The rapid growth of nanotechnologies is increasing the likelihood of contact between nanomaterials and human beings and their environment. Nanoparticles (NPs) can interact with proteins, membranes, cells, DNA and organelles. It is therefore important to establish a better understanding of the interface between nanoparticles and biological components. These nanoparticle/biological component interfaces depend on colloidal forces as well as numerous dynamic biophysicochemical interactions. These interactions lead to the formation of protein crowns enveloping the particles, resulting in modifications to intracellular absorption phenomena and biocatalytic processes. These modifications can have undesirable biological effects or alter biocompatibility. Biomolecules, for their part, can induce phase transformations, restructuring and dissolution of nanomaterial surfaces. Probing and analyzing these different interfaces and their dynamics enables the development of predictive relationships between the structure and activity of NPs. These relationships are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and coatings present on their surface. It is very important to establish this knowledge reliably, as it should enable nanomaterials to be used more safely.
It is in this context, at the interfaces between nanomaterials and biological systems, that the bio-organic and synthetic worlds merge into a new science, which studies not only the parameters for the safe use of nanotechnologies, but also the design of tailor-made nanomaterials for biological applications. The "nano-bio" interface encompasses the dynamic physico-chemical interactions, kinetics and thermodynamics of matter exchange between nanomaterial surfaces and the surfaces of biological components (proteins, membranes, phospholipids, endocytosis vesicles, other organelles, DNA and all biological fluids). To enable this field to evolve, we need to understand the dynamic forces and molecular components that shape these interactions. Today, it is still impossible to describe with certainty all the biophysicochemical interactions at play at the nano-bio interface. However, the unification of partial knowledge generated by different disciplines should provide us with a conceptual framework to guide this exploration. Within this framework, we explore these interfaces from the point of view of the elementary forces that govern colloidal chemistry and the adaptations that occur at biological interfaces. After nanoparticles have been suspended in tissue or biological media, and after interaction with cells (membrane surfaces of endosomal compartments, organelles and cytoplasm), we analyze nanoparticle-biocomponent interfaces and discuss methods for probing the "nano-bio" interface. Determining the interactions of processes such as protein corona formation, cell-cell contact, particle packaging on the cell surface, endocytosis and intracellular biocatalysis, and probing these different interfaces require new ideas and imaging techniques. A better understanding of these mechanisms should enable us to make more informed decisions on how to design nano-objects.
