Preparation Of Choline Phosphate Functionalized Chitosan And Evaluation Of Biocompatibility Of Its Drug-loaded Hygrogel

Chitosan(CS)is a natural polysaccharide with good biocompatibility and antibacterial properties.It is often used as a biomaterial in medical research.Chitosan and chitosan-based hydrogels are good drug carriers.Due to their hemostatic,antibacterial,and proliferation of fibroblasts,they have a positive effect on wound healing.In addition,chitosan can stimulate the secretion of natural hyaluronic acid in the wound area,promote faster wound healing and reduces the formation of scars.However,many amino groups on the main chain of chitosan make it appear weakly alkaline and insoluble in water or organic solvents.Only in acidic media,the amino groups of chitosan can be protonated to promote its solubility.In addition,strong intermolecular and intramolecular hydrogen bonds also limit its solubility,and it has the disadvantage of poor mechanical properties as a natural hydrogel,which is difficult to meet the clinical needs of tissue defect repair materials.Therefore,it is desired to develop chitosan derivatives that have good water solubility and retain their antibacterial properties,and at the same time prepare a series of biocompatible hydrogels to enhance their application prospects.Zwitterionic materials have been widely used in the field of biomedicine due to their good biocompatibility and strong hydration ability.As a new type of zwitterionic,choline phosphate(CP)has the opposite chemical structure and charge distribution to phosphocholine(PC)on the cell membrane surface,and CP can form two unique N-P pairs with PC and interact with the cell membrane.Polyvinyl alcohol(PVA)is a synthetic polymer material widely used in the field of biomedicine.It has been widely used in drug carriers,artificial organs,wound dressings,controlled release of proteins and other fields due to its good biocompatibility,biodegradability,and high mechanical strength.This thesis aims to improve the water solubility of chitosan,retain its biocompatibility and improve antibacterial properties,and develop biocompatible composite drug-loaded hydrogels with good mechanical properties.The Michael addition reaction was used to graft MCP onto the reactive amino group at the C2 position of chitosan,and the chitosan was successfully modified to obtain a chitosan derivative(CS-MCP)with both water solubility and antibacterial properties.We prepared polydopamine nanoparticles(PDA-NPs),loaded the model drug tetracycline hydrochloride(TH)using π-π stacking,and then compound the modified chitosan with PVA and TH-loaded polydopamine nanoparticles(PDA-TH)to form a hydrogel,systematically studied the mechanical properties,drug release ability,antibacterial properties and cell compatibility of hydrogels.The main research results are as follows:1.The Michael addition reaction was used to graft MCP on the amino group of CS,and the modified chitosan was characterized by H-NMR,FTIR,XRD,and TG to prove the successful preparation of choline phosphorylated chitosan.A series of water solubility experiments were carried out at a series of temperatures.The results showed that CS-MCP can dissolve well in water at 4 ℃,25 ℃ and 37 ℃,and the solubility in water at 37 ℃ can reach more than 50 mg/m L.A series of concentration gradient CS-MCP antibacterial experiments,cytotoxicity experiments and hemolytic experiments show that the introduction of MCP can improve the antibacterial properties of chitosan while maintaining good biocompatibility.2.Without adding any cross-linking agent,CS-MCP and PVA are cross-linked by repeated freeze-thaw cycles to form a hydrogel(CSM/PVA1 x,x=2-4).The study found that with the gradual increase of PVA content,the mechanical properties of the composite hydrogel continue to increase,the internal pore structure becomes smaller,and the swelling rate increases.The CSM/PVA13 hydrogel was selected to add PDA-NPs to it.Due to the addition of nanoparticles,the mechanical properties of the hydrogel are further enhanced.The PDANPs are used to load TH to form a composite drug-loaded hydrogel(CSM/PVA13-PDA-TH),and the drug release experiments showed that the hydrogel could realize the dual responsive drug release ability of near infrared(NIR)and p H.3.The in vitro biological properties of the drug-loaded composite hydrogel were further studied.Antibacterial experiments show that the drug-loaded hydrogel has good NIR-assisted antibacterial effects.Cytotoxicity and cell proliferation experiments show that CS-MCP-based hydrogels have good cell compatibility.Live/dead cell staining experiments prove CSM/PVA13-PDA hydrogels can well promote the growth and proliferation of endothelial cells.To sum up,the introduction of MCP not only improves the water solubility of chitosan,but also improves its antibacterial properties while maintaining its biocompatibility.The composite hydrogel prepared based on choline phosphorylated chitosan has good cell compatibility and mechanical properties,and exhibits a controllable antibacterial drug release behavior with dual responsiveness of near-infrared and p H.Therefore,this study provides a new idea for the water-soluble modification of CS and a new strategy for the preparation of a new type of intelligent functionalized hydrogel drug carrier.