Structural Design of Robust and Biocompatible Photonic Hydrogels from an in Situ Cross-Linked Hyperbranched Polymer System

Multifunctional hyperbranched poly(poly(ethylene glycol) diacrylate) (HB-PEGDA) polymers with well-defined composition, structure, and functionality are proposed in this work as photonic hydrogel scaffolds. By taking advantage of its unique transparency, low intrinsic viscosity, and high amount of vinyl groups, the HB-PEGDA can effectively penetrate inside the colloidal photonic crystal (CPC) substrate and be cross-linked with thiolated hyaluronic acid very quickly. This photonic hydrogel shows not only an unexpected protective effect to the untreated CPC substrate, but also nonswelling characteristics attributed to its relatively compacted network structure, which leads to robust structural integrity and credible, consistent optical performance under complex physiological conditions. Moreover, this photonic hydrogel shows good biocompatibility and can be easily modified to introduce specific functions (e.g., cell attachment), providing novel insights into the photonic hydrogel design toward diverse bio-optical applications.