Preparation And Study Of N,N,N-trimethyl Chitosan/Porcine Acellular Dermal Matrix Composites

Nowadays,porcine acellular dermal matrix(PADM)with a natural structure similar to human skin extracellular matrix has attracted more and more attention in the medical dressing field,as it has good biological activity,biocompatibility,mechanical property and so on.PADM dressings with the functions of promoting wound healing and reducing healing scars can be ideal medical dressings.However,currently available PADM dressings have some disadvantages,such as poor biological activity,low water vapor permeability,poor hemostasis,lack of antibacterial properties,which limit their clinical applications.In view of the deficiency of PADM,N,N,N-trimethyl chitosan(TMC)loaded PADM is prepared in this research.TMC,a quaternary ammonium salted derivative of chitosan,has the same biological properties as chitosan,what’s more,it has greater solubility and antibacterial properties than chitosan.In this paper,quaternary ammonium salt modification of chitosan was performed using dimethyl sulfate as methylating agent.The degree of quaternary ammonium salt substitution and the degree of methyl substitution on hydroxyl groups were analyzed by 1H NMR spectroscopy.The TMC with degree of quaternary ammonium substitution of 57%is prepared in this paper.PADM was prepared from porcine skin materials those are treated with physical,chemical and biological methods based on the previous studies of decellularization in the lab.Then the TMC and PADM materials were compounded by supramolecular interaction to obtain TMC-PADM composite biomaterials with good performances.The effects of different reaction conditions on the synthesis of TMC,and of different concentrations of TMC solution on the properties of TMC-PADM composites are studied in this paper.The following conclusions have been obtained:(1)The effects of three reaction conditions(including the amount of dimethyl sulfate,the amount of solvent and the reaction temperature)on the synthesis of TMC were studied.It was found that the higher the amount of dimethyl sulfate,the higher the degree of quaternization(DQ)and the O-methylation(DOM)of the TMC.And when the amount of dimethyl sulfate used exceeds 16 mL,the selectivity of O-methylation reaction is enhanced.The amount of solvent used has little effect on the DQ of TMC,but the higher the solvent amount,the lower the DOM.The higher the reaction temperature,the lower the DQ and DOM of TMC,but the rate of DOM decline is slower than the rate of DQ decline,it shows that the higher the temperature,the stronger the selectivity of O-methylation on the hydroxyl group.(2)Taking the yield of TMC as an indicator,orthogonal experiments of three factors(dimethyl sulphate dosage,solvent dosage and reaction temperature)were conducted.It was found that the effect of three factors on the yield was:dimethyl sulfate dosage>reaction temperature>solvent dosage.(3)TMC requires a suitable degree of quaternization,a lower degree of methyl substitution on hydroxyl groups,a faster reaction rate and a higher yield.According to these indicators,the optimal reaction conditions for the synthesis of TMC in this paper are:16 mL of DMS,20 mL of solvent,and 40℃ of reaction temperature.(4)The different concentration of TMC solutions(0.2%,0.4%,0.6%,0.8%)were reacted with PADM to examine the changes in porosity,water vapor permeability,tensile strength,and enzyme degradation resistance of TMC-PADM composite materials.It was found that as the TMC concentration increases,the porosity increases,the water vapor permeability decreases,the tensile strength increases,and the enzyme degradation time increases.The series of composite materials have a porosity of over 80%,a tensile strength of 7～16MPa,an enzyme degradation time of about 24 hours,and a water vapor velocity of 2500 g.m-2.24h-1.The prepared porcine acellular dermal matrix combined with N,N,N-trimethyl chitosan has good permeability and mechanical properties.As the combined N,N,N-trimethyl groups have good antibacterial and hemostasis properties,so composite materials should also have antibacterial and hemostasis properties,and it is expected to become a new excellent medical dressing.