Modifications of silk film for dual delivery.

Silk biomaterials can be designed to provide an architectural framework comparable to connate extracellular matrix in order to boost cell growth and eventual tissue regeneration. Silk (Bombyx mori) fibroins self-assemble into hydrophobic crystalline β sheets, which provide mechanical strength and tunable degradability. The next generation of tissue engineering scaffolds aim to provide spatially controlled modulation of cell adhesion and differentiation, which can be achieved by spatially controlled surface functionalization of the scaffolds. In this respect, it is even more important to be able to release molecules at timescales ranging from hours to days, as many biological processes require signals early on to initiate processes, and over prolonged periods to sustain them. Unfortunately, achieving spatio-temporal control over multiple release profiles from silk based substrates is challenging due to their intrinsic slow release behaviour. Here, we report a simple strategy that provides spatio-temporal control over the release of drugs from silk films (SFs). We have developed a UV based strategy to modify the SFs with nanogels, which can provide a fast as well as slow release profile from a single platform. We demonstrate that the release profile of encapsulated molecules on the SF substrate can be tuned from fast (within hours) to slow (within days), thus resulting in a dual release system, which can be eventually utilized to deliver bioactive molecules at specific regions with different rates to achieve the desired multiple biological effects.