Star-polymer unimolecular micelle nanoparticles to deliver a payload across the blood-brain barrier

Nanocarrier-mediated therapeutic delivery to brain tissue is impeded by tightly controlled transportation across the blood-brain barrier (BBB). Herein, we report a well-defined core-shell star-shaped unimolecular micelle (star-UMM; a single polymer entity) as an efficient BBB-breaching nanoparticle for brain-specific administration of the fluorescent anticancer drug doxorubicin and in vivo mapping of brain tissues by the near-infrared biomarker IR780 in mice. The star-UMM was engineered by precisely programming the polymer topology having hydrophobic and hydrophilic polycaprolactone blocks and in-built with lysosomal enzyme-biodegradation stimuli to deliver the payloads at intracellular compartments. In vivo imaging in mice revealed prolonged circulation of star-UMM in blood for >72 h, and whole-organ image-quantification substantiated its efficient ability to breach the BBB. Star UMM exhibited excellent stability in blood circulation and reduced cardiotoxicity, was non-hemolytic, had substantial uptake in the cortical neurons of the mouse brain, had lysosomal enzymatic-biodegradation, and exhibited negligible immunogenicity or necrosis. This newly designed star-UMM could have long-term applications in brain-specific drug delivery.