Elucidating the Influence of Serum Concentration, Sex, and Particle Size on Iron Oxide Nanoparticle–Lipid Biocorona Formation

Biocorona (BC) formation is a critical determinant of nanoparticle (NP) biological identity and downstream interactions, yet lipid association within BCs remains comparatively understudied relative to proteins, despite its potential relevance to NP stability, biodistribution, cellular interactions, and clearance. A more complete understanding of NP–lipid interactions is essential for optimizing NP-based therapies and supporting their safe clinical translation. In this study, we evaluated how serum concentration, biological sex, and NP size influence lipid association with iron oxide (Fe3O4) NP BCs. Lipids associated with 50 or 100 nm Fe3O4 NPs were characterized following incubation in male or female human serum across increasing serum concentrations of 5%, 10%, 25%, 50%, or 75% (v/v). Increasing serum concentration promoted greater lipid association and increased BC complexity, with higher serum conditions yielding more compositionally diverse lipid coronas. BCs formed on 50 nm Fe3O4 NPs consistently contained more lipid species than those formed on 100 nm Fe3O4 NPs, indicating pronounced size-dependent differences in lipid recruitment. BCs formed in male serum also contained more lipid species and a greater number of unique lipids than corresponding female BCs, demonstrating that biological sex significantly influenced both lipid composition and abundance within the BC. Rank-based comparisons further indicated that lipid association was governed not only by serum abundance but also by selective binding behaviors. Together, these findings demonstrate that lipid corona formation is strongly shaped by both the biofluid environment and NP design variables, emphasizing the importance of considering lipid coronas in NP design and evaluation, particularly for applications in drug delivery, nanomedicine, and precision diagnostics.