The well-defined incorporation of functional molecules into polymer networks is an attractive endeavor with promise throughout materials science, especially biomaterials. Biologically relevant small molecules and proteins within synthetic hydrogels have vast applications including adhesives, drug delivery, and tissue engineering. The formation of structured tissues within an organism is controlled by spatiotemporal patterns of extracellular signals which determine the cell fate decisions of differentiating cells. Replicating these extracellular signals in vitro has proven difficult to achieve. As a result, the patterning of biochemical cues within biologically-relevant hydrogels is limited to uniform application, which fails to mimic the structural information that guides in vivo cell development.
Researchers at the University of California, Santa Barbara have developed a Diels–Alder-based photopatterning platform that is capable of spatially controlled chemical functionalization of hydrogel systems. The platform achieves the precise patterning of biochemical cues within hydrogels by exposing cyclopentadienone–norbornadiene (CPD–NBD) adducts to a specific wavelength of light. The adducts undergo light-induced decarbonylation and subsequent cleavage, unveiling thermodynamically stable yet highly reactive cyclopentadiene for post-irradiation reaction with commercially available maleimides. Unlike existing photopatterning platforms, this strategy does not involve radical propagating photoclick reactions, making it compatible with natural protein-based hydrogels. This platform for preparing biomimetic microenvironments has the potential to facilitate new discoveries concerning cell fate decisions with direct application to cell-based therapeutics.