This study involved the synthesis and characterization of chitosan nanoparticles loaded with nobiletin (CNpN) and assessed their toxicity and cellular internalization in eukaryotic cell models (Saccharomyces cerevisiae and Candida albicans). Nanoparticles were prepared via the nanoprecipitation method and physicochemically characterized to determine their hydrodynamic diameter using dynamic light scattering (DLS), their surface charge through ζ-potential measurements, and their chemical structure via Fourier-transform infrared spectroscopy (FTIR). The hydrodynamic diameter and ζ-potential of chitosan nanoparticles (CNp) and CNpN were found to be 288.74 ± 2.37 nm and 596.60 ± 35.49 nm, and 34.51 ± 0.66 mV and 37.73 ± 0.19 mV, respectively. The scanning electron microscopy (SEM) images displayed a particle size of approximately 346 ± 69 nm, with notable sphericity for CNpN. FTIR analysis provided evidence of potential imine bonding between chitosan and nobiletin. Membrane integrity damage could be observed in both S. cerevisiae and C. albicans yeast stained with propidium iodide, demonstrating membrane integrity damage caused by CNp and CNpN, where higher concentration treatments inhibited the development of yeast cells. These findings suggest a selective therapeutic potential of CNpN, which could be promising for the development of antifungal and anticancer therapies. This study contributes to understanding the interaction between nanoparticles and eukaryotic cells, offering insights for future biomedical applications.

Colletotrichum species are among the most destructive phytopathogens worldwide, with appressorium-mediated penetration representing a critical stage in host infection. Targeting this morphogenetic transition offers a promising strategy for sustainable disease control by interfering with the infection process rather than solely inhibiting fungal growth. In this study, chitosan–κ-carrageenan nanoparticles (CS–κ-CRG) without and with lysozyme (CS–κ-CRG/Lz) were synthesized, characterized, and evaluated for their ability to inhibit appressorium formation in Colletotrichum siamense, a strain exhibiting low sensitivity to chitosan. The nanoparticles showed monodisperse size distributions, with hydrodynamic diameters of 503 and 333 nm for CS–κ-CRG and CS–κ-CRG/Lz, respectively, positive surface charges of approximately +26 mV, spherical morphology, and a lysozyme encapsulation efficiency of 63%. Both formulations significantly reduced conidial viability and delayed germination, inducing morphological alterations such as conidial swelling, hyphal deformation, and vacuolization. Fluorescence microscopy using calcofluor white and propidium iodide revealed disturbances in cell wall organization and loss of membrane integrity. Both nanomaterials markedly affected appressorium development in a concentration- and formulation-dependent manner. Notably, CS–κ-CRG/Lz showed stronger suppression of appressorium formation, whereas at 200 µg·mL⁻¹, CS–κ-CRG nanoparticles stimulated appressorium formation, suggesting that sublethal nanoparticle stress may trigger compensatory or hyper-pathogenic responses. These findings highlight the potential and complexity of utilizing chitosan-based nanomaterials for phytopathogen management and emphasize the importance of mechanistic and dose–response evaluations before field application.

Anthracnose is a disease caused by phytopathogenic fungi such as Colletotrichum siamense that attacks plants and fruits causing great postharvest losses. Different alternatives for the control of this fungus have been studied. In the present study, we evaluated the in vitro antifungal activity of the methanolic extracts of Baccharis glutinosa (ExB) and Jacquinia macrocarpa (ExJ) individually, as well as in combination with chitosan (CS), along with their toxicity in different models. Using the radial growth technique, it was observed that the mycelial development of C. siamense was altered and reduced during exposure to the different treatments evaluated during the first hours of incubation, indicating a fungistatic effect. While the cell viability, by colorimetric assay using the XTT salt, showed alteration since the chitosan reduced proliferation by 50%, while the plant extracts and their mixtures with chitosan reduced approximately 40% indicating cell damage, which was confirmed by fluorescence microscopy. In addition, toxicity tests demonstrated that the J. macrocarpa extract significantly affected the germination percentage of Lactuca sativa seeds, whereas radicle length was reduced in all treatments except for chitosan. The larval survival test for Artemia salina with the extracts indicated their potential toxicity by causing up to 60% mortality. The results indicate that ExB and ExJ mixed with CS are a good option for controlling C. siamense; however, at the concentrations used, they exhibit a toxic effect on the evaluated models.

Anthracnose is a disease caused by phytopathogenic fungi such as Colletotrichum siamense that attacks plants and fruits causing great postharvest losses. Different alternatives for the control of this fungus have been studied, and in the present study we evaluated the in vitro antifungal activity of chitosan mixed with methanolic extracts of Baccharis glutinosa and Jacquinia macrocarpa as well as toxicity in different models. Using the radial growth technique, it was observed that the mycelial development of C. siamense was altered and reduced during exposure to the different treatments evaluated during the first hours of incubation, indicating a fungistatic effect. While the cell viability, by colorimetric assay using the XTT salt, showed alteration since the chitosan reduced proliferation by 50 %, while the plant extracts and their mixtures with chitosan reduced approximately 40 % indicating cell damage, which was confirmed by fluorescence microscopy. In addition, toxicity tests showed that the extract of J. macrocapra affected the germination percentage of Lactuca sativa seeds while radicle length was reduced in all treatments, except with chitosan alone. The larval survival test for Artemia salina with the extracts indicated their potential toxicity by causing up to 60% mortality. The results indicate that the extracts of B. glutinosa and J. macrocarpa mixed with chitosan are a good option for the control of C. siamense, but at the concentrations used they show a toxic effect in the models evaluated.