Focused ultrasound-mediated nanocarrier delivery across the blood-brain barrier for neurodegenerative diseases

The development of effective therapies for neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis remains a major challenge due to the restrictive nature of the blood-brain barrier (BBB). Conventional systemic drug delivery strategies often fail to achieve sufficient central nervous system (CNS) penetration while avoiding peripheral toxicity. Focused ultrasound (FUS), particularly when combined with microbubbles or nanocarriers, has emerged as a non-invasive approach to transiently and precisely open the BBB, enabling targeted delivery of therapeutics to the brain parenchyma. This review provides a comprehensive overview of the mechanisms by which FUS enhances CNS drug delivery, with a dedicated focus on its integration with nanoparticle-based systems, including liposomes, polymeric nanoparticles, dendrimers, metallic nanoparticles, and exosomes. We discuss how these nanocarriers can be engineered for improved stability, targeting specificity, and stimulus-responsive release upon FUS exposure. Recent advances in ultrasound technology, image guidance (particularly MRI), and therapeutic formulations are summarized, along with preclinical and clinical evidence across key neurodegenerative conditions. Despite promising results, several challenges remain, including long-term BBB stability, regulatory standardization, and scalability for broad clinical application. By integrating principles from acoustics, pharmacology, and nanotechnology, FUS-mediated drug delivery, especially in combination with smart nano systems, represents a significant advancement in precision neurotherapeutics, offering new hope for previously untreatable CNS diseases.