A Unique Oligonucleotide Probe Hybrid on Graphene Decorated Gold Nanoparticles Modified Screen-Printed Carbon Electrode for Pork Meat Adulteration

A new oligonucleotide-based electrochemical biosensor was developed to detect the Sus scrofa mitochondrial cytochrome b (cytb) gene based on an in silico designed probe using bioinformatics tools and validated in wet-lab experiments. Screen-printed carbon electrodes (SPCE) modified with graphene (Gr), and gold nanoparticles (AuNPs) composite were used as a detection platform. The nanocomposite was characterized based on morphological, structural, and electrochemical properties. The modified SPCE showed better conductance due to the synergistic effects of the composite elements, giving it a better detection range. The thiol-modified synthetic oligonucleotide probe was immobilized on a composite modified SPCE to facilitate hybridization with the reverse complementary (RC) oligonucleotide. The Sus scrofa oligonucleotide was identified based on hybridization induced electrochemical change in the presence of methylene blue (MB) as a redox indicator measured by deferential pulse voltammetry (DPV). The analytical results demonstrated that Gr and AuNPs were successfully fabricated on the SPCE surface, as indicated by morphological and structural characteristics, effective surface area, and electrochemical properties. The developed biosensor exhibited a selective response towards complementary oligonucleotides and could discriminate mismatches and non-complementary DNA both in synthetic oligos and DNA isolated from real samples. The modified electrode displayed good linearity for RC oligonucleotides in the range of 1 × 10–11 M to 5 × 10–6 M (R2 = 0.9765) with a limit of detection of 0.98 × 10–12 M. The detection capability of the modified electrode indicates that the proposed biosensor has the potential to be applied for real-time porcine sample detection.