Direct observation of interactions of silk-elastinlike protein polymer with adenoviruses and elastase.

Silk-elastinlike protein polymer (SELP) hydrogels have been investigated for sustained local delivery of adenoviral gene carriers to solid tumors. These polymers degrade in the presence of proteases such as elastase. A detailed understanding of the interaction of SELPs with viruses and their degradation in the presence of elastase can provide useful information about mechanisms of sustained gene delivery from these systems. In this work, we investigated the interactions of SELPs with adenoviruses (Ads) and elastase using atomic force microscopy. We observed that viral particles interacted strongly with SELP networks formed by cross-linking of nanofibers. The presence of viruses contributed to enhanced network formation. Incubation of Ad with SELPs in the liquid state induced close packing of the viral colony. Morphological changes of SELP networks cleaved by enzymatic interaction with elastase were investigated. SELP-415K fiber networks were more responsive to temperature changes and were slowly degraded by elastases compared to SELP-47K, a SELP analogue with shorter elastin units in the monomer repeat. These studies provide insight into the influence of SELP structure on degradation and potential mechanisms of increased viral stability.