Direct electrochemistry of cytochrome c entrapped in agarose hydrogel in room temperature ionic liquids

Direct electrochemistry of cytochrome c (cyt-c) entrapped in agarose hydrogel on gold electrode (Au), edge plane pyrolytic graphite electrode (EPPGE) and glassy carbon electrode (GC) in two room temperature ionic liquids was investigated. The effects of the addition of N,N-dimethylformamide (DMF) in the agarose-cyt-c film, water concentration in ionic liquids and exterior metal ions on the electrochemical behavior of cyt-c were monitored, and electrocatalytic properties of cyt-c were also done. Results showed that a good quasi-reversible redox behavior of cyt-c could be found after adding DMF in agarose-cyt-c film, and peak shape would not change after continuously scanning for 50 cycles. In addition, a certain amount of water in hydrophilic ionic liquids is necessary to maintain electrochemical activities of cyt-c, electrochemical performance of cyt-c is the best when the water content is 5.2% and 5.8% for 1-butyl-3-methylimidazolium bromide ([Bmim][Br]) and 1-butyl-3-methylimidazolium tetrafluoroborate([Bmim][BF4]) respectively. However, electrochemical activities of cyt-c are inhibited by exterior metal ions. Interestingly, cyt-c entrapped in agarose hydrogel on EPPGE and GC could catalyze the electroreduction of trichloroacetic acid (TCA) and tert-butyl hydroperoxide (t-BuOOH) in [Bmim][BF4], but could not in [Bmim][Br]. Reasons for above-mentioned differences of electrochemical properties of cyt-c in different ionic liquids were preliminarily discussed.

► A good quasi-reversible redox behavior of cyt-c could be found after adding DMF in agarose-cyt-c film.
► Cyt-c entrapped in agarose hydrogel on EPPGE or GC could catalyze the electroreduction of TCA and t-BuOOH in [Bmim][BF4], but not in [Bmim][Br].
► Cyt-c entrapped in agarose hydrogel could catalyze the electroreduction of TCA or t-BuOOH in [Bmim][BF4] on EPPGE and GC, but not on Au electrode.