Optimization of Biodegradable Nanoparticles for Fluorescent Imaging with Drug and Cosmetic Coloring Dye Green 8

The development of bright, biocompatible fluorescent contrast agents is important for advancing biomedical imaging in applications ranging from early disease detection to surgical guidance. Clinically approved small-molecule dyes such as methylene blue (MB), indocyanine green (ICG), and fluorescein (FL) remain widely used, yet their performance is limited by rapid clearance and low specificity. Green 8 (G8), an FDA-approved drug and cosmetic coloring dye, exhibits a higher radiant efficiency under excitation and measurement conditions compared to these clinical dyes (1535× (MB), 2200× (ICG), and 1.3× (FL)). Green 8 is also known as HPTS, a fluorophore widely used as a free dye and incorporated into liposomal nanoparticles as a fluorescent reporter or hydrophilic tracer. To overcome limitations of small-molecule dyes, we encapsulated G8 into biodegradable nanoparticles (NPs) to enhance its brightness, stability, and tumor retention for improved imaging applications. Two different biodegradable NP constructs were developed and optimized as carriers for G8: silica NPs generated by a one-pot modified Stöber co-condensation of a G8-organosilane, and liposomal NPs fabricated via lipid film hydration. Each NP formulation was characterized for size, encapsulation efficiency, and fluorescence output, with iterative optimization to maximize imaging performance. Liposomal G8 NPs were selected for in vivo studies based on superior brightness and stability. Following intravenous administration in an oral squamous cell carcinoma xenograft model, G8 liposomes demonstrated significantly greater tumor accumulation relative to healthy adjacent tissue and controls, indicating passive tumor targeting for fluorescence-guided imaging. These findings highlight the potential of G8-loaded biodegradable NPs to improve tumor margin delineation during image-guided surgery, ultimately reducing reoperation rates and improving clinical outcomes.