In vitro cytotoxicity and in vivo efficacy of 5-fluorouracil-loaded enteric-coated PEG-cross-linked chitosan microspheres in colorectal cancer therapy in rats

Purpose: Microspheres of chitosan (CS) cross-linked with polyethylene glycol (PEG) were prepared by emulsion-cross-linking followed by the solvent evaporation technique. The formulations were characterized and subjected to in vitro and in vivo tests to assess cell growth, changes in cell morphology, and activities by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on human HT-29 colon cancer cell-lines. Methods: In vivo activity was evaluated for dimethyl hydrazine-induced colorectal cancer in albino male Wistar rats. Biochemical and histological parameters were evaluated to understand their effectiveness for colon cancer therapy. Results: The 5-FU immediate release (IR) formulations suspended in SCMC produced an immediate cytotoxic effect, whereas microspheres inhibited proliferation of tumor cells to induce apoptosis over an extended time. Minimum inhibitory concentration (IC50) values for both standard plain 5-FU and 5-FU-loaded microspheres were respectively 5.00 +/- 0.004 mu g/mL and 165 +/- 1.9 mu g/mL which showed the improved safety profile of the microsphere formulation. Tissue distribution showed high concentration of 5-FU in colon that was higher than IC50 value required to stop the growth or death of colon cancer cells from the colonic dysplasia in Duke's stage A. Significant reduction in tumor volume and multiplicity was observed with increased levels of liver enzymes in animals when treated with standard 5-FU formulation compared with 5-FU loaded microspheres. Elevated levels of serum albumin, creatinine, leukocytopenia, and thrombocytopenia were observed in animals for the standard 5-FU formulation. Conclusion: The PEG cross-linked CS microspheres of this study slowly released 5-FU up to 24 h to colonic region and enhanced the antitumor activity.