Physics in nanomedicine: Phenomena governing the in vivo performance of nanoparticles

Nanomedicine aims to increase the effectiveness of therapeutic and diagnostic agents by exploiting unique properties that arise when operating at the nanoscale. Despite the recent growth of the field, nanomedicine has only managed modest improvements over conventional molecular drugs and imaging probes. To increase the efficacy of nanomedicine requires understanding fundamental processes that govern the ability of nanoparticles to locate and remain at diseased sites within the body. These processes include a nanoparticle's interactions with cells and proteins, margination in blood vessels, permeation into diseased tissues, and diffusive ability to reach all diseased cells within the tissue. Each of these processes is governed by phenomena commonly studied within fields of the physical sciences. By employing knowledge of colloidal interactions, fluid dynamics, kinetics, statistical mechanics, and thermodynamics, researchers can rationally design nanoparticles to overcome previous limitations of nanomedicine. This review will highlight recent and exemplary studies that present valuable insights into the physical phenomena of nanomedicine and present improved next-generation nanoparticle designs by applying these insights.