INVESTIGATION OF SIZE STABILITY AND STRUCTURAL CHARACTERIZATION OF CHOLESTEROL-RICH NANOEMULSION (LDE)

Cholesterol-rich nanoemulsion (LDE) can transport chemotherapeutic agents through the bloodstream, targeting neoplastic and inflammatory tissues, thereby enhancing drug biodistribution and minimizing toxicity. However, the structural stability of LDE particles, both with and without drugs, has not been thoroughly examined. This study aims to investigate the size stability and structural characterization of LDE and LDE associated with methotrexate (MTX), paclitaxel (PTX) and etoposide (ETO) in aqueous solution over time using small-angle X-ray scattering (SAXS and Ultra-SAXS) and dynamic light scattering (DLS) over 3 months. Results demonstrate that LDE and its drug-associated shape maintain reproducible and stable particle diameter, physical structure, and aggregation behavior over a three-month period. DLS and USAXS measurements, taken at regular intervals, showed average particle diameters of approximately 32nm for LDE alone, 31nm for LDE-paclitaxel, 35nm for LDE-methotrexate, and 36nm for LDE-etoposide. USAXS indicated that LDE nanoparticles are quasi-spherical, while SAXS revealed a layered organization of drug molecules within the particles. The LDE-ETO I(q) curves show a weak peak at q=0.17 Å^-1, corresponding to a repeating distance of ~ 4 nm. This may indicate a periodic organization of the ETO in the core of the LDE particle. We obtained that LDE-ETO has a crystallite size of D = 8.4 nm. The LDE-MTX association presents a more pronounced peak at 0.11 Å^-1, corresponding to a repeating distance of 5.7 nm. LDE-MTX has a crystallite size of D = 2.5 nm. This may indicate a periodic organization of the MTX in the core of the LDE particle. In the LDE and LDE-PTX scattering curves it was not possible to clearly identify peaks, indicating a more homogeneous distribution of the molecules in the particle core. These formulations were effectively tested in animal models and patients with cancer or cardiovascular disease, exhibiting low toxicity, good tolerability, and potentially superior pharmacological effects. Our findings enhance the understanding of the structural characteristics of LDE formulations, supporting future clinical trials of this innovative nanomedicine.