Ligand-free alkyl-modified chitosan nanoparticles are preferentially internalized by microglia and deliver curcumin to suppress cytokine release.

Microglia become activated during glioblastoma multiforme (GBM) and release proinflammatory mediators that support tumor progression, making them an attractive delivery target. Chitosan nanoparticles (CsNPs) have been reported to cross the blood-brain barrier (BBB), and their behavior can be tuned by chemical modifications. This study developed lipophilic alkyl-modified CsNPs, quantified their uptake by brain endothelium and microglia, and assessed their ability to deliver curcumin as a lipophilic anti-inflammatory cargo. Chitosan was conjugated to butyl glycidyl ether, labeled with fluorescein isothiocyanate and formulated into NPs by ionic gelation. Uptake was quantified in an hCMEC/D3 Transwell model of the BBB, in primary rat microglia and in the SIM-A9 cells, under resting and lipopolysaccharide (LPS)-stimulated conditions, using sucrose to inhibit clathrin-mediated endocytosis and trypan blue (TB) to quench extracellular fluorescence. Preferential uptake was assessed by direct co-culture of SIM-A9 and U87 MG glioma cells. Butyl-CsNPs were larger (456 ± 5 nm) than CsNPs (170 ± 10 nm) yet internalized more efficiently. Uptake was unaffected by sucrose, suggesting the NPs were engulfed by macropinocytosis. The TB technique showed that NPs were effectively localized intracellularly. In co-culture, butyl-CsNPs were preferentially engulfed by microglia over glioma cells. Curcumin was encapsulated with an efficiency of approximately 69-70% and was retained more effectively by butyl-CsNPs. Finally, encapsulated curcumin was less cytotoxic than free curcumin while suppressing LPS-induced TNF-α and IL-6 release (p < 0.0001). Butyl-CsNPs therefore yield a ligand-free carrier that is preferentially internalized by microglia and can deliver a lipophilic anti-inflammatory drug in an active form.