Cytotoxicity and colloidal behavior of polystyrene latex nanoparticles toward filamentous fungi in isotonic solutions

• Aspergillus oryzae entrapped positively charged PSL NPs in 154 mM NaCl, but not Aspergillus nidulans.
• A. oryzae had soft cell walls compared with A. nidulans.
• Positively charged PSL NPs showed high toxicity in 292 mM sucrose.
• Agar cultivated cells were hydrophobic compared with liquid cultivated cells.
• Hydrophobin on agar cultivated cells inhibited the uptake of PSL NPs.

The effects of surface physicochemical properties of functionalized polystyrene latex (PSL) nanoparticles (NPs) and model filamentous fungi Aspergillus oryzae and Aspergillus nidulans cultivated in different environment (aqueous and atmospheric environment) on the colloidal behavior and cytotoxicity were investigated in different isotonic solutions (154 mM NaCl and 292 mM sucrose). When the liquid cultivated fungal cells were exposed to positively charged PSL NPs in 154 mM NaCl solution, the NPs were taken into A. oryzae, but not A. nidulans. Atomic force microscopy revealed that the uptake of NPs was more readily through the cell wall of A. oryzae because of its relatively softer cell wall compared with A. nidulans. In contrast, the positively charged PSL NPs entirely covered the liquid cultivated fungal cell surfaces and induced cell death in 292 mM sucrose solution because of the stronger electrostatic attractive force between the cells and NPs compared with in 154 mM NaCl. When the agar cultivated fungal cells were exposed to the positively charged PSL NPs, both fungal cells did not take the NPs inside the cells. Contact angle measurement revealed that the hydrophobin on the agar cultivated cell surfaces inhibited the uptake of NPs because of its relatively more hydrophobic cell surface compared with the liquid cultivated cells.

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