Nanoparticle Clearance and New Horizons in Engineered Drug Delivery

Nanomedicine has advanced rapidly as engineered nanoparticles have become increasingly capable of improving drug stability, targeting, controlled release, and biocompatibility. However, nanoparticle clinical utility relies on both delivery efficiency and how they are metabolized, retained, and cleared. This review examines the major biological pathways governing nanoparticle clearance and discusses how engineering parameters can be tuned to influence bioaccumulation, metabolism, excretion, and therapeutic performance with a wide range of available materials. This article is a narrative review of the recent and foundational literature on medically relevant nanoparticles, including lipid-based, polymeric, biopolymer, inorganic, polylactide, and bile-derived systems. All relevant translational, biochemical, chemical, and clinical literature from PubMed was searched from January 1971 to January 2026 to obtain a representative sample of work before information extraction. Nanoparticle clearance is governed by interconnected molecular and organ-level processes that vary according to composition, size, surface chemistry, and route of administration. Surface modifications with PEGylation, zwitterionic coatings, cholesterol, proteins, or responsive linkers can prolong circulation, alter immune recognition, and direct organ-specific handling. While rapid clearance remains desirable for many systemically acting drugs, prolonged intracellular or intratumoral retention may improve outcomes, particularly in boron neutron capture therapy and other activation-dependent treatments. Nanoparticle clearance should be regarded as a context-dependent design parameter rather than a universal limitation. Rational control of clearance kinetics may improve both safety and therapeutic effectiveness in next-generation engineered drug delivery systems.