Effects of substitution degree of photoreactive groups on the properties of UV-fabricated chitosan scaffold.

Hydroxypropyl chitosan (HPCS), a water-soluble chitosan derivate, was modified by introducing photoreactive azide groups (4-azidobenzoic acid, Az-) to the amino groups of HPCS, resulting in a photocrosslinkable Az-HPCS. Novel porous chitosan scaffolds thus were fabricated by ultraviolet (UV) light irradiation of Az-HPCS aqueous solutions. Fourier transform infrared spectroscopy, scanning electron microscopy, measurement of pore size and porosity, mechanical test, swelling test, in vitro biodegradation determination were used to analyze the effects of degree of substitution (DS) of Az-groups on the properties of the scaffolds. When DS of Az-groups increased from 2.8% to 5.6%, we found that (i) the pore size of Az-HPCS scaffolds increased by about twofold and the porosity increased slightly, probably due to more N(2) released from the crosslinking reaction with the increase of DS; (ii) both the tensile stress and strain increased by about threefold, relating to the increase of joint points, pore size, and porosity at a relative high DS; (iii) the swelling ratio and degradation rate decreased with the increase of Az-DS, because of the forming of a more compact network structure. Preliminary data of cell culture on Az-HPCS scaffold suggested its potential applicability for tissue engineering.