The electrochemical monitoring of (i) label-free and (ii) indicator based DNA hybridization related to Microcystis spp. (MYC) DNA was explored in this study via multiwalled carbon nanotube (MWCNT) based screen printed graphite electrodes (SPEs). The effect of CNT modification onto SPE was firstly investigated by measuring the oxidation signals of guanine and adenine before/after DNA immobilization onto the surfaces of bare SPE, MWCNT-SPE and SWCNT-SPE in combination with differential pulse voltammetry. MYC-DNA hybridization was monitored by following two procedures and measuring the guanine oxidation signal and the reduction signal of cobaltphenanthroline Co(phen) 3 3 + . Voltammetric results were complemented with electrochemical impedance spectroscopy (EIS).

Single-walled carbon nanotube (CNT) and chitosan composite (chitosan*CNT) based sensors were developed as DNA biosensors, and then they were applied for electrochemical investigation of the interaction between the anticancer drug mitomycin C (MC) and DNA. The oxidation signals of MC and guanine were monitored before and after the interaction process by differential pulse voltammetry (DPV). The DPV results were in good agreement with those of electrochemical impedance spectroscopy (EIS). Analytical parameters such as DNA concentration, MC concentration, and MC interaction time with DNA were optimized. The detection limits were 6.85 µ g/mL for DNA and 11.01 µ g/mL for MC.