Panpan Wang

Paper-based three-dimensional electrochemical immunodevice based on multi-walled carbon nanotubes functionalized paper for sensitive point-of-care testing

In this study, electrochemical immunoassay was introduced into the recently proposed microfluidic paper-based analytical device (μPADs). To improve the performance of electrochemical immunoassay on μPAD for point-of-care testing (POCT), a novel wax-patterned microfluidic paper-based three-dimensional electrochemical device (3D-μPED) was demonstrated based on the multi-walled carbon nanotubes (MWCNTs) modified μPAD. Using typical HRP-O-Phenylenediamine-H(2)O(2) electrochemical system, a sandwich immunoassay on this 3D-μPED for sensitive diagnosis of two tumor markers simultaneously in real clinical serum samples was developed with a linear range of 0.001-75.0 UmL(-1) for cancer antigen 125 and 0.05-50.0 ngmL(-1) for carcinoembryonic antigen. In addition, this 3D-μPED can be easily integrated and combined with the recently emerging paper electronics to further develop simple, sensitive, low-cost, disposable and portable μPAD for POCT, public health and environmental monitoring in remote regions, developing or developed countries.

Photoelectrochemical Lab-on-Paper Device Based on an Integrated Paper Supercapacitor and Internal Light Source

In this work, a photoelectrochemical (PEC) method was introduced into a microfluidic paper-based analytical device (μ-PAD), and thus, a truly low-cost, simple, portable, and disposable microfluidic PEC origami device (μ-PECOD) with an internal chemiluminescence light source and external digital multimeter (DMM) was demonstrated. The PEC responses of this μ-PECOD were investigated, and the enhancements of photocurrents in μ-PECOD were observed under both external and internal light sources compared with that on a traditional flat electrode counterpart. As a further amplification of the generated photocurrents, an all-solid-state paper supercapacitor was constructed and integrated into the μ-PECOD to collect and store the generated photocurrents. The stored electrical energy could be released instantaneously through the DMM to obtain an amplified (∼13-fold) and DMM-detectable current as well as a higher sensitivity than the direct photocurrent measurement, allowing the expensive and sophisticated electrochemical workstation or lock-in amplifier to be abandoned. As a model, sandwich adenosine triphosphate (ATP)-binding aptamers were taken as molecular reorganization elements on this μ-PECOD for the sensitive determination of ATP in human serum samples in the linear range from 1.0 pM to 1.0 nM with a detection limit of 0.2 pM. The specificity, reproducibility, and stability of this μ-PECOD were also investigated.

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.

A three-dimensional origami-based immuno-biofuel cell for self-powered, low-cost, and sensitive point-of-care testing.

A three-dimensional microfluidic origami glucose-air immuno-biofuel cell has been successfully demonstrated for the first time to implement self-powered, sensitive, and low-cost sandwich immunoassay for cancer markers based on the signal amplifications of a porous Au-paper electrode and Au nanoparticles attached to carbon nanotubes.

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.

Photoelectrochemical Sensor Based on Molecularly Imprinted Polymer-Coated TiO2 Nanotubes for Lindane Specific Recognition and Detection

A molecular imprinted polymer (MIP) thin film for photoelectrochemical (PEC) sensing of lindane molecules was constructed by electropolymerizing o-phenylenediamine (o–PD) monomer and lindane template molecule on titanium dioxide nanotubes. The resulting PEC sensors were characterized by scanning electron microscopy, ultraviolet (UV)-vis spectra and electrochemical impedance spectra. Clearly, the imprinted film showed high selectivity to lindane in our case. Under visible light irradiation, MIP film can generate the photoelectric transition from the highest occupied molecular orbital to the lowest unoccupied molecular orbital, delivering the excited electrons to the conduction band of titanium dioxide nanotubes. Simultaneously, it is believed that a positive charged hole (h+) of MIP that took part in oxidation process was consumed to promote the amplifying photocurrent response. The MIP-based PEC sensor had an excellent specificity and could be successfully applied to the recognition and detection of lindane, indicating a promising application in handling with organochlorine pesticide.

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.

Self-powered sensor for Hg2+ detection based on hollow-channel paper analytical devices

In this work, a novel and effective self-powered device was introduced in a microfluidic paper-based analytical device (μ-PAD) with hollow channels to transport fluids for mercury ion (Hg2+) detection. In this device, a mediator-less and compartment-less glucose/O2 biofuel cell (BFC) device served as the core component, using gold nanoparticle (AuNP) and platinum nanoparticle functionalized carbon nanotube (Pt/CNT) modified paper electrodes as the anodic and cathodic substrates, respectively. To construct the self-powered Hg2+ sensor, an Hg2+-specific oligonucleotide capture aptamer was first immobilized on an AuNP modified anode. In the presence of Hg2+, a AuNP@glucose dehydrogenase (GDH) labeled signal aptamer was hybridized with the immobilized capture probe through a thymine (T)–Hg2+–T interaction. Nicotinamide adenine dinucleotide (NAD+/NADH) was used as a cofactor in the proposed BFC device, and GDH in the anode could catalyze the oxidation of glucose used as fuel to generate gluconolactone, protons and electrons. Meanwhile the Pt/CNT in the cathode showed direct bioelectrocatalytic activity towards the oxygen reduction reaction (ORR). At the optimal conditions, this self-powered sensor could detect Hg2+ at the picomolar level, providing a simple approach to fabricate low-cost and portable powered devices on small-size paper for point-of-care testing. In addition, this self-powered sensor could be also used as a powerful tool for a wide range of potential applications in biotechnology and medicine.