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Figure 1. Electrical nanowell biosensor design, assembly and operation. Sensor device and operation (A) optical micrograph showing the gold microelectrodes, PDMS encapsulant and nanoporous alumina membrane (B) modified Randles equivalent circuit for label-free nonfaradaic impedance spectroscopy and (C) schematic representation of binding events at the electrical double layer. PDMS: Polydimethyl siloxane; PSA: Prostate-specific antigen.
(Figure omitted. See article PDF.)
Figure 2. Testing and validation of patient sample cohort with the nanoelectronic sensor device. Quantification of PSA in a total of 17 male patients was performed and the performance was compared with concentration estimated using Beckman Access system. Linear range of the Beckman Access system is 150 ng/ml and hence samples with concentration >150 ng/ml were diluted from the original specimen for detection with the Access system. PSA: Prostate-specific antigen.
(Figure omitted. See article PDF.)
Figure 3. Estimation of noise using linker and antibody. (A) Validation of DSP linker conjugation through debye length screening and impedance spectroscopy measurements. Resistive nature of DSP conforms with the increase in impedance upon conjugation to gold electrode surface. (B) PSA immobilization to DSP-conjugated surface validated through impedance spectroscopy. Conductive nature of anti-PSA conforms to decrease in impedance observed after immobilization of anti-PSA antibody. DSP: Dithiobis succinimidyl propionate; PSA: Prostate-specific antigen.
(Figure omitted. See article PDF.)
Figure 4. Electrical nanowell biosensor performance. (A) Estimation of noise signal due to buffer and nonspecific binding. Female serum samples were used as a control and noise signal was estimated. (B) Calibration dose-response correlating concentration of PSA and change in impedance observed. PSA over the concentration of 0.00001 and 10,000 ng/ml was tested. Specific signal threshold was estimated as three-times the noise signal. PSA: Prostate-specific antigen.
(Figure omitted. See article PDF.)
Long-standing goals in cancer biology have been to accurately detect cancer at the earliest time possible, predict prognosis and optimize therapeutic selection [1]. The use of biomarker tests could greatly accelerate the development of targeted cancer therapies by identifying the patients that are most likely to benefit from a given therapy. Recent technological advances, especially in the fields of genomics and proteomics, have made it easier to identify many biomarkers simultaneously using high-throughput screening. New genomic and proteomic molecular tools have been designed to identify the molecular signature of a targeted disease [2-5]....