Advanced materials - Food grade melatonin-loaded Lipid Surfactant Submicron Particles (LSSP)-environmental impacts

: Lipid-based nanoparticles (LNPs) are advanced materials (AdMa), particularly relevant for drug delivery of poorly water-soluble compounds, while also providing protection, stabilization, and controlled release of the drugs/active substances. The toxicological data available often focus on the specific applications of the LNPs-drug tested, with indication of low toxicity. However, the ecotoxicological effects of LNPs are currently unknown. In the present study, we investigated the ecotoxicity of a formulation of Lipid Surfactant Submicron Particles (LSSPs) loaded with melatonin at 1 mg/mL. The LSSPs formulation has been developed to be fully compliant with regulatory for its potential use in the market and all components are food additives. The same formulation without the thickening agent xanthan gum (stabilizer in water phase) designated as LSSP-xg, was also tested. Two soil model invertebrate species were tested in LUFA 2.2 soil: Enchytraeus crypticus (Oligochaeta) and Folsomia candida (Collembola). Effects were assessed based on the OECD standard guideline (28 days) and its extension, the longer-term exposure (56 days). Assessed endpoints were survival, reproduction, and size. LSSPs and LSSP-xg were toxic to E. crypticus and F. candida reducing their survival and reproduction in a dose-dependent way: e.g., 28-day exposure: E. crypticus: LC/EC50 = 30/15 mg LSSPs/kg soil and F. candida LC/EC50 = 55/44 mg LSSPs/kg soil, with similar values for LSSP-xg. Size was also reduced for F. candida but was the least sensitive endpoint. There were no indications that toxicity increased with longer term exposure. The results provide relevant information on ecotoxicity of a AdMa and highlights the need for awareness of the potential risks, even on products and additives usually used in food or cosmetic industry. Further information on single components and on their specific assembly is necessary for the interpretation of results, as it is not fully clear what causes the toxicity in this specific AdMa. This represents a typical challenge for AdMa hazard assessment scenario.