Amphiphilic polymeric photoinitiator composed of PEG-b-PCL diblock copolymer for three-dimensional printing of hydrogels

Herein, poly(ethylene glycol)-block-poly(epsilon-caprolactone) (PEG(114)-b-PCLx) copolymer is employed to enhance the water solubility of fashionable photoinitiator, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO). PEG(114)-b-PCLx copolymers are first polymerized via the conventional ring-opening polymerization. Subsequently, TPO encapsulated nanoparticles (TPO@PEG(114)-b-PCLx) are prepared through the nanoprecipitation method, followed by a water removal process using lyophilization. By altering the PEG(114)-b-PCLx molecular weights and TPO: PEG(114)-b-PCLx ratios, the resulting nanoparticles exhibited hydrodynamic average sizes ranging from 190 to 360 d.nm with the TPO encapsulation efficiency of approximately 21-35%. Afterward, these prepared photoinitiators were formulated with poly(ethylene glycol dimethacrylate) (PEGDMA) and methacrylate-functionalized dextran (Dex-MA) before fabricating the 3D-printed hydrogels through digital light processing (DLP). The compressive moduli of the hydrogels covered from 0.13 to 1.79 MPa, depending on the content of PEGDMA and Dex-MA and the degree of substitution of Dex-MA. The cytotoxicity results of printed specimens revealed that the hydrogels are noncytotoxic to chondrocyte and fibroblast.

Automated summary

In this study, PEG(114)-b-PCLx copolymer was used to enhance the water solubility of TPO, a fashionable photoinitiator. TPO@PEG(114)-b-PCLx nanoparticles were prepared through nanoprecipitation and subsequent lyophilization. The resulting nanoparticles had different sizes and encapsulation efficiencies depending on the molecular weights of PEG(114)-b-PCLx and the TPO:PEG(114)-b-PCLx ratios. The prepared photoinitiators were then used to fabricate 3D-printed hydrogels with PEGDMA and Dex-MA. The hydrogels exhibited good mechanical properties and were noncytotoxic to cells.