Highly Reactive Thiol-Norbornene Photo-Click Hydrogels: Toward Improved Processability

Abstract

In the present work, gelatin type B is modified with highly reactive norbornene functionalities (Gel-NB) following a one-pot synthesis approach to enable subsequent thiol-ene photo-click crosslinking. The modification strategy displays close control over the amount of introduced functionalities. Additionally, Gel-NB exhibits considerably improved processing capabilities in terms of two-photon polymerization when benchmarked to earlier-reported crosslinkable gelatin derivatives (e.g., gelatin-methacrylamide (Gel-MOD) and gelatin-methacrylamide-aminoethylmethacrylate (Gel-MOD-AEMA)). The improvement is especially apparent in terms of minimally required laser power (20 mW vs ≥60 mW (Gel-MOD) vs ≥40 mW (Gel-MOD-AEMA) at 100 mm s^-1 scan speed) and processable concentration range (≥5 w/v% vs ≥10 w/v% (Gel-MOD/Gel-MOD-AEMA)). Furthermore, the proposed functionalization scheme maintains the excellent biocompatibility and cell interactivity of gelatin. Additionally, the norbornene functionalities have potential for straightforward postprocessing "thiol-ene" surface grafting of active molecules. As a consequence, a very promising material toward tissue engineering applications and more specifically, biofabrication, is presented.

Keywords: gelatin; hydrogels; thiol-ene photo-click; tissue engineering; two-photon polymerization.