Antimycotic nail polish based on humic acid-coated silver nanoparticles for onychomycosis

BACKGROUND The objective of this work was the development of silver nanoparticles (AgNPs) coated with humic acid (HA) and their incorporation into an enamel for antifungal activity. AgNPs were synthesized by chemical reduction using sodium borohydride as a reducing agent and coated with HA. Uncoated AgNPs were synthesized as control. AgNPs and HA-AgNPs were characterized by ultraviolet-visible spectrophotometry, differential scanning calorimetry, dynamic light scattering, Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy and X-ray diffraction (XRD). Size of AgNPs and HA-AgNPs was recorded within the nano range, showing HA-AgNPs' higher stability than non-coated particles by presenting a single plasmatic band around 400 nm. RESULTS Thermal analysis showed conjugated endothermic peaks, which confirms the compatibility of HA-AgNPs. FTIR depicted absorptions between 1300 and 1000 cm(-1) (C(sic)C, Ar-H, respectively), demonstrating that HA is adsorbed onto AgNPs. Thermogravimetric analysis showed that HA does not alter the reduction in mass loss of AgNPs, while it was found by XRD that adding HA promoted the formation of more amorphous AgNPs. The effectiveness of HA-AgNPs was evaluated against three different fungal species. Minimum inhibitory concentration assays showed that similar to 0.5 mmol L-1 AgNPs was able to inhibit dermatophyte species growth. HA-AgNPs were incorporated into a commercial enamel at a concentration of 8% and their organoleptic characteristics, drying time, centrifugation test and thermal stress were evaluated. Enamels with AgNPs kept their physicochemical properties over 21 days of storage. CONCLUSION HA-AgNP nail polish is thus proposed as an innovative material for onychomycosis infections. (c) 2021 Society of Chemical Industry

Automated summary

The study successfully developed silver nanoparticles coated with humic acid for incorporation into enamel with excellent antifungal activity. Results demonstrated that HA-AgNPs exhibited higher stability and inhibition of fungal growth compared to uncoated particles.