In this work, a novel self-signal DNA electrochemical biosensor was constructed based on tungsten disulfide (WS2) nanosheets combined with poly(indole-6-carboxylic acid) (PIn6COOH) as the sensing interface. The WS2 nanosheets were synthesized via a simple solvent exfoliation method from bulk WS2, and then PIn6COOH was electropolymerized on the WS2 nanosheet-modified carbon paste electrode to obtain a unique nanocomposite. The electropolymerization efficiency was remarkably improved, ascribed to the physical adsorption between WS2 nanosheets and aromatic In6COOH monomers, resulting in an increase of the electrochemical response of PIn6COOH. Owing to the presence of π–π interactions between the conjugated PIn6COOH/WS2 nanocomposite and DNA bases, the probe ssDNA was noncovalently assembled on the nanocomposite substrate. After the hybridization of the probe ssDNA with the target DNA, the formation of the double-helix structure induced the resulting dsDNA to be released from the surface of the conjugated nanocomposite, accompanied with the self-signal regeneration of the nanocomposite (“signal-on”). The constructed PIn6COOH/WS2 nanocomposite was not only employed as an interface for DNA immobilization but also reflected the signal transduction stemming from DNA immobilization and hybridization without any external indicators or complex labeling processes. A detection limit of 2.3 × 10−18 mol L−1 has been estimated and a dynamic range of 1.0 × 10−17 mol L−1 to 1.0 × 10−11 mol L−1 has been shown for the detection of a PIK3CA gene related to lung cancer. Selectivity of the biosensor has been researched in the presence of noncomplementary and base mismatched DNA sequences.
As an essential biomarker for diagnosing and treating various diseases, low-cost, quantitative detection methods for complementary DNA (cDNA) have received much attention. The surface plasmon resonance (SPR) sensing technique is an effective measurement scheme, but the ambient temperature and pH variations have a non-negligible impact. In this work, we developed a triple-probe SPR sensing system for detecting cDNA concentration, temperature, and pH. In order to satisfy the triple parameter measurements, we used a microstructured optical fiber as the sensing platform, silver and gold films as the excitation layer, and a MoS 2 film as the modulation layer. First, we explore the modulation mechanism of SPR and the conditions for excitation of triple SPR and demonstrate that the carrier concentration is a crucial factor affecting the resonance wavelength. Then, the feasibility of the sensing system for triple-probing is theoretically analyzed. Finally, in the experiment, the optimal parameters of the sensor were determined, and the triple parameter detection was successfully realized. The experimental results show that the three probes can work independently, and the hybridized DNA probe can realize the selective detection of cDNA with a sensitivity of 0.249 nm/(nmol/l). The maximum sensitivity of the pH probe and the temperature probe are 51.5 nm/pH and 6.14 nm/°C. In addition, the experimental results show that the sensing probes have excellent reproducibility. This paper’s innovation is using the fiber optic SPR effect to achieve quantitative detection for cDNA, temperature detection, and pH detection. Therefore, the sensor has a promising future in early diagnosis and biosensing.
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