Guoqiang Sun

Photoelectrochemical sensor for pentachlorophenol on microfluidic paper-based analytical device based on the molecular imprinting technique.

Combining microfluidic paper-based analytical device (μ-PAD) and the molecular imprinting technique, a visible light photoelectrochemical (PEC) sensing platform for the detection of pentachlorophenol (PCP) was established on gold nanoparticles (AuNPs) decorated paper working electrode using polypyrrole-functionalized ZnO nanoparticles. Ascorbic acid (AA) was exploited as an efficient and nontoxic electron donor for scavenging photogenerated holes under mild solution medium and facilitating the generation of stable photocurrent. The microfluidic molecular imprinted polymer-based PEC analytical origami device is developed for the detection of PCP in the linear range from 0.01 ng mL(-1) to 100 ng mL(-1) with a low detection limit of 4 pg mL(-1). This disposable microfluidic PEC origami device would provide a new platform for sensitive, specific, and multiplex assay in public health, environmental monitoring, and the developing world.

Ultrasensitive electrochemical immunoassay for carcinoembryonic antigen based on three-dimensional macroporous gold nanoparticles/graphene composite platform and multienzyme functionalized nanoporous silver label.

Three-dimensional macroporous gold nanoparticles/graphene composites (3D-AuNPs/GN) were synthesized through a simple two-step process, and were used to modify working electrode sensing platform, based on which a facile electrochemical immunoassay for sensitive detection of carcinoembryonic antigen (CEA) in human serum was developed. In the proposed 3D-AuNPs/GN, AuNPs were distributed not just on the surface, but also on the inside of graphene. And this distribution property increased the area of sensing surface, resulting in capturing more primary antibodies as well as improving the electronic transmission rate. In the presence of CEA, a sandwich-type immune composite was formed on the sensing platform, and the horseradish peroxidase-labeled anti-CEA antibody (HRP-Ab2)/thionine/nanoporous silver (HRP-Ab2/TH/NPS) signal label was captured. Under optimal conditions, the electrochemical immunosensor exhibited excellent analytical performance: the detection range of CEA is from 0.001 to 10 ng mL(-1) with low detection limit of 0.35 pg mL(-1) and low limit of quantitation (LOQ) of 0.85 pg mL(-1). The electrochemical immunosensor showed good precision, acceptable stability and reproducibility, and could be used for the detection of CEA in real samples. The proposed method provides a promising platform of clinical immunoassay for other biomolecules.

An aptasensor for sensitive detection of human breast cancer cells by using porous GO/Au composites and porous PtFe alloy as effective sensing platform and signal amplification labels

A novel aptamer biosensor for cancer cell assay has been reported on the basis of ultrasensitive electrochemical detection. The assay uses the aptamer as a capture probe to recognize and bind the tumor marker on the surface of the cancer cells, forming an aptamer-based sandwich structure for MCF-7 cells detection. Functionalized nanoporous materials, porous graphene oxide/Au composites (GO/Au composites) and porous PtFe alloy have been introduced into the biosensor. Owing to the large surface area and versatile porous structure, the use of nanoporous materials can significantly improve the analysis performance of the biosensors by loading of large amounts of molecules and accelerating diffusion rate. Under the optimized experimental conditions, the proposed aptamer biosensor exhibited excellent analytical performance for MCF-7 cells determination, ranging from 100 to 5.0×10(7) cells mL(-1) with the detection limit of 38 cells mL(-1). The biosensor showed good selectivity, acceptable stability and reproducibility, and developed a highly sensitive and selective method for cancer cells detection.

Multiplexed enzyme-free electrochemical immunosensor based on ZnO nanorods modified reduced graphene oxide-paper electrode and silver deposition-induced signal amplification strategy.

Herein, an origami multiplexed enzyme-free electrochemical (EC) immunodevice is developed for the first time. Typically, ZnO nanorods (ZNRs) modified reduced graphene oxide (rGO)-paper electrode is used as a sensor platform, in which rGO improves the electronic transmission rate and ZNRs provide abundant sites for capture probes binding. Furthermore, by combining the large surface area of rGO and high catalytic activity of bovine serum protein (BSA)-stabilized silver nanoparticles (Ag@BSA) toward H2O2 reduction, rGO/Ag@BSA composites can be used as an excellent signal labels. The current signal is generated from the reduction of H2O2 and further amplified by a subsequent signal labels-promoted deposition of silver. Under optimal conditions, the proposed immunoassays exhibit excellent precision, high sensitivity and a wide linear range of 0.002-120 mIU mL(-1) for human chorionic gonadotropin, 0.001-110 ng mL(-1) for prostate-specific antigen, and 0.001-100 ng mL(-1) for carcinoembryonic antigen. The results for real sample analysis demonstrate that the newly constructed immunosensor arrays provide a simple and cost-effective method for clinical applications.

Microfluidic paper-based analytical device for photoelectrochemical immunoassay with multiplex signal amplification using multibranched hybridization chain reaction and PdAu enzyme mimetics

Combining multibranched hybridization chain reaction (mHCR), the photoelectrochemical (PEC) immunosensor was fabricated with a microfluidic paper-based analytical devices using different sizes of CdTe quantum dots (QDs) sensitized flower-like 3D ZnO superstructures as photoactive materials. Firstly, 4-aminothiophenol (PATP) functioned ZnO was anchored on gold-paper working electrode. With the aid of PATP, large-sized CdTe-COOH QDs (QDs1) were conjugated onto the ZnO surface because of the formation of a strong bond (Zn-S) between the thiol of PATP molecule and the ZnO, and the remaining amino group formed an amide bond with carboxylic acid group capping CdTe. Then the small-sized CdTe-NH2 QDs (QDs2) were modified on the QDs1 by forming amide bond, which leaded to a very strong photocurrent response because of the formation of cosensitized structure. The designed mHCR produced long products with multiple branched arms, which could attached multiple PdAu nanoparticles and catalyze the oxidation of hydroquinone (HQ) using H2O2 as anoxidant. Double strands DNA with multiple branched arms (mdsDNA) was formed by mHCR. In the presence of carcinoembryonic antigen (CEA), PdAu-mdsDNA conjugates-labeled CEA antibody was captured. The concentrations of CEA were measured through the decrease in photocurrent intensity resulting from the increase in steric hindrance of the immunocomplex and the polymeric oxidation product of HQ. In addition, the oxidation product of HQ deposited on the as-obtained electrode, which could efficiently inhibit the photoinduced electron transfer. Under optimal conditions, the PEC immunosensor exhibited excellent analytical performance: the detection range of CEA was from 0.001 to 90 ng mL(-1) with low detection limit of 0.33 pg mL(-1). The as-obtained immunosensor exhibited excellent precision, prominent specificity, acceptable stability and reproducibility, and could be used for the detection of CEA in real samples. The proposed assay opens a promising platform of clinical immunoassay for other biomolecules.

CuO-induced signal amplification strategy for multiplexed photoelectrochemical immunosensing using CdS sensitized ZnO nanotubes arrays as photoactive material and AuPd alloy nanoparticles as electron sink

In this work, multiplexed photoelectrochemical (PEC) immunoassays are introduced into an indium tin oxide (ITO) device. Firstly, the ITO device is fabricated using a simple acid etch treatment method. Secondly, AuPd alloy nanoparticles are electro-deposited on ITO working electrodes as electron sink to construct the immunosensor platform. After that, ZnO nanotubes (ZNTs) arrays are synthesized via chemical etching of ZnO nanorods that are grown on AuPd surface by electrochemical deposition method. Subsequently, CdS is electro-deposited on ZNTs arrays and used as photoactive material. Then, CuO nanoseeds are labeled with signal antibodies and firstly used as PEC signal amplification label. The introduction of CuO brings signal amplification because of the conduction band (CB) of both CuO and ZnO are lower than that of CdS, CuO will compete the photo-induced electrons in CB of CdS with ZnO, leading to the decrease of the photocurrent intensity. Using cancer antigen 125, prostate specific antigen and α-fetoprotein as model analytes, the proposed immunoassay exhibits excellent precision and sensitivity. Meanwhile, this work provides a promising, addressable and simple strategy for the multi-detection of tumor markers.

Gold nanorods-paper electrode based enzyme-free electrochemical immunoassay for prostate specific antigen using porous zinc oxide spheres–silver nanoparticles nanocomposites as labels

An ultrasensitive enzyme-free electrochemical immunosensor is constructed using a gold nanorods (AuNRs) modified paper electrode as the sensor platform and porous zinc oxide spheres (PZS)–silver nanoparticles (AgNPs) nanocomposites as signal labels. Significantly enhanced sensitivity for prostate specific antigen (PSA) comes from a dual signal amplification strategy. First, interconnected AuNRs layers, which can improve the electronic transmission rate, are grown on the surface of cellulose fibers on a paper sample zone to capture primary antibodies. Second, PZS, a porous material with large surface area, is synthesized to provide sites for AgNPs loading, which improves the catalytic capacity of the AgNPs towards H2O2 reduction. Under optimized conditions, the proposed immunosensor for PSA exhibits a wide linear detection range from 0.004 to 60 ng mL−1 with a detection limit of 1.5 pg mL−1. Moreover, the immunosensor shows excellent selectivity, high stability, and acceptable fabrication reproducibility. This strategy appears to be a simple method, which provides a promising platform for the detection of other proteins.

An enhanced photoelectrochemical immunosensing platform: Supramolecular donor–acceptor arrays by assembly of porphyrin and C60

A novel self-assemble approach was developed for constructing a linear bicontinuous donor-acceptor, (H2BCPP)n-C60, arrays on indium-tin oxide electrode. Electronic absorption spectra, fluorescence spectra and atomic force microscopy were used as powerful tools to characterize H2BCPP, (H2BCPP)n arrays and (H2BCPP)n-C60 arrays. The (H2BCPP)n-C60 arrays enhanced the photocurrent generation capability, and presented an efficient photoelectrochemical immunosensing platform for the ultrasensitive detection of carcinoembryonic antigen (CEA). The quantitative measurement of CEA was based on the decrease in the photocurrent intensity of the (H2BCPP)n-C60 arrays, which was resulted from the competition between CEA and CEA-CdTe. A linear relationship between the photocurrent decrease and the CEA concentration was obtained in the wide range from 0.01 to 60 ng mL(-1) with a detection limit of 3.4 pg mL(-1). The proposed sensor showed high sensitivity, stability and reproducibility, and provided a promising platform for other biomolecular detection.

A near-infrared light photoelectrochemical immunosensor based on a Au-paper electrode and naphthalocyanine sensitized ZnO nanorods

A label-free photoelectrochemical (PEC) immunosensor is introduced into a microfluidic paper-based analytical device using tetra-carboxyl naphthalocyanine zinc (ZnNc-COOH) sensitized ZnO nanorods (NRs) as photoactive materials. Firstly, ZnO NRs are grown on a Au nanoparticles modified paper working electrode (Au-PWE) via a simple and low temperature hydrothermal method. With the aid of 4-aminothiophenol (PATP), ZnNc-COOH can be attached onto the ZnO NRs surface due to the formation of a strong bond (Zn-S) between the thiol end of the PATP molecule and the ZnO NRs, and the remaining amino group forms an acrylamide bond with ZnNc-COOH. To perform the immunoassay, carcinoembryonic antigen (CEA) antibodies are conjugated onto the ZnNc-COOH sensitized electrode by using the classic 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) coupling reactions between COOH groups on the surfaces of the ZnNc-COOH and NH2 groups of the antibodies. The concentrations of CEA are measured through the decrease in photocurrent intensity resulting from the increase in steric hindrance due to the formation of the immunocomplex. Under the optimized experimental conditions, the paper-based PEC immunosensor exhibits excellent analytical performance for detection of CEA, ranging from 0.005-100 ng mL-1 with a low detection limit of 1.6 pg mL-1. The PEC immunosensor shows high sensitivity, stability, and reproducibility. The proposed method provides a new strategy for a sensitive, low-cost, specific, and multiplex assay.

Chemiluminescence excited paper-based photoelectrochemical competitive immunosensing based on porous ZnO spheres and CdS nanorods

A chemiluminescence excited photoelectrochemical (PEC) competitive immunosensor for sensitive and specific detection of the prostate specific antigen (PSA) is firstly developed by combining a microfluidic paper-based device. Firstly, porous ZnO spheres with large surface area and good biocompatibility are attached onto the Au nanoparticle modified paper working electrode, which serve as an effective matrix for antigens. CdS nanorods (NRs) are selected as the photoactive materials due to their excellent fast and long distance electron transport capability, which allow the binding of the horseradish peroxidase-labeled signal antibody onto CdS NRs (CdS NR-Ab-HRP). After a competitive immunoassay format, the CdS NR-Ab-HRP labels are captured onto the electrode surface. The chemiluminescent excitation is produced from the oxidation of luminol by H2O2 in the presence of HRP. The more antigens in solution can bind to CdS NR-Ab-HRP the less CdS NR-Ab-HRP can bind to antigens immobilized on the electrode, which result in the decrease of chemiluminescence emission and light absorption, leading to the decrease of photocurrent intensity. The PEC response from CdS NR-Ab-HRP successfully fulfilled the sensitive detection of PSA in the linear range from 0.005 to 150 ng mL-1 with a detection limit of 2.3 pg mL-1. The proposed immunosensor shows excellent analytical performance with high reproducibility and stability, and can become a promising platform for other protein detection.