Gelatin–Norbornene Thiol–Ene Bioinks: Macromer Identity, Stoichiometry, Oxygen Response and Cell-Compatible Cure

Gelatin-norbornene (GelNB) bioinks use thiol-ene step-growth photochemistry to separate the gelatin backbone from the choice of thiolated crosslinker. This architecture offers rapid, controllable gelation and is less sensitive to oxygen than conventional chain-growth methacrylate curing, but it introduces a different set of state variables: degree of norbornene substitution, thiol functionality, thiol-to-ene stoichiometry, crosslinker molecular size and photoinitiating conditions. This review treats GelNB as a family of stoichiometrically designed networks rather than a direct substitute for GelMA. It examines dithiothreitol and macromolecular thiol crosslinkers such as thiolated heparin, oxygen response, radical burden, network homogeneity and cell compatibility. It also emphasises that oxygen tolerance does not eliminate the need to characterise conversion or cytocompatibility. A qualification framework is proposed that links functional-group balance and light dose to mechanics, swelling, residual groups, cell response and printed fidelity.

ER-326 · Version 0.4.