Lithocholic acid conjugated mPEG-b-PCL micelles for pH responsive delivery to breast cancer cells

In this study, micelles composed of methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) copolymer (mPEG-b-PCL), which has ionically conjugated lithocholic acid (LCA) and providing pH sensitive release of LCA in acidic media, were prepared as drug carrier devices for cancer therapy. Micelles were produced by co-solvent evaporation method at two different temperatures (60 °C and 25 °C) and coded as LCA₆₀**M and LCA₂₅**M, respectively). Hydrodynamic diameters were 86.9 nm and 228.2 nm, and zeta potentials were -7.54 mV and -18.83 mV for LCA₆₀**M and LCA₂₅**M, respectively. For all micelles, release of LCA was higher in acidic media (pH 5.0) compared to physiological media (pH 7.4). Micelles loaded with a fluorescent dye, coumarin 6, demonstrated effective internalization into triple negative MDA-MB-231 breast cancer cells in 4 h. LCA₆₀**M (41.7 ± 1.5%) and LCA₂₅**M (44.5 ± 2.2%) had higher inhibitory effect on the cell migration compared to free LCA (64.7 ± 1.3%). Both LCA conjugated micelles decreased lipogenic activity and increased expressions of Bax (1.3 fold) and p53 (1.2 fold) apoptotic genes. Annexin V-FITC results exhibited high apoptotic cell number after the treatment of MDA-MB-231 cells with micelles. Free LCA and LCA conjugated LCA₆₀**M and LCA₂₅**M micelles decreased mitochondrial transmembrane potential of the cells by 41.8 ± 3.0%, 30.4 ± 0.9%, and 57.1 ± 0.5, respectively. Micelles also caused an effective decrease in angiogenesis ability of HUVECs. The novelty of this study is the prepared micelles, which have ionic conjugation of LCA to mPEG-b-PCL, and pH responsive release of LCA demonstrating effective apoptosis on breast cancer cells. These micelles may have great potential for cancer treatment. However, further in vivo studies are needed before clinical translation.