Nanoparticle-based Strategies for Overcoming the Blood-Brain Barrier in CNS Disorders and Brain Cancer: Precision Diagnostics and Therapeutics for Alzheimer’s, Parkinson’s, Multiple Sclerosis, and Glioblastoma

Nanoparticle (NP)-based technologies are transforming the management of central nervous system (CNS) disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and brain cancer (BC), glioblastoma, by surpassing the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB). This review integrates NP approaches, comprising organic (e.g. liposomes, polymeric NPs), inorganic (e.g. gold, iron oxide), carbon-based, and hybrid systems, to overcome disease-specific barriers. In AD, superparamagnetic iron oxide NPs (SPIONs) and gold NPs (AuNPs) improve amyloid-beta plaque and tau protein detection, while liposomes precisely deliver anti-amyloid drugs. For PD, dopamine-loaded liposomes and cerium oxide NPs reinstate dopaminergic function and decrease oxidative stress, with improved motor outcomes. In MS, PEGylated liposomes and PLGA NPs regulate autoimmune responses, inducing remyelination and attenuating neuroinflammation. For BC, dendrimers and magnetic NPs facilitate targeted chemotherapy delivery across the BBB/BBTB, improving glioblastoma treatment outcomes. We compare NP types critically based on physicochemical characteristics, efficacy, toxicity, and clinical translation potential, highlighting gaps in long-term safety and scalability. Challenges like NP toxicity and regulatory complexities are discussed, suggesting biocompatible designs and standardized FDA/EMA pathways. By consolidating diagnostic and therapeutic innovations, this review outlines a roadmap for NP-based precision medicine, paving the way for clinical translation and better patient outcomes in CNS disorders and brain cancer.