Cytotoxicity of 5-fluorouracil-loaded pH-sensitive liposomal nanoparticles in colorectal cancer cell lines.

5-Fluorouracil (5-FU) is widely used in cancer therapy, either alone or in combination with other anti-cancer drugs. However, poor membrane permeability and a short half-life (5-20 min) due to rapid metabolism in the body necessitate the continuous administration of high doses of 5-FU to maintain the minimum therapeutic serum concentration. This is associated with significant side effects and a possibility of severe toxic effects. This study aimed to formulate 5-FU-loaded pH-sensitive liposomal nanoparticles (pHLNps-5-FU) and evaluate 5-FU release characteristics and anti-cancer effect of pHLNps-5-FU. Particle size and zeta potential were determined using a particle size analyzer. The release patterns of pHLNps-5-FU formulations were evaluated at 37°C at pH 3, 5, 6.5, and 7.4, while drug release kinetics of 5-FU from a pHLNp3-5-FU formulation were determined at pH 3 and 7.4 at different time points (37°C). Cell viability and clonogenic studies were conducted to evaluate the effectiveness of pHLNps-5-FU against HCT-116 and HT-29 cell lines while cellular uptake of rhodamine-labeled pHLNps-5-FU was determined by flow cytometry and confocal imaging. The average sizes of the pHLNp1-5-FU, pHLNp2-5-FU and pHLNp3-5-FU liposomes were 200nm ± 9.8nm, 181.9 nm ± 9.1 nm, and 164.3 nm ± 8.4 nm respectively. In vitro drug release of 5-FU from different pHLNps-5-FU formulations was the highest at pH 3.8. Both cell lines treated with pHLNps-5-FU exhibited reduced viability, two- or three-fold lower than that of 5-FU-treated cells. Flow cytometry and confocal imaging confirmed high uptake of rhodamine-labeled pHLNps-5-FU in both cell lines. The drug release profile of the chosen pHLNp3-5-FU formulation was optimal at pH 3 and had the poorest release profile at pH 7.4. The release profile of pHLNp3-5-FU showed that 5-FU release was two-fold higher at pH 3 than that at pH 7.4. This study demonstrates that pHLNp3-5-FU may be a potential candidate for the treatment of colorectal cancer.