Small extracellular vesicles (SEVs) offer a promising strategy for tissue regeneration, yet their short lifetime at the injured tissue limits their efficacy. Here, we show that kinetics of SEV delivery impacts tissue regeneration at tissue, cellular, and molecular levels. We show that multiple carefully timed applications of SEVs had superior regeneration than a single dose of the same total concentration of SEVs. Importantly, diabetic and nondiabetic wounds treated with a single time point dose of an injectable light-triggerable hydrogel containing SEVs demonstrated a robust increase in closure kinetics relative to wounds treated with a single or multiple doses of SEVs or platelet-derived growth factor BB, an FDA-approved wound regenerative therapy. The pro-healing activity of released SEVs was mediated at the tissue/cell level by an increase in skin neovascularization and re-epithelization and at the molecular level by an alteration in the expression of 7 miRNAs at different times during wound healing. This includes an alteration of has-miR-150-5p, identified here to be important for skin regeneration.

Here, we present new antimicrobial nanoparticles based on silica nanoparticles (SNPs) coated with a quaternary ammonium cationic surfactant, didodecyldimethylammonium bromide (DDAB). Depending on the initial concentration of DDAB, SNPs immobilize between 45 and 275 μg of DDAB per milligram of nanoparticle. For high concentrations of DDAB adsorbed to SNP, a bilayer is formed as confirmed by zeta potential measurements, thermogravimetry, and diffuse reflectance infrared Fourier transform (DRIFT) analyses. Interestingly, these nanoparticles have lower minimal inhibitory concentrations (MIC) against bacteria and fungi than soluble surfactant. The electrostatic interaction of the DDAB with the SNP is strong, since no measurable loss of antimicrobial activity was observed after suspension in aqueous solution for 60 days. We further show that the antimicrobial activity of the nanoparticle does not require the leaching of the surfactant from the surface of the NPs. The SNPs may be immobilized onto surfaces with different chemistry while maintaining their antimicrobial activity, in this case extended to a virucidal activity. The versatility, relative facility in preparation, low cost, and large antimicrobial activity of our platform makes it attractive as a coating for large surfaces.

Small extracellular vesicles (sEVs), through their natural ability to interact with biological membranes and exploit endogenous processing pathways to convey biological information, are quintessential for the delivery of therapeutically relevant compounds, such as microRNAs (miRNAs) and proteins. Here, we used a fluorescently‐labelled miRNA to quantify the efficiency of different methods to modulate the cargo of sEVs. Our results showed that, compared with electroporation, heat shock, permeation by a detergent‐based compound (saponin) or cholesterol‐modification of the miRNA, Exo‐Fect was the most efficient method with > 50% transfection efficiency. Furthermore, qRT‐PCR data showed that, compared with native sEVs, Exo‐Fect modulation led to a > 1000‐fold upregulation of the miRNA of interest. Importantly, this upregulation was observed for sEVs isolated from multiple sources. The modulated sEVs were able to delivery miR‐155‐5p into a reporter cell line, confirming the successful delivery of the miRNA to the target cell and, more importantly, its functionality. Finally, we showed that the membrane of Exo‐Fect‐loaded sEVs was altered compared with native sEVs and that enhanced the internalization of Exo‐Fect‐loaded sEVs within the target cells and decreased the interaction of those modulated sEVs with lysosomes.

Here we report a two-step surface modification methodology to radiolabel small extracellular vesicles (SEVs) with 64 CuCl 2 for PET/MRI imaging. The modification did not change or damage the morphology, surface receptor proteins and internal RNA content. Radiolabeled SEVs could be detected in organs with low accumulation such as the brain (0.4-0.5% ID/g) and their brain location determined by MRI.SEVs are nanovesicles, with sizes ranging between 30 and 200 nm, secreted by cells.