Nano-flow intracalvariosseous infusion enables skull-to-brain delivery of BBB-impermeable molecular and nanoscale agents in mice and rabbits.

RATIONALE: The blood-brain barrier (BBB) remains a major obstacle to the delivery of therapeutics for central nervous system (CNS) diseases. Although several BBB-penetrating or BBB-bypassing strategies have been investigated, there remains a need for sustained, controllable delivery routes that can support prolonged CNS exposure of BBB-impermeable agents. Recent anatomical studies have shown direct connections between skull bone marrow and brain, suggesting that the skull may serve as an alternative access route to the brain. Here, we assessed the feasibility of sustained intracalvariosseous infusion (ICO) as skull-to-brain delivery approach for BBB-impermeable molecular and nanoscale agents in mice and rabbits. METHODS: Four-week ICO was performed using a species-adapted nano-flow pump-cannula configuration that positioned the cannula terminus within the skull diploic space. A positive comparator was established by positioning the terminus beyond the inner skull cortex. Placement was verified by conventional CT and micro-CT. Brain-associated exposure of BBB-impermeable paclitaxel, antisense oligonucleotides and gold nanoparticles was assessed, along with systemic toxicity, bone marrow-derived immune activation, and neuroinflammation. RESULTS: ICO produced measurable brain-associated exposure of all three model agents in both species. Relative to the positive comparator, ICO achieved the highest relative brain-associated exposure for ASO, reaching approximately 24-28% of comparator levels, whereas PTX and AuNP showed lower but detectable exposure. Four-week ICO was not associated with overt hematological, biochemical, histopathological, or neuroinflammatory abnormalities under the present experimental conditions. CONCLUSIONS: These findings support the technical feasibility of ICO-based sustained infusion as a skull-to-brain delivery platform for controlled and prolonged CNS exposure of BBB-impermeable molecular and nanoscale agents through an extracerebral skull compartment.