Effect of Processing Temperature on the Morphology and Drug-Release Characteristics of Elastin-Like Polypeptide-Collagen Composite Coatings

Elastin-like polypeptides (ELPs) exhibit an inverse phase transition temperature (T-t) in response to changes in their environment. We hypothesized that processing ELP-collagen composites at temperatures higher than the T-t of ELP (similar to 32 degrees C) will affect their microstructure and subsequently, achieve tunable release of model drugs. The composite coatings were prepared by formation of ELP-collagen hydrogels at 37 degrees C, incubation at 37, 45, or 55 degrees C, and finally air-drying at 37 degrees C. Scanning electron micrographs revealed that the fabrication process affected both the collagen and ELP microaggregate phases. A gradual time dependent bovine serum albumin (BSA) release that followed the power law and a burst antibiotic doxycycline release followed by a linear zero-order release were observed. Importantly, BSA and doxycycline releases were dependent on the ELP microaggregate size, which was governed by the processing temperatures. This study lays the foundation to achieve optimized composite microstructures by controlling processing conditions for drug delivery applications.