Ultrasensitive electrochemical DNA biosensor by exploiting hematin as efficient biomimetic catalyst toward in situ metallization

In this work, we presented a novel signal amplification approach to construct an electrochemical DNA biosensor for the ultrasensitive determination of sequence-specific DNA by exploiting hematin as biomimetic catalyst toward in situ metallization. Briefly, thiolated peptide nucleic acid (PNA) probes were firstly immobilized onto gold electrode through the formation of self-assembled monolayer (SAM) and then hybridization was accomplished in the ensuing step. After that, hematin molecules were introduced to the hybridized PNA/DNA heteroduplexes by employing phosphate-zirconium-carboxylate coordination chemistry. Next, the attached hematin molecules acted as catalyst in accelerating the reduction of silver ions in the presence of catechol, leading to the in situ deposition of silver particles onto the electrode. Finally, the deposited silver particles were electrochemically stripped into KCl solution and measured by square wave voltammetry (SWV). Under optimal conditions, the hematin-based electrochemical DNA biosensor presented a good linear relationship between the stripping peak currents and logarithm of single-stranded DNA (ssDNA) concentrations in the range from 0.1 fM to 0.1 nM with a low detection limit of 62.41 aM, and it rendered satisfactory analytical performance for the determination of ssDNA in serum samples. Furthermore, it exhibited good reproducibility and stability, meanwhile, it also showed excellent specificity toward single-nucleotide polymorphism (SNP). Therefore, the hematin-based signal amplification approach has great potential in clinical applications and is also suitable for quantification of biomarkers at ultralow level.