FUNCTIONALIZATION, ANTIBACTERIAL ACTIVITY AND CHARACTERIZATION OF AN ALUMINA NANOPARTICLE WITH THE ANTIMICROBIAL PEPTIDE Ac-LYETxImnΔKE

Antimicrobial peptides (AMPs) have emerged as a promising alternative against multidrug-resistant bacteria due to their low propensity for inducing resistance, rapid bactericidal action, broad spectrum, and relevant clinical efficacy. Naturally present in the innate immune system of various organisms, their in vivo application is limited by proteolytic degradation. To overcome this challenge, this study functionalized alumina nanoparticles with the AMP Ac-LyeTxImnΔKE, aiming to protect the peptide from peptidase activity. The objective was to evaluate the in vitro antimicrobial activity of the functionalized nanoparticle, the isolated nanoparticle, and the free peptides Ac-LyeTxImnΔKE and LyeTxImnΔK-NH2 (synthesized at LASEB/UFVJM) against strains of Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, and Pseudomonas aeruginosa. The broth microdilution method (Mueller Hinton medium) was employed, with concentrations ranging from 1.6 to 100 µmol/L. Chloramphenicol (30 mg/mL) was used as a negative control. Assays were performed in triplicate on three different days, incubated at 35 °C for 24 h, and the MIC (minimum inhibitory concentration) was determined using 0.01% resazurin as the growth indicator. Results showed that peptide Ac-LyeTxImnΔK exhibited MIC values of 6.25 µmol/L against S. aureus and 12.5 µmol/L against P. aeruginosa and S. typhimurium. In turn, Ac-LyeTxImnΔKE and the functionalized nanoparticle displayed MICs of 12.5 µmol/L against S. aureus and P. aeruginosa, and 6.25 µmol/L against S. typhimurium. No activity was observed against E. coli under the tested conditions. The isolated nanoparticle showed no significant activity. The peptide Ac-LyeTxImnΔK and the functionalized nanoparticle were more effective against S. aureus, whereas Ac-LyeTxImnΔKE performed better against S. typhimurium; both exhibited similar activity against P. aeruginosa. The compounds were characterized by zeta potential analysis and gas chromatography–mass spectrometry (GC-MS). In conclusion, the tested peptides, particularly when associated with nanoparticles, show relevant antimicrobial potential. However, further studies are needed to elucidate their mechanisms of action, expand the range of tested strains, and validate in vivo models.