CN111380846A - Portable fluorescent paper chip for detecting xanthine - Google Patents
Portable fluorescent paper chip for detecting xanthine Download PDFInfo
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- CN111380846A CN111380846A CN202010185840.5A CN202010185840A CN111380846A CN 111380846 A CN111380846 A CN 111380846A CN 202010185840 A CN202010185840 A CN 202010185840A CN 111380846 A CN111380846 A CN 111380846A
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- LRFVTYWOQMYALW-UHFFFAOYSA-N 9H-xanthine Chemical compound O=C1NC(=O)NC2=C1NC=N2 LRFVTYWOQMYALW-UHFFFAOYSA-N 0.000 title claims abstract description 84
- 229940075420 xanthine Drugs 0.000 title claims abstract description 41
- 238000001514 detection method Methods 0.000 claims abstract description 33
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000002135 nanosheet Substances 0.000 claims abstract description 20
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Inorganic materials O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000006243 chemical reaction Methods 0.000 claims abstract description 15
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 15
- 229910052799 carbon Inorganic materials 0.000 claims description 15
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 13
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- 238000004987 plasma desorption mass spectroscopy Methods 0.000 claims description 12
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- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims description 3
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- DVLFYONBTKHTER-UHFFFAOYSA-N 3-(N-morpholino)propanesulfonic acid Chemical compound OS(=O)(=O)CCCN1CCOCC1 DVLFYONBTKHTER-UHFFFAOYSA-N 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/645—Specially adapted constructive features of fluorimeters
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N2021/6417—Spectrofluorimetric devices
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
- G01N2021/6432—Quenching
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Abstract
The invention discloses a portable fluorescent paper chip for detecting xanthine, and belongs to the technical field of fluorescent sensors. The invention utilizes the excellent performance of carbon dots, covalently bonds the carbon dots on a fiber paper sheet through Schiff base reaction to construct fluorescent response Substrates (PCDs), and then MnO is added2Nanosheet (MnO)2NS) is introduced into the PCDs to make composite paper chips (PCDs/NS). Due to MnO2The introduction of NS quenches the fluorescence of PCDs, which are in an off state when encountering H2O2In time of MnO2NS is decomposed, and the fluorescence of PCDs is in an "on" state. Therefore, the fluorescent paper chips (PCDs/NS) of the present invention can be used for H2O2And H2O2Qualitative and quantitative detection of the relevant enzyme system.
Description
Technical Field
The invention belongs to the technical field of fluorescent sensors, and particularly relates to a portable fluorescent paper chip for detecting xanthine.
Background
The paper chip has the advantages of simple and convenient manufacture, low cost, small volume, light weight, convenient storage and transportation, good biocompatibility, high analysis speed and the like, thereby becoming a research hotspot in the field of analytical science and being widely applied to medical diagnosis, food safety and environmental monitoring. The porous structure of the paper enables the paper chip to have the capability of storing reagents required by analysis, and meanwhile, the paper chip can drive liquid on a paper chip channel through the capillary force of the paper chip without external power. In addition, the paper chip also has strong compatibility, and can be combined with signal reading systems such as fluorescence, colorimetry, electrochemistry, electrochemical luminescence, chemiluminescence and the like to realize the output of various detection signals on the paper chip and the construction of analysis strategies. Paper chips have shown good application prospects as a new analytical device, but at present, sensitivity and repeatability are two key factors that always restrict paper chips from developing from laboratory to clinical application. At present, a signal amplification strategy based on nano materials has proved to be one of effective ways to improve the sensitivity of the paper chip-based detection method.
Fluorescence sensing technology has made a great contribution to human health and health-related environments, and has been the subject of intense research, and researchers are constantly working on developing fluorescence sensors of different types, different detection mechanisms, and for different analytes. The paper is mainly composed of cellulose, the cellulose contains a large amount of hydroxyl (-OH) and a small amount of carboxyl (-COOH), and the groups not only reduce nonspecific adsorption, but also can be used as a bracket to crosslink required functional groups through chemical reaction. Among the types of nanomaterials, Carbon Dots (CDs) are favored by researchers because of their superior fluorescence emission properties and simple synthesis methods. The CDs have functional groups such as hydroxyl, carboxyl, amino, sulfydryl and the like on the surface, and have the advantages of low toxicity, good water solubility, good biocompatibility and the like. By controlling the preparation conditions, various types of carbon dots with different fluorescence emission properties and different surface groups can be obtained for analysis and detection, biological imaging, photocatalysis, drug delivery and the like.
Hydrogen peroxide (H)2O2) Active oxygen species, an important class of active oxygen species, are not only second messengers in cell proliferation, differentiation and migration processes, but also markers of oxidative stress. Thus, monitoring H2H produced by O-oxidase acting on different substrates2O2Not only is an important method for monitoring the hydrogen peroxide level in vivo, but also the physiological process in which a plurality of oxidases participate is monitored, and the method has important significance for clinical diagnosis. Xanthine is a purine nucleotide andthe metabolites of deoxynucleotides are present in body fluids such as blood and urine. The xanthine can be used as a marker of diseases such as hyperuricemia, xanthine urine, gout, renal failure and the like, and can also be used as a main index for evaluating the freshness of meat food, and the detection of the xanthine has important significance for clinical diagnosis and food safety. Modern analytical instruments are rapidly developed, but the resolution, sensitivity and stability of the detection methods are still to be further improved. Therefore, based on the important physiological significance of xanthine, it is very important to develop a xanthine detection method with high accuracy and strong applicability for the life health field and the food safety field.
Disclosure of Invention
The technical problem to be solved is as follows: in order to improve the sensitivity and repeatability of paper chip-based analysis, the invention designs a paper chip-based fluorescence sensor for detecting xanthine by constructing an optical system (namely, a fluorescence paper chip) on cellulose paper.
In order to achieve the purpose, the invention adopts the following technical scheme:
a fluorescent paper chip comprises cellulose paper, carbon dots are covalently bonded on the surface of the cellulose paper, and MnO is further adsorbed on the cellulose paper modified by the carbon dots2Nanosheets.
Further, the fluorescent paper chip also comprises a PDMS substrate.
The preparation method of the fluorescent paper chip comprises the following steps:
step 1, preparing carbon dots by a one-step hydrothermal method;
Further, the specific process for preparing the carbon dots in the step 1 is as follows: dissolving citric acid monohydrate in water, adding anhydrous ethylenediamine, stirring uniformly, transferring to a stainless steel reaction kettle with a polytetrafluoroethylene lining for hydrothermal reaction, and obtaining the carbon dots.
Further, the specific process of covalently bonding the carbon points on the surface of the cellulose paper in the step 2 is as follows: taking a cellulose paper sheet, firstly activating by using a hydrochloric acid solution, then oxidizing by using a periodic acid solution, and finally placing the paper sheet in a carbon dot solution for Schiff's base reaction to obtain the cellulose paper.
Further, MnO in step 32The preparation method of the nano sheet comprises the following steps: 3-morpholine propanesulfonic acid and KMnO4Dissolving in water, centrifuging after ultrasonic treatment, collecting precipitate, and cleaning with deionized water to obtain MnO2Nanosheets.
Further, the specific process in step 3 is as follows: MnO of2And mixing the aqueous dispersion of the nano-sheets with a phosphate buffer solution with the pH value of 7.00.01 mol/L, then adding cellulose paper sheets with covalently bonded carbon points, oscillating the cellulose paper sheets on a shaking table in a dark place, taking out the cellulose paper sheets, washing the cellulose paper sheets with water, and drying the cellulose paper sheets to obtain the nano-sheets.
Further, shaking table in dark place for 15-165 min.
The fluorescent paper chip is applied to hydrogen peroxide detection.
The fluorescent paper chip is applied to xanthine detection.
Further, the specific method for detecting xanthine is as follows: incubating the fluorescent paper chip with NaAc-HAc buffer solution of xanthine and xanthine oxidase to perform reaction, taking out the fluorescent paper chip, washing with NaAc-HAc buffer solution, and measuring the lambda of the fluorescent paper chip before and after reactionexThe concentration of xanthine can be calculated by fluorescence spectrum of =370 nm.
Has the advantages that: the invention utilizes the excellent performance of carbon points to covalently bond the carbon points on a fiber paper sheet through the Schiff base reaction to construct fluorescent response Substrates (PCDs), and then MnO is added2Nanosheet (MnO)2NS) is introduced into the PCDs to prepare composite fluorescent paper chips (PCDs/NS). Due to MnO2The introduction of NS quenches the fluorescence of PCDs, which are in an off state when encountering H2O2In time of MnO2NS is decomposed, and the fluorescence of PCDs is in an "on" state. Thus, the fluorescence of the inventionPhotonic paper chips (PCDs/NS) can be used for H2O2Can also be used for all the producible H2O2Such as an enzymatic reaction that produces hydrogen peroxide by reaction of an oxidase with a corresponding substrate.
H can be generated due to the enzymatic reaction from xanthine oxidase with the corresponding substrate xanthine2O2Therefore, the fluorescent paper chips (PCDs/NS) can be used for qualitative and quantitative detection of xanthine. In the quantitative detection of xanthine, the detection of xanthine by the PCDs/NS shows a good linear relation in a concentration range of 0.1-40 mu mol/L, the detection limit is 0.06 mu mol/L, and compared with most existing detection methods, the PCDs/NS has higher sensitivity.
Drawings
FIG. 1 is a schematic diagram of the preparation of carbon quantum dot modified cellulose Paper Sheets (PCDs) in example 1.
FIG. 2 is a graph showing the optimization of the oscillation time in the preparation of PCDs/NS in example 1.
FIG. 3 is a schematic diagram and a physical diagram of a PDMS plate in example 1 (see the drawing).
FIG. 4 shows examples 1 of PCDs (paper @ CDs), PCDs/NS, and PCDs/NS + H2O2(90. mu. mol/L) fluorescence spectrum.
FIG. 5 shows the use of PCDs/NS for detecting H in example 22O2Is shown in linear relationship.
FIG. 6 is a graph showing the effect of the concentration of xanthine oxidase on the fluorescence recovery effect in example 3.
FIG. 7 is a graph showing the effect of incubation time on xanthine detection in example 3.
FIG. 8 is a fluorescence spectrum of PCDs/NS in example 3 incubated with xanthine of various concentrations (xanthine concentrations: 0, 0.1, 0.5, 1, 5, 10, 15, 20, 25, 30,35, 40. mu. mol/L from bottom to top).
FIG. 9 is a graph showing the degree of fluorescence recovery of PCDs/NS versus xanthine (0.1-40. mu. mol/L) in example 3 at various concentrations of xanthine (0.1-90. mu. mol/L) (inset is a linear plot of the degree of fluorescence recovery versus xanthine (0.1-40. mu. mol/L)).
Detailed Description
The invention provides a catalyst with adsorbed MnO2The fluorescence response paper chip of the nano sheet is characterized in that MnO is absorbed after an optical system (namely, a fluorescence paper chip) is constructed on cellulose paper2And (4) nanosheet obtaining. On one hand, the paper chip has the advantages of simple structure, small volume, convenience in carrying and wide adaptability; on the other hand, the paper chip is for H2O2Has high sensitivity and can be used for H2O2And H2O2Qualitative and quantitative detection of the relevant enzyme system.
The invention utilizes the property that cellulose contains a large amount of hydroxyl (-OH), carbon points are covalently bonded on cellulose paper sheets through Schiff's base reaction to construct fluorescence response Substrates (PCDs), as shown in figure 1, specifically: firstly, hydrochloric acid is adopted to activate hydroxyl on the surface of the cellulose paper sheet so that the surface of the cellulose paper sheet contains a large amount of ortho-dihydroxy, and then periodic acid (H) is utilized5IO6) Oxidizing to form great amount of aldehyde groups on the surface of paper sheet, and final adding NaCNBH3As a reducing agent, carbon dots are grafted on the paper sheet through a Schiff base reaction to construct fluorescent response Substrates (PCDs). Then, MnO is added2Nanosheet (MnO)2NS) is introduced into the PCDs to prepare composite fluorescent paper chips (PCDs/NS). Due to MnO2The introduction of NS quenches the fluorescence of PCDs, which are in an off state when encountering H2O2In time of MnO2NS is decomposed, and the fluorescence of PCDs is in an "on" state. Therefore, the fluorescent paper chips (PCDs/NS) of the present invention can be used for H2O2Can also be used for all the producible H2O2Such as an enzymatic reaction that produces hydrogen peroxide by reaction of an oxidase with a corresponding substrate.
The following examples further illustrate the present invention but are not to be construed as limiting the invention. Modifications or substitutions to methods, procedures, or conditions of the invention may be made without departing from the spirit and scope of the invention. The experimental methods and reagents of the formulations not specified in the examples are in accordance with the conventional conditions in the art.
Whatman No.1 filter paper was used as the cellulose paper for the preparation of the paper chips in the examples of the present invention.
Example 1
1. Preparation of Carbon Dots (CDs)
Firstly, 2.630 g of citric acid monohydrate is weighed and dissolved in 25 mL of deionized water, 1256.5 mu L of anhydrous ethylenediamine is added, the mixture is stirred uniformly and then transferred to a stainless steel reaction kettle with a 50 mL volume and a polytetrafluoroethylene lining, the reaction is carried out for 6 h at the temperature of 130 ℃, and then the mixture is naturally cooled to the room temperature and kept away from light for standby at the temperature of 4 ℃.
2. Preparation of carbon Point modified cellulose Paper Sheets (PCDs)
Activation treatment: whatman No.1 filter paper was made into a circular paper sheet having a diameter of 6 mm with a punch, the circular paper sheet was placed in a glass petri dish, and treated with 0.2 mol/L HCl for 30 min. After activation, the paper sheet was washed with deionized water 3 times, 5min each time;
oxidation treatment: oxidizing the activated paper sheet with 34 mg/mL periodic acid for 2 h, and cleaning the paper sheet with deionized water for 3 times, 5min each time;
grafting CDs: mixing the oxidized paper with NaCNBH containing 40 mg/mL3The CDs solution was reacted for 8 min, and after completion, the sheet was washed with deionized water 3 times, 20 min each time, to thoroughly wash out the CDs immobilized on the paper by physical adsorption. The PCDs are dried after they are prepared and stored in a room temperature drying environment for use.
3. Preparation of portable fluorescent paper chip
3.1 MnO2Preparation of nanosheet-modified PCDs (PCDs/NS)
1 mmol of 3-morpholinopropanesulfonic acid (MOPS) and 0.1 mmol of KMnO4Dissolved in 10 mL of deionized water. After stirring uniformly, carrying out ultrasonic treatment for 30min at room temperature; centrifuging at 10000 rpm for 5min, washing the collected precipitate with deionized water for 5 times, and dispersing the precipitate into 80 mL of deionized water to obtain MnO2Nanosheet (MnO)2NS), room temperatureStanding for later use.
Placing the prepared PCDs in a 60 mm glass culture dish, and adding 5 mL MnO2NS dispersion and 5 mL phosphate buffer (0.01 mol/L, pH 7.0) were shaken on a shaker in the dark. Finally, washing the mixture for 3 times by using ultrapure water with the same amount, drying the mixture at 40 ℃ and storing the mixture at room temperature for later use.
In the invention, the fluorescence intensity of PCDs/NS prepared under different oscillation time is considered, and MnO can be judged according to the change of the fluorescence intensity2The amount of NS adsorbed. The results of the experiment are shown in FIG. 2, from which it can be seen that PCDs/NS gradually decrease with increasing oscillation time, indicating MnO2The NS adsorption quantity is gradually increased, and after 120 min, the fluorescence intensity is not changed any more, which indicates that PCDs are applied to MnO2The adsorption of NS has reached saturation, and therefore, 120 min was selected as the optimum oscillation time for the production of PCDs/NS.
3.2 preparation of PDMS substrate (PDMS plate)
The method comprises the steps of manufacturing Whatman NO.1 filter paper into a circular paper sheet with the diameter of 6 mm by a puncher without any treatment, fixing the circular paper sheet in a plastic culture dish in an arrangement mode that 6 × 2 (transverse × longitudinal) is arranged in an array by using a double-sided adhesive, stirring and mixing a prepolymer of PDMS and a cross-linking agent uniformly according to the mass ratio of 10:1, pouring the mixture into the plastic culture dish, vacuumizing the plastic culture dish to exhaust bubbles generated by stirring, then throwing glue for 18 s at the speed of 500 rpm by using a glue homogenizing machine, placing the plastic culture dish in an oven for treating for 1.5 h at the temperature of 80 ℃, cutting the plastic culture dish according to the size of 2.5 cm × 1.8.8 cm, removing a PDMS plate from the culture dish, arranging 12 circular grooves with the diameter and the thickness consistent with that of PCDs (shown in figure 3) on the PDMS plate, ultrasonically cleaning the PDMS plate for 10 min by using absolute ethyl alcohol, and drying the plate for later use at room temperature.
And placing the PCDs/NS in the circular groove of the PDMS plate to obtain the portable fluorescent paper chip.
To further confirm the successful preparation of PCDs/NS, both processes are characterized by fluorescence spectroscopy below. The results are shown in FIG. 4. The fluorescence intensity of PCDs/NS is much lower than that of PCDs, indicating MnO2NS has quenching effect on the fluorescence of CDs when addedH2O2Later, the fluorescence intensity of PCDs/NS is much higher than H2O2The addition of the former fluorescence intensity confirmed H2O2With destruction of MnO2NS capability also indicates that the paper chip can be used for H2O2And H2O2Detection of the relevant enzyme System, in the examples that follow, the enzymatic reaction of xanthine oxidase with the corresponding substrate xanthine was selected in the present invention to verify that the paper chip of the present invention can be used for H2O2And (5) detecting related enzyme systems.
Example 2
PCDs/NS for H2O2Detection of (2)
Under the condition of room temperature, PCDs/NS are mixed with H with different concentrations2O2The standard solution (1, 5, 10, 15, 20, 25, 30,35, 40, 45, 50, 60, 70, 80, 90, 100 μmol/L) was incubated with phosphate buffer (0.01 mol/L, pH 7.0) for 24 min. The results of the experiment are shown in FIG. 5, and the fluorescence recovery degree of the fluorescent paper chip is dependent on H2O2Increasing with increasing concentration, linear range of 0.5-45 μ M, linear equation of y =0.08679x +1.12599, R2=0.99174。
Thus, the fluorescent paper chip of the present invention can be used for H2O2Qualitative and quantitative detection.
Example 3
PCDs/NS for detection of xanthine
The detection method comprises the following steps: under room temperature conditions, PCDs/NS were incubated with varying concentrations of xanthine standard solutions, xanthine oxidase, and NaAc-HAc buffer (0.2 mol/L, pH 7.0) for 24min, followed by 3 washes with an equal amount of NaAc-HAc buffer and fluorescence spectroscopy (lambda. fluorescence spectroscopy) was performedex=370 nm), the fluorescence recovery ability of the xanthine solutions of different concentrations to PCDs/NS was calculated as follows.
F1And F2Respectively representing the fluorescence intensity before and after the incubation of the PCDs/NS;by F2/F1Indicating the degree of fluorescence recovery; k SV Is a constant; and c is the concentration of the xanthine solution.
1. Concentration optimization of xanthine oxidase
In the detection process of xanthine, if the concentration of enzyme is too low, the catalytic efficiency is reduced correspondingly, and in order to obtain the maximum catalytic efficiency, the catalytic effects of xanthine oxidase on xanthine of 0.04U/mL, 0.08U/mL, 0.12U/mL, 0.16U/mL, 0.2U/mL, 0.3U/mL, 0.4U/mL and 0.5U/mL are examined, respectively, and the incubation time is 24 min.
As shown in FIG. 6, it can be seen that F is increased with the increase in the concentration of xanthine oxidase2/F1The value of (A) is larger and larger, and when the value is increased to 0.2U/mL, F2/F1The value of (A) is not changed obviously any more, which shows that the catalytic efficiency of the enzyme to the substrate in the system is the highest at the moment, and the catalytic efficiency is not changed any more by increasing the concentration of the enzyme, so that the concentration of the xanthine oxidase is selected to be 0.2U/mL as the optimal experimental condition.
2. Incubation time optimization
The experiment respectively investigates the influence of the incubation time of 3 min, 6 min, 9 min, 12 min, 15 min, 18 min, 21 min, 24min, 27min, 30min and 33 min on the determination of xanthine.
The experimental result is shown in fig. 7, the fluorescence recovery degree gradually increases with the increase of the incubation time, and no obvious change occurs after 24min, which indicates that the xanthine in the system is catalyzed basically, so that 24min is selected as the incubation time for xanthine detection in the experiment.
3. Quantitative detection of xanthines
Under the optimal detection condition, the experiment examines the fluorescence response condition of PCD/NS to xanthine with different concentrations (0.1-90 mu mol/L), 3 parts of the PCD/NS is parallelly measured at each concentration, the concentration of the xanthine standard solution is subjected to a standard curve according to the fluorescence recovery degree, linear regression is carried out, and the experiment result is shown in FIG. 8. As can be seen from FIG. 8, the degree of fluorescence recovery of PCDs/NS increases with the xanthine concentration, and ranges from 0.1 to 40. mu. mol/LThe linear dependence is shown in the enclosure (FIG. 9), and the linear regression equation is (F)2/F1) -1=0.1329 c +0.2148, correlation coefficient R2=0.99705, limit of detection (LOD) 0.06 μmol/L.
From the above results, it is clear that in the quantitative detection of xanthine, the detection of xanthine by the fluorescent paper chip of the present invention exhibits a good linear relationship in the concentration range of 0.1-40. mu. mol/L, with a detection limit of 0.06. mu. mol/L, and PCDs/NS have higher sensitivity than most of the conventional detection methods.
Claims (10)
1. A fluorescent paper chip is characterized in that: comprises cellulose paper, carbon points are covalently bonded on the surface of the cellulose paper, MnO is also adsorbed on the cellulose paper modified by the carbon points2Nanosheets.
2. The fluorescent paper chip of claim 1, wherein: the fluorescent paper chip also comprises a PDMS substrate.
3. The method for preparing a fluorescent paper chip as claimed in claim 1, characterized in that: the method comprises the following steps:
step 1, preparing carbon dots by a one-step hydrothermal method;
step 2, covalently bonding carbon points on the surface of the cellulose paper;
step 3, placing the cellulose paper modified with carbon dots in MnO2And soaking and adsorbing the nano sheet dispersion liquid, taking out and fixing the nano sheet dispersion liquid on a PDMS substrate to obtain the fluorescent paper chip.
4. The production method according to claim 3, characterized in that: the specific process for preparing the carbon dots in the step 1 is as follows: dissolving citric acid monohydrate in water, adding anhydrous ethylenediamine, stirring uniformly, transferring to a stainless steel reaction kettle with a polytetrafluoroethylene lining for hydrothermal reaction, and obtaining the carbon dots.
5. The production method according to claim 3, characterized in that: the specific process of covalently bonding the carbon points on the surface of the cellulose paper in the step 2 is as follows: taking a cellulose paper sheet, firstly activating by using a hydrochloric acid solution, then oxidizing by using a periodic acid solution, and finally placing the paper sheet in a carbon dot solution for Schiff's base reaction to obtain the cellulose paper.
6. The production method according to claim 3, characterized in that: MnO in step 32The preparation method of the nano sheet comprises the following steps: 3-morpholine propanesulfonic acid and KMnO4Dissolving in water, centrifuging after ultrasonic treatment, collecting precipitate, and cleaning with deionized water to obtain MnO2Nanosheets.
7. The production method according to claim 3, characterized in that: the specific process in the step 3 is as follows: MnO of2And mixing the aqueous dispersion of the nano-sheets with a phosphate buffer solution with the pH value of 7.00.01 mol/L, then adding cellulose paper sheets with covalently bonded carbon points, oscillating the cellulose paper sheets on a shaking table in a dark place, taking out the cellulose paper sheets, washing the cellulose paper sheets with water, and drying the cellulose paper sheets to obtain the nano-sheets.
8. The method of claim 7, wherein: shaking table in dark place for 15-165 min.
9. The use of the fluorescent paper chip of claim 1 in hydrogen peroxide detection.
10. The use of the fluorescent paper chip of claim 1 in the detection of xanthine.
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