Sensitive Photoelectrochemical Immunoassay Research Articles

CdS quantum-dots-modified CuBi2O4 nanorods as highly active and etchable photocathodic materials for sensitive photoelectrochemical immunoassay

Cathodic photoelectrochemical (PEC) analysis is highly favored for bioassays due to its excellent anti-interference ability toward reductive biomolecules, but it is still challenging to develop highly active photocathodic materials. Herein, CdS quantum dots (QDs) modified CuBi2O4 nanorods are proposed as highly active and etchable photocathodic materials for sensitive PEC immunoassay. After the growth of CdS QDs on CuBi2O4 nanorods, the cathodic photocurrent is greatly boosted because of the formation of p-n heterojunctions. CdS QDs can be etched by H2O2 due to the oxidization of S2- to SO42-, so CdS/CuBi2O4 can serve as an etchable photocathodic material. PEC immunoassay of carcinoembryonic antigen (CEA) is realized by using glucose oxidase (GOx)-conjugated immunomagnetic beads as labels, because H2O2 generated in the GOx-based enzymatic reaction can etch the photoactive material, leading to a decrease in photocurrent. A wide linear range is obtained in the range of 0.1–5 × 103 pg mL−1 with a low detection limit of 0.02 pg mL−1 for CEA detection.

TiO2/CuInS2-sensitized structure for sensitive photoelectrochemical immunoassay of cortisol in saliva

TiO2/CuInS2-sensitized structure for sensitive photoelectrochemical immunoassay of cortisol in saliva

Sensitive photoelectrochemical immunoassay of Staphylococcus aureus based on one-pot electrodeposited ZnS/CdS heterojunction nanoparticles.

We report here a facile synthesis of ZnS/CdS heterojunction nanoparticles on an indium-tin oxide (ITO) electrode and their application in the ultrasensitive photoelectrochemical detection of Staphylococcus aureus (S. aureus). The ZnS/CdS/ITO electrode was prepared using one-pot electrodeposition in an acidic solution containing ZnCl2, CdCl2 and Na2S2O3. The optimal ZnS/CdS heterojunction nanoparticles with a Zn/Cd atomic ratio of 1 : 1 showed a high photoelectrochemical response to l-cysteine. l-Cysteine-encapsulated liposome (cysteine@liposome) immunonanocapsules were prepared and used as the labels for photoelectrochemical detection of S. aureus. By coupling cysteine@liposome immunonanocapsule labeling with immunomagnetic separation/enrichment and photoelectrochemical analysis using the ZnS/CdS/ITO electrode, sensitive photoelectrochemical detection of S. aureus was achieved. Under optimal conditions, the linear range for photoelectrochemical detection of S. aureus was from 1 to 4000 CFU mL-1. The proposed method was successfully used for photoelectrochemical detection of S. aureus in milk and juice samples.

Using PbS–Au heterodimers as signal quencher for the sensitive photoelectrochemical immunoassay of amyloid β-protein

By using PbS–Au heterodimers as the signal quencher, TiO2/BiOI as matrix, a novel sandwich-type photoeletrochemical (PEC) biosensor for sensitive determination of amyloid β-protein (Aβ, ∼4 KDa) was developed. BiOI was attached to the surface of TiO2 and formed a heterogeneous structure (p-n junction), which enlarged the light harvest range and enhanced the electron transfer rate of TiO2. In order to quench the PEC signal, PbS–Au heterodimers were used as the labels to combine with Aβ. Owing to the competitively light energy harvesting and electron donor consuming effect of PbS–Au heterodimers, less light energy and electron donor arrived at TiO2/BiOI. In addition, Au directly contacted with PbS could enhance the electron seperation and transfer rate, and lead to improved competitiveness consumption of the electron donor. PbS–Au integrated with secondary antibodies formed PbS–Au-Ab2 bioconjugate, which would further obstruct the electron transfer and impede the interreaction between electron donor and photoelectrode surfaces. Owing to the unique PbS–Au heterodimer structure and the quenching effect of PbS–Au-Ab2 bioconjugate, the fabricated immunosensor for Aβ detection exhibited good stability, high sensitivity, and a low detection limit of 0.028 pg/mL (S/N = 3).

Enhanced organic−inorganic heterojunction of polypyrrole@Bi2WO6: Fabrication and application for sensitive photoelectrochemical immunoassay of creatine kinase-MB

In this report, enhanced organic−inorganic heterojunction of polypyrrole@Bi2WO6 was fabricated and applied for sensitive photoelectrochemical (PEC) immunoassay of creatine kinase-MB (CK-MB). Specifically, heterostructured polypyrrole@Bi2WO6 photoelectrode was prepared and sandwich immunorecognition were integrated for the CK-MB immunoassay. In the detection, with the aid of alkaline phosphate (ALP)-induced biocatalytic precipitation (BCP), the precipitation-dependent suppression of the photocurrent can be recorded due to the impediment of the interfacial mass and electron transfer. On the basis of target-controlled BCP formation, a novel PEC immunoassay could be developed for the sensitive and specific CK-MB detection. This work manifested the great potential of polypyrrole@Bi2WO6 heterojunction as a novel platform for PEC bioanalysis development and also a PEC method for CK-MB detection. This work is expected to stimulate more interest in the design and implementation of numerous other organic−inorganic heterojunction for advanced PEC bioanalysis development.

Tyrosinase-encapsulated liposomes: Toward enzyme-induced in situ sensitization of semiconductor for sensitive photoelectrochemical immunoassay

Liposomal photoelectrochemical (PEC) bioanalysis holds enormous potential for future sensitive PEC bioanalysis. With tyrosinase (Tyr) and TiO2 as representative enzyme and electrode, respectively, this communication reports the elegant use of Tyr-loaded liposomes (TLL) toward in situ sensitization of the electrode and thereby the realization of ultrasensitive PEC immunoassay. Specifically, Tyr-encapsulated and detection antibody-functionalized liposomes were first prepared and used as the signal probe. The subsequent sandwich immunobinding could confine the functional liposomes, which were then lysed with surfactant to release the encapsulated Tyr. The free Tyr could then initiate the transformation of tyrosine to dopa, the latter could bind with the undercoordinated Ti sites, forming the stable dopa–Ti charge transfer complex and thus generating enhanced anodic photocurrent under visible light for signaling. Since different semiconductors and enzymes may be adapted into this format, this work is expected to stimulate more interest in the enzyme-induced activation of semiconductors for advanced liposomal PEC bioanalysis.

A sensitive photoelectrochemical immunoassay of N6-methyladenosine based on dual-signal amplification strategy: Ru doped in SiO2 nanosphere and carboxylated g-C3N4

A novel, simple and sensitive photoelectrochemical (PEC) immunosensing platform was constructed for detecting N6-methyladenosine (m6A) based on the carboxylated CN and avidin functionalized Ru@SiO2 (ARS) nanocomposite. Herein, the N6-methyladenosine-5′-triphosphate (m6ATP) was selected as the detection target molecule, m6A antibody was used as recognition unit for m6A, the carboxylated g-C3N4 (CN) was not only used as the photoactive substance, but the substrate for the m6A antibody immobilization, ARS was synthesized and used as signal amplification unit to improve the photocurrent of CN, Phos-tag-biotin was employed as bridge of m6ATP and Ru@SiO2 through the specific interaction between phosphate group of m6ATP and Phos-tag, biotin and avidin, respectively. Under the optimal condition, the fabricated PEC biosensor showed a linear range of 0.01–10nM and high detection sensitivity with low detection limit of 3.23pM for m6ATP. Besides, the developed strategy was also successfully applied to evaluate the content of m6A in human serum samples.

A sensitive photoelectrochemical immunoassay based on mesoporous carbon/core–shell quantum dots as donor–acceptor light-harvesting architectures

A label-free PEC biosensor based on the amplification of mesoporous conductive material and core–shell QDs as light-harvesting architecture.

Highly Sensitive Photoelectrochemical Immunoassay with Enhanced Amplification Using Horseradish Peroxidase Induced Biocatalytic Precipitation on a CdS Quantum Dots Multilayer Electrode

Herein we demonstrate the protocol of a biocatalytic precipitation (BCP)-based sandwich photoelectrochemical (PEC) horseradish peroxidase (HRP)-linked immunoassay on the basis of their synergy effect for the ultrasensitive detection of mouse IgG (antigen, Ag) as a model protein. The hybrid film consisting of oppositely charged polyelectrolytes and CdS quantum dots (QDs) is developed by the classic layer by layer (LbL) method and then employed as the photoactive antibody (Ab) immobilization matrix for the subsequent sandwich-type Ab-Ag affinity interactions. Improved sensitivity is achieved through using the bioconjugates of HRP-secondary antibodies (Ab(2)). In addition to the much enhanced steric hindrance compared with the original one, the presence of HRP would further stimulate the BCP onto the electrode surface for signal amplification, concomitant to a competitive nonproductive absorption that lowers the photocurrent intensity. As a result of the multisignal amplification in this HRP catalyzed BCP-based PEC immunoassay, it possesses excellent analytical performance. The antigen could be detected from 0.5 pg/mL to 5.0 ng/mL with a detection limit of 0.5 pg/mL.