Enhanced Fabry-Perot microcavity biosensor for low concentration detection

Abstract

The utility model belongs to the technical field of optical biosensors, and particularly relates to an enhanced Fabry-Perot microcavity sensor for ultralow-concentration biological detection. The sensing microcavity comprises a square capillary quartz tube, wherein high-reflectivity films are plated on the upper surface and the lower surface of the square capillary quartz tube; a liquid core area of the square tube is a micro-flow channel, and a polyethylene glycol polymerization promoting biomolecule solution is introduced into the micro-flow channel, so that the Fabry-Perot microcavity biosensor is obtained. According to the utility model, the square capillary quartz tube provides high-precision parallelism between the two reflectors, so that the diffraction and walk-off loss can be reduced, the mode volume in the cavity can be reduced, the light energy density can be increased, the strong interaction between light and substances can be realized, and the quality factor can be improved; polyethylene glycol can promote the polymerization of biomolecular protein, enhance the reaction of an antigen-antibody compound, and further promote the aggregation of an immune compound. The biosensor is simple in structure, convenient to prepare, good in repeatability and stability, high in response speed and free of surface modification and chemical labeling.

Description

Technical Field

[0001] This invention belongs to the field of optical sensor technology, specifically relating to a Fabry-Perot microcavity sensor. Background Technology

[0002] With the increasing demands of biomedicine, ultra-low concentration bioassay technology has become a key technology in early diagnosis, precision medicine, and drug development. In clinical samples, the concentration of biomarkers is typically in the picomolar to attomolar range, posing a significant challenge to traditional detection methods. Optical microcavities, through intense light-matter interactions, have become a powerful tool for highly sensitive detection. These interactions amplify the signal response, and even small changes in the mode field can induce significant responses in the resonance spectrum, such as wavelength shifts, linewidth broadening, and intensity changes, thereby achieving ultrasensitive biomarker detection. Among them, Fabry-Perot microcavities, with their high-quality factor and small mode volume, achieve intense light-matter interactions through high-quality light-matter overlap with the target analyte, providing a simple and efficient method for ultrasensitive bioassay.

[0003] Fabry-Perot microcavity biosensors typically amplify optical signals using gain media or fluorescent labels to suppress walk-off losses caused by the tilt of the two mirrors. However, label-based biosensors require additional chemical modification steps, which can be toxic to biomolecules and cause photobleaching of fluorescent materials during long-term testing, leading to signal artifacts and increased interference risks. In contrast, label-free biosensors directly measure biomolecular interactions by monitoring changes in optical signals, offering advantages such as non-invasiveness, simplicity, cost-effectiveness, high repeatability, and fast response time.

[0004] Immunoturbidimetry is a label-free biosensing technique that enhances the antigen-antibody reaction by using biomolecule polymerization promoters. The increased number and size of nanoparticles generated during this reaction lead to scattering and absorption of incident light, resulting in changes in solution turbidity. By measuring changes in the intensity of transmitted or scattered light, the concentration of the target biomolecule can be quantitatively analyzed. However, immunoturbidimetry faces the challenge of insufficient resolution in the detection of low-concentration biological samples. Summary of the Invention

[0005] The purpose of this invention is to provide a polyethylene glycol-enhanced Fabry-Perot microcavity sensor that can detect ultra-low concentrations of biomolecules.

[0006] This invention provides a Fabry-Perot microcavity sensor. By enhancing the interaction between light and matter through a high-quality Fabry-Perot microcavity, it enables the detection of minute changes in refractive index, thereby achieving the detection of low concentrations of biomolecules. Furthermore, the polymerization of biomolecules by polyethylene glycol enhances the antigen-antibody complex reaction, promoting the aggregation of immune complexes, thus increasing the size and concentration of antigen-antibody nanoparticles and amplifying the optical signal.

[0007] The enhanced Fabry-Perot microcavity sensor for ultra-low concentration biological detection provided by this invention has the following structure: Figure 1 As shown; specifically including: a hollow square capillary quartz tube, the central region of which serves as a microfluidic channel; the upper and lower surfaces of the square quartz tube are coated with a high-reflectivity thin film, serving as Bragg mirrors, thereby forming a Fabry-Perot microcavity; Teflon tubes are connected to both ends of the square capillary quartz tube for connection to a microfluidic system to extract biological solutions; polyethylene glycol is mixed and incubated with biomolecules, and the biological solution is introduced into the Fabry-Perot microcavity through the microfluidic system to achieve ultra-low concentration biological detection.

[0008] In this invention, the high-reflectivity film is composed of two dielectric films with different high and low refractive indices arranged alternately, and its reflectivity is 90-100%.

[0009] In this invention, the high reflectivity film reflects light in a range from near-ultraviolet to mid-infrared.

[0010] In this invention, the square quartz tube has a cross-sectional height and width of 100-1000μm, a wall thickness of 5-200μm, and a length of 0.5-10cm.

[0011] In this invention, the material of the square quartz tube is preferably silicon dioxide.

[0012] In this invention, the polyethylene glycol solution is used as a polymerization promoter to enhance biological signals, and the concentration of the polyethylene glycol solution is 10-100 mg / mL.

[0013] The technical principle of this invention is as follows: Bragg mirrors are directly deposited on the upper and lower surfaces of a high-precision square capillary quartz tube to form a high-quality Fabry-Perot optical microcavity. Based on the mature fabrication process of square capillary tubes, this overcomes the requirement of high parallelism between planar mirrors in traditional Fabry-Perot resonators. Furthermore, the lateral constraint of the quartz tube wall on the light field greatly reduces the mode volume within the cavity, increases the light energy density, and enhances the interaction between light and matter. Combined with the polymerization effect of polyethylene glycol on biomolecules, this enhances the antigen-antibody complex reaction, promotes the aggregation of immune complexes, and thus increases the size and concentration of antigen-antibody nanoparticles, achieving amplification of the optical signal. This high-quality Fabry-Perot resonator achieves specific detection of ultra-low concentrations of antigen protein molecules by monitoring transmission intensity and wavelength peak position. This biosensor not only achieves low cost, simple structure, convenient fabrication, high repeatability and stability, fast response time, and is free from surface modification and chemical labeling, but also achieves extremely high sensitivity and trace bioanalyte detection.

[0014] This utility model has the following features:

[0015] (1) This invention differs significantly from traditional Fabry-Perot resonators. In this invention, no additional planar mirror is required for assembly; the reflective film is directly deposited onto the surface of the square tube to form the Fabry-Perot microcavity. Due to the lateral constraint of the optical field by the square quartz tube wall, diffraction loss and walk-off loss are suppressed, which not only further increases the optical energy density but also greatly reduces the mode volume.

[0016] (2) The Fabry-Perot microcavity sensor provided by this utility model overcomes the requirement of high parallelism alignment of the two mirrors in the traditional Fabry-Perot resonant cavity, and greatly improves the quality factor of the sensor.

[0017] (3) The Fabry-Perot microtubule provided by this utility model is itself a microfluidic channel with a hollow structure, which can simultaneously realize the transmission and detection of the solution of the biological analyte to be tested;

[0018] (4) The Fabry-Perot microcavity provided by this utility model has a very high quality factor and a very high optical power density, which significantly increases the interaction between light and matter, and thus enables the detection of minute changes in refractive index.

[0019] (5) The Fabry-Perot microcavity provided by this invention monitors the spectral peak position changes caused by minute refractive index variations, achieving a peak position of 7.11 × 10⁻⁶. -8 Ultra-low detection limit of RIU and ultra-high resolution refractive index sensing of 201.0 nm / RIU;

[0020] (6) The Fabry-Perot microtubule provided by this utility model enhances the antigen-antibody complex reaction based on the polymerization of biomolecules by polyethylene glycol, promotes the aggregation of immune complexes, thereby increasing the size and concentration of antigen-antibody nanoparticles and realizing the amplification of optical signals.

[0021] (7) The Fabry-Perot microtubule provided by this utility model is based on uniformly oscillating a fully reacted antigen-antibody complex solution and introducing it into the Fabry-Perot microtubule through a microfluidic system to monitor the changes in transmission intensity and wavelength displacement in real time.

[0022] (8) The signal intensity enhancement effect of Fabry-Perot microtubule PEG provided by this utility model helps to achieve more sensitive biomolecule detection, especially in the detection of low concentration and single molecular weight.

[0023] (7) The Fabry-Perot microtubular biosensor provided in this utility model has the characteristics of low cost, simple structure, convenient preparation, high repeatability, fast response time, and high specificity of biological detection without surface modification and chemical labeling.

[0024] (8) The sensor detection system provided in this utility model is easy to build, the detection method is simple, and it is convenient for practical application. Attached Figure Description

[0025] Figure 1 This is a structural diagram of the Fabry-Perot microtubule sensor of this utility model.

[0026] Figure 2 This is a schematic diagram of the spatial optical path coupling system for the Fabry-Perot microcavity sensor detection of this utility model.

[0027] Figure 3 This is the measured transmission spectrum of the Fabry-Perot microlumen sensor of this utility model.

[0028] Figure 4 The transmission resonance spectra of the liquid core region of the Fabry-Perot microcavity sensor of this invention are obtained by passing solutions of different refractive indices through it.

[0029] Figure 5 This is a characterization diagram of the refractive index sensitivity of the Fabry-Perot microcavity sensor of this utility model.

[0030] Figure 6 This is a measured detection limit diagram of the refractive index sensing of the Fabry-Perot microcavity sensor of this utility model.

[0031] Figure 7 This is a graph showing the detection of polyethylene glycol-enhanced biomolecular optical signals using the Fabry-Perot microtubule sensor of this utility model.

[0032] The diagram is labeled as follows: 1 is a high-reflectivity thin film, 2 is a quartz tube, 3 is a biomolecule combined with polyethylene glycol, and 4 is a microfluidic channel. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but the present invention is not limited to these examples.

[0034] Example 1

[0035] In this embodiment, the Fabry-Perot microlumen sensor (see...) Figure 1 Specifically, it includes: a square quartz capillary tube with a cross-sectional height and width of 300μm and a wall thickness of 100μm, which is hollow; the upper and lower surfaces of the square quartz tube are coated with a high reflectivity film with a reflectivity of 99.8%.

[0036] The fabrication process of Fabry-Perot microtubules includes:

[0037] (1) Coating removal: Burn the coating on the surface of the square capillary quartz tube with an alcohol lamp, and then clean it with lens paper;

[0038] (2) Cleaning of square capillary quartz tubes: Clean the square capillary quartz tubes with acetone, alcohol and deionized water in sequence for 2 to 5 minutes, and then place them in a petri dish to air dry naturally.

[0039] (3) Bragg reflector preparation: Bragg reflectors are prepared on the upper and lower surfaces of a square capillary quartz tube using conventional coating processes. The working band and wavelength of the reflector can be controlled by coating technology.

[0040] (4) Tube wall corrosion: After the coating is completed, Teflon tubes are connected to both ends of the square capillary to form a Fabry-Perot microtubule sensor. In order to seek higher sensitivity, the tube wall was corroded by 12% hydrofluoric acid solution in the experiment. At a flow rate of 15 μL / min, about 8 μm was corroded in one hour.

[0041] (5) Pipe wall smoothing treatment: After the pipe wall is corroded into a thin wall, the pipe wall is smoothed by using 4%, 1% and 0.5% hydrofluoric acid solutions respectively to reduce the scattering loss introduced by roughness.

[0042] The Fabry-Perot microtubule sensor of this invention utilizes the lateral confinement effect of the Fabry-Perot cavity and its square tube wall on the light field, as well as the high parallelism of its upper and lower surfaces, to significantly increase the effective propagation path and light energy density within the cavity. This not only improves the quality factor of the microtubule but also reduces the mode volume, thereby achieving high-sensitivity detection of ultra-low concentrations of analytes, making it suitable for biomolecular sensing.

[0043] Example 2

[0044] In this embodiment, the performance of the Bripperrow microcavity sensor prepared by the method described in Example 1 is characterized based on the parameters of Example 1. First, a corresponding spatial optical path coupling system is designed and built, such as... Figure 2 As shown, the output light of the tunable laser serves as the signal light to excite the intrinsic modes of the Bripperow microcavity, and the transmission spectrum is collected in real time by a photodetector. This detection optical path system consists of three parts: an imaging optical path (dashed line), a signal detection optical path (solid line), and an optical microfluidics system.

[0045] Imaging optical path: A reflective illumination system is employed. It consists of a lens, a beam splitter, and a CCD imaging device. The sample's surface information is imaged through the lens, then sequentially folded 90° by the beam splitter before being transmitted to the CCD imaging device. The imaging optical path allows real-time observation of the incident light spot's position relative to the square capillary quartz tube, enabling precise and efficient coupling of the cavity mode of the Fabry-Perot microtube.

[0046] Signal detection optical path: After the output light of the tunable laser is collimated by the fiber collimator, it passes through the beam splitter and is focused by the lens to achieve coupling between the incident light and the cavity mode of the Fabry-Perot microcavity. In order to collect the transmitted light signal, the transmitted signal is first collimated into parallel light by the objective lens and transmitted to the photodetector at the far end. Finally, the light signal is coupled to the photosensitive area of ​​the photodetector by the lens. The photodetector detects the transmission spectrum and displays the spectrum on the computer for processing and analysis.

[0047] Microfluidic system: The microtubule is connected to the syringe and analyte via a Teflon tube. In actual testing, the injection speed of the syringe is controlled by a microfluidic pump to ensure that the solution in the microtubule moves at a constant flow rate.

[0048] Example 3

[0049] In this embodiment, the transmission spectrum of the Fabry-Perot microcavity is obtained based on the spatial optical path coupling system built in Embodiment 2. Figure 3 The transmission spectrum of the Fabry-Perot microcavity in its resonant mode near 910 nm is given, and its linewidth is fitted with a Lorentz line shape. Its quality factor can be calculated using the following formula:

[0050] Q=λ / w, (1)

[0051] Where λ is the resonant wavelength and w is the full width at half maximum (FWHM) of the resonant mode. Based on the detected spectrum and through Lorentz line fitting, the FWHM of the resonant mode of the Fabry-Perot microtubule near 910 nm is 0.9 pm. Therefore, the quality factor of this mode is calculated to be 1.0 × 10⁻⁶ using equation (1). 6This result indicates a high-quality factor. The Fabry-Perot microlumen means that light within the cavity experiences very little energy loss after multiple reflections. The optical signal within the cavity can be maintained for a long time, exhibiting very low energy loss. This low loss allows the cavity to maintain the optical signal for an extended period, thereby improving the sensitivity of the optical signal. The Fabry-Perot microlumen can more precisely select and enhance light of specific wavelengths, thus facilitating high-resolution spectral measurements and precise wavelength selection, enabling the detection of minute refractive index changes, and can be used for the detection of ultra-low concentrations of biomolecules.

[0052] Example 4

[0053] To evaluate the refractive index sensing performance of the Fabry-Perot microcavity, this case study introduced dimethyl sulfoxide and deionized water solutions at different volume ratios (0%, 0.02%, 0.04%, 0.06%, 0.08%, and 0.1%) into the microfluidic channel of the microcavity. The corresponding refractive index values ​​of the solutions ranged from 1.33 to 1.330142. Figure 4 The resonance spectra of the Fabry-Perot microtubules are shown when solutions with different refractive index values ​​are introduced. Figure 5 This study demonstrates the relationship between real-time monitoring of changes in solution refractive index and resonant wavelength shift. Experimental results show that with increasing dimethyl sulfoxide solution concentration, the resonant wavelength exhibits a significant redshift, and a significant linear relationship exists between the resonant wavelength and the refractive index value. Based on the experimental data fitting, the sensitivity is calculated to be 201.0 nm / RIU. Notably, the actual detection limit of the Fabry-Perot microlumen is as low as 7.11 × 10⁻⁶. -8 RIU (see) Figure 6 These outstanding performance indicators are attributed to the lateral optical field confinement of the microtube sidewalls, which significantly reduces the mode volume. Furthermore, the precise parallelism of the square capillary quartz tube minimizes diffraction and lateral drift losses, and the ultra-high detection sensitivity lays the foundation for the detection of ultra-low concentrations of biomolecules.

[0054] Example 5

[0055] This case study utilizes the protein-polymerization-promoting effect of polyethylene glycol (PEG) to enhance antigen-antibody complex reactions, promoting the aggregation of immune complexes and thereby increasing the size and concentration of antigen-antibody complex nanoparticles, thus amplifying the signal. This case study compares the wavelength shift changes of antigen-antibody complex solutions containing and without PEG in the range of human epidermal growth factor receptor 2 (HER2) protein concentrations from 100 ag / mL to 100 pg / mL. In this label-free biomolecular detection, HER2 solution was first mixed with PEG solution and incubated, followed by the addition of antibody solution for further reaction. The fully reacted antigen-antibody complex solution was uniformly agitated and introduced into a Fabry-Perot microtubule lumen via a microfluidic system to monitor the wavelength shift changes of the transmission spectrum in real time. With increasing HER2 protein concentration, the wavelength of the antigen-antibody complex solution exhibited a blue shift. It is noteworthy that, under the same human epidermal growth factor receptor 2 protein concentration, the antigen-antibody complex solution containing polyethylene glycol exhibited a significantly enhanced wavelength shift effect. Therefore, the experimental results indicate that polyethylene glycol promotes the polymerization reaction of proteins in antigen-antibody binding and enhances the biomonitoring signal, thus contributing to more sensitive biomolecular detection, especially in low-concentration detection, where it has significant advantages.

Claims

1. An enhanced Fabry-Perot microcavity biosensor for low-concentration detection, characterized in that, Specifically, it includes: A hollow square capillary quartz tube serves as a microfluidic channel in its central region. High-reflectivity thin films are coated on both the upper and lower surfaces of the square quartz tube, acting as Bragg mirrors to form a Fabry-Perot microcavity. Teflon tubes are connected to both ends of the square capillary quartz tube for connection to a microfluidic system, enabling the extraction of biological solutions. Polyethylene glycol is mixed and incubated with biomolecules, and the biological solution is introduced into the Fabry-Perot microcavity through the microfluidic system to achieve ultra-low concentration biological detection.

2. The enhanced Fabry-Perot microcavity biosensor according to claim 1, characterized in that, The high-reflectivity thin film is composed of two dielectric films with different high and low refractive indices arranged alternately, and its reflectivity is 90-100%.

3. The enhanced Fabry-Perot microcavity biosensor according to claim 2, characterized in that, The high-reflectivity film reflects light in the range from near-ultraviolet to mid-infrared.

4. The enhanced Fabry-Perot microcavity biosensor according to claim 3, characterized in that, The square quartz tube has a cross-sectional height and width of 100-1000 μm, a wall thickness of 5-200 μm, and a length of 0.5-10 cm.

5. The enhanced Fabry-Perot microcavity biosensor according to claim 4, characterized in that, The polyethylene glycol is used as a polymerization promoter to enhance biological signals, and the polyethylene glycol solution concentration is 10-100 mg / mL.

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