Polysaccharide hydroformylation modification method based on plasma technology

Abstract

The invention discloses a polysaccharide aldehyde modification method based on a plasma technology, relates to the technical field of biological material modification, and aims to solve the problems of environmental pollution, harsh reaction conditions and complex product purification in the conventional chemical oxidation method. Comprising the following steps: S1, preparing a polysaccharide solution; dissolving polysaccharide in a solvent, and stirring until the polysaccharide is completely dissolved to obtain a homogeneous polysaccharide solution; and S2, plasma in-situ oxidation treatment. In an inert gas atmosphere environment, plasma is generated by using a coaxial dielectric barrier discharge device, and active substances of the plasma directly act on a polysaccharide solution, so that an aldehyde group is introduced to a polysaccharide molecular chain, and an aldehyde polysaccharide solution is obtained. And S3, freeze-drying and forming. And freeze-drying the obtained aldehyde polysaccharide solution to obtain the aldehyde polysaccharide solid material with the three-dimensional porous network structure. The method is simple and convenient to operate, easy to popularize, simple in equipment, short in process, free of complex purification steps and beneficial to laboratory and large-scale production and application.

Description

Technical Field

[0001] This invention relates to the field of biomaterial modification technology, specifically a method for polysaccharide aldehyde modification based on plasma technology. Background Technology

[0002] Natural polysaccharides, as an important class of biomacromolecules, have shown broad application prospects in tissue engineering, drug delivery, and regenerative medicine due to their excellent biocompatibility, hydrophilicity, and biodegradability. However, these materials generally suffer from excessive water solubility, insufficient structural stability, and inadequate mechanical properties, limiting their direct application as structural scaffold materials. Converting the vicinal diol structure on their molecular chain into aldehyde groups via oxidation, and then crosslinking with amino compounds through a Schiff base reaction to construct hydrogels, is one effective strategy to overcome these limitations and expand their functions and applications.

[0003] Currently, the aldehyde conversion of these polysaccharides mainly relies on chemical oxidation methods, with sodium periodate oxidation being the most commonly used. However, traditional chemical oxidation methods have several significant drawbacks. For example, sodium periodate oxidant is highly toxic and environmentally hazardous, requiring complex and time-consuming purification processes to remove residues after the reaction, which not only increases process costs but may also introduce biosafety risks. Chemical residues may interfere with the activity of the aldehyde group and affect the biocompatibility of the final material. These drawbacks fundamentally limit the application of chemical oxidation methods in high-end, sensitive biomedical applications.

[0004] In recent years, atmospheric pressure cold plasma has shown great potential in the field of materials modification due to its unique physicochemical properties. As a non-thermal equilibrium plasma, atmospheric pressure cold plasma is rich in high-energy electrons, reactive nitrogen and oxygen species, and excited-state molecules, enabling oxidation treatment under mild conditions. Compared with traditional chemical oxidation methods, atmospheric pressure cold plasma technology has significant advantages such as no need for reagents, no solvent residue, and low energy consumption, and is considered a green and environmentally friendly materials modification technology. However, as a green and controllable tool, the technology of directly using low-temperature atmospheric pressure plasma to treat and modify polysaccharides has not yet been reported. Summary of the Invention

[0005] The purpose of this invention is to provide a polysaccharide aldehyde modification method based on plasma technology, which overcomes the problems of environmental pollution, harsh reaction conditions, and complex product purification of existing chemical oxidation methods.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a polysaccharide aldehyde modification method based on plasma technology, comprising the following steps.

[0007] S1. Prepare polysaccharide solution.

[0008] Dissolve the polysaccharide in a solvent and stir until completely dissolved to obtain a homogeneous polysaccharide solution.

[0009] S2, plasma in-situ oxidation treatment.

[0010] In an inert gas atmosphere, a coaxial dielectric barrier discharge device is used to generate plasma, and its active material directly acts on the polysaccharide solution, thereby introducing aldehyde groups onto the polysaccharide molecular chain to obtain an aldehyde-modified polysaccharide solution.

[0011] S3, freeze-drying and shaping.

[0012] The obtained aldehyde-modified polysaccharide solution was freeze-dried to obtain an aldehyde-modified polysaccharide solid material with a three-dimensional porous network structure.

[0013] Furthermore, the polysaccharide is selected from at least one of hyaluronic acid and its salts, alginate and its salts, chondroitin sulfate, dextran, or chitosan.

[0014] Furthermore, the polysaccharide weight-average molecular weight is 10kDa-500kDa, and the concentration of the polysaccharide solution is 1mg / mL to 10mg / mL.

[0015] Furthermore, the solvent is deionized water, and the stirring speed is 500 r / min-1000 r / min.

[0016] Furthermore, the discharge power of the plasma treatment is 10W to 50W, and the duration of the plasma treatment is 0.5 hours to 4 hours.

[0017] Furthermore, the inert gas atmosphere is pure argon, pure helium, a mixture of argon and oxygen, or a mixture of helium and oxygen.

[0018] Furthermore, when using an oxygen-containing mixed gas, the volume percentage of oxygen is 1% to 5%, and the gas flow rate is 0.2 SLM to 1.0 SLM.

[0019] Further, step S3 freeze drying includes: S3.1, firstly pre-freezing and solidifying the aldehyde-modified polysaccharide solution at a temperature of -80°C or below; S3.2, then sublimation drying under a vacuum of less than 10 Pa.

[0020] Furthermore, the sublimation drying time is 24 to 72 hours.

[0021] The beneficial effects of this invention are as follows: The entire aldehyde conversion process is carried out in the aqueous phase without the need for any chemical oxidants, catalysts, or initiators, thus avoiding chemical residues from the source. The product is pure, simple to process, and environmentally friendly. The coaxial dielectric barrier discharge structure allows direct contact between the plasma active region and the reaction solution, resulting in high utilization of active particles. The reaction can proceed rapidly at room temperature and pressure with relatively low energy consumption. By adjusting key parameters such as discharge power, processing time, gas composition, and flow rate, the amount of aldehyde groups introduced onto the polysaccharide chain can be controlled, thereby meeting the needs of different downstream applications. This technology is applicable to various natural polysaccharides containing oxidizable functional groups, demonstrating good versatility and potential for widespread application. It is simple to operate and easy to promote, requiring simple equipment and a concise process, eliminating the need for complex purification steps, which is beneficial for both laboratory and large-scale production applications. Attached Figure Description

[0022] Figure 1 A schematic diagram of the experimental setup for treating polysaccharide solutions using a coaxial dielectric barrier discharge device;

[0023] Figure 2 Discharge diagram for processing polysaccharide solutions using a coaxial dielectric barrier discharge device;

[0024] Figure 3 A comparison of the infrared spectra of raw hyaluronic acid and aldehyde-modified hyaluronic acid;

[0025] Figure 4 The graph shows the change in aldehyde group content of aldehyde-modified hyaluronic acid with plasma treatment time.

[0026] Figure 5 A comparison of the infrared spectra of sodium alginate raw material and aldehyde-modified sodium alginate;

[0027] Figure 6 This is a comparison diagram of plasma oxidation and sodium periodate chemical oxidation methods for preparing aldehyde-modified hyaluronic acid. Detailed Implementation

[0028] This invention discloses a method for aldehyde modification of polysaccharides based on plasma technology. The core of this method lies in utilizing low-temperature atmospheric pressure plasma generated by coaxial dielectric barrier discharge to perform in-situ, reagent-free oxidation treatment on polysaccharide aqueous solutions, thereby introducing aldehyde groups onto the molecular chains. Finally, porous materials are obtained through freeze-drying. The method comprises the following steps.

[0029] S1. Prepare polysaccharide solution.

[0030] Dissolve the polysaccharide in a solvent and stir until completely dissolved to obtain a homogeneous polysaccharide solution.

[0031] Specifically, the polysaccharide is selected from at least one of hyaluronic acid and its salts, alginate and its salts, chondroitin sulfate, dextran or chitosan, the weight average molecular weight of the polysaccharide is 10kDa-500kDa, the concentration of the polysaccharide solution is 1mg / mL to 10mg / mL, the solvent is deionized water, and the stirring speed is 500r / min-1000r / min.

[0032] S2, plasma in-situ oxidation treatment.

[0033] In an inert gas atmosphere, a coaxial dielectric barrier discharge device is used to generate plasma, and its active material directly acts on the polysaccharide solution, thereby introducing aldehyde groups onto the polysaccharide molecular chain to obtain an aldehyde-modified polysaccharide solution.

[0034] Specifically, the plasma treatment discharge power is 10W to 50W, and the plasma treatment duration is 0.5 hours to 4 hours. The inert gas atmosphere is pure argon, pure helium, a mixture of argon and oxygen, or a mixture of helium and oxygen. When using an oxygen-containing mixture, the oxygen volume percentage is 1% to 5%. The gas flow rate is 0.2 SLM to 1.0 SLM.

[0035] The active species in plasma can efficiently oxidize the vicinal diol structure on polysaccharide chains, converting it into aldehyde groups. This process requires no chemical oxidants and is environmentally friendly. Through this step, the amount of aldehyde groups introduced onto the polysaccharide molecule ranges from 5% to 40%.

[0036] S3, freeze-drying and shaping.

[0037] The obtained aldehyde-modified polysaccharide solution was freeze-dried to obtain an aldehyde-modified polysaccharide solid material with a three-dimensional porous network structure.

[0038] The freeze-drying process is as follows: S3.1, the aldehyde-modified polysaccharide solution is first pre-frozen and solidified at a temperature of -80℃ or below; S3.2, then sublimation drying is carried out under a vacuum of less than 10 Pa.

[0039] Specifically, the sublimation drying time is 24 to 72 hours.

[0040] The modification method of the present invention will be described below with reference to specific embodiments.

[0041] A gas discharge experimental platform was constructed, comprising a working gas control module and a discharge module. The working gas control module controls the working gas, while the discharge module generates plasma. The working gas control module includes a high-pressure gas tank and a gas flow meter. The gas flow meter is located at the outlet of the high-pressure gas tank and monitors the gas flow rate. The discharge device is triggered by a nanosecond pulse power supply. The discharge module uses a coaxial dielectric barrier discharge device to generate atmospheric pressure low-temperature plasma. A beaker containing a polysaccharide solution is used. Figure 1 As shown, the coaxial dielectric barrier discharge device includes inner and outer quartz tubes and a high-voltage electrode. The inner and outer quartz tubes effectively confine the plasma and prevent solution contamination of the high-voltage electrode. An air inlet is provided between the two quartz tubes, and the outlet of the gas pipe is connected to the air inlet. The air inlet is connected to the dielectric gap between the inner and outer quartz tubes to introduce working gas. This design ensures uniform distribution of the working gas, thereby generating a stable atmospheric pressure low-temperature plasma jet that directly acts on the polysaccharide solution below. The high-voltage electrode is made of stainless steel, and the entire discharge module is grounded via a grounding wire.

[0042] The concentration of the hyaluronic acid solution is 1 mg / mL-10 mg / mL, preferably 5 mg / mL. Dissolve 5 g of hyaluronic acid in 1 L of deionized water in a beaker, using a magnetic stirrer to accelerate the dissolution, to obtain a hyaluronic acid aqueous solution with a concentration of 5 mg / mL. Place the hyaluronic acid aqueous solution in the reaction zone of a coaxial dielectric barrier discharge plasma reactor. Use inert argon gas as the working gas for underwater discharge treatment, such as... Figure 2 As shown. The plasma treatment power is 10W-50W, preferably 15W; the treatment time is 0.5h-4h, preferably 2h. Under these conditions, the hydroxyl groups in hyaluronic acid can be effectively oxidized to aldehyde groups, resulting in an aldehyde-modified plasma-modified hyaluronic acid solution.

[0043] The obtained plasma-modified hyaluronic acid solution was characterized by Fourier transform infrared spectroscopy (FTIR) analysis, and the results are as follows: Figure 3 As shown. Plasma-modified hyaluronic acid at 1740 cm⁻¹ -1 A distinct characteristic absorption peak appeared at [wavenumber range], which corresponds to the C=O stretching vibration of the aldehyde group, while no characteristic peak was observed in the original hyaluronic acid sample within this wavenumber range. Experimental results indicate that plasma treatment of the hyaluronic acid solution can induce an oxidation reaction of its hydroxyl groups, successfully introducing aldehyde functional groups. Hydroxylamine titration determined that the aldehyde content of the obtained aldehyde-modified hyaluronic acid was 28%.

[0044] The effect of plasma treatment time on aldehyde content is verified below.

[0045] The aldehyde content of plasma-modified hyaluronic acid was determined by hydroxylamine titration. Under fixed plasma treatment power of 15W and hyaluronic acid solution concentration of 5mg / mL, treatment time gradients of 1h, 2h, 3h, and 4h were set for the experiment. The specific operation is as follows: During the measurement, the plasma-modified hyaluronic acid solution was taken and titrated according to the formula... Calculate the aldehyde content C of plasma-modified hyaluronic acid -CHO Where V1 is the volume of sodium hydroxide solution used for the titration of plasma-modified hyaluronic acid solution, and V2 is the volume of sodium hydroxide solution used for the titration of hyaluronic acid solution. The results are as follows: Figure 4 As shown, the aldehyde (-CHO) content increases with increasing plasma treatment time. After 2 hours of treatment, the aldehyde content reaches 28%, meaning 28 -CHO groups per 100 repeating units. When the treatment time is extended to 4 hours, the aldehyde content further increases to 41.48%, but its growth rate slows down compared to the previous period, indicating that the reaction is approaching saturation. These results show that within a treatment time of 1 to 4 hours, the aldehyde content is positively correlated with the treatment time. When the treatment time exceeds 3 hours, the growth rate of the aldehyde content decreases significantly. Therefore, considering the balance between reaction efficiency and modification effect, the preferred plasma treatment time is 1 to 3 hours.

[0046] The following verifies the universal oxidation effect of the present invention on polysaccharides containing vicinal diol structures.

[0047] Sodium alginate was used as the research object. Its aqueous solution was placed in a beaker and treated using a coaxial dielectric barrier discharge device. The plasma treatment power was 10W-50W, preferably 15W; the treatment time was 0.5h-4h, preferably 2h; and argon was used as the working gas. After underwater discharge treatment, an aldehyde-modified sodium alginate solution was obtained. The modified product was characterized and analyzed by Fourier transform infrared spectroscopy (FTIR), and the results are as follows: Figure 5 As shown. At 1732cm -1 A distinct characteristic absorption peak appeared at this wavenumber range, which is attributed to the characteristic stretching vibration of the C=O bond in the aldehyde group. No characteristic peaks were detected in the untreated raw sodium alginate sample within this wavenumber range. Experimental results show that plasma treatment of sodium alginate solution can induce oxidation of its hydroxyl groups, successfully introducing aldehyde functional groups. These results demonstrate that the atmospheric pressure low-temperature plasma oxidation method provided by this invention is not only applicable to hyaluronic acid but also effectively used for other polysaccharides containing vicinal diol structural units, such as sodium alginate, to achieve aldehyde modification, proving the universality of the method. This invention provides a new technical pathway for the functional modification of polysaccharide biomaterials and has broad application prospects in biomedicine and other fields.

[0048] Traditional chemical oxidation methods, such as sodium periodate oxidation, were used to oxidize the same natural polysaccharide raw material to introduce aldehyde groups onto the molecular chain, serving as a comparative reference for the plasma oxidation method of this invention. The steps of the sodium periodate oxidation method are as follows: Hyaluronic acid was selected as the polysaccharide. 1.0 g of hyaluronic acid was weighed and dissolved in 200 mL of deionized water. The solution was magnetically stirred at 1000 rpm at room temperature until completely dissolved, preparing a 5 mg / mL hyaluronic acid solution. This hyaluronic acid solution was transferred to a 500 mL brown, light-proof reaction flask and placed in a 4°C constant temperature water bath with stirring. 0.54 g of sodium periodate (NaIO4) was weighed and dissolved in 20 mL of pre-cooled deionized water to prepare a sodium periodate solution. Under light-proof, 4°C low-temperature, and continuous stirring conditions, the sodium periodate solution was slowly and dropwise added to the polysaccharide solution through a constant pressure dropping funnel. After the addition was complete, the reaction was continued under light-proof, 4°C low-temperature conditions with continuous stirring for 24 hours. After the reaction was complete, 1 mL of ethylene glycol was added to the reaction solution, and the mixture was stirred at room temperature for 2 hours to consume the remaining sodium periodate and terminate the oxidation reaction. The reaction solution was transferred to a dialysis bag with a molecular weight cutoff of 3500 Da and dialyzed with deionized water for 72 hours, changing the dialysate every 8 hours until the conductivity of the external solution was close to that of deionized water. The purified solution was then freeze-dried to obtain the dried product of aldehyde-modified hyaluronic acid.

[0049] like Figure 6 As shown, compared with the sodium periodate chemical oxidation method for preparing aldehyde-modified hyaluronic acid, the plasma oxidation method provided by this invention has revolutionary advantages in terms of ease of operation, time efficiency, environmental friendliness, and safety. It truly achieves green, rapid, and reagent-residue-free aldehyde modification, which is crucial for the preparation of biomedical materials.

Claims

1. A method for aldehyde modification of polysaccharides based on plasma technology, characterized in that, Includes the following steps: S1. Preparation of polysaccharide solution Dissolve the polysaccharide in a solvent and stir until completely dissolved to obtain a homogeneous polysaccharide solution; S2, Plasma in-situ oxidation treatment In an inert gas atmosphere, a coaxial dielectric barrier discharge device is used to generate plasma, and its active material directly acts on the polysaccharide solution, thereby introducing aldehyde groups on the polysaccharide molecular chain to obtain an aldehyde-modified polysaccharide solution. S3, freeze-drying molding The obtained aldehyde-modified polysaccharide solution was freeze-dried to obtain an aldehyde-modified polysaccharide solid material with a three-dimensional porous network structure.

2. The method for polysaccharide aldehyde modification based on plasma technology according to claim 1, characterized in that, In step S1, the polysaccharide is selected from at least one of hyaluronic acid and its salts, alginate and its salts, chondroitin sulfate, dextran, or chitosan.

3. The method for polysaccharide aldehyde modification based on plasma technology according to claim 2, characterized in that, In step S1, the weight-average molecular weight of the polysaccharide is 10kDa-500kDa, and the concentration of the polysaccharide solution is 1mg / mL to 10mg / mL.

4. The method for polysaccharide aldehyde modification based on plasma technology according to claim 3, characterized in that, In step S1, the solvent is deionized water, and the stirring speed is 500 r / min-1000 r / min.

5. The method for polysaccharide aldehyde modification based on plasma technology according to claim 4, characterized in that, In step S2, the discharge power of the plasma treatment is 10W to 50W, and the duration of the plasma treatment is 0.5 hours to 4 hours.

6. The method for polysaccharide aldehyde modification based on plasma technology according to claim 5, characterized in that, In step S2, the inert gas atmosphere is pure argon, pure helium, a mixture of argon and oxygen, or a mixture of helium and oxygen.

7. The method for polysaccharide aldehyde modification based on plasma technology according to claim 6, characterized in that, In step S2, when using an oxygen-containing mixed gas, the volume percentage of oxygen is 1% to 5%, and the gas flow rate is 0.2 SLM to 1.0 SLM.

8. The method for polysaccharide aldehyde modification based on plasma technology according to claim 7, characterized in that, Step S3 freeze drying includes: S3.1, firstly, pre-freezing and solidifying the aldehyde-modified polysaccharide solution at a temperature of -80℃ or below; S3.2, then sublimation drying under a vacuum of less than 10 Pa.

9. The method for polysaccharide aldehyde modification based on plasma technology according to claim 8, characterized in that, The sublimation drying time is 24 to 72 hours.

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