Intraneural delivery of CBD3A6K-RhB via PEG-PLGA nanoparticles for neuropathic pain therapy

Neuropathic pain, resulting from damage to the somatosensory nervous system, remains a clinical challenge with limited treatment options. Inhibiting the interaction between the upregulated N-type voltage-gated calcium channel (Ca_V2.2) and collapsin response mediator protein 2 (CRMP2) represents a promising therapeutic strategy. Here, we developed a novel, traceable peptide inhibitor (CBD3A6K-RhB) with enhanced binding affinity for this target. To overcome the delivery limitations of peptides, we engineered a targeted nano-delivery platform-CBD3A6K-RhB@PEG-PLGA nanoparticles (CRPPNs)-by encapsulating CBD3A6K-RhB into poly(ethylene glycol)-poly(lactic-co-glycolic acid) (PEG-PLGA) nanoparticles via microfluidic technology. The optimized CRPPNs exhibited uniform morphology, high encapsulation efficiency, and sustained peptide release in vitro. Importantly, CRPPNs were effectively internalized by dorsal root ganglion (DRG) neurons, leading to significant inhibition of calcium influx and calcitonin gene-related peptide (CGRP) release. In a rat model of chronic constriction injury (CCI) of the sciatic nerve, a single intraneural injection of CRPPNs produced potent and long-lasting anti-allodynic and anti-hyperalgesic effects, superior to the free peptide. Mechanistic investigations revealed that the analgesic effect was associated with the downregulation of Ca_V2.2 expression in both the DRG and spinal cord. Comprehensive biosafety evaluation confirmed the excellent biocompatibility of CRPPNs. Collectively, our study presents CRPPNs as an effective intraneural delivery system that enables sustained release of a potent peptide inhibitor, significantly enhancing therapeutic efficacy for neuropathic pain while minimizing systemic exposure.