Biosensor with high-density loading function and sensing system

Abstract

The utility model discloses a biosensor and a sensing system with a high-density loading function, which comprise an optical fiber body, a sensing area is formed on the optical fiber body, and a gold film layer, a titanium boride and gold nanoparticle film layer are respectively attached to the surface of the sensing area from inside to outside. According to the utility model, through the design of the gold film-titanium boride film-gold nanoparticle composite structure, the surface electric field intensity of the gold film is improved by utilizing the high carrier mobility and high light absorptivity of titanium boride, so that the sensitivity of the sensor is improved; by utilizing mutual coupling of titanium boride surface plasmon polaritons and local plasmon polaritons generated by the gold nanoparticles, an enhanced local electric field is generated between a titanium boride film and the gold nanoparticles, so that the interaction between surface plasmon waves and a to-be-detected substance is enhanced, the detection sensitivity is improved, the gold nanoparticles provide high-density probe load, and the detection sensitivity is improved. According to the utility model, the composite structure improves the detection range and the application scene through dielectric-plasma cooperative response.

Description

Technical Field

[0001] The utility model relates to the technical field of optical fiber sensing, in particular to a biosensor and a sensing system with a high-density load function. Background Art

[0002] Fiber-optic SPR biosensors, based on the surface plasmon resonance (SPR) principle, enable highly sensitive, highly selective, and real-time monitoring of biomolecules. They are widely used in disease monitoring, drug development, and clinical diagnostics. Traditional biosensors rely on the interaction of biomolecules with physical or chemical methods (fluorescence / electrochemistry) for detection. However, their limited sensitivity, susceptibility to interference, and the lengthy preparation and analysis processes required have increasingly limited their application in the biosensing field. SPR-based biosensors, with their high sensitivity, good biocompatibility, flexible steering, stability, and strong anti-interference capabilities, have garnered increasing attention in the biosensing field in recent years.

[0003] The traditional single gold film SPR sensor, as a single sensing layer, has a much lower sensitivity than the composite structure sensor. The gold film is easily oxidized or corroded by the environment during long-term use, resulting in signal drift. The single gold film has limited functional sites on the surface, making it difficult to load biological probes at a high density, resulting in insufficient detection specificity. Therefore, a biosensor with high-density loading function is needed to meet the needs. Utility Model Content

[0004] The purpose of the present invention is to provide a biosensor and a sensing system with a high-density loading function to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a biosensor with high-density loading function, comprising:

[0006] The optical fiber body, whose sensing area is composed of a 0.4-0.6 cm first multimode optical fiber with the coating removed, a 0.9-1.1 cm single-mode optical fiber, and a 0.4-0.6 cm second multimode optical fiber fused together, with a total length of 1.7-2.3 cm;

[0007] The following film layers are stacked in sequence on the surface of the sensing area:

[0008] Gold film layer, thickness 45-55nm;

[0009] Titanium boride film layer, thickness 40-50nm;

[0010] The gold nanoparticle film layer is composed of gold nanoparticles with a particle size of 20-50nm.

[0011] Preferably, the thickness of the gold film layer is 50 nm, and the thickness of the titanium boride film layer is 45 nm.

[0012] Preferably, the gold nanoparticle film layer is chemically adsorbed on the surface of the titanium boride film layer through an aminothiophenol coupling agent.

[0013] According to a second aspect of the present application, a sensing system is provided, comprising:

[0014] The optical fiber SPR sensor according to any one of the above items;

[0015] A broadband light source with an output spectrum range of 400-1000nm is connected to the input end of the optical fiber body;

[0016] a broadband spectrometer connected to the output end of the optical fiber body for detecting the transmission spectrum;

[0017] The computer is connected to the spectrometer via a data interface and is used to analyze the resonance wavelength shift.

[0018] The beneficial effects of the utility model are:

[0019] In the present invention, a gold film-titanium boride film-gold nanoparticle composite structure is designed. Titanium boride is a two-dimensional material with a high dielectric constant and electron mobility that can enhance the coupling efficiency between the gold film and the light field. Gold nanoparticles generate hot spots through the LSPR effect, thereby increasing the local electric field strength, and form double resonance peaks through plasma coupling with the gold film, thereby achieving the effect of synergistically improving sensitivity of multiple materials.

[0020] In the present invention, the microhardness of the titanium boride film is ≥30GPa, which can isolate oxygen and moisture, reduce the oxidation rate of the gold film by 80%, and effectively provide physical protection for the gold film. The gold nanoparticles provide a high-density probe load, and the chemical inertness of titanium boride reduces nonspecific adsorption, thereby achieving an optimized effect of surface functionalization.

[0021] The composite structure in this utility model expands the detection range from the traditional 1.33-1.40RIU through dielectric-plasma synergistic response, making it suitable for high-concentration biological samples. The double resonance peak (gold film main peak + gold nanoparticle secondary peak) can simultaneously monitor the refractive index change and molecular binding dynamics, effectively improving the application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the axial cross-sectional structure of the biosensor with high-density loading function proposed by the present invention;

[0023] Figure 2 This is a schematic diagram of the radial cross-sectional structure of the biosensor with high-density loading function proposed by the present invention;

[0024] Figure 3 This is a schematic diagram of the structure of the sensing system proposed in this utility model;

[0025] Figure 4 This is a projection spectrum curve diagram proposed by the utility model;

[0026] Figure 5 This is the sensitivity line graph proposed by the present invention.

[0027] In the figure: 100, optical fiber body; 200, broadband light source; 300, broadband spectrometer;

[0028] 110, sensing area; 111, first multimode optical fiber; 112, single-mode optical fiber; 113, second multimode optical fiber;

[0029] 120. Gold film layer; 130. Titanium boride film layer; 140. Gold nanoparticle film layer. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0031] Reference Figure 1-5 The biosensor with high-density loading capability includes: an optical fiber body 100, wherein a sensing region 110 is formed by fusion-joining a first multimode optical fiber 111 (0.4-0.6 cm) with its coating removed, a single-mode optical fiber 112 (0.9-1.1 cm) and a second multimode optical fiber 113 (0.4-0.6 cm), with a total length of 1.7-2.3 cm; and the following film layers are sequentially stacked on the surface of the sensing region 110: a gold film layer 120 (45-55 nm thick); a titanium boride film layer 130 (40-50 nm thick); and a gold nanoparticle film layer 140 (composed of gold nanoparticles with a particle size of 20-50 nm).

[0032] In this technical solution, the sensing area 110 is formed by using fiber stripping pliers to remove the outermost coating structure of the single-mode optical fiber 112 to expose its cladding, and then wiping the treated single-mode optical fiber 112 with a small amount of alcohol solution, and then using a fiber cleaver to cut off 0.9cm-1.1cm long single-mode optical fiber 112, and then cutting off the first multi-mode optical fiber 111 and the second multi-mode optical fiber 113, and using fiber stripping pliers to remove 2cm-3cm long coating structure at the end of the multi-mode optical fiber to expose the cladding, and then wiping the treated multi-mode optical fiber with a small amount of alcohol solution, and then using a fiber cleaver to cut off the end to remove the excess part of the coating, leaving 0.4cm-0.6cm removed coating part, and finally, using a fiber fusion splicer to connect the two sides of the single-mode optical fiber 112 to the treated multi-mode optical fiber end. The 0.4cm-0.6cm first multimode optical fiber 111 without coating, the 0.9cm-1.1cm single-mode optical fiber 112, and the 0.4cm-0.6cm second multimode optical fiber 113 constitute the sensor sensing area 110, and the total length of the sensing area 110 is 1.7cm-2.3cm.

[0033] In this technical solution, during the preparation process, the length ratio of the first multimode optical fiber 111, the single-mode optical fiber 112 and the second multimode optical fiber 113 should be approximately 1:2:1. At the same time, in order to make the total length of the formed sensing area 110 convenient for preparation and application, the lengths of the multimode optical fiber and the single-mode optical fiber 112 after removing the coating layer are set accordingly. At the same time, if the sensing area 110 is too long, it requires too much solution sample to be tested. If the sensing area 110 is too short, it is not convenient for preparation and is likely to affect the detection effect. Therefore, when the length of the sensing area 110 is 1.7 cm-2.3 cm, it can be convenient for preparation while meeting the detection effect. The length of the sensing area 110 is preferably 2 cm, and the length of the single-mode optical fiber 112 is 1 cm. The sensing area 110 is formed by a first multimode optical fiber 111 with a length of 0.5 cm, a single-mode optical fiber 112 with a length of 1 cm and a second multimode optical fiber 113 with a length of 0.5 cm. The total length of the sensing area 110 is 2 cm.

[0034] In this technical solution, the thickness of the gold film layer is 45nm to 55nm. When the thickness of the gold film layer is too low, the local electric field strength generated is insufficient, which cannot meet the use requirements, affects the sensitivity of the sensor, and is unrealistic to implement, and cannot obtain ideal results; at the same time, the thickness cannot be too high. Too high a thickness may cause insufficient penetration of the evanescent wave in the SPR resonance effect, a reduction in the interaction volume during wave vector matching, a shallower resonance depth, and poorer anti-interference ability. When the thickness is between 45nm and 55nm, the use requirements can be met.

[0035] Experimental results show that when the thickness of the gold film layer is 50nm, the sensor quality factor is the highest, the plasmon polaritons on the surface of the gold film layer are the strongest, the local electric field intensity generated is the best, and the excited SPR is the strongest.

[0036] Specifically, in this embodiment, the thickness of the gold film layer 120 is 50 nm, and the thickness of the titanium boride film layer 130 is 45 nm.

[0037] The gold film layer is fixed on the sensing area by ion sputtering. In this technical solution, the ion sputtering method is as follows:

[0038] The prepared optical fiber sensor was placed in a vacuum ion beam sputtering instrument to coat the sensor surface with a gold film. Based on experience, the vacuum ion beam sputtering current was 8 mA, the duration was 80 seconds, and the gold film thickness was 50 nm. The titanium boride film thickness was 40 nm to 50 nm.

[0039] In this technical solution, when the titanium boride film thickness is less than 40nm, the carrier mobility and light refractive index do not meet the required performance, resulting in low sensitivity. When the titanium boride film thickness exceeds 50nm, the material loss increases, a clear resonance trough is not obtained, the signal-to-noise ratio decreases, the anti-disturbance capability deteriorates, and the quality factor is low, which also does not meet the required performance. The optimal titanium boride film thickness is 45nm.

[0040] In this technical solution, the best technical effect is achieved when the titanium boride film is 45nm thick. When the thickness of the titanium boride film is 45nm, the carrier mobility and light refractive index reach their peak values. The titanium boride film is fixed to the gold film layer through electrostatic self-assembly.

[0041] Specifically, in this embodiment, the gold nanoparticle film layer 140 is chemically adsorbed on the surface of the titanium boride film layer 130 through an aminothiophenol coupling agent.

[0042] In this technical solution, the electrostatic self-assembly method is as follows: Before coating the titanium boride nanosheet dispersion, first, 50ml of 4% glacial acetic acid solution is prepared by diluting it with deionized water. 500mg of chitosan powder is weighed and poured into the glacial acetic acid solution, and stirred continuously for 15 minutes until the chitosan is completely dissolved. 3ml of the chitosan solution is pipetted into a small beaker, and 3ml of the titanium boride nanosheet dispersion is added to the chitosan solution. The resulting mixture is ultrasonically treated for 15 minutes to obtain a well-distributed titanium boride nanosheet dispersion with positive charge characteristics.

[0043] Sodium polystyrene sulfonate (PSS) is a negatively charged anionic polymer that can bind to cationic polymers. The sensing area of the gold film was immersed in a 5mg / ml PSS solution for 2 minutes. Afterward, the solution was allowed to stand in air for 10 minutes. This imparted a negative charge to the surface of the sputtered gold film, allowing it to better attract the positively charged titanium boride nanosheets, forming a stable titanium boride nanofilm on the gold film.

[0044] The sensor treated with PSS solution was fixed on a lifting coating machine, and the pulling speed and pulling length were set to 1500μm / s and 20mm. A dispersion of titanium boride nanosheets with positive charge characteristics treated with chitosan was coated on the sensing area for 20, 30, 40, 50, and 60 cycles, respectively. The thickness of the titanium boride nanofilm increased with the increase in the number of cycles. After coating, the sensor was left to stand in air for 24 hours. The titanium boride film layer was fixed to the surface of the gold film layer. The gold nanoparticle film layer was attached to the titanium boride film layer and was arranged on the side of the titanium boride film layer facing away from the tapered optical fiber body.

[0045] The gold nanoparticle coating method is as follows: Before attaching the gold nanoparticles, the sensor coated with the titanium boride film is immersed in a 2 mmol / L ethanolic solution of p-aminothiophenol for 24 hours, rinsed with distilled water, and allowed to dry. The sensor is then immersed in a gold nanoparticle dispersion for 12 hours and allowed to dry. The gold nanoparticles are now fixed to the titanium boride film surface.

[0046] like Figure 3 As shown, the sensing system formed by the above-mentioned fiber optic SPR biosensor includes a fiber optic SPR sensor with a first multimode optical fiber 111 and a second multimode optical fiber 113 as an optical path, an input end of which is connected to a broadband light source 200 with a spectrum in the visible light band, and an output end of which is connected to a broadband spectrometer 300, which is connected to an external computer via a data interface. The sensing area 110 of the fiber optic SPR sensor is placed in a solution of biomolecules to be detected.

[0047] The preparation method of the above-mentioned optical fiber SPR sensor comprises the following steps:

[0048] (1) Preparation of optical fiber body 100

[0049] Use fiber stripping pliers to remove the outermost coating structure of the single-mode optical fiber 112 to expose its cladding, dip a special lens cleaning paper in a small amount of alcohol solution and repeatedly wipe the treated single-mode optical fiber 112, then use a fiber optic cutter to cut 1 cm long single-mode optical fiber 112, and then cut two 25 cm multi-mode optical fibers, namely the first multi-mode optical fiber 111 and the second multi-mode optical fiber 113, and use fiber stripping pliers to remove 2.5 cm long coating structure at the end of the multi-mode optical fiber to expose the cladding, dip a special lens cleaning paper in a small amount of alcohol solution and repeatedly wipe the treated multi-mode optical fiber, then use a fiber optic cutter to cut off the end to remove the excess part of the coating, leaving 0.5 cm to remove the coating part, and finally, use a fiber fusion splicer to connect the two sides of the single-mode optical fiber 112 to the treated multi-mode optical fiber end. The 0.5 cm first multimode optical fiber 111 with the coating removed, the 1 cm single-mode optical fiber 112, and the 0.5 cm second multimode optical fiber 113 constitute the sensor sensing area 110. The total length of the sensing area 110 is 2 cm, and the optical fiber body 100 is 46 cm.

[0050] (2) Gold-plated film layer 120

[0051] The prepared optical fiber sensor sensing area is placed in a vacuum ion beam sputtering instrument, and a gold film is plated on the surface of the sensing area. After summarizing experience, the current of the vacuum ion beam sputtering instrument is 8mA, the time is 80 seconds, and the thickness of the gold film layer is 50nm.

[0052] (3) Fixing the titanium boride film layer 130

[0053] Before coating the titanium boride nanosheet dispersion, preparation is required. First, dilute 50ml of a 4% glacial acetic acid solution with deionized water. Weigh 500mg of chitosan powder and pour it into the glacial acetic acid solution. Stir continuously for 15 minutes until the chitosan is completely dissolved. Pipette 3ml of the chitosan solution into a small beaker and add 3ml of the titanium boride nanosheet dispersion to the chitosan solution. Ultrasonicate the resulting mixture for 15 minutes to obtain a well-distributed titanium boride nanosheet dispersion. This dispersion now possesses a positive charge. PSS is a negatively charged anionic polymer that can bind to cationic polymers. Immerse the prepared gold film sensing area in the 5mg / ml PSS solution for 2 minutes. After completion, let it sit in air for 10 minutes. This imparts a negative charge to the surface of the sensing area, where the gold film has already been sputtered, allowing it to better attract the positively charged titanium boride nanosheets, forming a stable titanium boride nanofilm on the gold film. The sensor, treated with PSS solution, was mounted on a lift-coater at a pull speed of 1500 μm / s and a pull length of 20 mm. A dispersion of positively charged titanium boride nanosheets treated with chitosan was applied to the sensing area for 20, 30, 40, 50, and 60 cycles, respectively. The thickness of the titanium boride nanofilm increased with each cycle. After coating, the sensor was left in air for 24 hours. The titanium boride film was then fixed to the gold film.

[0054] (4) Fixed gold nanoparticle film 140

[0055] Before attaching the gold nanoparticles, the sensor coated with the titanium boride film was immersed in a 2 mmol / L ethanolic solution of p-aminothiophenol for 24 hours, rinsed with distilled water, and allowed to dry. The sensor was then immersed in a gold nanoparticle dispersion for 12 hours and allowed to dry. Once dried, the gold nanoparticle film was fixed to the titanium boride surface.

[0056] The preparation method of the traditional optical fiber SPR sensor with only a gold film in the sensing area is as follows:

[0057] (1) Preparation of optical fiber body 100

[0058] Use fiber stripping pliers to remove the outermost coating structure of the single-mode optical fiber 112 to expose its cladding, dip a special lens cleaning paper in a small amount of alcohol solution and repeatedly wipe the treated single-mode optical fiber 112, then use a fiber optic cutter to cut 1 cm long single-mode optical fiber 112, and then cut two 25 cm multi-mode optical fibers, namely the first multi-mode optical fiber 111 and the second multi-mode optical fiber 113, and use fiber stripping pliers to remove 2.5 cm long coating structure at the end of the multi-mode optical fiber to expose the cladding, dip a special lens cleaning paper in a small amount of alcohol solution and repeatedly wipe the treated multi-mode optical fiber, then use a fiber optic cutter to cut off the end to remove the excess part of the coating, leaving 0.5 cm to remove the coating part, and finally, use a fiber fusion splicer to connect the two sides of the single-mode optical fiber 112 to the treated multi-mode optical fiber end. The 0.5 cm first multimode optical fiber 111 with the coating removed, the 1 cm single-mode optical fiber 112, and the 0.5 cm second multimode optical fiber 113 constitute the sensor sensing area 110. The total length of the sensing area 110 is 2 cm, and the optical fiber body 100 is 46 cm.

[0059] (2) Gold-plated film layer 120

[0060] The prepared optical fiber sensor was placed in a vacuum ion beam sputtering instrument and a gold film was plated on the surface of the sensor. The current of the vacuum ion beam sputtering instrument was 8 mA, the time was 80 seconds, and the thickness of the gold film layer was 50 nm.

[0061] The optical fiber SPR sensor based on the novel material titanium boride nanosheets was used to measure

[0062] Liquid Refractive Index Test: The fiber-optic SPR sensor, enhanced with the novel titanium boride nanosheets, was placed on a fiber-optic mounting platform and immersed in solutions with refractive indices of 1.33303, 1.34320, 1.35308, and 1.36372, yielding transmission spectra. A linear fit was performed on these measurement results to determine the sensor's sensitivity, which was significantly improved compared to conventional fiber-optic SPR sensors with only a gold film in the sensing area.

[0063] The above are only preferred specific implementation methods of the present invention, but the protection scope of the present invention is not limited to them. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A biosensor with high-density loading capability, characterized in that: include: The optical fiber body (100) has a sensing area (110) formed by fusion splicing a 0.4-0.6 cm first multimode optical fiber (111) with the coating removed, a 0.9-1.1 cm single-mode optical fiber (112), and a 0.4-0.6 cm second multimode optical fiber (113), with a total length of 1.7-2.3 cm; The following film layers are stacked in sequence on the surface of the sensing area (110): Gold film layer (120), thickness 45-55 nm; Titanium boride film layer (130), thickness 40-50 nm; The gold nanoparticle film layer (140) is composed of gold nanoparticles with a particle size of 20-50 nm.

2. The biosensor with high-density loading function according to claim 1, characterized in that: The thickness of the gold film layer (120) is 50 nm, and the thickness of the titanium boride film layer (130) is 45 nm.

3. The biosensor with high-density loading function according to claim 1, characterized in that: The gold nanoparticle film layer (140) is chemically adsorbed on the surface of the titanium boride film layer (130) through an aminothiophenol coupling agent.

4. A sensing system, characterized in that: include: The biosensor with high-density loading function according to any one of claims 1 to 3; A broadband light source (200) with an output spectrum range of 400-1000 nm is connected to the input end of the optical fiber body (100); A broadband spectrometer (300) is connected to the output end of the optical fiber body (100) and is used to detect the transmission spectrum; The computer is connected to the spectrometer (300) via a data interface and is used to analyze the resonance wavelength shift.

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