| Hyaluronan (HA) has been widely used in biophamaceutics, owing to itswonderful moisture-retention ability and biocompatibility. However, thetotal amount of HA is limited, and the price is high. Chitosan (CS) is anatural polymer and its chemical structure is close to that of HA. Recently,chitosan derivatives perparaed by chemical modification has explored theapplication of chitosan. In this paper, simple technics to prepare HA-likechitosan using CS with high deacetylation degree was investigated.Firstly, series of water soluble N-acylated chitosan derivatives have beenobtained via N-acylations with acid anhydrides in an acetic acid/ethanol/pyridine homogeneous solution. The results showed that N-maleoylchitosan exhibited best moisture-retention ability and moisture-absorptionability, markedly excelleding to those of HA. Moreover, N-maleoylchitosan owned excellent water solubility in wide pH range, and it has noskin irritation.Secondly, the N-acylated reaction conditions were optimized throughorthogonal experiment. The optimum conditions for N-maleoyltion were asfollows: the mole ratio of anhydride to amino group of chitosan in feed was2.0, the optimum reaction time was 2 hours, the reaction temperature was20℃, and the amount ofpyridine was 8mL in the 25mL chitosan(lg) aceticacid solution. Thirdly, Mal-U1 and Mal-H were prepared via optimum technics byusing two kinds of chitosan, whose molecular weight(Mw) were3.91×105 and 7.72×105, respectively. The Mw and [η] of Mal-H was 1.25×106Da and 1630 dL·g-1, both of which were close to those of HA. Incontrast, the Mw and [η] of Mal-U1 were 5.23×105Da and 840dL·g-1, bothof which were lower than those of HA. It was revealed that the chitosanderivative with higher Mw exhited better potential to substitute HA.The optimum conditions for N-maleoyltion were as follows: thecrooslinking temperature was 35℃, the pH of reaction medium was 7.0,crosslink agent was glutaraldehyde, and the amount of 25％glutaraldehydesolution was 50μL in 100mL 1.0％MalU-1 water solution. The crosslinkedmaleoy chitosan derivative GMal was obtained in optimum conditions, andits Mw and [η] was of GMal 1610 dL·g-1, both of which were close to thoseof HA.The moisture-retention abilities of Mal-U1 and GMal as well as themoisture-absorbtion abilities of Mal-U1 and GMal were better than thoseof HA. As a result, both Mal-U1 and Gmal had the potential to subistituteHA in many fields, and appeared to be suitable for preparing HA-likingsubstances. It was suggested that Mal-H and GMal had significantantimicrobial activity for S. aureus and E. coli.. In contrast, HA showed noantimicrobial activity. Stability research showed that the stabilities ofMal-H and GMal were good at bellow 40℃, while their viscosities were decreased when heated above 40℃. Two products represented goodantidepolymerization abilities in pH 7-10 medium, though depolymerizedin acid medium and pH 12 medium. In addition, their stir stabilitiesexhibited excellent in 48h.The two samples, both Mal-H and GMal, owned high Mw and [η],both of which were close to those of HA. Their moisture-retention abilitiesand moisture-absorbtion abilities were better than those of HA. In addition,two saples exhibit antimicrobial activity.
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