Cationic nanocrystalline suspensions: a potential approach for nose to brain delivery of L-dopa in Parkinson’s therapy

Levodopa (L-dopa) an effective treatment for Parkinson’s disease, but it exhibits low oral bioavailability. Intranasal L-dopa nanosuspensions were manufactured to improve bioavailability using the olfactory and trigeminal delivery routes for direct brain delivery. The development of L-dopa nanocrystals and in vitro characterization was undertaken. Nanosuspensions were optimized using Design of Experiments. The L-dopa nanosuspension was produced at 50 °C using sonoprecipitation and mechanical stirring. Water and ethanol were solvent and antisolvent, and Tween^® 80 and cetyltrimethylammonium bromide, stabilizing agents. The critical quality attributes (CQA) monitored were droplet size (PS), polydispersity index (PDI), Zeta potential (ZP), and percent yield (%), pH and osmolarity of the optimized formulation were monitored. SEM, pXRD, DSC, FTIR, and in vitro release were used for further characterization. Short-term stability testing at 4 °C and 22 °C was evaluated for 28 days. The mean PS, PDI, ZP, and % yield of the optimized nanosuspension were 161.4 ± 20.152 nm, 0.383 ± 0.090, +15.45 ± 1.664 mV, and 72.106 ± 0.023%, respectively. In vitro test results for the optimized formulation show the target CQA, had been met. The system may enhance the bioavailability of L-dopa when administered intranasally. In vivo studies are required to confirm nose-to-brain transport.