Effect of Ultrasound on the Physicochemical and Microbiological Performance Characteristics of Ampicillin-Loaded Chitosan-Phytic Acid Nanoparticles

The increasing prevalence of antimicrobial resistance has driven the development of nanocarrier-based antibiotic delivery systems. In this study, ampicillin-loaded chitosan nanoparticles crosslinked with phytic acid were synthesized by ultrasound-assisted ionic gelation using three sonication amplitudes (30, 35 and 40%). The influence of ultrasound energy on particle size, polydispersity, zeta potential, encapsulation efficiency and antibacterial activity against Staphylococcus aureus ATCC 25923 was investigated. Nanoparticles exhibited sizes ranging from 285.7 ± 6.9 to 670.1 ± 39.4 nm, positive zeta potentials between +31 mV and 49 mV, depending on molecular weight and deacetylation degree of chitosan, and encapsulation efficiencies up to 73%. Increasing ultrasound amplitude reduced particle size and enhanced antibacterial activity, decreasing the MIC of ampicillin from 1.0 μg/mL to 0.25 μg/mL for the nanoparticles. These findings demonstrate that ultrasound-assisted ionic gelation improves nanoparticle physicochemical properties and potentiates the antibacterial performance of ampicillin, representing a promising strategy for antibiotic delivery.