Pharmacological Breakthroughs with Extracellular Vesicles-BasedNanomedicine: A Targeted Strategy to Cross the Blood-Brain Barrier inAlzheimer’s Disease

Alzheimer's Disease (AD) is a disabling neurodegenerative illness characterized by Amyloid-beta (Aβ) plaque deposition, tau tangles, and neuroinflammation. These pathological characteristics lead to progressive cognitive decline, and drug therapeutic approaches are bedeviled by extreme difficulty with the Blood-Brain Barrier (BBB) that prevents most drugs from effectively crossing into the brain. Extracellular vesicle-based nanomedicine is a prospective approach to overcome this hurdle. Extracellular vesicles are endogenously derived extracellular vesicles that can cross the BBB and deliver a variety of therapeutic cargos, including small interfering RNAs (siRNAs), microRNAs (miRNAs), proteins, and other small molecules. Since they can cross the BBB and exhibit low immunogenicity and toxicity, extracellular vesicles represent a promising strategy for drug delivery against AD. Recent studies have highlighted the potential of extracellular vesiclebased treatments to deliver anti-amyloid and anti-tau therapies, neuroprotectants (e.g., antioxidants), and immune-modulatory factors. Engineered extracellular vesicles containing siRNA against βsecretase eta-site app cleaving enzyme 1 (BACE1), anti-tau oligonucleotides, and anti-inflammatory cytokines have shown promising preclinical efficacy by reducing Aβ deposition, tau aggregation, and neuroinflammation. These changes have been associated with enhanced cognitive function. Besides, extracellular vesicle-based systems were investigated for gene-editing therapeutics with Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated protein 9 (CRISPR/ Cas9) and Antisense Oligonucleotides (ASOs). Besides scalability concerns, cargo-loading efficiency, and long-term toxicity, extracellular vesicle-based nanomedicine is an innovative platform for targeted drug deli.