MoS2-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor and preparation method and application thereofTechnical Field
The invention belongs to the technical field of functional nano materials and electrochemistry, and particularly relates to a MoS2-ZnO nanocomposite germicidalMaterials, electrochemical impedance non-enzymatic bacterial sensors, and methods of making and using the same.
Background
In the present society, harm caused by pathogenic bacteria is proved for countless times, bacterial infection is the most common part of clinical infectious diseases in the present medicine, and the high-efficiency and simple detection of bacteria is the first step for controlling bacteria.
Since 1676 years of microscopic observation of a single microorganism, the monitoring of bacteria has become a persistent subject faced by scientists, but the existing bacteria detection means such as plate method, enzyme-linked immunosorbent assay and the like either need a long-time enrichment and purification process, or need expensive instruments and professional operations, or only can detect bacteria which are thoroughly researched, have high detection threshold and high cost, and are difficult to popularize in wider use scenes, and meanwhile, the detection technology is generally single in function, and needs a quicker, more accurate and more convenient detection method in actual detection.
In the field of biochemistry, electrochemical analysis has the advantages of high sensitivity, fast response, good selectivity, convenient operation, low instrument cost and the like, and attracts the common attention of researchers. Therefore, the development of a simple and sensitive sensor for detecting bacteria is a great trend in the field of bacteria detection.
However, most of the common bacterial electrochemical sensors at present need the participation of bioactive substances such as antibodies, enzymes and the like, the experimental process is complex, the limitation of the existing biotechnology is limited, the cost for purifying and separating the bioactive substances is high, and the test cost is greatly increased.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a MoS2the-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor and the preparation method and application thereof have the dual functions of resisting bacteria and detecting bacteria for gram-positive bacteria, and have the advantages of low cost, low construction difficulty, simple operation and easy storage.
In order to achieve the purpose, the invention adopts the following technical scheme:
MoS2The preparation method of the-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor comprises the following steps:
step one, mixing a molybdenum source and a sulfur source according to the mass ratio of 3:7, dissolving the mixture in deionized water, performing ultrasonic dispersion, transferring the mixture to a polytetrafluoroethylene lining, filling the polytetrafluoroethylene lining into a hydrothermal kettle, putting the hydrothermal kettle into an oven, performing hydrothermal reaction at the temperature of 200-240 ℃ for 20-24 hours, naturally cooling after the reaction is finished, centrifuging, washing and drying to prepare the MoS2Nanosheets;
step two, weighing zinc acetate and MoS accounting for 2-3% of zinc acetate by mass2Dispersing the nanosheets in ethanol, uniformly stirring, condensing and refluxing for 1-3 h at 60-100 ℃, and preparing the zinc acetate-MoS with the mass concentration of 10-20%2A nanosheet solution;
dropwise adding 0.03g/L LiOH-ethanol solution while stirring, continuously stirring for 20-50 min after titration, adding deionized water, stirring, standing for 5-20 min, pouring out supernatant, washing with a lotion, centrifuging, and drying to obtain MoS2-ZnO nanocomposite bactericidal material;
wherein, the addition amount of LiOH-ethanol solution and zinc acetate-MoS2The volume ratio of the nanosheet mixed solution to the deionized water is 1:1: 1.5;
step three, MoS is weighed2Adding deionized water into a round-bottom centrifuge tube made of the ZnO nano composite antibacterial material, injecting the deionized water into a nafion solution injection tube accounting for 4-8% of the volume fraction of the mixed solution, and performing ultrasonic treatment to uniformly disperse the solution to obtain an electrode modification solution; wherein MoS2The concentration of the-ZnO nano composite antibacterial material is 3-6 g/L;
step four, transferring 4-8 mu L of electrode modification liquid by using a liquid transfer gun, and dripping the electrode modification liquid on the surface of the pretreated glassy carbon electrode to obtain MoS2-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor.
Preferably, the molybdenum source is one or more of ammonium molybdate, sodium molybdate, molybdenum trioxide or molybdenum hexacarbonyl;
the sulfur source is thiourea or L-cysteine.
Preferably, the filling ratio of the polytetrafluoroethylene lining in the step one is 40-60%.
Preferably, the ultrasonic dispersion is to place the mixed solution in an ultrasonic cleaner for 5-10 min by ultrasonic treatment.
Preferably, the washing and centrifuging are performed repeatedly and repeatedly at 6000-8000 rpm for 5 times by using alcohol water.
Preferably, the drying is to place the sample in an oven at 50 ℃.
The invention also provides the MoS prepared by the method2-ZnO nanocomposite antibacterial-electrochemical impedance non-enzymatic bacterial sensor, said MoS2The ZnO nano composite material monomers are connected and alternately grown to form an intricate and porous island-shaped network, and ZnO nano particles uniformly grow on the sheet-shaped stacked MoS2The above.
Preferably, the antibacterial and bacteria detecting double functions are achieved.
The invention also protects the MoS2Application of-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor in gram-positive bacteria detection.
Preferably, MoS is2the-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor adopts an electrochemical impedance method to detect the bacteria in 5.0mmol/L (1:1) K in PBS as a solvent3[Fe(CN)6]-K4[Fe(CN)6]And EIS signal response effect in 0.1mol/L KCl electrolyte.
Compared with the prior art, the invention has the following technical effects:
MoS in the invention2MoS of-ZnO nanocomposites2The antibacterial agent has the characteristics of large specific surface area, a large number of active sites, high stability, biocompatibility, broad-spectrum and efficient antibacterial activity, difficulty in generating drug-resistant strains and the like; the nano zinc oxide is one of the most studied inorganic nano antibacterial agents, and the sterilization mechanism mainly comprises that Zn ions are released to destroy the structure and the physiological activity of thalli, the Zn ions interact with the surface of bacteria to destroy cell walls, and active oxygen ROS with the sterilization effect is induced and generated in cells; meanwhile, the nano zinc oxide has good biocompatibilitySex and higher biological activity, immunoregulation ability and high absorption rate; the gram-positive bacteria have a thick peptidoglycan multilayer network macromolecular structure, have certain viscosity and are easy to be firmly combined with a nano plane, and the MoS used by the invention2The ZnO nano composite material has a relatively large and uniform surface, is easy to combine with a peptidoglycan structure, achieves the purpose of detecting bacteria through the interaction of the nano material and the bacteria and the linear relation between an electrochemical impedance signal and the concentration of the bacteria, generates active oxygen through the molybdenum disulfide and the nano zinc oxide together to play an antibacterial role, and has double functions of efficiently sterilizing and detecting the bacteria;
the zinc oxide-loaded molybdenum disulfide antibacterial nano composite material has a certain detection effect on bacterial liquids with different concentrations under the conditions that the incubation time is more than 30min and the pH is 7.0-7.5;
MoS prepared by the invention2The bacterial electrochemical sensor constructed by the ZnO nano composite material does not need bioactive substances such as enzyme, antibody and the like, and has the advantages of low cost, low construction difficulty, simple operation and easy storage;
the invention provides certain application value and reference value for further exploring the field of bacteria detection of nano antibacterial materials in the electrochemical biosensor as basic research.
Drawings
FIG. 1 shows ZnO nanoparticles and different MoS2Addition amount of MoS2-X-ray powder diffraction pattern of ZnO nanocomposite;
FIG. 2 shows MoS2X-ray powder diffraction pattern of (a);
FIG. 3 is the synthesis of MoS in example 12The TEM image of the 100nm transmission electron microscope;
FIG. 4 shows the synthesis of MoS in example 12The 10nm transmission electron microscope TEM picture;
FIG. 5 is a diffraction lattice diagram of the selected area of FIG. 4;
FIG. 6 shows MoS in example 12-Scanning Electron Microscope (SEM) photographs of ZnO nanocomposites;
FIG. 7 is a blank control group of Staphylococcus aureus;
FIG. 8 is a photograph showing the growth of Staphylococcus aureus treated with ZnO nanoparticles;
FIG. 9 shows MoS in example 12A picture of the growth condition of staphylococcus aureus after the nanosheet treatment;
FIG. 10 shows the MoS obtained in example 22-a picture of the growth of staphylococcus aureus after being treated by the ZnO nano composite antibacterial material;
FIG. 11 shows the MoS obtained in example 32-a picture of the growth of staphylococcus aureus after being treated by the ZnO nano composite antibacterial material;
FIG. 12 shows the MoS obtained in example 12-a picture of the growth of staphylococcus aureus after being treated by the ZnO nano composite antibacterial material;
FIG. 13 is an impedance profile of the modified electrode after incubation with the same concentration of bacteria for different periods of time;
FIGS. 14 and 15 are impedance maps of bacteria solutions with different concentrations and incubation time of 30 min;
FIG. 16 shows MoS2Schematic diagram of preparation process of-ZnO nano composite antibacterial-electrochemical impedance non-enzyme bacteria sensor.
Detailed Description
The present invention will be explained in further detail with reference to examples.
Example 1
Firstly, mixing ammonium molybdate and L-cysteine according to the mass ratio of 3:7, dissolving the mixture in 50ml of deionized water, placing the mixture in an ultrasonic cleaner for ultrasonic treatment for 5min, transferring the mixture to a polytetrafluoroethylene lining, placing the lining into a hydrothermal kettle with the filling ratio of 50%, placing the kettle into an oven, carrying out hydrothermal reaction for 22h at 220 ℃, naturally cooling after the reaction is finished, repeatedly centrifuging and washing the mixture for 5 times at 6000rpm alternately by using alcohol water, placing the mixture in the oven at 50 ℃ for drying, and preparing MoS2Nanosheets;
step two, weighing zinc acetate and MoS prepared in step one and accounting for 3% of zinc acetate by mass2Dispersing 1g of nano-sheets in 100ml of ethanol, uniformly stirring, condensing and refluxing at 80 ℃ for 2h, dropwise adding 100ml of LiOH-ethanol solution while stirring, and continuously stirring for 30min after the titrationAdding 150ml of deionized water, stirring, standing for 10min, pouring out supernatant, repeatedly centrifuging at 6000rpm with alcohol-water alternately, washing for 5 times, and oven drying at 50 deg.C to obtain MoS2-ZnO nanocomposite bactericidal material;
step three, weighing 4mg MoS2Putting the ZnO nano composite antibacterial material in a 1.5mL round-bottom centrifuge tube, injecting 1mL deionized water and 60 mu L nafion solution into the centrifuge tube, and putting the centrifuge tube in an ultrasonic cleaner for 5min to uniformly disperse the deionized water and the nafion solution to obtain an electrode modification solution; wherein MoS2The concentration of the-ZnO nano composite antibacterial material is 4 g/L;
step four, transferring 6 mu L of electrode modification liquid by using a liquid transfer gun, and dripping the electrode modification liquid on the surface of the pretreated glassy carbon electrode to obtain MoS2-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor.
Example 2
Step one, mixing and dissolving sodium molybdate and thiourea according to the mass ratio of 3:7 in 50ml of deionized water, placing the mixture in an ultrasonic cleaner for ultrasonic treatment for 8min, transferring the mixture to a polytetrafluoroethylene lining, placing the polytetrafluoroethylene lining into a hydrothermal kettle with the filling ratio of 40%, placing the polytetrafluoroethylene lining into an oven, carrying out hydrothermal reaction for 24h at 200 ℃, naturally cooling after the reaction is finished, repeatedly centrifuging and washing the mixture for 5 times at 7000rpm alternately by using alcohol water, placing the mixture in the oven at 50 ℃ for drying, and preparing the MoS2Nanosheets;
step two, weighing zinc acetate and MoS prepared in step one and accounting for 2% of zinc acetate by mass2Dispersing 1.5g of nano sheets in 100ml of ethanol, uniformly stirring, condensing and refluxing at 60 ℃ for 3 hours, dropwise adding 100ml of LiOH-ethanol solution while stirring, continuously stirring for 20min after titration, adding 150ml of deionized water, stirring, standing for 5min, pouring out supernatant, repeatedly centrifuging and washing 5 times at 7000rpm by using alcohol water alternately, drying in a 50 ℃ oven to obtain MoS2-ZnO nanocomposite bactericidal material;
step three, weighing 3mg MoS2Putting the ZnO nano composite antibacterial material in a 1.5mL round-bottom centrifuge tube, then taking deionized water and 40 mu L nafion solution to inject into the tube, and putting the tube in an ultrasonic cleaner for ultrasonic treatment for 8min to uniformly disperse the solution to obtain an electrode modification solution; wherein MoS2The concentration of the-ZnO nano composite antibacterial material is 3 g/L;
step four, transferring 4 mu L of electrode modification liquid by using a liquid transfer gun, and dripping the electrode modification liquid on the surface of the pretreated glassy carbon electrode to obtain MoS2-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor.
Example 3
Step one, mixing molybdenum trioxide and L-cysteine according to the mass ratio of 3:7, dissolving the mixture in 50ml of deionized water, placing the mixture in an ultrasonic cleaning instrument for ultrasonic treatment for 10min, transferring the mixture into a polytetrafluoroethylene lining, placing the lining into a hydrothermal kettle, placing the kettle into an oven with the filling ratio of 60%, performing hydrothermal reaction for 20h at 240 ℃, naturally cooling after the reaction is finished, repeatedly centrifuging and washing the mixture for 5 times at 8000rpm by using alcohol water alternately, placing the mixture in the oven at 50 ℃ for drying, and preparing the MoS2Nanosheets;
step two, weighing zinc acetate and MoS prepared in step one and accounting for 2.5 mass percent of zinc acetate2Dispersing 2g of nano sheets in 100ml of ethanol, uniformly stirring, condensing and refluxing at 100 ℃ for 1h, dropwise adding 100ml of LiOH-ethanol solution while stirring, continuously stirring for 50min after titration, adding 150ml of deionized water, stirring, standing for 20min, pouring out supernatant, repeatedly centrifuging and washing 5 times by using alcohol water alternately at 8000rpm, drying in a 50 ℃ oven to obtain MoS2-ZnO nanocomposite bactericidal material;
step three, weighing 6mg MoS2Putting the ZnO nano composite antibacterial material in a 1.5mL round-bottom centrifuge tube, then taking deionized water and 80 mu L of nafion solution, injecting into the tube, and putting into an ultrasonic cleaner for ultrasonic treatment for 10min to uniformly disperse the deionized water and the nafion solution to obtain an electrode modification solution; wherein MoS2The concentration of the-ZnO nano composite antibacterial material is 6 g/L;
step four, transferring 8 mu L of electrode modification liquid by using a liquid transfer gun, and dripping the electrode modification liquid on the surface of the pretreated glassy carbon electrode to obtain MoS2-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor.
FIG. 1 shows different MoS2Addition amount of MoS2-X-ray powder diffraction (XRD) pattern of ZnO nanocomposite. The XRD spectrum result shows that the peak position of the XRD spectrum of the composite material is in accordance with the ZnO standardCard correspondence with MoS2The ZnO peak intensity gradually decreases with increasing introduction amount, and FIG. 2 shows MoS2XRD pattern, MoS of nanosheet2The (002), (2 θ ═ 14 °) diffraction peaks of the hexagonal crystal were shifted, the diffraction peaks at 2 θ ═ 32 °, 34 °, and 57 ° corresponded to (100) (102) (110) (2H phase), respectively, and MoS was observed2MoS is known because the diffraction peaks of the nanosheets are weak as a whole2The crystallinity is poor, the XRD peak is covered by the ZnO peak, and the XRD spectrum is not obvious. Thus, MoS2Need to be verified by other means such as SEM.
FIGS. 3 to 6 show the MoS synthesized in this experiment2The Transmission Electron Microscope (TEM) photo shows that the molybdenum disulfide nanosheet prepared by the experiment has thinner lamella and fewer edge layers, is formed by assembling and stacking a plurality of molybdenum disulfide monolayers, and has the interlayer spacing of about 0.63nm corresponding to the hexagonal MoS2The (002) crystal face of the crystal has clear crystal lattice stripes. TEM results were processed with Digital Micrograph software to obtain Selected Area Electron Diffraction (SAED) patterns, which can be seen in FIG. 5, MoS2The crystallinity of the nanosheets ranges from polycrystalline to amorphous, and is poor.
For the prepared MoS2The antibacterial performance of the-ZnO nanocomposite is studied, and a sample is dispersed in PBS buffer solution to 4mg/mL and irradiated under an ultraviolet lamp. 1mL of the suspension was diluted with sterilized PBS buffer until the absorbance (OD) was 0.03. And (3) putting 1mL of diluted bacterial suspension into a 5mL centrifuge tube, adding 1mL of sample into the centrifuge tube, and placing the centrifuge tube into a constant-temperature water bath oscillator at 37 ℃ and the rotating speed of 150r/min to oscillate for 16-20 h to obtain the flat antibacterial experimental bacterial suspension. Pouring the sterilized D-mannitol sodium chloride agar culture medium into a sterilized culture dish, wherein the volume of the culture dish is about one half of that of the culture dish, naturally cooling the culture dish in a super clean bench under ultraviolet irradiation, sucking 50 mu L of the shaken bacterial suspension, inoculating the bacterial suspension onto the solidified culture medium, and respectively and uniformly coating the bacterial suspension by using a sterile coating rod. Placing the coated culture dish and the blank control culture dish without the sample into a constant temperature and humidity box at 37 ℃ for 48-72 h, taking out the culture dishes, taking a colony photo of each culture dish, and as shown in figure 12, showing MoS2When the mass fraction is 3 percent,compared with ZnO nanoparticles shown in figure 8 and MoS2 nanosheet shown in figure 9, the antibacterial effect of the composite material is obviously improved;
MoS prepared in example 12the-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor adopts an alternating current impedance method to detect an impedance spectrogram of the sensor after the sensor is incubated in bacterial liquids with different concentrations for different times. FIG. 13 is an impedance spectrum of the modified electrode in the same concentration of bacterial solution before and after different incubation times. The staphylococcus aureus is adsorbed on the surface of the sensor, and the electronic shielding effect of the cell membrane can cause the interface to change, thereby generating the change of an impedance map, RctIt is interface electron transfer resistance, and the electron shielding effect of the biological membrane becomes stronger along with the capture of bacteria, so RctObvious change can be generated, and the change Delta R of the interface charge transfer resistance is obtained by comparisonctThereby realizing the detection of the staphylococcus aureus.
The half-circle evident in the Nyquist plot (Nyquist) shown in fig. 13 corresponds to the reaction resistance of the working electrode, as can be seen from the plot, with MoS2The incubation time of the ZnO nano composite antibacterial material modified electrode in a bacterial solution with the absorbance of about 0.06 is increased, and the arc of the high-intermediate frequency region represents that the charge transfer impedance of the electrode related to the Faraday reaction is also increased in a generally linear manner, because more and more Staphylococcus aureus is captured to the surface of the sensor along with the increase of time, the cell membrane of bacteria has an electronic shielding effect and obstructs the transfer of a redox couple, so that the interface conduction resistance is increased, namely, the EIS can be timely and effectively changed correspondingly along with the increase of the concentration of bacteria adsorbed to the electrode, so that the electronic conduction speed of the surface of the sensor and an electroactive substance is reflected. Thus, R in this experimentctThe size of (d) is correlated with the concentration of the bacteria. The impedance data were further fitted with ZSimDemo software, and a fitting circuit Rs (crq (rw)) was used to observe the specific relationship between the impedance change and the concentration, where the square points in the impedance plot represent the raw data, and the circular points correspond to the fitted data, respectively. As can be seen from the good overlapping relationship, the fitted circuit is more consistent with the experimental result. Estimating the dynamics of an electrode process by means of an analog circuitThe learning mechanism is consistent with the guess. Preferably, when the incubation time is more than 30min, the impedance signal is linear;
FIGS. 14 and 15 are impedance profiles of bacteria solutions of different concentrations with incubation time of 30 min. It can be seen that when the culture medium is incubated for 30min, the linear correlation degree of the impedance signal and the bacterial liquid concentration is good, and the impedance signal and the fitting circuit also show a good overlapping relation. Illustrating the MoS prepared by the invention2the-ZnO nano composite antibacterial-electrochemical impedance non-enzymatic bacterial sensor shows a certain detection effect on bacterial liquids with different concentrations under the conditions that the incubation time is 30min and the pH value is 7.3-7.4, and provides a certain reference value for further exploring a nano antibacterial material in the field of detecting bacteria by an electrochemical biosensor as a basic research.