Disposable Noncompetitive Immunosensor for Free and Total Prostate-Specific Antigen Based on Capacitance Measurement

Abstract

This work reports on the successful integration of a one-step lateral flow immunoassay format and impedance detection of the specific affinity event using an electrochemical transducer coated with a pH-sensitive polymer layer. This approach was particularly applied to the development of a rapid single-use immunosensor for the sensitive detection of free and total prostate-specific antigen (f-PSA, t-PSA) tumor marker. Strips of nitrocellulose membrane were coated with appropriate antibodies to f-PSA and t-PSA and used as solid supports for the performance of noncompetitive immunoassays where PSA was allowed to react with both immobilized anti-PSA antibody and anti-PSA urease enzyme conjugate for less than 1 min. An additional piece within the device consisting of a storage blister filled with a urea solution allowed the rapid washing of unbound species from the membrane strips and simultaneous urea hydrolysis catalyzed by the bound urease conjugate in an automatic fashion. The hydrolysis of urea increased the pH of the reaction media, which in turn induced a breakdown of the polymer layer on the transducer and a consequent measurable change in capacitance of the system. This was easily recorded at a given frequency over a 30-min period. Overall, we describe a one-step immunosensor prototype that exhibits enough sensitivity to detect both forms of PSA at concentration levels down to 3 ng/mL. With the possibility of being portable and considering its ease of use, robustness, and simplicity, this device has great potential as a tool for the screening and early detection of prostate cancer.

Polysilicon interdigitated electrodes as impedimetric sensors

“…Their robust and simple structure, their long term stability and reliability, and easy fabrication have attracted much attention from the sensor research community. Applications that have been proposed for these microelectrodes include measurement of the concentration of calcium [1], potassium [2], p(CO2) [3], pH [4], ethanol/methanol in gasoline [5], heavy metals [6], nitrate [7], urea [8][9], glucose [10], total prostate-specific antigen (PSA) [11], bacteria [12], red blood cells (hematocrit) [13], and detection of specific sequences of DNA [14]. In some applications, the measurement of a physical magnitude such as dielectric constant or conductivity of the media provides direct information of the analyte concentration [5,13].…”

“…In some applications, the measurement of a physical magnitude such as dielectric constant or conductivity of the media provides direct information of the analyte concentration [5,13]. In other applications, the deposition of a membrane or functional monolayer on top of the electrodes as a recognition element is necessary to obtain sensitivity and selectivity to particular species [1][2][3][4][6][7][8][9][10][11][12][13][14]. Different arrangements of electrodes (i.e.…”

Local detection of enzymatic ion generation with polycrystalline silicon interdigitated electrodes and its application to biosensing

“…They can be easily conjugated to biomolecules via different cross linkers and well known chemical procedures, and the reactions they catalyze can be detected either optically 6,7 or electrochemically. [8][9][10][11] In this letter, a biosensing principle is presented and tested. It consists in the generation of ions by an enzyme and the local detection of them by polycrystalline silicon interdigitated electrodes.…”

Impedance Analysis of Colloidal Gold Nanoparticles in Chromatography Paper for Quantitation of an Immunochromatographic Assay

“…30,31 The measurement principle using EIS is to measure the capacitance on a color line using the modified electrodes with polymer layers. 32,33 However, both methods using CA and EIS are costly because they need additional factors such as enzymes, mediators or polymers in addition to electrodes. On the other hand, a study to quantitate IST only with electrodes has been reported.…”