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A short peptide, FHHF-11, was designed to change stiffness as a function of pH due to changing degree of protonation of histidines. As pH changes in the physiologically relevant range, G′ was measured at 0 Pa (pH 6) and 50,000 Pa (pH 8). This peptide-based hydrogel is antimicrobial and cytocompatible with skin cells (fibroblasts). It was demonstrated that the incorporation of unnatural AzAla tryptophan analog residue improves the antimicrobial properties of the hydrogel. The material developed can have a practical application and be a paradigm shift in the approach to wound treatment, and it will improve healing outcomes for millions of patients each year. 

Abstract The ability of bacteria to colonize and grow on different surfaces is an essential process for biofilm development. Here, we report the use of synthetic hydrogels with tunable stiffness and porosity to assess physical effects of the substrate on biofilm development. Using time-lapse microscopy to track the growth of expanding Serratia marcescens colonies, we find that biofilm colony growth can increase with increasing substrate stiffness, unlike what is found on traditional agar substrates. Using traction force microscopy-based techniques, we find that biofilms exert transient stresses correlated over length scales much larger than a single bacterium, and that the magnitude of these forces also increases with increasing substrate stiffness. Our results are consistent with a model of biofilm development in which the interplay between osmotic pressure arising from the biofilm and the poroelastic response of the underlying substrate controls biofilm growth and morphology. 

Abstract Infection of human cells by pathogens, including SARS‐CoV‐2, typically proceeds by cell surface binding to a crucial receptor. The primary receptor for SARS‐CoV‐2 is the angiotensin‐converting enzyme 2 (ACE2), yet new studies reveal the importance of additional extracellular co‐receptors that mediate binding and host cell invasion by SARS‐CoV‐2. Vimentin is an intermediate filament protein that is increasingly recognized as being present on the extracellular surface of a subset of cell types, where it can bind to and facilitate pathogens’ cellular uptake. Biophysical and cell infection studies are done to determine whether vimentin might bind SARS‐CoV‐2 and facilitate its uptake. Dynamic light scattering shows that vimentin binds to pseudovirus coated with the SARS‐CoV‐2 spike protein, and antibodies against vimentin block in vitro SARS‐CoV‐2 pseudovirus infection of ACE2‐expressing cells. The results are consistent with a model in which extracellular vimentin acts as a co‐receptor for SARS‐CoV‐2 spike protein with a binding affinity less than that of the spike protein with ACE2. Extracellular vimentin may thus serve as a critical component of the SARS‐CoV‐2 spike protein‐ACE2 complex in mediating SARS‐CoV‐2 cell entry, and vimentin‐targeting agents may yield new therapeutic strategies for preventing and slowing SARS‐CoV‐2 infection.