Highly Sensitive Electrochemical Biosensor Based on Polyaniline and Gold Nanoparticles for DNA Detection

In recent years, development of sensitive, selective, and rapid detection of deoxyribonucleic acid (DNA) is very important in various fields of science and technology. DNA biosensors present an alternate approach for detecting DNA sequence in a faster, simpler, and less expensive manner as compared with conventional hybridization methods. In this paper, an electrochemical biosensor was developed based on the sandwich hybridization strategy for the highly specific detection of target DNA molecules without amplification. The surface of screen-printed carbon electrode (SPCE) was first modified using polyaniline (PANI). Then, gold nanoparticles were electrodeposited on the surface of working electrode. Next, the biotinylated nucleic acid capture probe sequence was immobilized onto the avidin-modified SPCE surface via biotin/avidin interaction. After the addition of the target sequence and digoxigenin-labeled detector probe, anti-digoxigenin antibody conjugated to horseradish peroxidase (HRP) was dropped onto the electrode prior to electrochemical analysis. The accomplishment of these steps of biosensor fabrication was carefully studied and approved by scanning electron microscopy and cyclic voltammetry. The results showed that our biosensor has offered a stable sensitive platform with a linear range from 1000 to 0.001 pM and a limit of detection of 0.01 fM. Hence, it is believed that by taking advantage of unique properties of PANI, AuNPs, and HRP enzyme, the proposed biosensor can facilitate the detection and quantification of desired DNA sequences in various biological samples.