Drug nanocrystals: A review of their application in the topical treatment of skin infections

Drug nanocrystals, nano-sized delivery systems consisting of drug and stabilizers only, may be a valuable tool in the treatment of cutaneous infections, which remain a serious public health problem worldwide. This review aimed to compile scientific information published over the past 10 years on the topical use of nanocrystals for the treatment of cutaneous infections caused by fungi or bacteria (14 selected articles). Most articles synthesized nanocrystals by a top-down method, mainly the bead milling technique. After synthesis, nanocrystals were typically lyophilized and/or incorporated into a pharmaceutical formulation. The most used techniques for nanocrystal characterization were dynamic light scattering (particle size and polydispersity), electron microscopy (ultrastructural morphology) and high-performance liquid chromatography (solubility, dissolution, and drug release). A temperature of 4 °C was deemed optimal for storage. Several articles found that nanocrystals improved drug skin permeation and/or skin retention. Four articles conducted tests with fungi, nine articles with bacteria, and one article with fungi and bacteria, either in vitro or in vivo. In general, microbiological tests confirmed the greater effectiveness of nanocrystal formulations over conventional systems. The findings of this review demonstrate the potential of nanocrystals as safe and promising alternatives for the topical treatment of cutaneous infections caused by fungi or bacteria.