Targeting the brain through the nose: Advances in polymeric nanoparticle delivery for schizophrenia.

Intranasal delivery of polymeric nanoparticles (PNPs) offers a promising approach for improving drug delivery to the central nervous system (CNS), particularly for treating schizophrenia. This delivery method enables direct nose-to-brain transport via olfactory and trigeminal pathways, bypassing the blood-brain barrier (BBB) and increasing therapeutic agent bioavailability in brain tissue while reducing systemic exposure and adverse effects. PNPs fabricated from natural polymers (chitosan, alginate, gelatin) and synthetic polymers (PLGA, polycaprolactone) provide controlled and sustained drug release, enhanced stability, and prolonged nasal residence time. Surface modifications with targeting ligands such as transferrin and lactoferrin have demonstrated 3.2 to 5.8 fold increases in brain accumulation compared to non-functionalized systems. Coating agents including polysorbate 80 and PEG further enhance nanoparticle transport efficiency and stability, with documented improvements of up to 10.86-fold in brain uptake. Beyond traditional antipsychotics, these nanocarrier platforms show significant potential for delivering neuropeptides (oxytocin, vasopressin) that address negative symptoms and cognitive deficits in schizophrenia. Novel nanoparticle-based delivery systems, including dendrimers, nanoemulsions, and lipid-based carriers, complement polymeric approaches to overcome limitations of conventional drug therapies. Despite robust preclinical efficacy data, clinical translation faces substantial challenges including interspecies anatomical differences (human olfactory epithelium represents only 3-5% of nasal surface area versus 50% in rodents), limited nasal cavity dose capacity, device-dependent delivery variability, absence of standardized assessment protocols, and insufficient long-term safety data for chronic administration. Future research must prioritize nanoparticle design optimization for enhanced mucoadhesion and mucopenetration, improved brain targeting through ligand engineering, validation in physiologically relevant models including ex vivo human tissue, comprehensive chronic toxicity evaluation, and alignment with evolving regulatory frameworks. Intranasal PNPs represent a paradigm shift in treating schizophrenia and other neuropsychiatric disorders, offering a non-invasive, patient-friendly, and potentially more effective therapeutic modality.