Traditional methods for controlling plant pathogens rely on toxic chemicals, posing environmental and health risks. Developing sustainable, eco-friendly alternatives is crucial. Chitosan (CS)-based materials offer promising solutions for sustainable agriculture. We aimed to synthesize and characterize CS-based microparticles with varying properties and assess their antimicrobial performance to establish correlations between variations in physicochemical characteristics and their impact on performance within biological systems. We adjusted the synthesis parameters, producing particles labeled P1, P2, and P3, which have sizes of 0.19 ± 0.07 μm, 0.45 ± 0.32 μm, and 1.22 ± 0.32 μm, and zeta potentials of +7.6 ± 4.25 mV, +22 ± 3.51 mV, and + 12.9 ± 4.54 mV, respectively. Extensive toxicological screenings showed that these CS-based microparticles were non-toxic across cell cultures, mouse red blood cells, soil microbiota, nitrogen-cycling bacteria, and plant toxicity assays. Encouraged by these results, we evaluated their antimicrobial potential against economically important crop pathogens. The CS-based microparticles exhibited antimicrobial effects against the bacterium Pseudomonas syringae pv. tomato DC3000 and the fungus Fusarium solani f. sp. eumartii. Higher zeta potentials correlated with greater antimicrobial efficacy, evidenced by lower IC50 and minimum inhibitory concentration (MIC) values. These findings indicate that all three microparticles analyzed displayed antimicrobial activity against two economically significant crop pathogens, with P2 showing solid performance attributed to its physicochemical characteristics. Therefore, CS-based microparticles represent a promising, nontoxic, and environmentally friendly alternative for modern agriculture, with their biological activities potentially predictable through careful selection of physicochemical properties before the synthesis process.
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