The interplay between silk fibroin's structure and its adhesive properties.

Bombyx mori-derived silk fibroin (SF) is a well-characterized protein employed in numerous biomedical applications. Structurally, SF consists of a heavy chain (HC) and a light chain (LC), connected via a single disulfide bond. The HC sequence is organized into 12 crystalline domains interspersed with amorphous regions that can transition between random coil/alpha helix and beta-sheet configurations, giving silk its hallmark properties. SF has been reported to have adhesive properties and shows promise for development of medical adhesives; however, the mechanism of these interactions and the interplay between SF's structure and adhesion is not understood. In this context, the effects of physical parameters (i.e., concentration, temperature, pH, ionic strength) and protein structural changes on adhesion were investigated in this study. Our results suggest that amino acid side chains that have functionalities capable of coordinate (dative) bond or hydrogen bond formation (such as those of serine and tyrosine), might be important determinants in SF's adhesion to a given substrate. Additionally, the data suggest that fibroin amino acids involved in beta-sheet formation are also important in the protein's adhesion to substrates.

Nanoparticulate Poly(glucaramide)-Based Hydrogels for Controlled Release Applications.

In 2004, D-Glucaric acid (GA) was identified as one of the top value-added chemicals from renewable feedstocks. For this study, a patented synthetic method was used to obtain gel forming polymers through the polycondensation of GA and several aliphatic diamines. The first time characterization and a potential practical application of such hydrogels is reported herein. Our findings indicate that the physical properties and gelling abilities of these materials correlate with the chemical structure of the precursor diamines used for polymerization. The hydrogels appear to have nanoparticulate nature, form via aggregation, are thermoresponsive, and appear suitable as controlled release systems for small molecules. Overall, this study further highlights the versatility of GA as a building block for the synthesis of sustainable materials, with potential for a wide array of applications.

A Controlled Antibiotic Release System for the Development of Single-Application Otitis Externa Therapeutics.

Ear infections are a commonly-occurring problem that can affect people of all ages. Treatment of these pathologies usually includes the administration of topical or systemic antibiotics, depending on the location of the infection. In this context, we sought to address the feasibility of a single-application slow-releasing therapeutic formulation of an antibiotic for the treatment of otitis externa. Thixotropic hydrogels, which are gels under static conditions but liquefy when shaken, were tested for their ability to act as drug controlled release systems and inhibit Pseudomonas aeruginosa and Staphylococcus aureus, the predominant bacterial strains associated with outer ear infections. Our overall proof of concept, including in vitro evaluations reflective of therapeutic ease of administration, formulation stability, cytocompatibility assessment, antibacterial efficacy, and formulation lifespan, indicate that these thixotropic materials have strong potential for development as otic treatment products.