Preparation of Novel Ropivacaine Hydrochloride-Loaded PLGA Microspheres Based on Post-loading Mode and Efficacy Evaluation

Abstract Low encapsulation efficiency of the drug usually exist in hydrophilic drug which was embedded by hydrophobic materials directly in traditional method. In order to solve this problem, a novel preparation strategy which called “post-loading mode” was innovatively designed in this study: ropivacaine hydrochloride (ROP), a hydrophilic drug used in the field of anesthesia and analgesia, was encapsulated into the pre-prepared porous Poly (lactic-co-glycolic acid) (PLGA) microspheres; the porous PLGA microspheres (PLGA-Ms) with self-healing characteristic were used to obtain ROP-PLGA-Ms (with particle size around were 38 μm), in which drug loading (DL) was 8.72%. A rat sciatic nerve block model was established to evaluate the efficacy of ROP-PLGA-Ms. Exparel®, a bupivacaine liposome suspension approved by the FDA, was defined as reference agents in this study. The results showed that the injection of ROP, Exparel®, and ROP-PLGA-Ms were injected to the peripheral sciatic nerve could lead to motor dysfunction and sensory nerve block unanimously, and the onset time was less than 10 minutes for all cases. In addition, in comparison with ROP injection and Exparel®, the nerve block time of ROP-PLGA-Ms was significantly prolonged (P