Detection of pH and LOXL2/HER2 Breast Cancer Biomarker by Using CdSe-ZnS/IrOx Nanostructures in Electrolyte-Insulator-Semiconductor Structure

• Main Authors: Pankaj Kumar, 喬班愷
• Other Authors: S. Maikap
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/686m8d

博士 === 長庚大學 === 電子工程學系 === 105 === Early stage disease diagnosis of human body is the goal of this study. Among other sensors available in market, nanostructure modified electrolyte-insulator-semiconductor (EIS) structures have shown one of the promise candidates due to simplicity in layout, label-free detection, short time with repeatable detection, and low cost. Therefore, different nanostructures in EIS structure have been fabricated for multi-analytes detection. The label-free detection of common serum bioanalytes as well as specific breast cancer biomarker detection has been investigated. The SiO2 and CdSe-ZnS nanoparticles observed by both transmission electron microscope (TEM) and field-emission scanning electron microscope (FESEM) have been studied for reliable urea/glucose sensing, and common serum analyte detection comparable with market available urea “Assay Kit”. Thermally grown SiO2 membrane has shown lower pH detection limit (0.081) and lowest drift rate (2.9 mV/hr) than those of the sputtering and e-beam deposited SiO2 membranes. The urea detection at physiological buffer pH 7.4 with sensitivity of ~1.6 mV/mg.dl-1 at linear range of 6 to 36 mg/dl is observed. In addition, other bio-analytes such as acetylcholine, creatinine, and tributyrine have also been detected by using specific enzymes. The lower detection of pH change is reduced further (0.074) by using chaperonin protein mediated CdSe-ZnS nanoparticles assembly over SiO2 surface owing to high pH sensitivity of 55 mV/pH. In addition, the nanoparticles based sensor show improved sensitivity compared to bare SiO2 sensor over time period of 24 months, owing to the reduction of defects in the nanoparticles.The sensing mechanism is due to the SiOx content decreased with increasing pH value. This suggests the lower H+ ions on the sensing membrane surface, which is observed by X-ray photo-electron spectroscopy (XPS). The glucose concentration is detected by using the core-shell CdSe-ZnS nanoparticles through H2O2 sensing because of reduction/oxidation (redox) properties of Zn as well as Zn2+ ions generation. Due to the high catalytic activity for H2O2 sensitivity, low detection limit of 1µM is obtained, which will help to detect glucose using this bio-chip in future. To develop the sensing system for lysyl-oxidase-like-2 (LOXL2),a breast cancer biomarker detection using enzyme-free H2O2 catalysis, an iridium oxide (IrOx) nano-net membrane is fabricated on a SiO2 surface in an IrOx/SiO2/p-Si structure for the first time. The IrOx nano-net membrane observed by TEM is both thickness- and oxygen-dependent and has an optimized pH sensitivity of 148.7 mV/pH with a small drift of 1.95 mV/hr as well as a lower detection of pH change of 0.013 is obtained because of the high porosity, the high dielectric permittivity, and the good reduction-oxidation (redox) properties of the nano-structure. This IrOx nano-net sensor demonstrates good catalytic behavior for H2O2 reduction because the oxidation state changes from Ir3+ to Ir4+. The reference voltage shift increases linearly with increasing H2O2 concentration owing to generation of Ir4+ ions. The breast cancer biomarker LOXL2 is detected at low concentration of approximately 150 nM by using novel IrOx nano-net membrane. To achieve the high pH sensitivity and breast cancer biomarker of human epidermal growth factor receptor (HER2) detection, the IrOx nano-net structure have been deposited on different high-κ films (Al2O3, HfO2, and Ta2O5) in EIS structure. A high pH sensitivity of 160 mV/pH is obtained by using IrOx nano-net on Ta2O5 films, which allow detect urea with a low concentration of approximately 50 µM in 5 ml buffer solution. It is interesting to note that the IrOx nano-net structure is functionalized with the HER2 antibody and optimized for the HER2 biomarker detection in linear range from 2.5-160 ng/ml, which will help to detect breast cancer at early stage.