# PLGA nanoparticles loaded with recombinant antimicrobial protein PIP significantly improves the survival state and pathological damage caused by ETEC O8-induced sepsis in mice

## TL;DR

A new nanoparticle drug improves survival and reduces organ damage in mice with ETEC O8-induced sepsis.

## Contribution

A novel oral nano-platform using PLGA and PIP protein is developed and tested for treating bacterial sepsis in mice.

## Key findings

- PLGA-PIP nanoparticles reduced ETEC O8 loads in organs and improved clinical symptoms in septic mice.
- PLGA-PIP enhanced intestinal barrier function and suppressed pro-inflammatory cytokines in septic mice.
- Treatment with PLGA-PIP showed good biocompatibility and resistance to trypsin degradation.

## Abstract

Peptide-based antimicrobial drugs are promising alternatives to antibiotics owing to their broad-spectrum bactericidal activity and unique pathogen membrane disruption mechanism. Our previous study demonstrated that the recombinant antimicrobial protein PIL22-PBD-2 (PIP) inhibits pathogens and repairs intestinal cell damage in vitro, but its in vivo therapeutic potential against bacterial infections remains uncharacterized.

In this study, we developed an oral drug delivery nano-platform composed of PIP and poly(lactic-co-glycolic acid) (PLGA) using the double emulsion solvent evaporation method, and evaluated its therapeutic efficacy in a mouse model of sepsis induced by enterotoxigenic Escherichia coli O8 (ETEC O8).

PLGA-PIP nanoparticles were successfully prepared and showed excellent resistance to trypsin degradation as well as good biocompatibility in vivo. In septic mice, treatment with 300 mg/kg PLGA-PIP significantly alleviated weight loss and clinical symptoms (p < 0.05), reduced serum biochemical indices and organ indexes (p < 0.05), and decreased ETEC O8 loads in feces, liver, spleen, and kidneys (p < 0.01). PLGA-PIP also mitigated pathological damage in major organs, increased duodenal villus height and VH/CD ratio (p < 0.05), upregulated the expression of tight junction proteins (ZO-1, E-cadherin) and endogenous antimicrobial factors (Cryptdin-1, Reg3γ) (p < 0.01), and suppressed the expression of pro-inflammatory cytokines IL-6, IL-1β, and TNF-α (p < 0.01).

These findings demonstrate that PLGA-PIP effectively ameliorates ETEC O8-induced sepsis in mice by enhancing intestinal barrier function, reducing pathogen burden, and inhibiting inflammation. Therefore, PLGA-PIP represents a promising oral antibiotic alternative for the treatment of bacterial infections.