Bioactive Silk Protein Biomaterial Systems for Optical Devices

Silk-based biomaterial systems have been previously explored for a variety of medical and nonmedical materials needs. The unique biophysical features of silks provide options to generate highly tailored structures and morphologies with this unique family of fibrous proteins. To exploit these features, we have optimized the all aqueous processing of silk fibroin into novel surface nanopatterned protein materials. We have exploited control of this nanomorphology to optimize the optical features of these silk protein systems. We demonstrate control of surface morphology down to 125 nm, with fidelity over large length scales. This surface nanopatterning allows the silk protein to be formed into diffractive optics such as diffraction gratings, pattern generators, and lenses due to novel aqueous processing into optically clear materials via control of beta sheet crystallinity. Further, we incorporate biological components, such as hemoglobin and the enzyme peroxidase, during the process of forming the silk diffraction gratings. The ambient processing of the silk protein in water, in combination with these bioactive components, allows these entrained molecules to retain activity and provide added functions and selectivity to the optically active silk films. Thus, combinations of biochemical and optical readout is feasible and provides in a single, disposable/all degradable element with both spectral discrimination and biological function. These new surface nanopatterned, bioactive silk protein-based material systems offer a unique combination of features potentially useful for a range of biosensor needs, particularly when considered in concert with the remarkable mechanical properties of these proteins, their biocompatibility, and controllable biodegradation.