Lyotropic Liquid Crystalline Based Nasal Spray for Improved Parkinson's Treatment: Enhanced Superior Nasal Tract Deposition and Antioxidation Strategy

The blood–brain barrier is one of the serious challenges in the treatment of Parkinson's disease (PD), which severely hinders the drug's brain bioavailability. In this study, a lyotropic liquid crystalline (LLC) based in situ gel nasal spray loaded with the first-line drug Levodopa (LDA) for PD is developed to resolve this issue based on a nose-to-brain drug delivery approach. Specifically, the two key stages of LLC-based in situ gel nasal spray, droplet deposition, and drug retention are tailored. By adjusting LLC's precursor solution's viscosity, the droplet deposition on the superior nasal tract can be increased by 18 times. Through nasal mucus-triggered sol–gel transition, the LDA nasal cavity retention is prolonged by three times. The epigallocatechin gallate is incorporated into the LLC-based in situ gel nasal spray to inhibit the autoxidation of LDA and alleviate the oxidative stress response in PD. The results show that the LLC-based in situ gel nasal spray has a 26-fold higher brain bioavailability of LDA compared to oral administration. The PD rats show a significant improvement in behavioral and cognitive disorders after administration. The LLC-based in situ gel nasal spray is proved to work by reducing oxidative damage. This study is anticipated to offer a promising strategy for the clinical application of LDA.