Lipid nanocapsules for transdermal delivery of ropivacaine: in vitro and in vivo evaluation

The objective of this research was to develop novel ropivacaine-loaded lipid nanocapsules (RPV-LNCs) and evaluate the potential of RPV-LNCs as external preparation for transdermal delivery. RPV-LNCs were prepared by phase inversion technique and optimized by response surface design. The permeation ability of RPV-LNCs was characterized both in vitro and in vivo. The results showed that the optimized RPV-LNCs represented typical core-shell structure with the mean diameter of 62.1 +/- 1.7 nm. The entrapment efficiency and drug loading were 92.6 +/- 1.3% and 1.35 +/- 0.20%, respectively. Moreover, the cumulative amount of RPV penetrated through excised skin from LNCs was 2.17 folds than that of the propylene glycol. In vivo, RPV-LNCs contributed a higher RPV concentration in plasma (5.743 mu g/mL). The RPV retained within dermis was 27.9 +/- 5.2 mu g/mL for LNCs, obviously remarkable than that of the propylene glycol group (15.6 +/- 3.9 mu g/mL). The skin histopathology study and scanning electron microscope (SEM) showed that interaction between LNCs and skin surface changed the apparent morphology of stratum corneum and broke the close conjugation of corneocyte layers. All the detailed evidence showed that LNCs could provide a promising tuning as a transdermal delivery system of ropivacaine. (C) 2014 Elsevier B.V. All rights reserved.