THE PROTEIN CORONA AT THE NANO-BIO INTERFACE: MECHANISMS, BIOLOGICAL CONSEQUENCES, AND TRANSLATIONAL HURDLES IN NANOMEDICINE

When nanoparticles enter biological fluids, they are immediately enveloped by a dynamic layer of proteins and other biomolecules, forming what is known as the protein corona. This corona fundamentally alters the nanoparticle's physicochemical properties, confers a new biological identity, and critically determines its in vivo fate—from cellular uptake and biodistribution to immune recognition and clearance. Despite two decades of intensive research, the protein corona remains a formidable barrier to the clinical translation of nanomedicines. This review provides a comprehensive overview of the fundamental mechanisms governing protein corona formation, including the Vroman effect, the distinction between hard and soft corona, and the influence of nanoparticle physicochemical properties such as size, charge, surface chemistry, and hydrophobicity. We critically examine how the corona modulates cellular interactions, endocytic pathways, immune responses, and targeting efficiency. The translational barriers posed by the corona—including loss of targeting functionality, batch-to-batch variability, and patient-specific corona compositions—are discussed in depth. Emerging strategies to overcome these barriers, including rational surface engineering, biomimetic coatings, and pre-coating approaches, are evaluated. We further highlight the potential of artificial intelligence and machine learning to predict corona composition and biological outcomes. Finally, we outline future directions, including the need for standardized methodologies, the exploration of the personalized protein corona, and the integration of multi-omics approaches to accelerate the safe and effective translation of nanoparticle-based therapeutics.