Reusable OIRD Microarray Chips Based on a Bienzyme-Immobilized Polyaniline Nanowire Forest for Multiplexed Detection of Biological Small Molecules

Abstract

Quantitative detection of multiple biological small molecules is critical for health evaluation and disease diagnosis. In this study, a microarray chip featuring a bienzyme-immobilized polyaniline nanowire forest on fluorine-doped tin oxide (bienzyme-PANI/FTO) is developed for this purpose. On such a chip, the target molecules are oxidized under the catalysis of their attached oxidases to produce hydrogen peroxide, which further induces the partial oxidation of local PANI nanowires in the presence of horseradish peroxidase (HRP) enzyme. The redox state change of PANI nanowires is monitored by the oblique incident reflectivity difference (OIRD) technique in a real-time and wireless manner, thus allowing for quantitative analysis of the target molecules. As typical model targets, hydrogen peroxide, glucose, lactic acid, and cholesterol are successfully detected with low detection limits, excellent specificities, and broad detection ranges, all of which fully meet the requirements for clinical analysis of human serum samples. Simultaneous detection of multiple targets on an individual chip is further demonstrated using the OIRD scanning mode. Meanwhile, by simple electrochemical reduction of the PANI nanowires, the chip is reusable for more than eight detection cycles without evident decay in its performance. The detection principle of this chip is also universal to other small molecules, and thus, it shows great promise as a valuable device to analyze biological small molecules.

Spatiotemporal Mapping of Extracellular Electron Transfer Flux in a Microbial Fuel Cell Using an Oblique Incident Reflectivity Difference Technique

“…During this scanning, the PANI was reduced from the emeraldine to the leucoemeraldine state, accompanied by the change of its conjugated structure and dielectric constant. Interestingly, the in situ OIRD signal simultaneously responds to the potential sweeping with a significant monotonic decrease in the whole potential range, indicating that the OIRD signal can sensitively monitor the redox state change of the PANI film, consistent with our previous investigation. , Therefore, it is clear that the OIRD signal from the bioanode strongly correlates to the redox state of the PANI and thus the EET flux, which sets the basis for OIRD imaging of EET flux. Meanwhile, the PANI film thickness shows considerable influence on the OIRD response (Figure S7), and the one polymerized with five potential cycles was selected as the optimal one for subsequent investigation.…”

“…The PANI-FTO electrode was prepared via electrochemical polymerization of aniline on FTO as reported previously . After 15 min ultrasonic cleaning with acetone, ethanol, and deionized water, clean FTO was used as the working electrode for electrochemical polymerization in 0.5 M H 2 SO 4 solution containing 0.1 M aniline.…”

“…OIRD is a newly established optical technique susceptible to the interfacial dielectric constant and surface properties (see its principle and setup in Figure S1 in the Supporting Information) . It has demonstrated intriguing ability for real-time and label-free monitoring of various surface/interface processes. − PANI is one of the most used conducting polymers in MFCs due to its good biocompatibility and conductivity. , PANI can be reversibly oxidized and reduced with simultaneous ion doping/de-doping, leading to its dielectric constant change to arouse the OIRD signal, as demonstrated in previous work. − In the present work, as in Scheme , a model bioanode was constructed by inhabiting Shewanella putrefaciens CN32, a robust exoelectrogenic bacterium, on the PANI nanowire film-coated fluorine-doped tin oxide (FTO) electrode (denoted bacteria-PANI-FTO) . In the open-circuit state, the PANI film was reduced by the inhabited cells via EET, and its redox state and dielectric constant change were monitored by OIRD to enable spatiotemporal mapping of the EET flow.…”

Polyaniline-Based Biological and Chemical Sensors: Sensing Mechanism, Configuration Design, and Perspective

“…In addition, they systematically studied the effects of surface modification on suppression of humidity response using seven types of fatty acids. 60 Long-chain alkyl acid-modified PANI sensors exhibited strong suppression of the humidity sensing response, while a behenic acid-modified sensor presented an ultra-low water sensitivity (0.008% ppm −1 ). Such studies on gas selectivity and stability in humid environments are essential for further biomedical applications of PANI-based sensors.…”

Label-free OIRD microarray chips with a nanostructured sensing interface: enhanced sensitivity and mechanism

“…A case in point is the SPR-based immunoassay chip, in which the strict requirement on the gold film thickness (∼48-50 nm) and the low penetration depth of surface plasmon waves (∼200 nm in aqueous solution) limit the application of the 3D sensing surface. 43,44 Fortunately, the OIRD technique has exhibited its capability to probe thick films up to tens of microns due to its transmission-reflectivity nature, 36,45 which implies that OIRD is potentially compatible with the 3D sensing interface for protein microarray detection.…”