CN110937595B - Method for preparing polypeptide-graphene composite material by utilizing silk fibroin oligopeptide water phase to strip graphite and application of polypeptide-graphene composite material - Google Patents
Method for preparing polypeptide-graphene composite material by utilizing silk fibroin oligopeptide water phase to strip graphite and application of polypeptide-graphene composite material Download PDFInfo
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Abstract
The invention discloses a method for preparing a polypeptide-graphene composite material by utilizing silk fibroin oligopeptide water-phase stripping graphite and application thereof, and the method comprises the following specific steps: weighing silk fibroin oligopeptide powder, dissolving with a water solution with the pH value of 8.0, and preparing silk fibroin oligopeptide solutions with different concentrations; weighing 0.5mg of graphite powder by a balance, putting the graphite powder into a small bottle, and adding 2ml of fibroin oligopeptide solution into the small bottle filled with the graphite powder by a pipette; performing water bath ultrasound; centrifuging and taking out supernatant after ultrasonic treatment; adding the supernatant into a new centrifugal tube for secondary centrifugation; and adding the remained precipitate into a water solution with the pH of 8.0, and dissolving the precipitate to obtain the fibroin oligopeptide-graphene nano composite material solution. According to the invention, the amphiphilicity of the fibroin polypeptide is utilized, the graphene is prepared by stripping graphite, and the hydrophobic graphene is endowed with better hydrophilicity, so that the obtained composite material is stably dispersed in an aqueous solution, has good biocompatibility and is suitable for hydrophobic drug delivery.
Description
Technical Field
The invention relates to the technical field of graphene composite material preparation, in particular to a method for preparing a polypeptide-graphene composite material by utilizing fibroin oligopeptide water-phase stripping graphite and application thereof.
Background
The graphene-based nanomaterial has unique electrical, mechanical, optical and electrochemical properties, and has various structures and chemical properties; this expands their biomedical applications, from biosensors and imaging to tissue engineering scaffolds to drug and gene delivery for cancer therapy. However, the most common synthetic methods do not appear to be able to directly produce biocompatible and water-dispersible graphene for biomedical applications.
China is the hometown of natural silk, has found and used silk for thousands of years and is the origin of reeling technology. The silk is a natural animal protein fiber, has bright luster and soft texture, is mainly used for manufacturing clothes for a long time, and is popular. Since the research on the new application of silk in 1993 japan, the research on new functions and new applications of silk protein began. The fibroin is a natural product extracted from the silk, has high biological activity, good biocompatibility and lower extraction cost, and has good application prospect.
Graphene has many excellent physicochemical properties, but its relatively low biocompatibility and water dispersibility limit its application in biological, medical and wearable fields. The silk and the products thereof still have the defects of easy wrinkling, no wear resistance, easy fading and yellowing, poor antibacterial and ultraviolet resistance in the using process.
In recent years, researchers are constantly searching for new preparation methods of graphene, for example, in patent CN109036868 a, graphene oxide is used for preparing graphene by stripping assistance, and graphene oxide is used as a raw material of a dispersing agent and a composite material, so that the method is simple, easy and nontoxic, and convenient for post-treatment, but the prepared composite material still has the defects of the graphene material, such as low water dispersibility, poor biocompatibility and limited application. The patent CN 108383114A uses conjugated ionic liquid to assist stripping of graphite to prepare graphene, the process is simple, the cost is low, the stripping effect on graphite is good, the size of the prepared graphene is large, the number of layers is small, and the number of defects is small, but the temperature required by the reaction of the conjugated ionic liquid is high, the reaction is severe, and the later-stage separation preparation time on graphite is long.
In order to expand the application range of the two materials, some researchers also begin to research novel materials with physical and chemical characteristics of graphene and silk fibroin. For example, liang Yanbing, li Linhao and others, they have used silk fibroin and graphene to construct composite thin film biomaterials by vacuum filtration technology. Some researchers also feed silkworms with graphene or graphene oxide by various methods, so that the silk produced by the silkworms is modified and has some characteristics of the graphene. 5363 the method of Liang Yanbing, etc. is complicated in process, requires a lot of reagents, and is not easy to operate; the experimental process of the feeding method has too many influencing factors which are not well controlled. How to find a simple and convenient method for obtaining the composite material of the fibroin and the graphene is a considerable problem.
Heretofore, zhang Lei et al (Nanoscale 11.6 (2019): 2999-3012.) successfully exfoliate graphite by artificially designing synthetic peptides, and they mixed the designed peptide chain with graphene and obtained peptide-graphene nanomaterials by means of ultrasound assistance. A cyclic mechanism of peptide molecule stripping and functionalized graphene is proposed through research, the mechanism is divided into 5 steps, and in the first step, graphite is contacted with peptide. The slight positive charge at the hydrogen end edge of the graphite comes from the weak acidity of the C-H bond, so the C-H/pi interaction between the graphite edge and the histidine of the fibroin oligopeptide occurs, very similar to a weak hydrogen bond. In the second step, the histidine in each peptide molecule interacts with the sp2 carbon of the graphite through pi-pi stacking. In the third step, these interactions (i.e. hydrogen bonding, pi-pi stacking) facilitate the assembly of peptides on the outer surface of the graphite. At the end of this step, the graphite flakes are coated with an interconnected porous microstructure of peptide molecules. In the fourth step, the work of adhesion between the assembled porous microstructure and the graphite becomes sufficiently high, which, together with the ultrasonic assistance, leads to exfoliation of the graphite layer. During exfoliation, it is helpful for more peptide molecules to penetrate into the spaces between the graphite layers, where they will subsequently adsorb in the interstices of the graphite and surface assist assembly. The first step then starts again, followed by the second and third steps. Since the silk fibroin oligopeptide peptide molecules are much smaller than DNA and protein, graphitic layers (assuming a spacing of 0.37 nm) can be easily inserted to achieve a more efficient exfoliation and functionalization process. Baati et al (Advanced Functional Materials,2012,22 (19): 4009-4015.) reported that inter-chain contribution of hexa-histidine peptides to beta-sheet formation would enhance peptide stability and self-assembly, facilitating insertion of peptide molecules into graphitic layers. In the fifth step, few-layer graphene nanoplatelets are exfoliated and the entire cycle is repeated until peptide-functionalized few-layer graphene nanoplatelets are obtained.
In summary, the prior art still has some defects, although the preparation of graphene is simplified, the application of the obtained graphene in biomedicine still has certain limitations; the novel graphene fibroin material has the advantages of long feeding time, simple preparation process and more uncontrollable factors; the graphene is stripped by the aid of the polypeptide, the polypeptide needs to be designed, early preparation work is complex, and cost is relatively high. Therefore, the development of the graphene composite material which is simple and convenient to operate, green and pollution-free, low in cost and good in biological performance has great significance.
Disclosure of Invention
Aiming at the defects that graphene prepared by existing graphene is poor in biological performance, the graphene composite material preparation technology is complex to operate, the cost is high and the like, the invention provides a method for preparing a polypeptide-graphene composite material by utilizing fibroin oligopeptide water phase to strip graphite and application thereof.
In order to solve the problems of the prior art, the invention adopts the technical scheme that:
a method for preparing a polypeptide-graphene composite material by stripping graphite from silk fibroin oligopeptide water phase comprises the following steps:
Cleaning silkworm cocoon, and cutting into pieces of 0.5-1.5cm 2 Then according to the bath ratio of 1:200 by soaking in 0.5% of Na 2 CO 3 Degumming in the solution at 100 deg.C for 30-60 min, filtering, cleaning, and repeating degumming and filtering for 2-3 times; drying the degummed silk according to a bath ratio of 1:30 amount is set to 50% by mass of CaCl 2 In the solution, water bath reaction is carried out for 40 to 60 minutes at a temperature of between 80 and 98 ℃, and stirring is continuously carried out in the reaction process; centrifuging the dissolved mixed solution at 1000-3500rpm for 15-60min, collecting supernatant, loading into dialysis bag with molecular weight cutoff of 8000-14000Da, dialyzing with flowing water for 1-2d,dialyzing with distilled water for 1-2 days, concentrating in 10% polyethylene glycol solution, and freeze drying to obtain fibroin powder;
carrying out water bath reaction on silk fibroin and alkaline protease at 60 ℃, wherein the pH value of a reaction system is maintained at 8.5 in the reaction process; boiling for 10-20min after the reaction is finished to inactivate the enzyme; naturally cooling, centrifuging the reaction system at 10000-15000rpm for 15-30min, removing enzyme protein and incompletely hydrolyzed silk protein, collecting supernatant, and concentrating to obtain crude product of silk peptide; the solid-liquid ratio of the silk fibroin peptide crude product to 8600U of actinomycete enzyme is 100:1, performing enzymolysis at 50-60 ℃ and pH8.5 for 60-80min to obtain a fibroin enzymolysis solution; dialyzing the fibroin enzymolysis solution with dialysis bag flowing water with cut-off molecular weight below 1500Da for 2-3 days to obtain fibroin enzymolysis oligopeptide solution, and freeze-drying at ultralow temperature of-80 deg.C to obtain fibroin oligopeptide powder;
dissolving fibroin oligopeptide powder in a solution obtained by adjusting water to pH of 8.0 with sodium hydroxide to obtain a 10.0mg/ml fibroin oligopeptide solution;
step 4, placing the unbound fibroin oligopeptide-graphite mixture into an ultrasonic water bath kettle for ultrasonic treatment for more than 4 hours at the temperature of 20-30 ℃;
and 6, putting the supernatant into a new centrifugal tube, centrifuging, removing the peptide attached to the graphite, removing the supernatant, retaining the precipitate, and drying to obtain the polypeptide-graphene composite material.
The silk fibroin oligopeptide solution in the step 2 is 1.0mg/ml as a modification.
The improvement is that in the step 5, the centrifugal speed is 800-1600rpm, the centrifugal time is more than 50min, the large graphite particles which are not peeled cannot be completely removed due to too low centrifugal speed or too short centrifugal time, and the composite material which is prepared can be centrifuged due to too high centrifugal speed, so that the following experiment is affected.
The improvement is that in the step 6, the centrifugal speed is 10000-15000rpm, the centrifugal time is more than 50min, the composite material prepared cannot be completely centrifuged due to too low centrifugal speed or too short centrifugal time, and the fibroin oligopeptide which is not combined with graphite is centrifuged due to too high centrifugal speed, so that the preparation of the composite material aqueous solution and the subsequent characterization experiment are influenced.
The application of the polypeptide-graphene composite material in hydrophobic drug delivery, such as the delivery of hydrophobic anticancer drug ellipticine, namely, the drug is transmitted from the outside of a cell membrane to the inside of the cell membrane, so that the absorption and the drug effect are promoted.
Has the advantages that: compared with the prior art, the invention has the advantages that:
1. compared with the traditional methods such as a mechanical stripping method, a chemical precipitation method and the like for preparing graphene, the method 1) is simple and easy to operate, and polypeptide and graphite can be mixed by a one-step method; 2) Ultrasonic stripping is carried out in the water phase, no chemical reagent is added, and no pollution is caused; 3) The stripping can be completed in a short time to obtain a graphene compound;
2. the fibroin oligopeptide is used as an auxiliary stripping agent, the natural product is extracted from silk, the cost is lower than that of other artificially synthesized polypeptides, the fibroin oligopeptide-graphene nano composite material does not have biotoxicity, and the biocompatibility is good, so that the safety guarantee is provided for the application of the fibroin oligopeptide-graphene nano composite material to biomedicine;
3. compared with the traditional feeding method of a graphene fibroin new material, the method adopting ultrasonic-assisted stripping has the advantages of simple and convenient operation, short preparation time and controllable factors, and provides technical support for industrialization;
4. the fibroin oligopeptide-graphene nanocomposite prepared by the method has good biocompatibility and good hydrophilicity, can be stably dispersed in an aqueous solution, has the size of less than 500nm, and is expected to be applied to biomedicine.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a diagram of the stripping process and mechanism of the present invention;
fig. 3 is a photograph of an aqueous solution of the polypeptide-graphene composite material prepared in embodiment 1 and embodiment 3 of the present invention, where a is an aqueous solution of the polypeptide-graphene composite material prepared from the silk fibroin oligopeptide solutions with different concentrations used in embodiment 1, and B is an aqueous solution of the polypeptide-graphene composite material prepared from the silk fibroin oligopeptide solutions with different concentrations used in embodiment 3;
fig. 4 is an ultraviolet absorption spectrum of the silk fibroin oligopeptide-graphene nanocomposite prepared in example 1 of the present invention, wherein (a) is an ultraviolet absorption spectrum of the composite, and (b) is an analytical statistical chart;
fig. 5 is a scanning electron microscope image of the fibroin oligopeptide-graphene nanocomposite prepared in example 1 of the present invention, wherein a and B are scanning electron microscope images of a fibroin oligopeptide solution of 1.0mg/ml, and coordinatographs of a polypeptide-graphene composite prepared by exfoliating graphite from a fibroin oligopeptide solution of 1 μm and 100nm, and c and D are 1.0mg/ml, and the coordinatographs are scanning electron microscope images of 1 μm and 200nm, respectively.
Detailed Description
The present invention is further illustrated by the following examples, but the scope of the invention is not limited thereto but by the description of the invention and the claims.
Example 1
The process flow of the invention is shown in figure 1, and the method for preparing the polypeptide-graphene composite material by stripping graphite from silk fibroin oligopeptide water phase comprises the following steps:
(1) Preparing a fibroin oligopeptide solution: cleaning silkworm cocoon, and cutting into pieces of 1cm 2 . Soaking the cut silkworm cocoon in 0.5% 2 CO 3 In the solution, degumming is carried out for 30 minutes at 100 ℃ (bath ratio is 1. Drying the cleaned degummed silk, and placing the degummed silk in a position with the mass fraction of 50 percentCaCl 2 In the solution, the mixture was stirred in a water bath at 98 ℃ for 40min (bath ratio 1. The dissolved solution was centrifuged at 3500rpm for 15min. Collecting supernatant, loading into dialysis bag with cut-off molecular weight of 8000-14000Da, dialyzing with running water for 1d, and dialyzing with distilled water for 1d. Then putting the mixture into a polyethylene glycol solution with the mass fraction of 10% for concentration. And (3) freeze-drying the concentrated silk fibroin solution to obtain silk fibroin powder.
Taking alkaline protease as degrading enzyme, reacting fibroin with a certain concentration with an enzyme preparation in a constant-temperature water bath kettle (60 ℃), continuously adding 1mol/l NaOH to maintain the pH value of a reaction system to be 8.5, stopping a hydrolysis reaction, and boiling for 10min to inactivate the enzyme. After cooling, the enzymolysis liquid is centrifuged for 15min at 15000rpm, the enzyme protein and the incompletely hydrolyzed silk fibroin are removed, the supernatant is taken and concentrated to obtain a crude product of the silk fibroin peptide. According to the solid-liquid mass of 100:1, mixing the low molecular weight fibroin solution after the enzymolysis of the alkaline protease or the crude product of the fibroin peptide with actinomycete enzyme (8600U), and carrying out enzymolysis at 60 ℃ at the pH of 8.5 for 60min to obtain the fibroin enzymolysis solution. Dialyzing with flowing water of dialysis bag with cut-off molecular weight below 1500Da for 2-3 days to obtain fibroin enzymolysis oligopeptide solution. Freeze-drying at ultralow temperature (-80 deg.C) to obtain fibroin oligopeptide powder.
Weighing 5g of silk fibroin oligopeptide powder, dissolving in 500ml, and dissolving with a solution of which the pH is 8.0 by adjusting water with sodium hydroxide to obtain a 10.0mg/ml silk fibroin oligopeptide solution;
(2) The different concentrations were adjusted by adding a solution of water adjusted to pH8.0 with sodium hydroxide, in the range of 0-2.5mg/ml. As shown in fig. 3B, fibroin oligopeptide solutions with different concentrations are prepared into a polypeptide-graphene compound through the processes of ultrasound-centrifugation and the like described in the patent for color comparison, and the solution prepared at 1.0mg/ml has the deepest color, namely the most dissolved graphene; and ultraviolet absorption spectrum analysis shown in fig. 4 finds that the polypeptide-graphene absorption peak prepared from 1.0mg/ml silk fibroin oligopeptide is the highest, we conclude that the silk fibroin oligopeptide solution with the concentration of 1.0mg/ml has the best effect for synthesizing the composite material under the solubility;
(3) Weighing graphite, and adding fibroin oligopeptide solution
Weighing 0.5mg of graphite powder by using a balance with the precision of 0.1mg, putting the graphite powder into a small bottle, and adding the fibroin oligopeptide solution with the concentration of 1.0mg/ml into the small bottle filled with the graphite powder by using a liquid transfer gun to obtain an unbound fibroin oligopeptide-graphite mixture;
(4) Ultrasound
Putting the obtained fibroin oligopeptide-graphite mixture into an ultrasonic water bath kettle for ultrasonic treatment, wherein the ultrasonic temperature is controlled at 20 ℃ for more than 4 hours;
(5) Centrifuging for the first time: transferring the solution after ultrasonic treatment to a centrifuge tube with the volume of 1.5ml by using a liquid transfer gun, placing the centrifuge tube in a centrifuge for centrifuging for more than 50min, setting the rotating speed at 800-1600rpm, removing un-peeled large-particle graphite, and taking supernatant;
(6) And (3) second centrifugation: and putting the obtained supernatant into a new centrifugal tube, putting the centrifugal tube into a centrifugal machine, centrifuging for more than 50min at the rotating speed of 10000-15000rpm, removing peptides which are not attached to the graphite, taking out the supernatant, reserving the precipitate, and drying to obtain the polypeptide-graphene composite material.
Experimental example 2
The polypeptide-graphene composite material prepared in example 1 of the present invention is schematically described, and the exfoliation process is shown in FIG. 2, that is
and 4, under the ultrasonic-assisted action, stripping graphene to generate peptide functionalized graphene, namely the polypeptide-graphene composite material of the embodiment 1, so that the composite material has the characteristics of biocompatibility and good water dispersibility of the fibroin oligopeptide.
Experimental example 3 Effect of concentration of fibroin oligopeptide solution on composite Material Performance
Through the preparation experiment processes such as ultrasonic-centrifugation and the like, a final composite material aqueous solution sample is obtained.
The results are shown in fig. 3, wherein fig. 3A is a sample photograph obtained by exploratory experiments and using polypeptide concentrations of 0, 0.1, 2.0, and 10mg/ml to prepare the silk fibroin oligopeptide-graphene composite material. From the pictures, it can be seen that only 2.0mg/ml of the silk fibroin oligopeptide prepared sample is significantly darker in color, and the others are substantially colorless.
The reason is that: graphite itself is insoluble in water, so graphite in water, subjected to the above-described ultrasonic-centrifugation, should be colorless, i.e., as shown in the 0mg/ml sample in fig. 3A. With the increase of the concentration of the fibroin oligopeptide, graphite is prepared into graphene, so that the graphene is dissolved in water, the obtained water solution is black, and the black color is more obvious when the content of the graphene is higher. But not the higher the concentration of silk oligopeptide the better.
The experimental result shows that the color of the compound aqueous solution prepared from the silk fibroin oligopeptide with the concentration of 10mg/ml is not as dark as 2.0 mg/ml. The reason is that after the concentration of the silk fibroin oligopeptide reaches a certain critical point, the silk fibroin oligopeptide can gather, so that the silk fibroin oligopeptide does not have enough interaction with graphite to prepare a compound. By further exploring the optimal preparation concentration of the silk fibroin oligopeptide, the sample prepared from 1.0mg/ml silk fibroin oligopeptide has the darkest color, namely the synthesis effect of the silk fibroin oligopeptide and graphene is the best under the concentration of 1.0mg/ml.
Example 4
The fibroin oligopeptide-graphene nanocomposite prepared in the embodiment 1 of the invention is dissolved by a solution of sodium hydroxide adjusting water to pH8.0, and the fibroin oligopeptide-graphene nanocomposite can be placed in an ultrasonic water bath to accelerate dissolution during dissolution, so as to obtain an aqueous solution of the polypeptide-graphene composite.
The ultraviolet absorption spectrum analysis is carried out on the aqueous solution, the result is shown in fig. 4, the obtained composite material has an obvious peak value at 267nm, the ultraviolet absorption peak at 267nm comes from the effect of graphene, meanwhile, the higher the ultraviolet absorption peak is, the higher the content of graphene is, and the best effect is obtained when the fibroin oligopeptide solution with the concentration of 1.0mg/ml is used for synthesizing the composite material.
Experimental example 5
The fibroin oligopeptide-graphene nanocomposite prepared in the embodiment 1 of the invention is dissolved by a solution with pH of 8.0 adjusted by sodium hydroxide, and the fibroin oligopeptide-graphene nanocomposite can be placed in an ultrasonic water bath to accelerate dissolution during dissolution, so that an aqueous solution of the polypeptide-graphene composite is obtained.
SEM scanning of the aqueous solution is carried out, and the result is shown in figure 5, and it can be seen from the figure that the average size of the fibroin oligopeptide is about 100nm, and the size of the obtained fibroin oligopeptide-graphene nano composite material is between 200 and 500nm, which meets the requirements of nano carriers in biomedicine.
The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, and any simple modifications or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the technical scope of the present invention are included in the present invention.
Claims (5)
1. A method for preparing a polypeptide-graphene composite material by utilizing silk fibroin oligopeptide water phase stripping graphite is characterized by comprising the following steps:
step 1, preparing fibroin oligopeptide solution
Cleaning silkworm cocoon, and cutting into pieces of 0.5-1.5cm 2 Then, according to the bath ratio of 1:200 in a proportion of 0.5% by weight of Na 2 CO 3 Degumming in the solution at 100 deg.C for 30-60 min, filtering, cleaning, and repeating degumming and filtering for 2-3 times; drying the degummed silk according to a bath ratio of 1:30 in an amount of 50% by mass of CaCl 2 In the solution, water bath reaction is carried out for 40-60 minutes at 80-98 ℃, stirring is carried out continuously in the reaction process, the dissolved mixed solution is centrifuged for 15-60min at the rotating speed of 1000-3500rpm, the supernatant is put into a dialysis bag with the molecular weight cutoff of 8000-14000Da for flowing water dialysis for 1-2d, distilled water dialysis for 1-2d is carried out, then the solution is put into polyethylene glycol solution with the mass fraction of 10% for concentration, and the concentrated silk fibroin solution is freeze-dried to obtain silk fibroin powder;
carrying out water bath reaction on silk fibroin and alkaline protease at 60 ℃, and maintaining the pH value of a reaction system at 8.5 in the reaction process; boiling for 10-20min after the reaction is finished to inactivate the enzyme; naturally cooling, centrifuging the reaction system at 10000-15000rpm for 15-30min, removing enzyme protein and incompletely hydrolyzed silk fibroin, collecting supernatant, and concentrating to obtain crude product of silk peptide; the solid-liquid ratio of the silk fibroin peptide crude product to 8600U of actinomycete enzyme is 100:1, mixing, performing enzymolysis at 50-60 ℃ and pH8.5 for 60-80min to obtain a fibroin enzymolysis solution; dialyzing the fibroin enzymolysis solution with dialysis bag flowing water with cut-off molecular weight below 1500Da for 2-3 days to obtain fibroin enzymolysis oligopeptide solution, and freeze-drying at ultralow temperature of-80 deg.C to obtain fibroin oligopeptide powder;
dissolving fibroin oligopeptide powder in a solution obtained by adjusting water to pH of 8.0 with sodium hydroxide to obtain a 10.0mg/ml fibroin oligopeptide solution;
step 2, taking 10.0mg/ml silk fibroin oligopeptide solution, and adding a solution of which the pH is 8.0 by adjusting water with sodium hydroxide to adjust the concentration to 0.2-5.0mg/ml silk fibroin oligopeptide solution;
step 3, weighing 0.1-0.5mg of graphite powder, putting the graphite powder into a small bottle, and then adding 0.4-2.0ml of fibroin oligopeptide solution with the concentration of 0.2-5.0mg/ml to obtain an unbound fibroin oligopeptide-graphite mixture;
step 4, placing the unbound fibroin oligopeptide-graphite mixture into an ultrasonic water bath kettle for ultrasonic treatment for more than 4 hours at the temperature of 20-30 ℃;
step 5, transferring the solution after the ultrasonic initial tension to a centrifugal tube for centrifugation, removing the un-peeled large-particle graphite, and taking supernatant;
and 6, putting the supernatant into a new centrifugal tube, centrifuging, removing the peptide attached to the graphite, removing the supernatant, retaining the precipitate, and drying to obtain the polypeptide-graphene composite material.
2. The method for preparing the polypeptide-graphene composite material by using the silk fibroin oligopeptide water phase exfoliated graphite according to claim 1, wherein the concentration of the silk fibroin oligopeptide solution in the step 2 is 1.0mg/ml.
3. The method for preparing the polypeptide-graphene composite material by using the silk fibroin oligopeptide water phase exfoliated graphite according to claim 1, wherein the centrifugation rotating speed in the step 5 is 800-1600rpm, and the centrifugation time is more than 50 min.
4. The method for preparing the polypeptide-graphene composite material by using the silk fibroin oligopeptide water phase exfoliated graphite according to claim 1, wherein in the step 6, the centrifugal rotation speed is 10000-15000rpm, and the centrifugal time is more than 50 min.
5. Use of the polypeptide-graphene composite material prepared according to claim 1 for hydrophobic drug delivery.
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