Sensitive NADH detection in a tumorigenic cell line using a nano-biosensor based on the organic complex formation.

A robust amperometric sensor for ß-nicotinamide adenine dinucleotide (NADH) detection was developed through the organic complex formation with ethylenediaminetetraacetic acid (EDTA) bonded on the polyethylenimine (PEI)/activated graphene oxide (AGO) layer. The EDTA immobilized sensor probe (GCE/AGO/PEI-EDTA) revealed a catalytic property towards NADH oxidation that allows for the highly sensitive electrochemical detection of NADH at a low oxidation potential. Surface characterization demonstrated that the negatively charged AGO acted as nanofillers in the positively charged PEI matrix through the charge interaction. The immobilization of EDTA on the polymer layer provided more surface area for NADH to interact with through the enhanced chemical interlocking between them. We observed the strong interaction between NADH and EDTA on the AGO/PEI layer using a quartz crystal microbalance (QCM), X-ray photoelectron spectroscopy (XPS), and the calculation of the minimized energy for complex formation. The dynamic range of NADH was determined to be between 0.05µM and 500µM with a detection limit (LD) of 20.0±1.1nM. The reliability of the developed sensor for biomedical applications was examined by detecting NADH in tumorigenic lung epithelial cells using the standard addition method.

Ultrasensitive cytosensing based on an aptamer modified nanobiosensor with a bioconjugate: Detection of human non-small-cell lung cancer cells.

A novel aptamer-based amperometric nanobiosensor was designed for the sensitive and selective detection of A549 human non-small-cell lung cancer (NSCLC) cells. The cytosensing was performed using a MUC1 aptamer probe with a bioconjugate, where the probe was fabricated by the covalent immobilization on a conducting polymer nanocomposite formed through the self-assembly of 4-([2,2':5',2''-terthiophen]-3'-yl) benzoic acid (TTBA) on AuNPs. A bioconjugate composed of hydrazine and aptamer attached on AuNPs was used to reveal the selectively amplified detection signal. The cells were quantitatively analyzed using chronoamperometric measurements, and the results were further compared and confirmed using microscopic and DPV methods based on silver staining cytosensing experiments. The proposed aptasensor showed a high affinity for MUC1 positive lung cancer cells (A549) compared with the other control cancer cells, including human prostate (PC3), MUC1 negative normal lung (MRC-5), and liver tumors (HepG2) cells. An excellent dynamic range of the proposed method was obtained from 15 to 1×10(6) cells/mL with a detection limit of 8 cells/mL.