Modified starch paste as well as preparation method and application thereof

Abstract

The invention relates to a preparation method and application of a modified starch paste, and the method comprises the following steps: S1, adding an oxidizing agent into gelatinized starch, and reacting to obtain hydroformylated starch; s2, adding phytic acid into the hydroformylated starch solution, and reacting to obtain a first intermediate; s3, adding polyhexamethylene guanidine hydrochloride into the first intermediate solution, and reacting to obtain a second intermediate; and S4, mixing the second intermediate solution, a phosphate solution and a calcium ion solution, and freeze-drying to obtain the modified starch paste. According to the preparation method, the gelatinized starch is subjected to hydroformylation to obtain the hydroformylated starch, then the phytic acid and the polyhexamethylene guanidine hydrochloride are grafted by utilizing hydroxyl and aldehyde groups of the hydroformylated starch respectively, and finally the amorphous calcium phosphate is stabilized by utilizing the phytic acid, so that the modified starch paste has excellent antibacterial property and remineralization ability.

Description

Technical Field

[0001] The invention relates to the field of biomaterials, and in particular to a modified starch paste and a preparation method and application thereof. Background Art

[0002] Dental caries is a chronic bacterial infectious disease that occurs in the hard tissues of teeth. Its development process can be summarized as the imbalance of oral flora homeostasis caused by abnormal dietary structure or host health status, the overgrowth of caries-related bacteria, which in turn leads to increased acidity in the oral microenvironment, destroying the balance between demineralization and remineralization of the hard tissue surface, resulting in continuous demineralization of the hard tissues of teeth and ultimately causing dental caries.

[0003] Due to the inseparable relationship between oral flora and dental caries, oral antimicrobial treatment has received extensive attention, including chemical antimicrobial treatment using antibiotics, metal ions, polyphenols, antimicrobial peptides or other compounds with oxidative stress properties, or physical antimicrobial treatments such as photothermal antimicrobial treatment, mechanical antimicrobial treatment, and magnetic response antimicrobial treatment. 2+ and PO4 3- Ion-guided mineralization restoration, or replacing the hydroxyl groups in HAP with fluoride ions to form fluorapatite, enhances its anti-caries and corrosion resistance, thereby preventing further development of caries.

[0004] However, the oral environment is special and there are many factors that affect dental caries, including microecological system, dietary structure, host health, bacterial invasion time, etc. Therefore, simply removing or killing plaque microorganisms cannot effectively prevent and treat dental caries. How to achieve both high antibacterial efficiency and promote remineralization of hard tissue surfaces is a challenge currently faced by oral caries prevention and treatment materials. Summary of the invention

[0005] An object of the present invention is to provide a method for preparing a modified starch paste, which comprises the following steps: hydroformylating starch, using the hydroxyl group of the hydroformylated starch to graft phytic acid (PA) to stabilize amorphous calcium phosphate (ACP), and then using the aldehyde group to graft a high molecular weight antibacterial drug polyhexamethyleneguanidine hydrochloride (PHMG), so that the modified starch paste can not only promote remineralization, but also have excellent antibacterial ability, and can regulate the acidity of the oral microenvironment during the antibacterial process, thereby significantly improving the prevention and treatment effect of caries.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a modified starch paste comprises the following steps:

[0008] S1: adding an oxidant to gelatinized starch to obtain hydroformylation starch;

[0009] S2: Add phytic acid to the aldehyde - modified starch solution and react to obtain a first intermediate;

[0010] S3: Add polyhexamethylene guanidine hydrochloride to the first intermediate solution and react to obtain a second intermediate;

[0011] S4: Mix the second intermediate solution, phosphate solution, and calcium ion solution, and obtain the modified starch paste after freeze - drying.

[0012] In this technical solution, in step S1, an oxidant is added to the gelatinized starch to oxidize the hydroxyl groups in the starch into aldehyde groups, obtaining aldehyde - modified starch OS containing aldehyde groups. Among them, starch is a natural polysaccharide with wide sources, green and safe, which is composed of glucose units connected by glycosidic bonds. In one or more embodiments, the starch can be leguminous plant starch, tuberous plant starch, or cereal plant starch. In some preferred embodiments, the starch is potato starch, sweet potato starch, or cassava starch. In one or more embodiments, the oxidant can be sodium periodate, sodium hypochlorite, or hydrogen peroxide. In some preferred embodiments, sodium periodate is preferably used as the oxidant to oxidize two adjacent hydroxyl groups into aldehyde groups, obtaining dialdehyde starch. In some embodiments, the aldehyde degree of the aldehyde - modified starch can be adjusted by regulating the mass ratio of starch to the oxidant, that is, the number of hydroxyl groups oxidized into aldehyde groups.

[0013] In this technical solution, in step S2, after adding water to the aldehyde - modified starch to form a suspension, phytic acid (PA) is added under stirring conditions. Phytic acid is a non - toxic small - molecule compound that can be extracted from plants and contains six phosphine groups in its molecular structure. In this technical solution, the un - aldehyde - modified hydroxyl groups in the glucose units of the aldehyde - modified starch, that is, two non - adjacent hydroxyl groups, react with the phosphate groups in phytic acid to undergo an esterification reaction, thereby grafting phosphate onto the starch to obtain a first intermediate OSP.

[0014] In this technical solution, the steps of S1 and S2 cannot be interchanged. If the hydroxyl groups in the gelatinized starch are first connected with phytic acid and then the hydroxyl groups of the starch are oxidized to obtain aldehyde groups, the aldehyde degree of the starch may be weakened because the pre - grafted phytic acid occupies some sites to be aldehyde - modified, affecting the antibacterial effect and rheology of the subsequent modified starch paste.

[0015] In this technical solution, in step S3, after dissolving the first intermediate, polyhexamethylene guanidine hydrochloride (PHMG) is added to the solution of the first intermediate. The amino group of polyhexamethylene guanidine hydrochloride reacts with the aldehyde group in the aldehyde-modified starch to undergo a Schiff base reaction, thereby connecting polyhexamethylene guanidine hydrochloride to the aldehyde-modified starch to obtain a second intermediate, that is, modified starch OSP-PHMG. In this technical solution, polyhexamethylene guanidine hydrochloride is a broad-spectrum antimicrobial agent. As a high-molecular polymer, it is not easily absorbed by tissues in the animal body, and with the increase in the degree of polymerization, its toxicity is greatly reduced, making it basically have no effect on the cells of higher organisms.

[0016] In this technical solution, in step S4, a phosphate solution and a calcium ion solution are added to the solution of the second intermediate to introduce calcium and phosphorus ions. After grafting phytic acid, the second intermediate contains abundant phosphate groups to maintain the metastable state of amorphous calcium phosphate (ACP), avoiding its rapid and spontaneous phase transformation into a more stable crystalline state of Hap, and achieving the purpose of stabilizing amorphous calcium phosphate ACP. After freeze-drying, modified starch paste OSP-PHMG@ACP is obtained. In some preferred embodiments, the soluble calcium salt is anhydrous calcium chloride, and the soluble phosphate used is dipotassium hydrogen phosphate or disodium hydrogen phosphate.

[0017] In this technical solution, aldehyde-modified starch is obtained by aldehyde-modifying gelatinized starch, and then phytic acid and polyhexamethylene guanidine hydrochloride are grafted respectively using the hydroxyl group and aldehyde group of the aldehyde-modified starch. Finally, amorphous calcium phosphate is stabilized by phytic acid, so that the modified starch paste has both excellent antibacterial properties and remineralization ability; in addition, in the slightly acidic microenvironment of the caries-affected area, through the reverse Schiff base reaction, not only can the antibacterial drug polyhexamethylene guanidine hydrochloride be released in a responsive manner, but also the reverse Schiff base reaction will consume H + , thereby achieving the regulation of the pH microenvironment of the caries-affected area and better realizing the prevention and treatment of dental caries; moreover, this modified starch paste is convenient to use. After being redissolved in water, it enters a gelatinized state. In this state, the material has a certain viscosity and can adhere to the tooth surface, providing sufficient residence time and sites for subsequent antibacterial and remineralization functions.

[0018] As a preferred embodiment of the present invention, in step S1, the mass ratio of the starch to the oxidant is 1.6-5.

[0019] The mass ratio of starch to an oxidant, such as sodium periodate, will directly affect the aldehyde degree of aldehyde starch. The more sodium periodate accounts for, the more aldehyde groups in the aldehyde starch, and the fewer hydroxyl groups available for grafting phytic acid, which affects the stable amount of subsequent amorphous calcium phosphate. On the contrary, the less sodium periodate accounts for, the fewer aldehyde groups in the aldehyde starch, which affects the grafted polyhexamethylene guanidine hydrochloride. Moreover, different contents of phytic acid, polyhexamethylene guanidine hydrochloride, and amorphous calcium phosphate will also affect the rheology of the final modified starch paste. Therefore, in this technical solution, considering comprehensively the antibacterial efficiency, drug toxicity, remineralization ability, and rheology of the modified starch paste, the mass ratio of starch to the oxidant in step S1 is set to 1.6 - 5. In some preferred embodiments, the oxidant is sodium periodate, and the mass ratio of starch to sodium periodate is 2 - 3. Further preferably, the mass ratio of starch to sodium periodate is 2 - 2.5.

[0020] Further, in step S1, deionized water is added to the starch, and then it is stirred at 60 - 90 °C to obtain gelatinized starch. Subsequently, an oxidant is added to the gelatinized starch for reaction under light - shielding conditions. After centrifuging the reaction solution, the lower - layer precipitate is taken, washed, and dried to obtain the aldehyde starch. In one or more embodiments, the reaction time is 3 - 6 hours, preferably 4 hours. In some embodiments, it is washed three times alternately with deionized water and absolute ethanol, and then the final product is transferred to a freeze - dryer for drying and forming to obtain the aldehyde starch.

[0021] Further, in step S2, the mass ratio of the aldehyde starch to phytic acid is 2.5 - 5.

[0022] In this technical solution, in each glucose unit of the aldehyde starch, the hydroxyl groups not oxidized by the oxidant react with phytic acid to undergo an esterification reaction. Since some hydroxyl groups in the aldehyde starch have been oxidized by the oxidant, the amount of phytic acid used should not be too much, so as to avoid waste of phytic acid and make the post - treatment more complex. At the same time, the amount of phytic acid used should not be too little, because less phytic acid will affect the amount of amorphous calcium phosphate that can be stabilized subsequently and reduce the remineralization effect of the modified starch paste. Therefore, in this technical solution, the mass ratio of the aldehyde starch to phytic acid is set to 2.5 - 5. In some preferred embodiments, the mass ratio of the aldehyde starch to phytic acid is 2.5 - 4.

[0023] Further, in step S2, after adding phytic acid, the pH value of the reaction system is adjusted to 3.0 - 4.0 with an alkali. Preferably, the pH value of the reaction system is adjusted to about 3.5 after adding phytic acid.

[0024] Further, in the step S2, after adjusting the pH value, the reaction is carried out for 8 to 12 hours. The reaction solution is centrifuged to obtain the lower-layer precipitate, which is washed and dried to obtain the first intermediate. After the pH value is stabilized, the reaction solution is transferred to react at 30 to 50 °C for 8 to 12 hours. After the reaction is completed, the lower-layer precipitate is centrifuged, washed three times with deionized water, and then the product is transferred to a freeze dryer for drying and forming to obtain the first intermediate of modified starch. In one or more preferred embodiments, the reaction time is 10 hours.

[0025] Further, in the step S3, after mixing the first intermediate, polyhexamethylene guanidine hydrochloride and a solvent, the reaction is carried out at room temperature for 6 to 10 hours. The reaction solution is centrifuged to obtain the lower-layer precipitate, which is washed and dried to obtain the second intermediate. In some embodiments, after centrifuging the reaction solution, the lower-layer precipitate is taken, washed three times alternately with deionized water and absolute ethanol, and then the product is transferred to a freeze dryer for drying and forming to obtain the second intermediate of modified starch.

[0026] Another object of the present invention is to provide a modified starch paste prepared by any of the foregoing preparation methods. When the modified starch paste is at a cariogenic site with a slightly acidic pH, the antibacterial drug PHMG grafted through a Schiff base reaction will be released under the action of H + to achieve responsive antibacterial. And during the process of releasing the drug, the Schiff base reaction can consume H + in the microenvironment to achieve responsive antibacterial and regulate the oral microenvironment at the same time. Moreover, amorphous calcium phosphate in the material in the water system will continuously release calcium ions and phosphate ions, solving the problem of lack of mineral ion sources such as calcium ions and phosphates in the oral cavity, so that calcium ions and phosphate ions can quickly react with the surface of demineralized tooth enamel, accelerating mineral deposition and remineralization.

[0027] In addition, the modified starch paste is convenient to use. After adding water, it forms a gelatinized state. Compared with unmodified starch under the same conditions, the modified starch paste is more viscous in physical state and conforms to the rheological properties of a weak gel state, having a certain viscosity and being able to adhere to the tooth surface, providing sufficient residence time and sites for subsequent antibacterial and remineralization functions.

[0028] Further, the modified starch paste includes aldehyde starch prepared by oxidizing gelatinized starch. Phytic acid is grafted to the hydroxyl group of the aldehyde starch to stabilize amorphous calcium phosphate, and polyhexamethylene guanidine hydrochloride is grafted to the aldehyde group of the aldehyde starch through a Schiff base reaction.

[0029] Another object of the present invention is to provide any of the foregoing paste-like modified starch pastes. Specifically, after mixing the modified starch paste with water, the modified starch paste enters a gelatinized state, and the gelatinized modified starch paste is coated on the tooth surface, providing sufficient residence time and sites for subsequent antibacterial and remineralization functions.

[0030] Further, the concentration of the modified starch paste is 50 - 65 μg / mL. Through experiments, it is found that within this concentration range, the paste - like modified starch paste has more excellent bactericidal effects, and with the increase of the concentration, the bactericidal efficiency is higher. At the same time, when the concentration of the modified starch paste is within this range, it can have better rheological properties and viscosity, which is conducive to its adhesion to the tooth surface.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] 1. In the present invention, aldehyde - modified starch is obtained by aldehyde - modifying gelatinized starch, and then phytic acid and polyhexamethylene guanidine hydrochloride are grafted onto the hydroxyl and aldehyde groups of the aldehyde - modified starch respectively. Finally, phytic acid is used to stabilize amorphous calcium phosphate, so that the modified starch paste has both excellent antibacterial properties and remineralization ability.

[0033] 2. In the slightly acidic micro - environment of the caries - affected site of the present invention, through the Schiff - base reaction occurring in the reverse direction, not only can the antibacterial drug polyhexamethylene guanidine hydrochloride be released in a responsive manner, but also the Schiff - base reaction occurring in the reverse direction will consume H + , thereby achieving the regulation of the pH micro - environment of the caries - affected site and better realizing the prevention and treatment of dental caries.

[0034] 3. The modified starch paste of the present invention is convenient to use. After being redissolved in water, it enters a gelatinized state. In this state, the material has a certain viscosity and can adhere to the tooth surface, providing sufficient residence time and sites for subsequent antibacterial and remineralization functions.

[0035] 4. By adjusting the mass ratio of starch to oxidant, the present invention effectively determines the degree of aldehyde modification of aldehyde - modified starch, balances the antibacterial efficiency, drug toxicity, remineralization ability and rheological properties of the modified starch paste, and further improves the prevention and treatment effect of dental caries and the operation convenience of modified aldehyde - modified starch.

[0036] 5. The preparation process of the modified starch paste of the present invention is simple, and the reaction conditions are mild, which is conducive to large - scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0038] Figure 1 is a flowchart of the preparation method in a specific embodiment of the present invention;

[0039] Figure 2 is the synthesis route of the preparation method in a specific embodiment of the present invention;

[0040] Figure 3Shows the degrees of aldehyde formation of OS1(5:2), OS2(5:1), and OS3(5:3) in specific embodiments of the present invention;

[0041] Figure 4 Is the antibacterial effect diagram of the modified starch paste OSP-PHMG@ACP in specific embodiments of the present invention;

[0042] Figure 5 Is the mineralization effect diagram of the modified starch paste OSP-PHMG@ACP in specific embodiments of the present invention;

[0043] Figure 6 Is the physical state comparison diagram of the pure starch S and the modified starch paste OSP-PHMG@ACP forming a weak gel after adding water under the same conditions in specific embodiments of the present invention;

[0044] Figure 7 Is the rheological property of the modified starch paste OSP-PHMG@ACP after forming a weak gel by adding water in specific embodiments of the present invention. Detailed implementation manners

[0045] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in combination with embodiments and drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and do not limit the present invention.

[0046] There are no special restrictions on the sources of all raw materials of the present invention. They can be purchased on the market or prepared by conventional methods well-known to those skilled in the art. There are no special restrictions on the purity of all raw materials of the present invention. The present invention preferably adopts analytical pure or the conventional purity requirements in the field of biological materials. All raw materials of the present invention, their trade names and abbreviations are all conventional trade names and abbreviations in the art. Each trade name and abbreviation is clear and definite in the field of its relevant uses. Those skilled in the art can purchase them from the market or prepare them by conventional methods according to the trade name, abbreviation, and corresponding uses.

[0047] The present invention has no special restrictions on the expression methods of the substituents, and all adopt the expression methods well-known to those skilled in the art. Those skilled in the art can correctly understand their meanings based on common sense according to their expression methods.

[0048] I. Preparation of Modified Starch Paste

[0049]

Example 1

[0050] (1) Weigh 5 g of potato starch and add it to a 250 ml round-bottom flask. Add 100 ml of deionized water and stir in an oil bath at 90 °C for 20 min to obtain the first solution. After the first solution cools to room temperature, weigh 2 g of sodium periodate in the dark and add it to the first solution. Wrap the round-bottom flask with tin foil to avoid light and stir and react in a water bath at 37 °C for 4 h to obtain the second solution. Centrifuge the second solution at 5000 rpm for 5 min, take the lower viscous precipitate, wash it three times alternately with deionized water and absolute ethanol, and then transfer the product to a freeze dryer for drying and forming to obtain aldehyde-modified starch OS1.

[0051] (2) Weigh 5 g of aldehyde-modified starch and add it to a 250 ml round-bottom flask. Add 100 ml of deionized water, add a magnetic stirrer and stir evenly, then add 2 ml of phytic acid PA while stirring. Then adjust the pH to 3.5 with 0.1 M NaOH solution. After the pH stabilizes, transfer it to a water bath at 40 °C and stir and react for 10 h. After the reaction is completed, centrifuge at 5000 rpm for 5 min, take the lower precipitate, wash it three times with deionized water, and then transfer the product to a freeze dryer for drying and forming to obtain the first intermediate OSP of modified starch.

[0052] (3) Weigh 8 g of the modified intermediate OSP and 10 g of polyhexamethylene guanidine hydrochloride PHMG and put them into a 250 ml round-bottom flask. Add 100 ml of absolute ethanol, and stir and react the mixed solution at room temperature for 8 h. After the reaction is completed, centrifuge at 5000 rpm for 5 min, take the lower precipitate, wash it three times alternately with deionized water and absolute ethanol, and then transfer the product to a freeze dryer for drying and forming to obtain the second intermediate OSP-PHMG of modified starch.

[0053] (4) Weigh 45.6 mg of K2PO4·3H2O powder, add 1 ml of deionized water to prepare a phosphate solution with a concentration of 120 mM. Weigh 29.6 mg of CaCL2·H2O powder, add 1 ml of deionized water to prepare a calcium ion solution with a concentration of 200 mM. Weigh 250 mg of modified starch OSP-PHMG, add 960 μL of deionized water, 20 μL of phosphate solution and 20 μL of calcium ion solution to obtain an ACP composite modified starch solution with a calcium ion concentration of 10 mM and a phosphate concentration of 6 mM, and transfer it to a freeze dryer for drying and forming to obtain the modified starch paste OSP-PHMG@ACP.

[0054]

Example 2

[0055] The steps of Example 2 are substantially the same as those of Example 1, except for the preparation of aldehyde-modified starch in step (1).

[0056] Specifically, weigh 5 g of potato starch and add it to a 250-ml round-bottom flask. Add 100 ml of deionized water and stir in an oil bath at 90 °C for 20 min to obtain the first solution. After the first solution cools to room temperature, weigh 1 g of sodium periodate under light-shielded conditions, add it to the first solution, wrap the round-bottom flask with tin foil to avoid light, and stir and react in a water bath at 37 °C for 4 h to obtain the second solution.

[0057] Centrifuge the second solution at 5000 rpm for 5 min, take the lower viscous precipitate, wash it alternately three times with deionized water and absolute ethanol, and then transfer the final product to a freeze dryer for drying and shaping to obtain aldehyde-modified starch OS2.

[0058]

Example 3

[0059] The steps of Example 3 are substantially the same as those of Example 1, except for the preparation of aldehyde-modified starch in step (1).

[0060] Specifically, weigh 5 g of potato starch and add it to a 250-ml round-bottom flask. Add 100 ml of deionized water and stir in an oil bath at 90 °C for 20 min to obtain the first solution. After the first solution cools to room temperature, weigh 3 g of sodium periodate under light-shielded conditions, add it to the first solution, wrap the round-bottom flask with tin foil to avoid light, and stir and react in a water bath at 37 °C for 4 h to obtain the second solution.

[0061] Centrifuge the second solution at 5000 rpm for 5 min, take the lower viscous precipitate, wash it alternately three times with deionized water and absolute ethanol, and then transfer the final product to a freeze dryer for drying and shaping to obtain aldehyde-modified starch OS3.

[0062] II. Testing of Modified Starch Paste

[0063]

Example 4

[0064] In this example, the aldehyde degree -CHO% of the aldehyde-modified starches synthesized in Examples 1 to 3 was tested.

[0065] Specifically, weigh 0.2 g of aldehyde-modified starch and place it in a conical flask, and mix 10 mL of 0.25 M NaOH solution therein. The conical flask was then heated at 70 °C for 2 minutes. After cooling, a reddish-brown solution was obtained. Next, add 15 mL of 0.125 mol H2SO4 and 30 mL of deionized water to the conical flask, and shake well until the solution turns light yellow. Subsequently, add 1 mL of phenolphthalein solution to the conical flask and titrate with 0.25 M NaOH. When the solution color turns orange-red and remains stable for 30 seconds, the test is considered complete.

[0066] The aldehyde modification was calculated by the following formula:

[0067]

[0068] Among them, C1 is the NaOH solution with a concentration of 0.25 mol / L, V1 is the volume of the NaOH solution used for titration, which is 10 mL; C2 represents the concentration of the NaOH solution used for titration, and V2 is the volume used for titration; C3 is the concentration of the H2SO4 solution, which is 0.125 mol / L, and V3 is 15 mL; m represents the mass of the aldehyde-modified starch added, and 161 represents the average relative molecular mass of the glucose units in the aldehyde-modified starch.

[0069] As Figure 3 shown, the aldehyde degree of OS1 is 20.7%, the aldehyde degree of OS2 is 7.8%, and the aldehyde degree of OS3 is 28.2%. As the mass ratio of sodium periodate increases, the aldehyde degree will be further improved. A higher aldehyde degree means that the number of hydroxyl groups available for grafting phytic acid will decrease, which is not conducive to the stable amount of amorphous calcium phosphate in the subsequent process, while a lower aldehyde degree will affect the introduction of polyhexamethylene guanidine hydrochloride and reduce the antibacterial ability of the modified starch paste. Therefore, in the preferred embodiment, the mass ratio of starch to sodium periodate is determined to be 5:1 to 5:3. The subsequent performance tests are selected for the modified starch paste prepared based on the aldehyde-modified starch OS1.

[0070]

Example 5

[0071] In this example, a method for detecting the pH-responsive antibacterial performance of modified starch composites OSP-PHMG@ACP with different concentrations is provided, and the steps are as follows:

[0072] To detect the antibacterial activity of modified starch composites OSP-PHMG@ACP with different concentrations, a Streptococcus mutans solution (BHI, 0.05 M) containing 10 8 CFU / mL was diluted to 10 6 CFU / mL with PBS solutions at pH 5.5 and 7.0. Modified starch pastes OSP-PHMG@ACP with different concentrations (15.625, 31.25, 62.5 μg / mL) were prepared with PBS solutions at pH 5.5 and 7.0. The diluted bacterial solution was incubated with the OSP-PHMG@ACP solution at the corresponding pH at 37 °C for 4 h, and the antibacterial performance was detected by plating.

[0073] The experimental results are as Figure 4 shown, indicating that the modified starch composite OSP-PHMG@ACP has pH-responsive antibacterial performance, reflecting that the use of Schiff base reaction to connect the modified starch first intermediate OSP and the polymer antibacterial drug PHMG in this application can effectively achieve the function of pH-responsive antibacterial.

[0074]

Example 6

[0075] In this embodiment, an experimental detection method for the mineralization and repair performance of functional particles is provided, and the steps are as follows:

[0076] Weigh 250 mg of the modified starch paste OSP-PHMG@ACP in Example 1, add 1 ml of deionized water to obtain a paste-like modified starch paste. Take 30 mg and coat it on the surface of acid-etched enamel, and continuously treat it for 5 days. Observe the mineralization of the acid-etched enamel treated with the paste-like modified starch paste for 5 days and the natural mineralization of the acid-etched enamel for 5 days. As Figure 5 shown, after being treated with the paste-like modified starch complex for 5 days, the remineralization effect is good, indicating that the modified starch paste not only does not have a negative impact on stable amorphous calcium phosphate, but also is beneficial to improving the bactericidal ability of the modified starch paste during the remineralization process, further promoting the remineralization ability of the modified starch paste.

[0077]

Example 7

[0078] In this embodiment, an experimental test method for the physical state of freeze-dried OSP-PHMG@ACP and pure starch S is provided, and the steps are as follows:

[0079] Weigh 250 mg of the freeze-dried powder of the modified starch OSP-PHMG@ACP in Example 1, add 1 ml of deionized water, mix it on a vortex shaker, and let it stand for 10 minutes to obtain a paste-like modified starch paste. The paste-like modified starch is in a weak gel state, has a certain viscosity, and still adheres to the bottom of the bottle after being inverted.

[0080] Weigh 250 mg of commercially available potato starch purchased, add 1 ml of deionized water, mix it on a vortex shaker to obtain a starch suspension, and let the starch solution layer after standing for 10 minutes.

[0081]

Example 8

[0082] In this embodiment, a rheological test method for the OSP-PHMG@ACP paste is provided, and the steps are as follows:

[0083] After mixing the modified starch paste prepared in Example 1 with water, the paste-like modified starch paste as shown in Figure 6 is obtained. Place the paste-like modified starch paste on a rheometer, with a plate diameter of 40 mm and a gap of 0.5 cm. Scrape off the excess sample and equilibrate at 25 °C for 30 seconds. Perform a frequency sweep in the range of 0.1 - 100 rad at 1% strain, and record the changes of storage modulus, loss modulus, and loss tangent with angular frequency.

[0084] The experimental results are as shown in Figure 7 : The measured storage modulus (G′) of the samples is greater than the loss modulus (G″) and there is no crossover, showing a weak gel dynamic rheological spectrum.

[0085] As used herein, terms such as "first", "second" (e.g., first intermediate, second intermediate, etc.) are only used to distinguish the corresponding components for clarity and are not intended to limit any order or emphasize importance, etc. In addition, the term "connected" used herein, without special explanation, may be directly connected or indirectly connected via other groups.

[0086] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a modified starch paste, characterized in that: The following steps are involved: S1: adding an oxidant to gelatinized starch to obtain hydroformylation starch; S2: adding phytic acid to the hydroformylation starch solution to react and obtain the first intermediate; S3: adding polyhexamethyleneguanidine hydrochloride to the first intermediate solution to react to obtain a second intermediate; S4: mixing the second intermediate solution, the phosphate solution and the calcium ion solution, and freeze-drying to obtain the modified starch paste.

2. The method for preparing a modified starch paste according to claim 1, characterized in that: In the step S1, the mass ratio of the starch to the oxidant is 1.6-5.

3. The method for preparing a modified starch paste according to claim 2, characterized in that: In the step S1, deionized water is added to the starch, and then stirred at 60-90° C. to obtain gelatinized starch. Subsequently, an oxidant is added to the gelatinized starch under light-proof conditions to react, the reaction solution is centrifuged, and the lower precipitate is removed, washed, and dried to obtain the hydroformylated starch.

4. The method for preparing a modified starch paste according to claim 1, characterized in that: In the step S2, the mass ratio of the hydroformyl starch to the phytic acid is 2.5-5.

5. The method for preparing a modified starch paste according to claim 4, characterized in that: In the step S2, after adding phytic acid, the pH value of the reaction system is adjusted to 3.0-4.0 with alkali.

6. The method for preparing a modified starch paste according to claim 1, characterized in that: In the step S3, the first intermediate, polyhexamethyleneguanidine hydrochloride and a solvent are mixed and reacted at room temperature for 6 to 10 hours, the reaction solution is centrifuged to remove the lower precipitate, and the second intermediate is obtained after washing and drying.

7. A modified starch paste, characterized in that: The preparation method is described in any one of claims 1 to 6.

8. The modified starch paste according to claim 7, characterized in that: The modified starch paste comprises hydroformylation starch obtained by oxidizing gelatinized starch, the hydroxyl groups of the hydroformylation starch are grafted with phytic acid to stabilize amorphous calcium phosphate, and the aldehyde groups of the hydroformylation starch are grafted with polyhexamethylene guanidine hydrochloride through Schiff base reaction.

9. A paste-like modified starch paste, characterized in that: After mixing the modified starch paste according to claim 7 or 8 with water, a paste-like modified starch paste in a gelatinized state is obtained.

10. The modified starch paste according to claim 9, characterized in that: The concentration of the modified starch paste is 50-65 μg / mL.

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