Influence of photoinitiator concentration and irradiation time on the crosslinking performance of visible-light activated pullulan-HEMA hydrogels

In-situ forming hydrogels were prepared from pullulan-HEMA copolymer using three-component visible-light system composed of camphorquinone carboxylic acid-folic acid-iodonium salt. The relevance of double bond conversion and crosslinking density of hydrogels with the photoinitiator concentration and irradiation time were estimated by FT-IR analysis and swelling calculation using Flory-Rehner theory, respectively. The results revealed that the crosslinking density and degree of conversion of hydrogels were improved by photoinitiator concentration increasing until certain extend, then they decreased due to a primary radicals termination reaction occurred. The shortest irradiation time of 10 s was essential to obtain acceptable hydrogels for further characterizations. For the probability use of hydrogels as scaffold was investigated in vitro by measuring of the indirect cytotoxicity assay by MTT-assay using human bone Sarcoma cell as a reference cell lines. The majority of seeded SW1353 cells maintained a live with an accepted viability of ~85-92% over a four days culture period with irradiation of hydrogel 10 s, while cell viability has improved to ~95-98% with prolonging the irradiation time of hydrogel to 60 s. The current photoinitiating system is a proper system for in-situ crosslinking the activated-light biomaterials for bone regeneration, dental, or tissue engineering applications.