Interference-free photoelectrochemical immunoassays using carboxymethylated dextran-coated and gold-modified TiO2 nanotube arrays

An interference-free photoelectrochemical (PEC) immunoassay was developed for cardiac troponin I (cTnI) detection. Covalent linkage of cTnI antibody to carboxymethylated (CM-) dextran pre-immobilized onto a gold nanoparticles (AuNPs)-modified TiO2 nanotube array (NTA) affords five consecutive analyte captures with surface regenerations in between. Changes in the photocurrents at this photoanode before and after cTnI captures can be well fitted with the Langmuir isotherm from 0.220 pM to 2.20 nM cTnI. Owing to the inherently high sensitivity of the PEC detection, the detection limit (2.20 pg/mL) is lower than the range attainable with the enzyme-linked immunosorbent assay (ELISA) (6.00-40.0 pg/mL). Furthermore, CM-dextran prevents species in complex biological matrices from nonspecifically adsorbing onto the sensor surface, a feature not attainable with uncoated semiconductor electrodes or those coated with non-hydrogel-based chemical modifiers. The excellent anti-fouling property of dextran hydrogel allowed us to validate the accuracy of our regenerable sensors through a comparison of PEC immunoassays of patient sera to those of ELISA.

Automated summary

A novel interference-free photoelectrochemical immunoassay was developed for the detection of cardiac troponin I. The modified sensor exhibited high sensitivity and anti-fouling properties, enabling accurate detection of analytes at low concentrations and preventing non-specific adsorption in complex biological matrices. The performance of the regenerable sensor was validated through comparison with enzyme-linked immunosorbent assays of patient sera.