# Bacterial vesicles-initiated in-situ spray-polymerized coating enables synergistic antibacterial-photothermal functionality for accelerating wound healing

## TL;DR

A new wound healing coating combines bacterial vesicles and a polymer to fight infection and boost tissue repair using heat from light.

## Contribution

A novel in-situ spray-polymerized coating integrating antibacterial and photothermal functions for wound healing is developed.

## Key findings

- LBEVs-PPy coating effectively inhibits pathogens like S. aureus, E. coli, and S. epidermidis.
- NIR-induced hyperthermia enhances angiogenic regulators VEGFA and ANGPT1 in HUVECs.
- The coating accelerates wound healing in a mouse model through synergistic antibacterial and photothermal effects.

## Abstract

Although microbial therapies can address the harm to beneficial bacteria and microbiome balance caused by traditional antibacterial treatments in skin damage and infection, their pathogenic potential limits clinical application. Bacterial extracellular vesicles (BEVs) offer a safer alternative by targeting microbes and modulating immunity.

Lactobacillus reuteri-derived BEVs (LBEVs) are functionalized with Fe3+ via electrostatic adsorption, and co-sprayed with pyrrole monomers onto wounds to initiate oxidative polymerization and then form conformal polypyrrole coatings (LBEVs-PPy). Thanks to the natural antibacterial activity of LBEVs, the LBEVs-PPy coating could inhibit the growth of pathogens efficiently. Furthermore, the mild hyperthermia induced by PPy's NIR-triggered photothermal activation significantly upregulates the expression of angiogenic regulators.

In vitro, LBEVs effectively inhibited the growth of S. aureus, E. coli, and S. epidermidis, demonstrating potent antibacterial efficacy. Following mild hyperthermia (42 °C for 1 h), HUVECs showed elevated expression of angiogenic regulators, including VEGFA and ANGPT1. This treatment also activates HSP90/p-eNOS pathway in HUVECs, thereby accelerating angiogenesis. In a mouse model of skin damage and infection, LBEVs-PPy coating significantly accelerates wound healing through synergistic mechanisms that integrate the antibacterial activity of LBEVs and the photothermal effect of PPy.

Our research developed an in-situ spray-polymerized coating integrating antibacterial and photothermal modalities, thus presenting a promising biotherapeutic platform for clinical wound management and tissue regeneration.