2.2 Synthesis and characterization of deacetylated chitosan
Chitosan was deacetylated by adapting a method previously described in liteture and then purified. The recovered chitosan was dissolved in 1M acetic acid solution filtered with a 0.22 micro m filter to remove traces of any solid particles. Afterwards, the pH was adjusted to 7 with 1M NaOH, which resulted in the precipitation of the chitosan material. The product was then centrifuged at 4500 rpm , this procedure was repeated three times and finally the recovered pellet was lyophilized for one day. The degree of deacetylation was measured by using the first derivation UV-spectroscopy method. UV-vis chitosan spectra were obtained using a Shimadzu 1700 UV-vis spectrophotometer. Table S1 shows the degree of deacytylation for the commercial and deacetylated chitosan samples. The chitosan used for hydrogel production had deacetylation degree of 95.08%+-0.48, meaning that almost all of the primary amine groups of the chitosan polymer chain are positively charged.