Shaohuang Weng

In Situ Growth of Porous Platinum Nanoparticles on Graphene Oxide for Colorimetric Detection of Cancer Cells

A green approach is proposed for in situ growth of porous platinum nanoparticles on graphene oxide (PtNPs/GO). The resulting nanocomposite has been proven to function as peroxidase mimetics that can catalyze the reaction of peroxidase substrate in the presence of hydrogen peroxide. On the basis of the peroxidase-like activity, we used the PtNPs/GO as a signal transducer to develop a colorimetric assay for the direct detection of cancer cells. By using folic acid as a recognition element, a total of 125 cancer cells (MCF-7) can be distinguished by naked-eye observation. We envision that this nanomaterial could be used as a power tool for a wide range of potential applications in biotechnology and medicine.

Colorimetric detection of sulfide based on target-induced shielding against the peroxidase-like activity of gold nanoparticles

Colorimetric recognition and sensing of sulfide with high sensitivity was proposed based on target-induced shielding against the peroxidase-like activity of bare gold nanoparticles. Significant features of the new assay system are its simplicity and cost-effectiveness. The recognition of sulfide by bare gold nanoparticles can be fulfilled in a few seconds and the assay can be accomplished in about 10 min. Furthermore, the new assay system does not require surface modification of GNPs to obtain the specificity for sulfide, and a salt-induced aggregation step is not needed. The detection limit of this method for sulfide was 80 nM. These features make this sensor a potentially powerful tool for the quantitative determination of sulfide in water samples.

Ratiometric electrochemical immunoassay based on internal reference value for reproducible and sensitive detection of tumor marker

A ratiometric assay in an electrochemical immunosensor for tumor marker, herein carcinoembryonic antigen (CEA) was chosen as a model analyte, was developed to improve simplicity and accuracy. The immunosensor was fabricated via the simple expedient way of using Polythionine-gold (PTh-Au) as electrode modified material to be an internal reference signal and K3[Fe(CN)6] in electrolyte as an indicator signal. When the CEA was fixed on the modified electrode via immunoreaction, only the indicator signal sensitively altered; by contrast, the internal reference signal of PTh-Au remained constant at a suitable pH of the electrolyte. The ratio between the alterations of the indicator signal of K3[Fe(CN)6] and the constant internal reference signal can be used to monitor the concentration of CEA reliably, reproducibly, and sensitively. The prepared ratiometric electrochemical immunosensor could detect CEA with good specificity within a wide linear range from 0.005ng/ml to 40ng/ml with a detection limit of 2.2pg/ml. Additionally, experimental results confirm that our proposed method is practical. Thus, this method can expand to recognize and test other protein markers.

Sensitive electrochemical immunoassay of metallothionein-3 based on K3[Fe(CN)6] as a redox-active signal and C-dots/Nafion film for antibody immobilization

The fabrication of a facile, sensitive, and versatile immunosensor for the quantification of metallothionein-3 (MT-3) is proposed in this work. The K3[Fe(CN)6]-chitosan-glutaraldehyde (K-CS-GA) conjugate prepared from K3[Fe(CN)6], chitosan and glutaraldehyde was employed as the redox-active signal source. Carbon nanodots (C-dots) were coupled with Nafion to form the nanocomposite architecture layer to carry antibodies (Abs). C-dots enhanced the electrochemical response of the proposed immunosensor to improve the detection sensitivity. The fabrication steps of the immunosensor were characterized using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Antigen determination was achieved via the decreased current response of the K3[Fe(CN)6] caused by the insulated coupled antigen. The detected signals were proportional to the logarithm of the concentrations of MT-3 ranging from 5 pg mL(-1) to 20 ng mL(-1) with a detection limit of 2.5 pg mL(-1) in PBS. The proposed immunosensor showed high sensitivity, good selectivity and reproducibility. Furthermore, detection results using real serum samples showed the immunosensors potential applications in clinical diagnostics.

PRSS1_p.Leu81Met mutation results in autoimmune pancreatitis

AIM To describe protease serine 1 (PRSS1) gene mutations in patients with autoimmune pancreatitis (AIP) and the clinical features of AIP. METHODS Fourteen patients with AIP, 56 with other chronic pancreatitis, 254 with pancreatic cancer and 120 normal controls were studied. The mutations and polymorphisms of four genes involved with pancreatitis or pancreatic cancer, PRSS1, SPINK1, CFTR and MEN1, were sequenced. The pathogenic mechanism of AIP was investigated by comparing the wild-type expression system with the p.81Leu→Met mutant expression system. RESULTS Two novel mutations (p.81Leu→Met and p.91Ala→Ala) were found in PRSS1 gene from four patients with AIP. PRSS1_p.81Leu→Met mutation led to a trypsin display reduction (76.2%) combined with phenyl agarose (Ca(2+) induced failure). Moreover, the ratio of trypsin/amylase in patients with AIP was higher than in the patients with pancreatic cancer and other pancreatitis. A large number of lymphocytes and plasma cells were found in the bile ducts accompanied by hyperplasia of myofibroblasts. CONCLUSION Autoimmune pancreatitis may be related to PRSS1 gene mutations.

Signal-on fluorescent sensor based on GQDs–MnO2 composite for glutathione

Graphene quantum dots (GQDs) exhibit strong photoluminescence, biocompatibility, and low toxicity and can easily functionalize surfaces to improve the detection of biomolecules. As-prepared MnO2 nanosheets were applied in the fabrication of GQDs–MnO2 composite to develop a signal-on fluorescent platform for sensing glutathione (GSH). The fluorescence of the GQDs was quenched by MnO2 in the GQDs–MnO2 composite as a result of fluorescence resonance energy transfer within the composite. The fluorescence of GQDs was restored when GSH was introduced because GSH reduced the MnO2 nanosheets into Mn2+ and released GQDs. Under the optimized conditions, the concentration of GSH can be accurately detected with high sensitivity and specificity in Tris–HCl buffer and simulated serum. The proposed sensing strategy was successfully used to measure GSH in the range of 1–1000 μM with a detection limit of 0.45 μM. In addition, GSH in reduced glutathione injection and reduced glutathione tablets can be determined accurately using the proposed method. GQDs–MnO2 composite is thus a promising GSH fluorescence sensor for the analysis of complex systems and for quality control in the pharmaceutical industry.

A chronocoulometric LNA sensor for amplified detection of K-ras mutation based on site-specific DNA cleavage of restriction endonuclease

An amplified chronocoulometric Locked nucleic acid (LNA) sensor (CLS) for selective electrochemical detection of K-ras mutation was developed based on site-specific DNA cleavage of restriction endonuclease EcoRI. Thiolated-hairpin LNA probe with palindrome structure of stem was immobilized on the gold nanoparticles modified gold electrode (NG/AuE). It can be cleaved by EcoRI in the absence of K-ras mutation-type DNA (complementary with the loop part of hairpin probe), but cannot be cleaved in the presence of mutation-type DNA. The difference before and after enzymatic cleavage was then monitored by chronocoulometric biosensor. Electrochemical signals are generated by chronocoulometric interrogation of Hexaammineruthenium (III) chloride (RuHex) that quantitatively binds to surface-confined hairpin LNA probe via electrostatic interactions. The results suggested this CLS had a good specificity to distinguish the K-ras mutation-type, wild-type and non-complementary sequence. There was a good linear relationship between the charge and the logarithmic function of K-ras mutation-type DNA concentration. The detection limit had been estimated as 0.5 fM. It is possible to qualitatively and quantitatively detect K-ras point mutation in pancreatic cancer.

Selective electrochemical determination of dopamine in serum in the presence of ascorbic acid and uric acid by using a CuO nanoleaf electrode

A simple, selective, and sensitive electrochemical sensor for detecting dopamine (DA) using a copper oxide (CuO) nanoleaf electrode as an active platform was developed in this work. The CuO nanoleaf electrode was fabricated via one-step chemical oxidation of copper foil immersed in an alkaline solution with a strong oxidant. The electrode exhibits selective and sensitive DA detection in the presence of ascorbic acid and uric acid in phosphate buffered saline (pH 8.0). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were conducted to test the electrochemical behaviour of DA in the CuO nanoleaf electrode. DPV anodic peak currents at approximately 0.20 V were enhanced by increasing DA concentrations. The developed electrochemical sensor presents two linear ranges of 1 μM to 7.5 μM and 7.5 μM to 140 μM, respectively. And the detection limit of the proposed method is 0.5 μM for DA. Applying the CuO nanoleaf electrode in actual determination of DA injection yields accurate results. Furthermore, the analytical results of DA in serum show that the developed method is a promising alternative approach for complex systems.

A label-free electrochemical immunosensor based on poly(thionine)–SDS nanocomposites for CA19-9 detection

In this paper, poly(thionine) doped sodium dodecyl sulphate nanocomposites (PThi–SDS NCs) were synthesised for the first time. The morphology and characteristics of the PThi–SDS NCs were investigated by using atomic force microscopy (AFM), UV-vis spectroscopy and electrochemical methods. Owing to the unique structure and properties of the PThi–SDS NC, it was used as a redox electrochemical mediator to construct immunoassay combining gold nanoparticles (AuNPs) as the immobilization matrix for antibody. A novel biomolecular immobilization strategy based on PThi–SDS/AuNPs was used to develop a highly sensitive label-free electrochemical immunosensor for the CA19-9 detection. Under optimal conditions, the present immunosensor exhibited a wide linear range of 5 to 400 U mL−1 with a detection limit of 0.45 U mL−1. Meanwhile, the novel immunosensor exhibited high selectivity, good reproducibility and stability.

Coupling technique of random amplified polymorphic DNA and nanoelectrochemical sensor for mapping pancreatic cancer genetic fingerprint.

Objective To review the feasibility of coupling the techniques of random amplified polymorphic DNA (RAPD) with carbon nanotube-based modified electrode for guanine/deoxyguanine triphosphate (dGTP) electrochemical sensing for mapping of the pancreatic cancer genetic fingerprint and screening of genetic alterations. Methods We developed a new method to study the electrochemical behavior of dGTP utilizing carbon multiwalled nanotube (MWNT)-modified glassy carbon electrodes (GCEs). RAPD was applied for amplification of DNA samples from healthy controls and patients with pancreatic cancer under the same conditions to determine the different surplus quantity of dGTP in the polymerase chain reaction (PCR), thereby determining the difference/quantity of PCR products or template strands. Using this method we generated a genetic fingerprint map of pancreatic cancer through the combination of electrochemical sensors and gel electrophoresis to screen for genetic alterations. Cloning and sequencing were then performed to verify these gene alterations. Results dGTP showed favorable electrochemical behavior on the MWNTs/GCE. The results indicated that the electrical signal and dGTP had a satisfactory linear relationship with the dGTP concentration within the conventional PCR concentration range. The MWNTs/GCE could distinguish between different products of RAPD. This experiment successfully identified a new pancreatic cancer-associated mutant gene fragment, consisting of a cyclin-dependent kinase 4 gene 3′ terminal mutation. Conclusion The coupling of RAPD and nanoelectrochemical sensors was successfully applied to the screening of genetic alterations in pancreatic cancer and for mapping of DNA fingerprints.