An aptasensor for rapid and sensitive detection of estrogen receptor alpha in human breast cancer.

The analysis of estrogen receptor (ER) expression in breast carcinomas plays a crucial role in determining the endocrine responsiveness of tumors for systemic adjuvant therapy. Conventionally, the ER levels in breast carcinomas had been detected using the dextran-coated charcoal assay and radioimmunoassay, which are now substituted with safer and economic antibody-based assays such as immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA). Despite a gold (Au) standard method, the IHC has been criticized for factors such as tissue fixation, antibody selection, and threshold staining for result interpretation that could falsify test accuracy and reproducibility. The quest for alternative methods of ER quantification in tissue samples paved the way for aptamer-based diagnostics. Previously, we have isolated a DNA aptamer against human ER alpha (ERα) using an in vitro evolution system. In this study, we developed an electrochemical sensor using the 76-nucleotide DNA ERα- aptamer for rapid, precise, and cost-effective detection of ERα expression in human breast cancer patients. The aptasensor was constructed by covalently immobilizing the thiolated ERα- aptamer onto a screen-printed Au electrode. Construction of aptasensors was confirmed through atomic force microscopy and differential pulse voltammetry measurements. A detection limit of 0.001 ng/ml was calculated for full-length ERα (66.2 kDa) in a detection time of 10 min. Analysis of the cancerous breast tissue samples using the ELISA and aptasensor methods enabled distinctive classification of samples into the categories of ER -ve, weak ER +ve, and strong ER +ve samples. The current change of this aptasensor lies within 5% after a storage of 60 days at 4°C. Further studies on a reasonably large sample size are required to realize the clinical potential of the sensor.

A solution processed carbon nanotube modified conducting paper sensor for cancer detection.

A solution processed poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-carbon nanotube (CNT) nano-composite has been utilized for the fabrication of a conducting paper (CP) via dip coating. Further, high conductivity of this paper (from ∼6.5 × 10-4 to 2.2 × 10-2 S cm-1) obtained by treating it with formic acid (CNT/FA@CP) is due to the removal of the non-conducting PSS molecules from its surface. This smart conducting platform has been used for the conjugation of the anti-carcinoembronic antigen (CEA) protein for quantitative estimation of CEA, a cancer biomarker. Transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and amperometric techniques have been used to characterize the low cost, flexible and environmentally friendly conducting BSA/anti-CEA/CNT/FA@CP) paper electrode that is found to be highly sensitive (7.8 µA ng-1 ml cm-2) in the physiological range (2-15 ng ml-1) of CEA. The response of the paper electrode is validated using CEA concentration of serum samples of cancer patients obtained via the immunoassay technique.

Reduced graphene oxide modified smart conducting paper for cancer biosensor.

We report results of the studies relating to the fabrication of a paper based sensor comprising of poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PEDOT: PSS) and reduced graphene oxide (RGO) composite. The effect of various solvents like methanol, ethylene glycol and H2SO4 on the electrical conductivity of PEDOT: PSS coated Whatman paper has been investigated. The conductivity of this solution processed conducting paper significantly increases from ~1.16×10(-4) S cm(-1) up to ~3.57×10(-2) S cm(-1) (~300 times) on treatment with ethylene glycol. The observed significant increase in electrical conductivity is due to conformational rearrangement in the polymer and is due to strong non-covalent cooperative interaction between PEDOT and the cellulose molecules. Further, incorporation of RGO into the conducting paper results in improved electrochemical performance and signal stability. This paper electrode is a promising alternative over the expensive conventional electrodes (ITO, gold and glassy carbon), that are known to have limited application in smart point-of-care (POC) devices. This low cost, flexible and environment friendly conducting paper based biosensor utilized for cancer biomarker (carcinoembryonic antigen, CEA) detection reveals high sensitivity of 25.8 µA ng(-1) mL cm(-2) in the physiological range, 1-10 ng mL(-1).