Electroactive polyglycine coatings for nanobiosensing applications: Label-free DNA hybridization, DNA-Antitumor agent interaction and antitumor agent determination.

Bioinspired materials have attracted great attention due to their great functionality, bioactivity and biocompability. In particular, electroactive polyamino acid surfaces endow preparation of robust coatings for various applications. In this research article, preparation of carbon nanotubes doped polyglycine coated electrodes and their applications in the biomedical field such as DNA hybridization, DNA-antitumor agent interaction and antitumor agent determination were described. This biosensing platform was created using a simple, reproducible and fast in situ and one-pot electropolymerization procedure onto graphite surfaces by cyclic voltammetry. The coated electrodes were characterized with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). After the characterization studies, bioapplications of the proposed electrode were demonstrated. The new electrode led to significant improvement for the investigation of the electrochemical behavior of double-stranded DNA (dsDNA). 6-fold and 5-fold improvements were obtained for oxidation of the electroactive DNA bases, guanine (G) and adenine (A), respectively over the bare electrode. For these steps, each electrode was characterized with scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Then, DNA hybridization studies were performed in the light of these results. The proposed electrode allowed the quantification of specific target DNA down to 11.2 fM in serum samples (n = 3). In addition, it constituted a sensitive biosensing platform for electrochemical monitoring of the interaction between dsDNA and a commonly used antitumor agent, Mitomycin C. Mitomycin C determination was also carried out using the inhibition effect occurred at the guanine oxidation signal. The detection limit of this antitumor agent was found as 1.78 mg L ^-1 in untreated serum samples (n = 3).
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