin, thus realizing the effective detection of heparin.

[0006] The present invention is realized through the following technical solutions: A probe-type tilted fiber Bragg grating sensor for detecting heparin, which consists of a broadband light source (1), a single-mode optical fiber (2), a polarization controller (3), an optical fiber circulator (4), a spectral analyzer (5), a wire (6), a computer (7), a sensor (8), an optical fiber fixture rack (9), an optical fiber fixture (10), a waste liquid pool (11), a valve (12), a solution pool (13), a heating table (14), a peristaltic pump (15), a heparin solution test tube (16), a deionized water test tube (17), and a diversion tube (18). The sensor (8) is composed of a flange head (19), a single-mode optical fiber (20), a steel pipe (21), a side gold film (22), a tilted fiber Bragg grating (23), and an end face gold film (24); the polarization controller (3) is composed of a quarter-wave plate, a half-wave plate, and a polarizer; the polarization controller (3) is located on the left side of the optical fiber circulator (4), and the spectral analyzer (5) is placed on its right side and is connected to the computer (7) through a wire (6); the broadband light source (1) is connected to the polarization controller (3) through a single-mode optical fiber (2), and the polarization controller (3) is used to adjust the incident light to the P polarization state. The sensor (8) is installed on the optical fiber fixture rack (9) through the optical fiber fixture (10) and is connected to the optical fiber circulator (4); at the same time, the solution pool (12) is fixed on the heating table (9) and is arranged directly opposite the sensor (8); in addition, the waste liquid pool (11) and the peristaltic pump (15) are respectively arranged on the right side and the left side of the solution pool (13) and are connected to the solution pool (13) through a diversion tube (18) equipped with a valve (12). The left side of the peristaltic pump (15) is connected to the heparin solution test tube (16) and the deionized water test tube (17) respectively through a diversion tube (18); the optical path process is: the light emitted by the broadband light source (1) is transmitted through the single-mode optical fiber (2) to the polarization controller (3), and then is guided to the sensor (8) through the optical fiber circulator (4); the sensor (8) is responsible for monitoring the change of the external solution concentration and transmitting the captured spectral signal to the spectral analyzer (5) through the optical fiber circulator (4), and the computer (7) extracts and analyzes the spectral data, and then the result is displayed; after the detection process is completed, the sensor (8) can be conveniently removed by adjusting the height of the optical fiber fixture rack (9).

[0007] The sensor is composed of a flange head (19), a single-mode optical fiber (20), a steel pipe (21), a side gold film (22), a tilted fiber Bragg grating (23), and an end face gold film (24); among them, the length L1 of the steel pipe (21) is 3 cm, the length L2 of the grating region of the tilted fiber Bragg grating (23) is 1 cm, and the distance L3 from its end face to the grating region is 0.5 cm; on the end face of the tilted fiber Bragg grating (23), the thickness L4 of the deposited gold film (24) is 200 nm, and a gold film (22) with a thickness of 50 nm is deposited on its side surface.

[0008] A functional film is modified on the gold film (21) deposited on the side of the tilted fiber grating (22); wherein, the functional film is formed by electrostatic self-assembly of negatively charged 11-hydroxyundecanoic acid and positively charged chitosan.

[0009] The working principle of the present invention is: The relationship between the effective refractive index of each cladding mode of the TFBG and its resonance wavelength can be expressed as: λ clad，i =(n eff，cl +n eff，co )Λ / cosθ wherein, n eff，cl and n eff，co respectively represent the effective refractive indices of the i-th cladding mode and the core mode. Where Λ is the grating period and θ is the tilt angle between the grating plane and the fiber axis. T=1-tanh 2 (κL) In the formula, T represents the resonance intensity of the cladding mode resonance, κ is the coupling coefficient between the cladding mode and the core mode, and L is the length of the TFBG. Due to the evanescent field of the cladding mode, the effective refractive index n eff，cl depends on the surrounding refractive index. The resonance intensity of the cladding mode resonance in the TFBG transmission spectrum can be expressed as:

[0010] The beneficial effects of the present invention are: The present invention proposes a probe-type tilted fiber grating sensor for detecting heparin. Specifically, a 50-nanometer-thick gold film is deposited on the grating region of the tilted fiber grating by magnetron sputtering. Subsequently, 11-mercaptoundecanoic acid is introduced onto the gold film by the gold-sulfur bond self-assembly technique to form a sensing film layer. Further, through the principle of electrostatic self-assembly, positively charged chitosan is combined with negatively charged 11-mercaptoundecanoic acid to construct a probe structure. Finally, the electrostatic interaction between the positively charged property of chitosan and the negatively charged property of heparin is utilized to achieve the effective capture and detection of heparin. In addition, in this design, a single-mode fiber with a flange head is connected to the tilted fiber grating and encapsulated by a steel pipe to form a probe-type structure, which not only enhances the structural stability of the sensor but also realizes the convenience of plug-and-play, significantly improving its application value and practicality.

[0011] Figure 1 is a schematic diagram of a probe-type tilted fiber grating device for detecting heparin according to the present invention.

[0012] Figure 2 is a schematic diagram of the structure of the probe-type tilted fiber grating sensor according to the present invention.

[0013] Figure 3It is a schematic structural diagram of the fiber optic circulator flange head of the present invention.

[0014] Figure 4 It is the SPR spectrogram of the probe-type tilted fiber Bragg grating sensor of the present invention in heparin solutions with different concentrations. Detailed implementation manners

[0015] Such as Figure 1As shown in the figure, a probe-type tilted fiber Bragg grating sensor for detecting heparin consists of a broadband light source (1), a single-mode fiber (2), a polarization controller (3), an optical fiber circulator (4), a spectrum analyzer (5), a wire (6), a computer (7), a sensor (8), an optical fiber fixture rack (9), an optical fiber fixture (10), a waste liquid pool (11), a valve (12), a solution pool (13), a heating table (14), a peristaltic pump (15), a heparin solution test tube (16), a deionized water test tube (17), and a diversion tube (18). The sensor (8) is composed of a flange head (19), a single-mode fiber (20), a steel pipe (21), a side gold film (22), a tilted fiber Bragg grating (23), and an end face gold film (24). The polarization controller (3) is composed of a quarter-wave plate, a half-wave plate, and a polarizer. The polarization controller (3) is located on the left side of the optical fiber circulator (4), and the spectrum analyzer (5) is placed on its right side and connected to the computer (7) through a wire (6). The broadband light source (1) is connected to the polarization controller (3) through the single-mode fiber (2). The polarization controller (3) is used to adjust the incident light to the P polarization state. The sensor (8) is installed on the optical fiber fixture rack (9) through the optical fiber fixture (10) and connected to the optical fiber circulator (4). At the same time, the solution pool (12) is fixed on the heating table (9) and arranged facing the sensor (8). In addition, the waste liquid pool (11) and the peristaltic pump (15) are respectively arranged on the right and left sides of the solution pool (13) and connected to the solution pool (13) through a diversion tube (18) equipped with a valve (12). The left side of the peristaltic pump (15) is connected to the heparin solution test tube (16) and the deionized water test tube (17) respectively through the diversion tube (18). The optical path process is as follows: The light emitted by the broadband light source (1) is transmitted to the polarization controller (3) through the single-mode fiber (2), and then guided to the sensor (8) through the optical fiber circulator (4). The sensor (8) is responsible for monitoring the change of the external solution concentration and transmitting the captured spectral signal to the spectrum analyzer (5) through the optical fiber circulator (4). The computer (7) extracts and analyzes the spectral data, and then displays the results. After the detection process is completed, the sensor (8) can be conveniently removed by adjusting the height of the optical fiber fixture rack (9). The detection process is as follows: First, open the valve connecting the diversion tube (18) of the heparin solution test tube (16), and then start the peristaltic pump (15) and preset the parameters to make the heparin solution flow into the solution pool (13). After the solution stands for a preset period, scan through the spectrum analyzer (5) and save the obtained data. Then, open the diversion tube valve (12) connecting the waste liquid pool (11). After the heparin solution in the solution pool (13) is completely transferred to the waste liquid pool (11), close the valve of the diversion tube (18) of the heparin solution test tube (16), and immediately open the valve of the diversion tube (18) connecting the deionized water test tube (17) to rinse the solution pool (13) with deionized water until there is no heparin residue. Then, close the valves (12) of the diversion tubes of the deionized water test tube (17) and the waste liquid pool (11).At this time, start the heating table (14) under the solution pool (13), set the temperature to 60 °C, and keep it for 10 minutes. Then turn off the heating table (14) until the deionized water in the solution pool (13) is completely dried. This process is for the detection of heparin solutions of a single concentration. Subsequently, repeat the above steps to detect a series of heparin solutions with different concentrations. Finally, by adjusting the height of the optical fiber fixture rack (9), the sensor (8) can be conveniently removed.

Claims

1. An optical fiber probe for detecting heparin, characterized in that: It consists of a broadband light source (1), a single-mode optical fiber (2), a polarization controller (3), an optical fiber circulator (4), a spectral analyzer (5), a wire (6), a computer (7), a sensor (8), an optical fiber fixture rack (9), an optical fiber fixture (10), a waste liquid pool (11), a valve (12), a solution pool (13), a heating table (14), a peristaltic pump (15), a heparin solution test tube (16), a deionized water test tube (17), and a diversion tube (18). The sensor (8) is composed of a flange head (19), a single-mode optical fiber (20), a steel pipe (21), a first gold film (22), an inclined fiber grating (23), and a second gold film (24); the surface of the first gold film (22) is modified with negatively charged 11-hydroxyundecanoic acid and positively charged chitosan; the polarization controller (3) is composed of a quarter-wave plate, a half-wave plate, and a polarizer; the polarization controller (3) is located on the left side of the optical fiber circulator (4), and the spectral analyzer (5) is placed on its right side and is connected to the computer (7) through the wire (6); the broadband light source (1) is connected to the polarization controller (3) through the single-mode optical fiber (2), and the polarization controller (3) is used to adjust the incident light to the P polarization state. The sensor (8) is installed on the optical fiber fixture rack (9) through the optical fiber fixture (10) and is connected to the optical fiber circulator (4); the solution pool (13) is fixed on the heating table (14) and is placed directly opposite the sensor (8); the waste liquid pool (11) and the peristaltic pump (15) are respectively arranged on the right side and the left side of the solution pool (13) and are connected to the solution pool (13) through the diversion tube (18) of the valve (12). The left side of the peristaltic pump (15) is connected to the heparin solution test tube (16) and the deionized water test tube (17) through the diversion tube (18); the light emitted by the broadband light source (1) is transmitted to the polarization controller (3) through the single-mode optical fiber (2) and is transmitted to the sensor (8) by the optical fiber circulator (4); the sensor (8) monitors the change in the solution concentration in the solution pool (13) and transmits the captured spectral signal to the spectral analyzer (5) through the optical fiber circulator (4), and the spectral analyzer (5) transmits the data to the computer (7) through the wire (6).

2. The optical fiber probe for detecting heparin according to claim 1, characterized in that: The length of the steel pipe (21) is 3 cm, the grating region length of the inclined fiber grating (23) is 1 cm, and the distance from its end face to the grating region is 0.5 cm; on the end face of the inclined fiber grating (23), the thickness of the deposited second gold film (24) is 200 nm, and on the side of the inclined fiber grating (23), a first gold film (22) with a thickness of 50 nm is deposited.

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