Current Issue : July-September Volume : 2026 Issue Number : 3 Articles : 1 Articles
Neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) remain difficult to treat because therapeutic molecules must act within complex, spatially heterogeneous brain pathology while the blood-brain barrier (BBB) limits central nervous system exposure. Nanocarrier-based delivery can improve solubility, protect labile cargo, prolong circulation, enable controlled release and exploit endogenous or externally induced transport pathways. This narrative review critically examines the biological basis of the BBB, mechanisms of nanocarrier translocation, major carrier classes, disease-specific applications in AD and PD and the translational barriers that separate promising preclinical systems from clinically useful products. Liposomes and other lipid nanoparticles offer flexible cargo loading and surface engineering; polymeric nanoparticles provide tunable degradation and release; dendrimers provide multivalent functionalization; exosomes and cell-membrane-coated systems offer biomimetic interfaces; and inorganic or hybrid particles can add imaging, magnetic, catalytic, or stimulus-responsive functions. Receptor-mediated transcytosis, adsorptive transport, carrier-mediated pathways, intranasal delivery and focused ultrasound are complementary rather than interchangeable strategies. Importantly, brain delivery depends not only on nanoparticle composition but also on size, charge, ligand density, protein corona, disease stage, age, route and the integrity of the neurovascular unit. AD applications increasingly target amyloid-β, tau, neuroinflammation, oxidative stress and synaptic dysfunction, whereas PD systems focus on dopaminergic replacement, α-synuclein, mitochondrial stress, neuroinflammation and neurotrophic support. Despite compelling preclinical evidence, scalable manufacturing, long-term safety, quantitative biodistribution, human-relevant BBB models, reproducible characterization and regulatory standardization remain major bottlenecks. Future progress will depend on disease-stage-aware targeting, dual or multivalent ligands, biomimetic and stimuli-responsive designs and integrated pharmacokinetic, imaging and biomarker strategies that establish where intact nanocarriers travel, where cargo is released and whether this exposure changes clinically meaningful disease biology....
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