RETRACTED ARTICLE: Preparation and characterization of novel lipid nanocapsules of ropivacaine for transdermal delivery.

Ropivacaine, a novel long-acting local anesthetic, has been proved to own superior advantage. However, the application form used in clinic, ropivacaine hydrochloride (Naropin Injection), which should be administed intravenously, is causing poor patient convenience. The purpose of this study was to formulate ropivacaine (RPV) in lipid nanocapsules (LNCs) and character the potential of LNCs in delivering RPV transdermally to exploit novel external preparation. The RPV-LNCs were successfully prepared by phase inversion technique and the formulation was characterized in terms of size, zeta potential, ex vivo permeation study, and pharmacodynamics. The prepared RPV-LNCs displayed a typical core-shell structure with a narrow size distribution of 62.1 ± 1.7 nm and drug loading of 1.35 ± 0.20%. The results of differential scanning calorimetry (DSC) analysis and X-ray diffraction showed that RPV was in amorphous crystalline state when encapsulated into LNCs. Furthermore, the results of ex vivo permeation study displayed that RPV-LNCs had an improved permeability (349.0 ± 11.5 μg cm(-2) versus 161.0 ± 1.3 μg cm(-2)) compared with free RPV. The results of histopathology study showed that interaction between LNCs and skin could break the close conjugation of corneocyte layers. In the mice writhing test, RPV-LNCs exhibited obvious analgesic effect by both prolonging pain latency and reducing the writhing response with an inhibition rate of 91.3% compared to the control group. In conclusion, RPV-LNCs could be a promising delivery system to encapsulate RPV and deliver RPV for transdermal administration.