Low-dielectric-constant filter membrane based on biological enzyme and preparation method and application of low-dielectric-constant filter membrane

Abstract

A preparation method of the low-dielectric-constant filter membrane based on the biological enzyme comprises the following steps: drying the low-dielectric-constant filter membrane, dripping the biological enzyme onto the surface of the dried filter membrane, performing cold drying, and obtaining the low-dielectric-constant filter membrane based on the biological enzyme after moisture is completely volatilized, meanwhile, the invention further discloses application of the low-dielectric-constant filter membrane based on the bio-enzyme in a waveguide gas sensor, after the low-dielectric-constant filter membrane based on the bio-enzyme is fixed to a resonance piece resonance window in the waveguide gas sensor, the sensor is assembled for testing, and the filter membrane which is small in size and convenient to mount and dismount is used, so that the filter membrane is convenient to mount and dismount; the low-dielectric-constant filter membrane based on the bio-enzyme is favorable for repeatedly testing the same sample for multiple times, has good reusability, and can enable the enzyme to be in full contact with gas due to better air permeability, so that the sensitivity of the sensor is further improved.

Description

Technical Field

[0001] The invention relates to the field of waveguide gas sensors, and in particular to a low dielectric constant filter membrane based on a biological enzyme, and a preparation method and application thereof. Background Art

[0002] At present, microwave gas sensors mostly use planar circuits, which have the advantages of small size, simple processing and low cost. However, the electric field and magnetic field in the planar circuit are often intertwined, and the quality factor and electromagnetic field strength are limited by the planar circuit structure. The three-dimensional structure of the waveguide cavity can transmit TE mode and TM mode, and can well separate the electric field concentration area and the magnetic field concentration area, making the circuit quality factor much higher than the planar circuit, greatly improving the sensitivity of the microwave sensor.

[0003] At present, waveguide structure sensors are mainly used for non-destructive testing and imaging of objects, surface crack detection, thickness detection, humidity detection and dielectric constant detection. In the field of gas sensors, there are many related studies based on optical waveguide gas sensors. However, the optical waveguide test system is relatively complex, the instrument price and processing cost are relatively expensive, and it is easily affected in an environment with limited light propagation. For microwave waveguide gas sensors, so far only JL Jordan et al. have proposed using the microwave band waveguide cavity structure to sense SO2, but the sensor does not contain sensitive materials and has limited sensitivity, and the detection limit is low.

[0004] At present, most bio-enzyme sensors are electrochemical sensors, and the most commonly used enzyme fixation method is to fix the enzyme on the electrode by physical or chemical methods. At present, there is no precedent for combining bio-enzymes with waveguides to make microwave gas sensors. The three-dimensional waveguide cavity structure is large, and the sensitive area is concentrated in the center of the cavity. It is impossible to directly fix the enzyme in the sensitive area, and there is a lack of fixed positions similar to electrochemical sensors.

[0005] At present, biological enzymes are widely used in electrochemical and resistive sensors. However, due to the special cavity structure of the waveguide cavity, they cannot be directly used in the waveguide cavity, which makes all biological enzymes sensitive to gas useless on the waveguide. Moreover, the method of fixing enzymes in electrochemical sensors also has many shortcomings. Since the enzymes used in gas biosensors are not in their natural environment, they are often unstable due to changes in environmental conditions. If naked enzymes (enzymes not fixed in substances) are modified on the electrode surface, the enzyme load will become smaller, resulting in reduced enzyme activity. In addition, the efficiency of electron transfer between the enzyme and the electrode will also decrease. During the enzyme immobilization process, the introduction of adhesive substances will block gas adsorption. The sample tube currently used for waveguide cavity testing also has many disadvantages. First, its dielectric constant is large, which has a great impact on the electromagnetic field, making the electromagnetic field less sensitive to the material; second, the sample tube cannot be directly loaded with liquid biological enzymes; third, the sample tube is too large and has poor air permeability, which greatly reduces the contact area between the enzyme and the sensitive gas, which weakens the gas sensing performance. Summary of the invention

[0006] The present invention designs and develops a low dielectric constant filter membrane based on biological enzymes. The purpose of the present invention is to solve the problem in the prior art that the biological enzymes cannot be fixed in the sensitive area of ​​the waveguide cavity.

[0007] The present invention designs and develops a method for preparing a low dielectric constant filter membrane based on biological enzymes. The purpose of the present invention is to solve the problem of preparing a low dielectric constant filter membrane based on biological enzymes.

[0008] The present invention also relates to an application of a low dielectric constant filter membrane based on biological enzymes. The present invention solves the problem in the prior art that biological enzymes cannot be used in waveguide cavities to realize gas detection using enzyme microwave sensors.

[0009] The technical solution provided by the present invention is:

[0010] A method for preparing a low dielectric constant filter membrane based on biological enzymes comprises: drying the low dielectric constant filter membrane, dropping biological enzymes onto the surface of the dried filter membrane and then cold drying, and obtaining the low dielectric constant filter membrane based on biological enzymes after the water is completely volatilized.

[0011] Preferably, the low dielectric constant filter membrane is dried at 60°C.

[0012] Preferably, the biological enzyme is dropped onto the dried filter membrane surface and then refrigerated for 24 hours.

[0013] Preferably, the biological enzyme is porcine pancreatic enzyme, alcohol dehydrogenase, secondary alcohol dehydrogenase, ethanol oxidase or peroxidase.

[0014] Preferably, the low dielectric constant filter membrane is a quartz fiber filter membrane, paraffin or molecular sieve.

[0015] Preferably, the biological enzyme is a solution containing 2.5 g / L trypsin in a HBSS solution containing phenol red, and 20 μl to 60 μl is pipetted and dripped onto the filter membrane surface in multiple times.

[0016] Preferably, the low dielectric constant filter membrane is cut into squares of 0.9 cm×0.9 cm and then dried.

[0017] A low dielectric constant filter membrane based on biological enzyme is prepared using the preparation method of the low dielectric constant filter membrane based on biological enzyme.

[0018] The invention discloses an application of a low dielectric constant filter membrane based on a biological enzyme in a waveguide gas sensor. After the low dielectric constant filter membrane based on the biological enzyme is fixed on a resonant plate resonant window in the waveguide gas sensor, the sensor is assembled for testing.

[0019] Preferably, the waveguide cavity in the waveguide gas sensor is a rectangular waveguide cavity, a cylindrical waveguide cavity or an annular cavity.

[0020] The beneficial effects of the present invention are:

[0021] 1. The low dielectric constant filter membrane based on biological enzymes provided by the present invention has little effect on the electromagnetic field of the waveguide. By using a small-volume and conveniently installed and disassembled filter membrane, it is conducive to repeated testing of the same sample and has good reusability;

[0022] 2. The low dielectric constant filter membrane based on biological enzymes provided by the present invention can be weighed, so the mass of the coated sample can be weighed and controlled, which is conducive to variable control;

[0023] 3. The preparation method of the low dielectric constant filter membrane based on biological enzyme provided by the present invention can load the biological enzyme by the drop coating method, so that the biological enzyme can be combined with the waveguide to make a microwave gas sensor;

[0024] 4. The low dielectric constant filter membrane based on biological enzymes provided by the present invention has good air permeability, which can allow the enzyme to fully contact with the gas, further improving the sensitivity of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of a waveguide gas sensor using a rectangular waveguide resonant cavity according to the present invention.

[0026] Figure 2 This is a schematic diagram of the structure of a waveguide gas sensor using a rectangular waveguide resonant cavity according to the present invention.

[0027] Figure 3This is a digital photo of the resonance plate loaded with the bio-enzyme filter membrane described in the present invention.

[0028] Figure 4 This is a schematic diagram of the response curve of the quartz fiber filter based on porcine pancreatic enzyme prepared in Example 1 of the present invention to ethanol at room temperature.

[0029] Figure 5 This is a schematic diagram of the response curve of the quartz fiber filter based on porcine pancreatic enzyme prepared in Example 2 of the present invention to ethanol at room temperature.

[0030] Figure 6 This is a schematic diagram of the response curve of the quartz fiber filter based on porcine pancreatic enzyme prepared in Example 3 of the present invention to ethanol at room temperature. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0032] The present invention provides a method for preparing a low dielectric constant filter membrane based on a biological enzyme, which specifically comprises the following steps:

[0033] Step 1: Cut the low dielectric constant filter membrane into a 0.9 cm × 0.9 cm rectangle and dry it in an oven at 60°C for later use;

[0034] Step 2: Use a pipette to draw a fixed amount of enzyme liquid and drop it onto the fiber surface of the low dielectric constant filter membrane several times, and place it in a refrigerator to dry for 24 hours;

[0035] Step 3: After the water is completely evaporated, the bio-enzyme is attached to the fiber to obtain a low dielectric constant filter membrane based on the bio-enzyme.

[0036] In another embodiment, the low dielectric constant filter membrane is a quartz fiber filter membrane, paraffin or molecular sieve.

[0037] In another embodiment, the biological enzyme is porcine pancreatic enzyme, alcohol dehydrogenase, secondary alcohol dehydrogenase, ethanol oxidase or peroxidase; preferably, the biological enzyme is a solution containing 2.5 g / L pancreatic porcine protease in an HBSS solution containing phenol red, and 20 μl to 60 μl is pipetted and dripped onto the filter membrane surface in multiple times.

[0038] The present invention also provides a low dielectric constant filter membrane based on biological enzymes, which is prepared by the above-mentioned preparation method. The present invention uses a low dielectric constant filter membrane chip to drip the biological enzyme on the surface of the filter membrane. It only needs to place the filter membrane in the sensitive area of ​​the waveguide cavity to solve the problem that the biological enzyme cannot be loaded, simplify the sensing system, and the filter membrane is used to carry the biological enzyme and is combined with the waveguide cavity and is an ideal choice for gas sensing; the three-dimensional structure of the waveguide cavity itself can provide a closed atmosphere environment, further simplifying the test system. At the same time, the quartz fiber filter membrane has a low dielectric constant, so the impact on the electromagnetic field of the waveguide is very small. The quartz fiber filter membrane is small in size and convenient to install and disassemble, which is conducive to repeated testing of the same sample and has good reusability. At the same time, the method of coating the quartz fiber filter membrane can fix the biological enzyme, which solves the problem that the waveguide cannot fix the enzyme. The excellent air permeability of the filter membrane allows the gas molecules to fully contact the enzyme, further improving the sensitivity of the sensor.

[0039] The present invention also provides an application of a low dielectric constant filter membrane based on a biological enzyme in a waveguide gas sensor. The low dielectric constant filter membrane coated with the biological enzyme is fixed in the strong electric field area in the middle of the resonant window of the resonant plate in the waveguide gas sensor, and the sensor is assembled for testing.

[0040] In another embodiment, the waveguide cavity in the waveguide gas sensor is a rectangular waveguide cavity, a cylindrical waveguide cavity or an annular cavity.

[0041] like Figure 1 , Figure 2 , Figure 3 As shown, the present invention uses a waveguide gas sensor with a rectangular waveguide resonant cavity for application. The rectangular waveguide is a standard straight waveguide made of aluminum material without coating. Two conductive metal shells 110 are relatively coaxially arranged and have an axially penetrating waveguide cavity 111. The metal shell 110 does not absorb electromagnetic waves but only reflects them. An air inlet is made on the outer surface of the cavity of the metal shell 110. The air inlet is connected to the glass tube 112 with hot melt adhesive to ensure its airtightness. The end of the glass tube 112 is connected with a rubber hose. A window 121 of a certain size is made on a flange (made of metal copper) as a resonant plate 120. Both ends of the resonant plate 120 are fixedly connected to the ports of the metal shell 110. A low dielectric constant filter membrane 200 based on biological enzymes is placed at the window 121. The resonant plate 120 is sandwiched between two identical waveguide cavities 111. The low dielectric constant filter membrane 200 based on biological enzymes can adsorb gas and seal the ports of the metal shell 110, so that a closed cavity is formed inside the entire device. A waveguide converter 130 is fixedly connected to the outer ports of the two metal shells 110. Both sides of the waveguide cavity 111 are connected to a vector network analyzer through ports 131 on the waveguide converter 130 and a coaxial cable, so that real-time testing of microwave signals transmitted in the waveguide cavity 111 is performed.

[0042] Example 1

[0043] The invention provides a method for preparing a low dielectric constant filter membrane based on biological enzymes, which specifically comprises the following steps:

[0044] Step 1: Cut the quartz fiber filter into a 0.9 cm × 0.9 cm rectangle and dry it in an oven at 60°C for later use;

[0045] Step 2: Use a pipette to draw 20 μl of porcine pancreatic enzyme liquid and drop it onto the fiber surface of the low dielectric constant filter membrane several times, and place it in a refrigerator to dry for 24 hours;

[0046] Step 3: After the water is completely evaporated, the biological enzyme is attached to the fiber to obtain a quartz fiber filter membrane based on porcine pancreatic enzyme.

[0047] Example 2

[0048] The invention provides a method for preparing a low dielectric constant filter membrane based on biological enzymes, which specifically comprises the following steps:

[0049] Step 1: Cut the quartz fiber filter into a 0.9 cm × 0.9 cm rectangle and dry it in an oven at 60°C for later use;

[0050] Step 2: Use a pipette to draw 40 μl of porcine pancreatic enzyme liquid and drop it onto the fiber surface of the low dielectric constant filter membrane several times, and place it in a refrigerator to cool and dry for 24 hours;

[0051] Step 3: After the water is completely evaporated, the biological enzyme is attached to the fiber to obtain a quartz fiber filter membrane based on porcine pancreatic enzyme.

[0052] Example 3

[0053] The invention provides a method for preparing a low dielectric constant filter membrane based on biological enzymes, which specifically comprises the following steps:

[0054] Step 1: Cut the quartz fiber filter into a 0.9 cm × 0.9 cm rectangle and dry it in an oven at 60°C for later use;

[0055] Step 2: Use a pipette to draw 60 μl of porcine pancreatic enzyme liquid and drop it onto the fiber surface of the low dielectric constant filter membrane several times, and place it in a refrigerator to cool and dry for 24 hours;

[0056] Step 3: After the water is completely evaporated, the biological enzyme is attached to the fiber to obtain a quartz fiber filter membrane based on porcine pancreatic enzyme.

[0057] Test Case

[0058] Adopt national standard BJ32 waveguide (QWS-284-100), (σ=3.816107S·m -1). It operates in the frequency range of 2.60-3.95GHz. The gas inlet is integrated into the cavity surface and carefully sealed to the glass tube with hot melt adhesive to ensure airtightness. The end of the glass tube is connected to a rubber tube. The sealed measuring cell has a gas outlet on the opposite side.

[0059] The porcine pancreatic enzyme-based quartz fiber filter membrane prepared in Example 1, Example 2, and Example 3 was firmly fixed to the resonant window, and then the resonant plate was carefully clamped between two identical rectangular waveguides. A waveform converter and a coaxial cable were used to connect both sides of the waveguide cavity to a vector network analyzer (VNA, Anritsu MS46122B) to measure the transmitted microwave signal in real time. The rectangular waveguide cavity was seamlessly connected to the VNA through input and output transmission lines. During the measurement, the microwave transmission signal of the waveguide resonator was recorded by a laptop computer. A microwave gas sensing system was formed by the above operations. All gas sensing tests were performed at room temperature (25°C) and 1atm using the assembled microwave sensing system. 10ppb-500ppm ethanol gas was injected into the waveguide through the gas inlet. Subsequently, the response signal (especially S 22 ) is used to calculate the gas sensing response. Therefore, the gas sensitivity is carefully defined as:

[0060] Response = S 22 air -S 22 gas

[0061] like Figure 4 , Figure 5 , Figure 6 As shown in Figure 2, with the increase of ethanol concentration, the response of the sensor (defined as S 22 air -S 22 gas ) continues to increase, showing a certain linear response, which shows that the microwave sensor assembled by porcine pancreatic enzyme and waveguide can realize sensitive detection of ethanol gas in a wide range of 10ppb-500ppm at room temperature, and the sensor has a high response of 1.14 in 500ppm ethanol gas. As the contact between porcine pancreatic enzyme and gas molecules increases, the response of the sensor increases rapidly, and there is a good linear relationship. The porcine pancreatic enzyme microwave gas sensor material has a low detection limit (10ppb) and a wide detection range (10ppb-500ppm), which shows that the waveguide resonant cavity structure and the quartz fiber chip loaded with biological enzymes have great advantages in the development of high-performance microwave gas sensors. This sensor has created a new era of gas-sensitive detection combining microwave sensors with biological enzymes.

[0062] The present invention combines biological enzymes with waveguide structures for the first time to obtain a microwave gas sensor with high sensitivity, low detection limit and wide detection range, which can replace expensive optical waveguides for gas sensing. Due to the characteristics of biological enzymes, it is difficult to place them directly in the waveguide for detection. The biological enzymes can be loaded onto a quartz fiber filter membrane by means of drop coating, etc., and the filter membrane is attached to the location where the electromagnetic field of the resonant plate is concentrated. The resonant plate is directly placed in the waveguide cavity, which greatly improves the reconfigurability of the sensor: that is, for different target gases, only different types of biological enzymes need to be replaced to detect different gases.

[0063] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing a low dielectric constant filter membrane based on biological enzymes, characterized in that: include: After the low dielectric constant filter membrane is dried, a biological enzyme is dropped onto the surface of the dried filter membrane and then cold-dried, and after the water is completely evaporated, the low dielectric constant filter membrane based on the biological enzyme is obtained.

2. The method for preparing a quartz fiber filter membrane based on biological enzymes according to claim 1, characterized in that: The low dielectric constant filter membrane is dried at 60°C.

3. The method for preparing a low dielectric constant filter membrane based on biological enzymes according to claim 1 or 2, characterized in that: Drop the enzyme onto the dried filter membrane surface and freeze-dry for 24 hours.

4. The method for preparing a low dielectric constant filter membrane based on biological enzymes according to claim 3, characterized in that: The biological enzyme is porcine pancreatic enzyme, alcohol dehydrogenase, secondary alcohol dehydrogenase, ethanol oxidase or peroxidase.

5. The method for preparing a low dielectric constant filter membrane based on biological enzymes according to claim 3, characterized in that: The low dielectric constant filter membrane is a quartz fiber filter membrane, paraffin or molecular sieve.

6. The method for preparing a low dielectric constant filter membrane based on biological enzymes according to claim 3, characterized in that: The biological enzyme is a solution containing 2.5 g / L trypsin in a HBSS solution containing phenol red, and 20 μl to 60 μl is pipetted and dripped onto the filter membrane surface in multiple times.

7. The method for preparing a low dielectric constant filter membrane based on biological enzymes according to any one of claims 1, 2, 4-6, characterized in that: The low dielectric constant filter membrane was cut into squares of 0.9 cm×0.9 cm and then dried.

8. A low dielectric constant filter membrane based on biological enzymes, characterized in that: The low dielectric constant filter membrane is prepared using the method for preparing a biological enzyme-based low dielectric constant filter membrane as described in any one of claims 1 to 7.

9. Application of a low dielectric constant filter membrane based on biological enzyme in a waveguide gas sensor, characterized in that: After fixing the resonant plate resonant window in the waveguide gas sensor using the low dielectric constant filter membrane based on biological enzyme as claimed in claim 8, the sensor is assembled and tested.

10. The use of the low dielectric constant filter membrane based on biological enzyme in a waveguide gas sensor as claimed in claim 9, characterized in that: The waveguide cavity in the waveguide gas sensor is a rectangular waveguide cavity, a cylindrical waveguide cavity or an annular cavity.

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