Nanoemulsion Reformulation of Nitrosylcobalamin (NO-Cbl) Enhances Solubility, Stability, and Anti-Tumor Potency.

BACKGROUND: Nitrosylcobalamin (NO-Cbl), a vitamin B12-based nitric oxide donor, has demonstrated selective antitumor activity. However, its translational development has been limited by formulation challenges, including restricted solution concentration and concerns regarding stability. To address these limitations, we developed a nanoemulsion reformulation of NO-Cbl (NanoE-NO-Cbl). MATERIALS AND METHODS: NO-Cbl was reformulated into a nanoemulsion composed of soy lecithin, soybean oil, sucrose, and water using a high-shear Microfluidizer® processor. HPLC analysis and physicochemical characterization were used to assess NanoE-NO-Cbl for identity and stability across multiple storage conditions. Quantitative stability was evaluated by assay, chromatographic purity, pH, and droplet-size measurements. Antitumor activity was assessed in A375 melanoma cells using the sulforhodamine B (SRB) proliferation assay. RESULTS: Reformulation of NO-Cbl into a nanoemulsion increased the achievable formulation concentration relative to buffer-based preparations and enhanced potency approximately five-fold in A375 melanoma cells in vitro. NanoE-NO-Cbl demonstrated improved formulation stability under frozen and refrigerated storage conditions. CONCLUSION: Reformulation of NO-Cbl into a nanoemulsion improves formulation concentration, stability, and antitumor potency, providing a strong rationale for further preclinical development.