Pyrithione Zinc

Pyrithione zinc (ZnPT) exerted its antifungal activity through a dual mechanism of action involving intracellular zinc elevation and copper-mediated growth inhibition.
As a zinc ionophore, ZnPT transported zinc ions across the microbial cell membrane, causing elevated intracellular zinc levels that resulted in mismetallation and cellular stress. Additionally, endogenous copper released during skin renewal or supplied by the immune system participated in the antifungal effect through an extracellular transchelation reaction, converting ZnPT into copper pyrithione. This conversion further enhanced the antimicrobial activity against Malassezia species, the yeast primarily responsible for dandruff and seborrheic dermatitis. The mechanism depended critically on the gradual dissolution of ZnPT particles in lipid-rich skin environments, which liberated the bioactive monomeric form capable of membrane penetration. This multitarget approach, affecting both metal homeostasis and membrane integrity, explained the potent and broad-spectrum antifungal activity of pyrithione zinc in topical applications.

Fig. 1 Anti-fungal mechanisms of action for Zinc pyrithione. (Mangion S E.; et al. 2021)

Pyrithione zinc was successfully encapsulated into biodegradable poly(lactic acid) (PLA) nanoparticles using the emulsification-solvent evaporation technique at a biocide-to-polymer ratio of 40%. The encapsulation process was optimized using dichloromethane as the organic solvent due to the poor solubility of pyrithione zinc in acetone. The resulting PLA nanoparticles exhibited a submicron size range suitable for incorporation into water-based antifouling coatings.
Encapsulation addressed two major challenges of pyrithione zinc in marine applications: its sensitivity to photolysis, with a half-life ranging from 15 minutes to over 30 days depending on degradation conditions, and the need for controlled release to maintain long-term antifouling activity. The nanoparticle formulation enabled sustained release of the biocide while protecting it from premature environmental degradation. This approach demonstrated the feasibility of using biodegradable polymeric nanoparticles to deliver pyrithione zinc for eco-friendly antifouling applications, reducing the environmental impact compared to conventional heavy metal-based coatings.

Fig. 2 Size (PS), size distribution (PdI), zeta potential and encapsulation efficiency (EE) values of the prepared PLA particles. (Kamtsikakis A.; et al. 2017)