Development of theranostic pH-sensitive liposomal nanoparticle for early detection and treatment of colon cancer

Purpose: 5-Fluorouracil (5-FU) is a main drug used in the treatment of cancer alone or in combination with other anticancer drugs. 5-FU is associated with poor permeability and short membrane half-life (5-20 min), due to its rapid metabolism in the body. Therefore it has become necessary for the continuous administration of high doses of 5-FU to maintain the minimum therapeutic serum concentration, which gives rise to associated severe side effect, and ultimately lead to severe toxic effect. The aim of this study is to formulate 5-FU-loaded pH-sensitive liposomal nanoparticles (pHLNps-5-FU) and evaluate the 5-FU release characteristics and anticancer effect of pHLNps-5-FU both in vitro and in vivo. Methods: Particle size and zeta potential were determined using particle size analyzer. Release pattern of pHLNps-5-FU formulations was evaluated at 37oC at pH 3, 5, 6.5 and 7.4 while drug release kinetics of 5-FU from pHLNp3--5-FU formulation was determined at pH 3 and 7.4 at different time points (37oC). Cell viability and clonogenic studies were conducted to evaluate the effectiveness of pHLNps-5-FU on 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 biodistribution and pharmacokinetics parameters of the administered 5-FU and pHLNps-5-FU were compared in nude mice while the efficacy of 5-FU and pHLNps-5-FU were determined in subcutaneous models of HT-29 and HCT-116 mice. Results: The average size of the pHLNps-5-FU liposome was 200 +/- 9.8, 181.9 +/- 9.1 and 164.3 +/- 8.4 nm. In-vitro drug release of 5-FU from pHLNps-5-FU was highest at pH of 3.8 from the different pHLNps-5-FU was observed. Both cells treated with pHLNps-5-FU reduced their viability to 2--3 fold lower compared to that of 5-FU. Flow cytometry and confocal imaging confirmed higher uptake of rhodamine labeled pHLNps-5-FU on both cell lines. Drug release profile of the chosen pHLNp-5-FU was best in pH of 3 and least release was observed at the pH of 7.4. Release kinetics of pHLNp-5-FU showed the release of 5-FU was 2-fold in pH of 3 when compared to 5-FU release at pH of 7.4. Pharmacokinetics studies showed a longer plasma circulation of pHLNps-5-FU and a more significant body exposure while accumulation of pHLNps-5-FU in the tumor was significantly greater than that of free 5-FU. Further, the efficacy of pHLNps-5-FU, as determined in both HT-29 and HCT-116 subcutaneous cancer mouse models, was better than free 5-FU when treatments were compared at equivalent doses. Conclusion: Study demonstrates that pHLNp-5-FU may be a potential candidate for the treatment of colorectal cancer.