Frequent and inappropriate usage of
antibiotics has changed the natural evolution of bacteria by reducing susceptibility and increasing resistance towards
antibacterial agents. New resistance mechanisms evolved in the response to host defenses and
pharmaceutical interventions are threatening our ability to treat common
infections, resulting in increased mortality. In the face of this rising epidemic,
antibiotic drug discovery, which has long been overlooked by big pharma, is reaching a critical low. Thus, the development of an
infection-responsive drug delivery system, which may mitigate multidrug resistance and preserve the lifetime of our current
antibiotic arsenal, has garnered the attention of both popular science and funding agencies. The present work describes the development of a
thrombin-sensitive linker embedded into a recombinant spider
silk copolymer to create a
nanosphere drug delivery vehicle. Recent studies have suggested that there is an increase in
thrombin-like activity during
Staphylococcus aureus infection; thus, drug release from this new "smart"
nanosphere can be triggered in the presence of
infection. A
thrombin sensitive
peptide (TSP) was synthesized, and the
thrombin cleavage sensitivity was determined by HPLC. The results showed no cleavage of the
peptide when exposed to human serum whereas the
peptide was cleaved when incubated with S. aureus exudate. Subsequently, the
peptide was coupled with a
silk copolymer via
EDC-NHS chemistry and formulated into
nanospheres encapsulating
antibiotic vancomycin. These
nanospheres were evaluated for in vitro
infection-responsive drug release and antimicrobial activity. Finally, the
drug responsive
nanospheres were assessed for efficacy in an in vivo
septic arthritis model. Our study provides evidence that the
protein conjugate was
enzyme responsive and can be used to formulate targeted drug release to combat
infections against multidrug-resistant bacterial strains.