Nano Self-assembly of μ-Conotoxin CnIIIC with Enhanced Muscle Relaxation Effect

INTRODUCTION: Muscle relaxants are fundamental to modern anesthesia, primarily targeting voltage-gated sodium channels. While μ-conotoxin CnIIIC is a potent peptide inhibitor, its clinical translation is hindered by poor metabolic stability and rapid systemic clearance. This study aimed to overcome these limitations and enhance its therapeutic potential via a rational molecular self-assembly strategy. METHODS: Two novel derivatives of μ-conotoxin CnIIIC (S1-CnIIIC and S2-CnIIIC) were designed and synthesized through site-specific side-chain modification. Their self-assembly properties were systematically characterized, and their efficacy was evaluated in a mouse model by measuring the duration of neuromuscular blockade, which was compared against the native peptide. RESULTS: S1-CnIIIC demonstrated a moderate propensity for self-assembly. In contrast, S2-CnIIIC efficiently formed micellar structures with a critical micelle concentration of 524.8 μM, indicating a superior self-assembly capability. In vivo, S2-CnIIIC not only exhibited a significantly prolonged duration of neuromuscular blockade but also showed a reduced systemic toxicity profile compared to the native CnIIIC. DISCUSSION: The molecular self-assembly approach markedly enhanced the stability and overall pharmacological performance of the peptide inhibitor. Our findings indicate that side-chain engineering effectively modulates the supramolecular assembly process, which in turn facilitates a more controlled drug release kinetics. The exceptional in vivo performance of S2-CnIIIC underscores the potential of rationally designed peptide nanostructures to address key challenges in peptide-based drug development. CONCLUSION: Molecular self-assembly presents a robust strategy to advance the clinical translation of μ-conotoxin derivatives. Specifically, the S2-CnIIIC derivative emerges as a highly promising candidate for next-generation muscle relaxants, successfully combining a prolonged neuromuscular blockade with an improved safety profile.