Local delivery of rhenium-188 colloid into hepatic tumor sites in rats using thermo-sensitive chitosan hydrogel: effects of gelling time of chitosan as delivery system

A previously developed internal radiation therapy mode adopting a thermo-sensitive, chitosan-based hydrogel intended for local delivery of 188 Re–Tin colloid drug was extended to test for its applicability to the treatment of hepatoma in rats. The effects of two formulations of hydrogel with different gel times and two methods of delivering the hydrogel containing 188 Re–Tin colloid into tumors on the accumulated dose and duration of radioactivity within tumor were first studied by in vitro release, planar scintigraphy, and bio-distribution evaluations. Results from this initial study suggest that a treatment mode using the intratumoral delivery method and a 4 min gel time hydrogel to deliver the 188 Re–Tin colloid into the tumor is more effective for treating hepatoma in rats. The treatment mode was then further verified through efficacy evaluations based on hepatic tumor growth in hepatoma-bearing rats. In conclusion, the application of chitosan/β-glycero-phosphate (C/GP) hydrogel for the local delivery of 188 Re–Tin colloid to treat hepatoma in rats is feasible. The effective and efficient treatment mode consists of the intratumoral injection of 188 Re–Tin colloid premixed with 4 min gel time C/GP hydrogel.