A novel signal amplification label based on AuPt alloy nanoparticles supported by high-active carbon for the electrochemical detection of circulating tumor DNA.

The detection of circulating tumor DNA (ctDNA) has increasingly received a great deal of attention considering its significance in cancer diagnosis. And the signal amplification plays an important role in the development of sensitive ctDNA biosensors. Herein, the nanocomposites (denoted as HAC-AuPt), integrating from high-active carbon (HAC) and AuPt alloy nanoparticles, were synthesized and subsequently used as a signal amplification label to fabricate a sandwich-type ctDNA electrochemical biosensor. Characterizations demonstrated that HAC presents uniform size distribution and AuPt alloy nanoparticles were successfully loaded on HAC. The current response could be amplified to a great extent by the resultant HAC-AuPt due to its excellent electrochemical property. The nanocomposites were further bounded with DNA signal probes (SPs) via Au-S or Pt-S assembly to form SPs-label. After the capture probes (CPs) were immobilized on the electrode surface, the target DNA (tDNA) and SPs-label were stepwise incubated on the CPs-modified electrode, thus forming a sandwich-type structure. By monitoring the catalytic signal of HAC-AuPt towards the reduction process of HO, this biosensor provided a wide linear range of 10 mol/L - 10 mol/L with a low detection limit of 3.6 × 10 mol/L (S/N = 3) for the detection of the tDNA. Furthermore, obvious differences in response signals among different DNAs were observed benefitting from the excellent selectivity of the biosensor. Besides, the long-term stability, reproducibility, and recovery rate were proved to be outstanding. These results indicate that the established biosensor holds a potential application in the clinical diagnosis of ctDNA.