Electrochemical monitoring of the interaction of cisplatin with cystine and ascorbic acid

The interaction of cisplatin with cystine (RSSR) and ascorbic acid (AA) has been investigated in aqueous solution at physiological pH, using drug concentration of 0.835×10-6 M to 46.76×10-6 M with RSSR concentration of 6.5×10-5 M by voltammetric techniques. Voltammetric results show that at low drug concentration (<0.835×10-6 M), the interaction between cisplatin and RSSR occurs slightly, while at higher drug concentrations (0.835×10-6 M), cisplatin binds to RSSR and gives an unseparated-reduction peak at -0.610 V. Based on the voltammetric behaviour of RSSR, it has been suggested that binding of cisplatin to RSSR occurs mainly at the disulphide bond. It has been shown that the interaction of cisplatin with RSSR in the presence of AA is very rapid with regards to the interaction without AA, and a new peak, probably corresponding to the interaction of cisplatin with RSSR and AA is appeared at -0.970 V. The fractional coefficient for the binding of cisplatin to RSSR with or without AA was calculated to be 0.031 and 0.055, respectively.