Simultaneous electrochemical determination of DNA nucleobases using AgNPs embedded covalent organic framework

An efficient electrochemical biosensor has been developed for the simultaneous evaluation of DNA bases using AgNPs-embedded covalent organic framework (COF). The COF (p-Phenylenediamine and terephthalaldehyde) was synthesized by reflux (DMF; 150 degrees C; 12 h) and the nanoparticles were embedded from the aqueous solutions of AgNO3 and NaBH4. The nanocomposite-modified COF was confirmed by spectral, microscopic, and electrochemical techniques. The nanocomposite material was deposited on a glassy carbon electrode (GCE) and the redox behavior of AgNPs was confirmed by cyclic voltammetry. The electrocatalytic activities of DNA bases were analyzed by differential pulse voltammetry (DPV) in a physiological environment (PBS; pH =7.0) based on simple and easy-to-use electrocatalyst. The AgNPs-COF/GCE showed well-defined anodic peak currents for the bases guanine (+ 0.63 V vs. Ag/AgCl), adenine (+ 0.89 V vs. Ag/AgCl), thymine (+1.10 V vs. Ag/AgCl), and cytosine (+1.26 V vs. Ag/AgCl) in a mixture as well as individuals with respect to the conventional, COF, and AgNPs/GCEs. The AgNPs-COF/GCE showed linear concentration range of DNA bases from 0.2-1000 mu M (guanine; (G)), 0.1-500 mu M (adenine (A)), 0.25-250 mu M (thymine (T)) and 0.15-500 mu M (cytosine (C)) and LOD of 0.043, 0.056, 0.062, and 0.051 mu M (S/N = 3), respectively. The developed sensor showed reasonable selectivity, reproducibility (RSD =1.53 +/- 0.04%-2.58 +/- 0.02% (n =3)), and stability (RSD =1.22 +/- 0.06%-2.15 +/- 0.04%; n = 3) over 5 days of storage) for DNA bases. Finally, AgNPs-COF/GCE was used for the determination of DNA bases in human blood serum, urine and saliva samples with good recoveries (98.60-99.11%, 97.80-99.21%, and 98.69-99.74%, respectively).