Exosomal Bupivacaine: Integrating Nerve Barrier Penetration Capability and Sustained Drug Release for Enhanced Potency in Peripheral Nerve Block and Reduced Toxicity

Peripherally injected local anesthetics exhibit limited ability to penetrate peripheral nerve barriers, which limits their effectiveness in peripheral nerve block and increases the risk of adverse effects. In this work, it is demonstrated that exosomes derived from Human Embryo Kidney 293 cells can effectively traverse the perineurium, which is the rate‐limiting barrier within PNBs that local anesthetics need to cross before acting on axons. Based on this finding, these exosomes are used as a carrier for bupivacaine (BUP), a local anesthetic commonly used in clinical settings. The in vitro assessments revealed that the prepared exosomal bupivacaine (BUP@EXO) achieves a BUP loading capacity of up to 82.33% and sustained release of BUP for over 30 days. In rats, a single peripheral injection of BUP@EXO, containing 0.75 mg of BUP, which is ineffective for BUP alone, induced a 2‐h sensory nerve blockade without significant motor impairments. Increasing the BUP dose in BUP@EXO to 2.5 mg, a highly toxic dose for BUP alone, extended the sensory nerve blockade to 12 h without causing systemic cardiotoxicity and local neurotoxicity and myotoxicity. Exosomes derived from Human Embryo Kidney 293 cells are found to efficiently traverse the perineurium, which is the rate‐limiting barrier within peripheral nerve barriers that local anesthetics need to cross before acting on axons. By loading bupivacaine into exosomes, the prepared exosomal bupivacaine (BUP@EXO) formulation combines the ability to cross the peripheral nerve barrier with the function of sustained drug release. In a rat sciatic nerve model, the BUP@EXO formulation demonstrated enhanced potency in nerve blockade and reduced side effects compared to the bupivacaine control group.