Development of a ropivacaine-loaded nanostructured lipid carrier formulation for transdermal delivery

• Novel ropivacaine loaded nanostructured lipid carriers (RPV-NLCs) were prepared.
• RPV-NLCs showed improved permeation flux with Js of 5.386 μg cm−2 h−1.
• RPV-NLCs achieved a Cmax value of 5.98 μg/mL in blood.
• The permeation mechanism was studied by skin histopathology and DSC.

The main objective of this study was to evaluate the potential of ropivacaine-loaded nanostructured lipid carriers (RPV-NLCs) as a transdermal delivery system. RPV-NLCs were prepared by the method of emulsion evaporation–solidification at low temperature. The average entrapment efficiency and drug loading of the optimized RPV-NLCs were 81.45 ± 2.16% and 2.95 ± 0.37%, respectively. The average particle size was 203.5 ± 1.2 nm and the zeta potential was −40.2 ± 3.3 mV. The results of in vitro permeation study showed that RPV-NLCs could promote the permeation of RPV through skin to achieve transdermal delivery with Qn of 345.6 ± 12.4 μg cm−2. In the mice writhing test, RPV-NLCs provided analgesic effect by reducing the writhing response with an inhibition rate of 89.1% compared to the control group. In addition, the mechanism of permeation enhancement for NLCs investigated by histopathology study and DSC analysis showed NLCs could interact with stratum corneum, weaken the barrier function and facilitate drug permeation. In conclusion, NLCs could be a promising vehicle for transdermal delivery of RPV.

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