Enhanced Photoelectrochemical Proximity Assay for Highly Selective Protein Detection in Biological Matrixes

Abstract

This work proposes the first photoelectrochemical proximity assay (PECPA) method via the sensitization of CdTe quantum dots (QDs) on photoelectrochemical response of ITO/TiO2/CdS electrode for highly selective and sensitive detection of proteins. This detection was performed on a sensing interface formed via the hybridization of capture DNA immobilized on ITO/TiO2/CdS electrode with labeled antibody-DNA (DNA-Ab1). Upon the recognition of Ab1 to target protein, the immunocomplex of DNA-Ab1, target, and the detection antibody-DNA (DNA-Ab2) was formed, which led to the proximity hybridization of the DNA in DNA-Ab2, capture DNA, and signal DNA-CdTe QDs, and brought CdTe QDs to the ITO/TiO2/CdS electrode to produce a sensitized photocurrent. The photocurrent intensity increased with the increasing concentration of the specific target protein. Using insulin as a target, this sensitized method showed a detectable range of 10 fM to 10 nM and a detection limit of 3.0 fM without the need of a washing step. It possessed high selectivity and good accuracy for detection of proteins in biological matrixes. This method is extremely flexible and can be extended to varieties of protein targets.

Affinity-Based Detection of Biomolecules Using Photo-Electrochemical Readout

“…The NPC-ZnO is also photoactive and thereby generated a signal-on response under visible light excitation. This creative design strategy enabled ultrasensitive miRNA detection with a limit-of-detection of 49 aM (linear range of 0.1 fM−10 nM), which is much lower than the previously reported photoelectrochemical miRNA detection bioassays (Wen and Ju, 2016; Chu et al, 2018).…”

“…Coupling two or more inorganic semiconductors extends the absorption spectrum and increases the charge separation efficiency of the PEC system (Wen and Ju, 2016). As a result, hybrid material systems offer a higher photon-to-current conversion efficiency, which is important for enhancing the performance of biosensors (Zhao et al, 2014).…”

“…As a result, hybrid material systems offer a higher photon-to-current conversion efficiency, which is important for enhancing the performance of biosensors (Zhao et al, 2014). For example, when TiO 2 NPs are used with CdS QDs in insulin detection (Wen and Ju, 2016), CdTe is excited using visible light, and the photo-induced electrons are transferred from CdTe to the conduction band of TiO- 2 NPs. Liu et al (2017b) demonstrated improved sensitivity of microcystin detection by forming Z-scheme heterojunction of CdTe with Bi 2 S 3 nanorods due to enhanced charge separation.…”

“…In addition to nucleic acid sensing, QDs are widely used in PEC biosensors created for protein analysis. In an assay of this type, the presence of insulin instigated the formation of an immunocomplex containing DNA-labeled antibody, insulin, secondary DNA labeled antibody and CdTe-labeled reporter DNA (Wen and Ju, 2016). CdTe induces a sensitization effect on the CdS/TiO 2 /ITO electrode, thereby enhancing the photocurrent under white light excitation (spectral range 200–1,200 nm) (Figure 4C).…”

DNA-Based Scaffolds for Sensing Applications

“…Wen et al also proposed a similar approach based on photoelectrochemical detection on an ITO/TiO 2 /CdS electrode for the monitoring of insulin, displaying a linear range from 10 fM to 10 nM and a detection limit of 3.0 fM without the need for a washing step. 167 Furthermore, proximity-dependent complementation of DNAzyme has also been successfully tested to generate a chemiluminescence-based (CL) imaging method for the rapid and high-throughput detection of protein targets in bioanalysis. 168 Most of these examples reported above take advantage of the use of a DNA−antibody conjugate, but efficient chemical methods for producing high-quality conjugates from commercially available antibodies are still lacking.…”