Sequence-dependent mechanical, photophysical and electrical properties of pi-conjugated peptide hydrogelators

The ability to modulate intermolecular interactions in such a way as to impact nano-, micro- and even macroscale properties is an attractive aspect of self-assembling systems. We present an investigation of sequence-dependent rheological, photophysical and electrical properties of semiconducting peptide hydrogelators. Five different pi-conjugated peptides containing a quaterthiophene core were studied, wherein the relative size and hydrophobicity of the amino acid residues adjacent to the pi-electron core were varied in order to assess the impact of molecular variation on nanoscale and bulk material properties. Steady-state spectroscopic measurements of the peptides once assembled into 1D-nanostructures show distinct spectral characters as the relative size of the amino acid side chain adjacent to the pi-electron core increases. Those peptides that formed hydrogels differed in network topography and rheological properties, with storage modulus (G') values ranging from similar to 3 to 20 kPa. The electrical properties of the peptide nanostructures were characterized by measuring the sheet resistance of dried peptide films on glass substrates. This study provides insights on the effects of amino acid sequence on the nanoscale to the macroscale electrical transport and mechanical properties of nanostructure-forming pi-conjugated peptides

Endothelial extracellular vesicles contain protective proteins and rescue ischemia-reperfusion injury in a human heart-on-chip

Extracellular vesicles (EVs) derived from various stem cell sources induce cardioprotective effects during ischemia-reperfusion injury (IRI). These have been attributed mainly to the antiapoptotic, proangiogenic, microRNA (miRNA) cargo within the stem cell-derived EVs. However, the mechanisms of EV-mediated endothelial signaling to cardiomyocytes, as well as their therapeutic potential toward ischemic myocardial injury, are not clear. EV content beyond miRNA that may contribute to cardioprotection has not been fully illuminated. This study characterized the protein cargo of human vascular endothelial EVs (EEVs) to identify lead cardioactive proteins and assessed the effect of EEVs on human laminar cardiac tissues (hlCTs) exposed to IRI. We mapped the protein content of human vascular EEVs and identified proteins that were previously associated with cellular metabolism, redox state, and calcium handling, among other processes. Analysis of the protein landscape of human cardiomyocytes revealed corresponding modifications induced by EEV treatment. To assess their human-specific cardioprotection in vitro, we developed a human heart-on-a-chip IRI assay using human stem cell-derived, engineered cardiac tissues. We found that EEVs alleviated cardiac cell death as well as the loss in contractile capacity during and after simulated IRI in an uptake- and dose-dependent manner. Moreover, we found that EEVs increased the respiratory capacity of normoxic cardiomyocytes. These results suggest that vascular EEVs rescue hlCTs exposed to IRI possibly by supplementing injured myocytes with cargo that supports multiple metabolic and salvage pathways and therefore may serve as a multitargeted therapy for IRI