Genetically Encoded Photocleavable Linkers for Patterned Protein Release from Biomaterials

Given the critical role that proteins play in almost all biological processes, there is great interest in controlling their presentation within and release from biomaterials. Despite such outstanding enthusiasm, previously developed strategies in this regard result in ill-defined and heterogeneous populations with substantially decreased activity, precluding their successful application to fragile species including growth factors. Here, we introduce a modular and scalable method for creating monodisperse, genetically encoded chimeras that enable bioactive proteins to be immobilized within and subsequently photoreleased from polymeric hydrogels. Building upon recent developments in chemoenzymatic reactions, bioorthogonal chemistry, and optogenetics, we tether fluorescent proteins, model enzymes, and growth factors site-specifically to gel biomaterials through a photocleavable protein (PhoCl) that undergoes irreversible backbone photoscission upon exposure to cytocompatible visible light (λ ≈ 400 nm) in a dose-dependent manner. Mask-based and laser-scanning lithographic strategies using commonly available light sources are employed to spatiotemporally pattern protein release from hydrogels while retaining their full activity. The photopatterned epidermal growth factor presentation is exploited to promote anisotropic cellular proliferation in 3D. We expect these methods to be broadly useful for applications in diagnostics, drug delivery, and regenerative medicine.