Abstract

Nanostructured lipid carriers (NLCs) are widely investigated as versatile drug delivery systems. In this study, we aimed to design, synthesize, and characterize a novel fluorescently labeled NLC platform incorporating a rhodamine B-oleic acid conjugate (Rd-OA) as a proof-of-concept model for future therapeutic applications. NLCs were prepared using Precirol (R) ATO 5, oleic acid and Rd-OA, and Tween (R) 20 (T20) or Tween (R) 80 (T80). The resulting nanoparticles exhibited sizes of 350-500 nm, narrow polydispersity indices (<0.2), and highly negative zeta potentials (similar to-30 mV), confirming stable colloidal properties. Rd-OA was efficiently integrated (100 % incorporation efficiency) with different concentrations. Molecular dynamics simulations provided atomic-level structural insights, revealing surfactant-dependent differences in component organization consistent with experimental data. NLCs were stable over a period of three months. In vitro assays in keratinocytes cells demonstrated a concentration-dependent cytotoxicity effect influenced by Rd-OA content, while fluorescence microscopy confirmed efficient cellular internalization of the NLCs. Collectively, these findings support the developed fluorescent NLC system as a stable, reproducible, and traceable platform suitable for future adaptation in drug delivery and imaging applications."