Synthesis and antifungal efficacy of chitosan nanoparticles against notorious mycotoxigenic phytopathogens

Pathogenic fungi such as Fusarium verticillioides, Alternaria alternata, and Macrophomina phaseolina pose significant threats to agriculture and human health due to their production of carcinogenic mycotoxins. This study explored the antifungal potential of chitosan nanoparticles (ChNPs) against these fungi. ChNPs, synthesized via an ionic gelation method, exhibited a prominent UV–visible absorption peak at 250 nm, confirming successful nanoparticle formation. X-ray diffraction patterns revealed their amorphous structure, while FTIR analysis identified key functional groups, including hydroxyl and amine groups, with an average particle size of 50 nm. Antifungal assays demonstrated that ChNPs inhibited fungal growth in a concentration-dependent manner. Specifically, for F. verticillioides, ChNPs reduced growth by 20–60 % at concentrations ranging from 0.03 to 0.15 %, achieving complete inhibition at 0.21 %. Similarly, A. alternata exhibited a MIC of 0.24 %, and M. phaseolina reached a MIC of 0.26 % for complete growth suppression. Higher concentrations of ChNPs caused pronounced structural alterations in the fungi, including discoloration, fragmentation, and distortion of hyphae and conidia/sclerotia, which were linked to significant metabolic changes within the fungal cells. This study highlights the effectiveness of ChNPs as robust antifungal agents, demonstrating their ability to disrupt fungal morphology and enzyme activities.