Nanoparticles and Their Applications in Biology: Synthesis, Nano–Bio Interactions, Biomedical Applications, Toxicity and Future Perspectives

Abstract

Nanoparticles have emerged as versatile platforms at the interface of materials science and biology because their small dimensions, high surface-area-to-volume ratio, tunable surface chemistry and size-dependent optical, magnetic and electronic properties permit interactions with biomolecules and cells that are difficult to achieve with bulk materials. This review summarizes the state of knowledge available through December 2012 on the classification and synthesis of biologically relevant nanoparticles, their interactions with biological systems, major biomedical applications, and the principal concerns surrounding biocompatibility and safety. Metallic, metal-oxide, magnetic, polymeric, lipid-based and semiconductor nanoparticles are discussed together with conventional physicochemical fabrication and biological or “green” synthesis using microorganisms and other biological systems. Particular attention is given to the nano–bio interface. In physiological fluids, nanoparticles rapidly adsorb proteins and other biomolecules, forming a corona that can alter their biological identity, cellular uptake, biodistribution, targeting and toxicity. Biomedical applications include drug and gene delivery, cancer therapy, diagnostic imaging, biosensing, magnetic separation and combined diagnostic–therapeutic approaches. Despite substantial promise, translation is constrained by variable physicochemical properties, aggregation, dose-dependent toxicity, oxidative stress, inflammatory responses, uncertain long-term fate, manufacturing reproducibility and the need for standardized characterization and risk assessment. The evidence available by 2012 indicates that biological performance cannot be predicted from composition alone; size, shape, surface charge, coating, dose, exposure route and the surrounding biological environment must be considered together. Future progress therefore depends on reproducible synthesis, rigorous nano–bio characterization and safety-by-design strategies that integrate therapeutic performance with biocompatibility.