A deadly hug: chitosan microspheres functionalized with MSI-78A antimicrobial peptide kill Helicobacter pylori

With the end of antibiotic era, newer therapeutic options, as anti- microbial peptides (AMPs), are a demand. Helicobacter pylori (Hp) was classified as 1 of the 16 antibiotic-resistant bacteria1 . MSI-78A is one of the fewer AMPs that demonstrated bactericidal effects against Hp2 . However, in vivo AMPs undergo protease degradation and proteins aggregation, reducing their effectiveness. AMPs immobilization onto a biomaterial surface is an advocated strategy to overcome these drawbacks 3 . This work intended the development of biocompatible chitosan microspheres decorated with MSI-78A (AMP-ChMic) capable of crossing the gastric mucosa and kill Hp in situ, after oral administration. Chitosan microspheres (ChMic), average diameter of 5 μm, were produced by spray drying. A heterobifunctional spacer (NHS-PEG- MAL) was bonded to the ChMic, allowed immobilizing the MSI-78A modified with a terminal cysteine on the C-terminal (MSI-78A-SH) in a controlled orientation. The resulting AMP-ChMic were able to retain their integrity in a wide range of acidic pH, proving their pH-resistance and validating this approach for gastric settings. The microparticles were tested in vitro against Hp J99 strain (highly pathogenic human strain), at different timepoints and in a microspheres’ range of concentrations (10 5 -107 mics/mL). Antimicrobial effect was seen after 2 hours in higher concentrations and it was maintained up to 6 hours. The fast-bactericidal effect indicates that MSI-78A can retain its activity when immobilized onto ChMic. AMP-ChMic demonstrated high poatential for Hp infection management, being an innovative strategy to non-antibiotic therapeutics.