In vitro evaluation of antimicrobial food packaging: Assessing its inflammatory and sensitization potential

Skin sensitization is a key endpoint in chemical safety assessment for cosmetics and personal care products and is increasingly suggested for consideration in the evaluation of packaging materials, especially food packaging materials. Keratinocyte activation, involving oxidative stress, cytokine release, and the engagement of stress-related signaling pathways, represents an early and critical event in this process. In this study, we evaluated the responses of primary keratinocytes (PK), epidermis equivalents exposed to solutions (Epi-Sol), and coatings (Epi-Coat) to known skin sensitizers and antimicrobial agents included in food packaging. Cytokine measurements (IL-1α, IL-6, IL-8, IL-18), gene expression profiling of stress and immune-related genes (HMOX1, MMP10, DUSP1, HSP90AA1, ICAM1, IL4R, IL23A, IL33), and histological analyses were performed. PK models exhibited the strongest and most diverse responses, with consistent HMOX1 upregulation and robust inflammatory signaling. Epi-Sol models exhibited moderate responses, whereas Epi-Coat models showed lower reactivity, emphasizing the impact of both exposure method and model selection. Nanoparticles (Ag-NPs, ZnO-NPs) triggered exposure-dependent effects, with coatings limiting inflammatory signaling and tissue penetration. Histological changes confirmed barrier disruption and keratinocyte hyperproliferation in models exposed to stronger sensitizers. Overall, these findings demonstrate that no single biomarker or model is sufficient for accurate safety assessment and support the use of multi-test, multi-endpoint evaluation strategies - particularly for emerging applications like food-contact materials - to ensure reliable hazard identification and material safety evaluation.