Nanomedicine & Nanoparticle Drug Delivery

Introduction & rationale

• Definition — Nanomedicine = a medicinal dosage form derived from nanotechnology — engineering of materials in the nanometre range (usually <100–200 nm) whose surface area, optical/magnetic/electrical and chemical/biological properties differ fundamentally from the same material at bulk scale.
• FDA two-parameter test — a product "involves nanotechnology" if it is engineered to have a dimension/structure in the 1–100 nm nanoscale, OR to exhibit dimension-attributable properties even up to 1 µm (1000 nm) — a deliberately broad, property-driven definition.
• Regulatory stance — the FDA has created no separate framework — nanomedicines are complex drug products that must meet the same quality/safety/efficacy standards as conventional medicines, which is why generic "nanosimilars" of most nanomedicines remain unapproved.
• Why nanoscale matters — nanomedicines have a complex in-vivo transport biology absent from conventional forms — opsonization & MPS/reticuloendothelial clearance, enhanced permeability & retention (EPR), lymphatic transport, receptor-mediated internalization.
• Therapeutic-index rationale — a free drug distributes to diseased and healthy cells → narrow therapeutic index; a targeted nanocarrier widens the TI by giving targeted, localized, prolonged and protected drug exposure, also shielding labile peptides/oligonucleotides from degradation.
• Conceptual lineage — targeted nanocarriers operationalise Paul Ehrlich's 1900 "magic bullet" — selectively hitting the disease target without harming the host; they contrast with conventional non-selective sustained-release forms (oral SR, depot parenterals, transdermal patches).