The selection of photoinitiators for photopolymerization of biodegradable polymers and its application in digital light processing additive manufacturing.

Digital light processing additive manufacturing (DLP-AM) technology has received a lot of attention in the field of biomedical engineering due to its high precision and customizability. However, some photoinitiators, as one of the key components in DLP-AM, may present toxicity and limit the application of DLP-AM toward biomedical applications. In order to gain further insights into the correlation between biocompatibility and photoinitiators in photoresins, a study on the selection of photoinitiators used in DLP-AM is conducted. The light absorbance range and cytocompatibility of four photoinitiators, vitamin B2 combined with triethanolamine (B2/TEOA), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), 2-dimethoxy-2-phenylacetophenone (DMPA), and 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), are characterized. Each photoinitiator is then combined with poly(glycerol sebacate) acrylate (PGSA) and poly(ε-caprolactone) diacrylate (PCLDA), to evaluate their miscibility and film formation ability through photopolymerization. The mechanical properties, in vitro and in vivo biocompatibility studies on bulk films are investigated. It is found that B2/TEOA and TPO exhibit a wider light absorbance range than I2959 and DMPA. PGSA films with B2/TEOA (PGSA-B2/TEOA) is capable of sustaining cell proliferation up to 10 days and showing low immune responses after 14 days post implantation, proving its biocompatibility. Although B2/TEOA requires longer photopolymerization time, the mechanical strength of PGSA-B2/TEOA is comparable to PGSA films with TPO and DMPA, and this combination is 3D-printable through DLP-AM at the rate of 100 s per layer. In summary, B2/TEOA is a promising photoinitiator for 3D printing.