Nanostructured oleic acid/polysorbate 80 emulsions with diminished toxicity in NL-20 cell line: Insights of potential drug carriers.

Nanoemulsions (NE) are nowadays required drug nanocarriers. We have selected i) oleic acid (OA) as oil (O), ii) polysorbate 80 (PS80) as surfactant (S), and iii) water (W) in a prototype NE. Our best formulation had O:S ratio [OA]/[PS80] = 0.0708/0.0382 = 1.85 [mol·L-1], implying 1.85 parts of OA covered/stabilized by 1 part of PS80, giving 71.86 nm and 0.42 polydispersity index (PDI) in NE, determined by DLS and TEM. These nanosystems stored at room temperature/darkness stabilized up to 12 months (measured by DLS and TEM) maintaining very similar particle sizes and sometimes decreasing PDI. NE stability was determined by DSC, evidencing reversibility upon heating from 25 to 100 °C, increasing to 125 °C (sealed systems) produced more attenuated heating profiles in second and third cycles, compared with first, indicating partial but enough stability for storage means. NE cytotoxicity tests were conducted on immortalized normal lung epithelial cells (NL-20), as reference. The results show 50 % inhibitory concentrations (IC50,µM) of 1100, OA, and 2.6, PS80. The IC50 was 20.5, PS80 (PS80@NE) and 37.9, OA (OA@NE) clearly indicating that components changed their toxicities upon nanostructuring, OA exhibited 30-fold increase (IC50(OA) 1100.0→37.9) while PS80, decreased 7.9-fold (IC50(PS80) 2.6→20.5). PS80 is the most toxic component but when is included in PS80@NE, less toxic nanocarriers were generated.