In Vitro Analysis of Heavy Metal Adsorption by Zeolite Skin Care Formulations Using a Quality by Design Approach

Zeolites are microporous aluminosilicate minerals widely recognized for their adsorption and ion-exchange properties. Their capacity to capture toxic heavy metals has prompted growing interest in their use as anti-pollution agents in skin care formulations. This study investigates zeolite-based creams through an in vitro permeation test using Franz diffusion cells within a Quality by Design (QbD) framework. A 2 × 2 × 2 full factorial design was applied to evaluate the effects of three critical factors: membrane type (Strat-M^® vs. silicone), dosage (10 vs. 20 mg), and dosage regimen. The adsorption and retention of five heavy metals, cadmium (Cd), cobalt (Co), chromium (Cr), lead (Pb), and nickel (Ni), were assessed over 12 h using an in vitro membrane model. The cream containing Zeolite demonstrated significantly higher adsorption of Cr, Co, and Cd compared to placebo and membrane controls, while Ni and Pb exhibited less consistent patterns. No sampling of the receptor compartment was performed; therefore, the analysis focused on metal residues in the donor and membrane compartments. Statistical analyses confirmed the significance of these findings, and graphical trends further supported zeolite's selective adsorption behavior. Overall, the results provide mechanistic and statistical evidence supporting zeolite as a promising active ingredient for the development of anti-pollution skin care formulations and offer a methodological framework for assessing metal adsorption in topical products.