MnO2 nanosheets and gold nanoparticles supported electrochemical detection of circulating tumor cells.

The concentration of circulating tumor cells (CTCs) in peripheral blood is strongly correlated with the progress of certain metastatic cancers. In this study, we have developed a novel and facile electrochemical biosensor for the detection of CTCs based on the use of manganese dioxide nanosheets (MnO2 NSs) and gold nanoparticles (AuNPs). Aptamer sequence of target cell is modified on the surface of AuNPs for specifical recognition. With low-speed centrifugation, numerous AuNPs@DNA can be removed from the supernatant. On the other hand, MnO2 NSs are modified on the electrode surface to capture unreacted AuNPs@DNA. The declined electrochemical signal intensity can be used to reflect the level of CTCs. This biosensor achieves a wide linear range from 10 to 104 cells mL-1 and a limit of detection as low as 3 cells mL-1. Due to the specific aptamer as the recognition element, interfering cells can be successfully distinguished and this method performs satisfactorily in clinical samples. Therefore, it has great potential to be used as a powerful tool benefiting rare cells analysis and the investigation of dynamics of cellular interactions.

Highly Sensitive Endotoxin Assay Combining Peptide/Graphene Oxide and DNA-Modified Gold Nanoparticles.

Endotoxin is a highly toxic stimulator originated from the outer membrane of Gram-negative bacteria, which should be monitored sensitively and selectively for human health concerns. Traditional detection methods mainly rely on limulus amoebocyte lysate assay. However, it suffers drawbacks like the narrow detection range, and the results may be environment-dependent. In this work, we have developed a sensitive electrochemical biosensor for endotoxin assay. Peptide is first designed as specific recognition element toward endotoxin. Graphene oxide and DNA-modified gold nanoparticles are then used to enhance the electrochemical signal. The analytical performances are excellent with the limit of detection as low as 0.001 EU mL-1. This method has also been successfully applied in endotoxin assay in complex biological samples, which may have great potential use.