INVESTIGATION OF CHITOSAN FOR DECORPORATION OF 60Co IN THE RAT

With the increased threat of terrorist release of radioactive materials, there is a need for non-toxic decorporation agents to treat internal contamination with radionuclides. In this study, low molecular weight chitosan was evaluated for decorporation of radioactive cobalt (Co-60). The affinity of chitosan for Co(II) was tested in vitro using spectrophotometric and potentiometric titration techniques. For in vivo studies, the effect of chitosan on ingested Co-60 was evaluated using F344 rats administered a single dose followed by oral chitosan. Chitosan was also evaluated for systemic decorporation of Co-60 following intravenous injection with repeated chitosan administration over 5 d. Control animals received Co-60 without chelation treatment. Excreta and tissues were collected for analysis using gamma-counting techniques. Results from in vitro experiments confirmed the binding of Co(II) to chitosan, with the postulated formation of a mixed cobalt-chitosan-hydroxide complex species; a stability constant was calculated for this complex. For in vivo studies, oral administration of chitosan significantly reduced systemic absorption of orally administered Co-60 as evidenced by an increase in fecal elimination and decrease in urinary elimination. However, oral administration of chitosan lactate slightly decreased fecal excretion of Co-60. Further, oral administration of chitosan significantly reduced Co-60 levels in kidney, liver, and skeleton compared to control animals receiving Co-60 alone. By the IV route, chitosan slightly reduced levels of Co-60 in tissues compared to controls, although statistically significant reductions were only observed for blood and kidney. Overall, this commercially available chitosan oligosaccharide exhibited promising potential; further studies are warranted to evaluate the optimal dosing regimen and chemical modifications to increase effectiveness. Health Phys. 97(2):115-124; 2009