Microwave-mediated synthesis of zinc oxide nanoparticles: a therapeutic approach against Malassezia species

Abstract

A successful protocol was developed to aid in the reduction in dandruff-causing fungi, namely Malassezia globasa and Malassezia furfur. Both the species were isolated from volunteers aged between 20 and 22 suffering from dandruff, cultured ex vivo, and tested against the presence of synthesised zinc oxide nanoparticles (ZnNP). Direct microscopy, scanning electron microscopy (SEM), and biochemical assays specific to Malassezia species were conducted to identify dandruff-causing fungal species. Microwave-mediated synthesis of ZnNP was performed and characterised by UV-vis, X-ray diffraction, and SEM. The nanoparticles were tested against both Malassezia species and proved highly effective in inhibiting these fungi, although M. furfur was more susceptible than M. globosa. An optimum amount of 100 ppm was found to be sufficient to work as an antifungal agent. Synergistic effects of ZnNP with commercial shampoos were tested, and the result showed enhanced antifungal effects. To mimic the natural biofilm formed by these species on human skin, the formation of fungal biofilm was allowed on polystyrene coverslips. ZnNP was effective in eradication biofilm. Since zinc is an essential mineral for all living organism and is considered as biocompatible, the synthesised nanomaterials can be used in the formulation of antidandruff shampoos.

Fig. 1

Characterisation of Zinc oxide nanoparticles (a) UV–visible spectra, (b) XRD profile, (c, d) SEM image of ZnO nanoparticles (ZnNP)

Fig. 2

In vitro growth and morphological study of Malassezia species. Colonies grown on (a, b) Dixon agar medium, (c, d) simple microscopic, (e, f) SEM images of M. globosa and M. furfur

Fig. 3

Characterisation of Malassezia yeasts (a, b) Catalase test, (c, d) Tween assimilation test, (e, f) Splitting of esculin of M. globosa and M. furfur

Fig. 4

Zone of inhibition around the well loaded with ZnNP (1, 25 ppm; 2, 50 ppm; 3, 100 ppm; and 4, 150 ppm). The central well was filled with sterile deionised water. Plate a, M. globosa and plate b, M. furfur

Fig. 5

Agar well diffusion assay (a, c) Inhibition of fungal growth on account of shampoos. (b, d) Synergistic effect of shampoo and ZnNP on fungal growth. Plate a and b, M. globosa and plate c and d, M. furfur. Wells 1–4 represent commercial shampoos tested (Head & Shoulders, Clinic Plus MEN, Clinic Plus WOMEN, and Clinic All Clear, respectively)

Fig. 6

Biofilm formed by co‐culture of two Malessizia species (M. furfur and M. globosa) (a, c) In the absence of nanoparticles, (b, d) In the presence of nanoparticles. (a, b) Light microscope image, (c, d) SEM image

Fig. 7

Cytoplasmic leakage (protein) from fungal cells due to membrane damaged by ZnNP treatment

Fig. 8

Effect of ZnNP on cell surface hydrophobicity of Malessizia species