Photoinactivation mechanism of hypericin nanoencapsulated in P123 against Microsporum canis.

Aim: To evaluate the photodynamic mechanism of hypericin nanoencapsulated in P123 copolymer micelles against Microsporum canis in vitro.Material & methods: Antifungal susceptibility tests were performed, including the determination of the minimum fungicidal concentration and time-kill curve. Flow cytometry was used to evaluate the internalization of P123-Hyp in conidia and the activation of PDT type I and II mechanisms via the detection of reactive oxygen species (ROS), as well as to assess changes in the cell membrane using propidium iodide (PI) and cell morphology.

Results

P123-Hyp-PDT exerted a fungistatic action on fungus, maintaining this action up to 24 h after exposure, corroborating the PS internalization results, which showed satisfactory uptake of P123-Hyp from a concentration of 3.125 μmol/l. Among the ROS studied, singlet oxygen was detected. Furthermore, the increased fluorescence intensity of PI in treated cells indicated necrotic cell death, while the size and granularity of the cells were also altered.

Conclusion

Our results show, for the first time, a proposal for the mechanism of action of P123-Hyp-mediated PDT against M. canis, proving that it has a prolonged action on the fungus through activation of the type II photodynamic pathway, which resulted in disruption of the plasma membrane and cellular alterations.