Preparation And Properties Of Modified Chitosan Antibacterial Hydrogels

Hydrogel,a kind of three-dimensional network structure of polymer,can swell in the water and keep a large number of water.At the same time,it has good biocompatibility.These advantages make hydrogel get more and more attention in wound dressing research,although most of hydrogel could provide a moist environment for wound,but the effect in preventing infection was poor.Chitosan(CS),due to its good biocompatibility,biodegradability,non-toxic,environment-friendliness,is often used as raw material of the research and development of hydrogel.While chitosan can only be dissolved in the weak acid,and its antibacterlal is weak,so its applications are greatly limited.It is necessary to develop water-soluble chitosan derivatives.In this paper,chitosan derivatives were synthesized by chemical modification.The lincomycin and poly(amidoamine)dendrimer have excellent antibacterial materials,was introduced to improve the antibacterial activities of hydrogels,which made the hydrogels satisfy the needs of the wound dressing.The followings are the topic main research contents and conclusions:(1)Firstly,O-carboxymethyl(O-CMCS)chitosan was synthesized by the chemical reaction of chitosan and chloroacetic acid.Then the hydrogel was prepared with O-CMCS as the raw material,EDC/NHS as the crosslinking agent and the addition of lincomycin.The structure and morphology of the hydrogels were characterized by FTIR and SEM.The results showed thatO-CMCS and the hydrogels were successfully prepared.It also could be seen from the SEM images that there were close and ordered pore structure inside the hydrogels,which had different pore structures under the different conditions.The swelling properties of hydrogel in different pH buffer solutions showed that it had good pH sensitivity.The results of the swelling tests showed that the hydrogels reached the swelling equilibrium in about 3 h.And the swelling property firstly increased and then decreased gradually with the increase of the cross-linking agent,decreased gradually with the increase of the concentration of O-CMCS.The swelling property in the pH 1.0 buffer solution was obviouslybetter than pH 7.4.The antibacterial experiments showed that the pure O-CMCS hydrogel had no antibacterial.However,with the increase of concentration of lincomycin,the antibacterial effect of hydrogel against Staphylococcus aureus and Escherichia coli increased,namely,the antibacterial activity gradually became better,finally reached 100%,which showed the bactericidal action.As the dosage of crosslinking agent and the concentration of O-CMCS increased,the antibacterial effect of hydrogel against S.aureus and E.coli decreased.(2)Poly(amidoamine)dendrimer(2.0G PAMAM)was synthesized by Michael addition reaction and amidation reaction,with ethylenediamine and methylmethacrylate as the raw materials.Then the hydrogel were prepared through PAMAM crosslinking modification of N-carboxy propionyl chitosan.The structure and morphology of the hydrogels were characterized by FTIR and SEM.The results showed that PAMAM was synthesized,and the hydrogels were also prepared successfully,in which there pore structureswere compact and orderly.The results showed that the hydrogels reached the swelling equilibrium in about 2 h.And the swelling property decreased gradually with the increase of PAMAM blending ratio,increased firstly and then decreased gradually with the increase of the dosages of EDC/NHS,and decreased gradually with the increase of the concentration of N-CS.The swelling property in the pH 1.0 buffer solution was better than pH 7.4,which showed that the hydrogel had good pH sensitivity.The hydrogel had significant antibacterial activity: With the increase of PAMAM blending ratio,the antibacterial effect of hydrogel against Staphylococcus aureus and Escherichia coli increased,finally reached 100%,which suggested that the antibacterial effect became gradually better,and finally performed the capacity to kill bacteria.With the increase of the dosage EDC/NHS and the concentration of N-CS,the antibacterial effects of hydrogel against Staphylococcus aureus and Escherichia coli decreased.(3)2-hydroxypropyltrimethyl ammonium chloride chitosan(HACC)with different degrees of substitution were synthesized by the reaction of chitosan with glycidyltrimethylammonium chloride(GTMAC),and then were crosslinked by glutaraldehyde to prepare the hydrogels.The structure and morphology of the hydrogels were characterized by FTIR and SEM,the results showed that the HACC and HACC hydrogels were prepared successfully.The pore structuresof hydrogel were loose,and the internal surfaces of pores were smooth.The swelling tests confirmed that the swelling property increased firstly and then decreased with the increase of HACC degree of substitution andthe crosslinking agent dosage,and the swelling property decreased gradually with the increase of HACC concentration.The swelling property in the pH 1.0 buffer solution was obviously better than pH 7.4,which showed that the hydrogel had good pH sensitivity.The antibacterial experiments showed that HACC hydrogels had significant antibacterial activities: with the increase of HACC degree of substitution,the antibacterial effect of hydrogel against Staphylococcus aureus and Escherichia coli increased,finally reached 100%,and finally performed the capacity to kill bacteria.With the increase of crosslinking agent dosage,the antibacterial effect of hydrogel against the two bacteria firstly increasedand then decreased,with the increase of HACC concentration,the antibacterial effect both increased.