Multifunctional to multistage delivery systems: The evolution of nanoparticles for biomedical applications

Nanomaterials are advancing in several directions with significant progress being achieved with respect to their synthesis, functionalization and biomedical application. In this review, we will describe several classes of prototypical nanocarriers, such as liposomes, silicon particles, and gold nanoshells, in terms of their individual function as well as their synergistic use. Active and passive targeting, photothermal ablation, and drug controlled release constitute some of the crucial functions identified to achieve a medical purpose. Current limitations in targeting, slow clearance, and systemic as well as local toxicity are addressed in reference to the recent studies that attempted to comprehend and solve these issues. The demand for a more sophisticated understanding of the impact of nanomaterials on the body and of their potential immune response underlies this discussion. Combined components are then discussed in the setting of multifunctional nanocarriers, a class of drug delivery systems we envisioned, proposed, and evolved in the last 5 years. In particular, our third generation of nanocarriers, the multistage vectors, usher in the new field of nanomedicine by combining several components onto multifunctional nanocarriers characterized by emerging properties and able to achieve synergistic effects.