Preparation of Tetrodotoxin Extracellular Nanoparticles and Its Long-Term Local Anesthesia

Abstract

Tetrodotoxin (TTX) can be applied in local anesthesia by blocking the sodium channel on the cell membrane. However, TTX can cause systemic toxicity and neurotoxicity, which limits its application. In this study, we prepared tetrodotoxin-Extracellular vesicles (TTX-EVs) and evaluated their capability to achieve long-term local anesthesia without nervous system or systemic damage. Anesthesia effects and safety of TTX-EVs were evaluated by sciatic nerve block and neurobehavioral test, respectively. The local toxicity was evaluated by histological score of injection site and characterization of sciatic nerve. Systemic toxicity was assessed for side nerve injury and mortality. We found that when TTX was 10 μg/mL (3 μg/0.3 mL), the average duration of sensory block of TTX-EVs was 4.23 hours, much longer than that of free drugs (P < 0.001). This TTX-EVs complex had minimal muscle toxicity and inflammation, and had no change in the percentage or diameter of unmyelinated nerve fiber compared with the blank group. In conclusion, the entrapped TTX can prolong the nerve block time obviously, and the sustained-release carrier will not cause the neurotoxicity or systemic toxicity.