Direct acupuncture of nitric oxide by an electrochemical microsensor with high time-space resolution.

Measurement of signal molecule is critically important for understanding living systems. Nitric oxide (NO) is a key redox signal molecule that shows diverse roles in virtually all life forms. However, probing into NO's activities is challenging as NO has restricted lifetime (<10 s) and limited diffusion distance (usually <200 µm). So, for the direct acupuncture of NO within the time-space resolution, an electrochemical microsensor has been designed and fabricated in this work. Fabrication of the microsensor is achieved by (1) selective assembly of an electrocatalytic transducer, (2) attaching the transducer on carbon fiber electrode, and (3) covered it with a screen layer to reduce signal interference. The fabricated microsensor exhibits high sensitivity (LOD, 13.5 pM), wide detection range (100 pM-5 µM), and good selectivity. Moreover, studies have revealed that the availability of the sensor for efficient detection of NO is due to the formation of a specific DNA/porphyrin hybrid structure that has synergetic effects on NO electrocatalysis. Therefore, NO release by cells and tissues can be directly and precisely traced, in which we have obtained the release pattern of NO by different cancer cell lines, and have known its dynamics in tumor microenvironment. The fabricated electrocatalytic microsensor may provide a unique and useful tool for the direct assay of NO with high time-space resolution, which promisingly gives a technical solution for the bioassay of NO in living systems.

Electrochemical Trans-Channel Assay for Efficient Evaluation of Tumor Cell Invasiveness.

Efficiently assessing the invasive capability of tumor cells is critical both for the research and treatment of cancer. Here, we report a novel method called the electrochemical trans-channel assay for efficient evaluation of tumor cell invasiveness. A bioinspired extracellular matrix degradation model (EDM) has been first fabricated on a porous anodic alumina (PAA) membrane to construct the electrochemical apparatus. Upon contacting the invasive tumor cells, invasive capability can be sensitively evaluated by the degree of EDM impairment, which is recorded by the electrochemical trans-channel ionic currents in a label-free manner. Compared to the most commonly used trans-well migration method, this assay can be accomplished in an efficient way that is significantly faster (20 min) and more convenient. Besides, quantitation can also be realized for monitoring the invasion process, which cannot be achieved by other currently used methods. Our proposed electrochemical trans-channel assay method has shown a synergistic effect for the evaluation of tumor cell invasiveness, providing a promising method for clinical assessment or prognostic applications of tumor metastasis.

Rhodopsin-Like Ionic Gate Fabricated with Graphene Oxide and Isomeric DNA Switch for Efficient Photocontrol of Ion Transport.

Rhodopsin, composed of opsin and isomeric retinal, acts as the primary photoreceptor by converting light into electric signals. Inspired by rhodopsin, we have fabricated a light-regulated ionic gate on the basis of the design of a graphene oxide (GO)-biomimetic DNA-nanochannel architecture. In this design, photoswitchable azobenzene (Azo)-DNA is introduced to the surface of porous anodic alumina (PAA) membrane. With modulation of the interaction between the GO blocker and Azo-DNA via flexibly regulating trans and cis states of Azo under the irradiation of visible and ultraviolet light, alternatively, the ionic gate is switched between ON and OFF states. This newly constructed ionic gate can possess high efficiency for the control of ion transport because of the high blocking property of GO and the rather tiny path within the barrier layer which are both first employed to fabricate ionic gate. We anticipate that this rhodopsin-like ionic gate may provide a new model and method for the investigation of ion channel, ion function, and ion quantity. In addition, because of the advantages of simple fabrication, good biocompatibility, and universality, this bioinspired system may have potential applications as optical sensors, in photoelectric transformation, and in controllable drug delivery.

DNA nanoflower blooms in nanochannels: a new strategy for miRNA detection.

By employing DNA nanoflower blooming in the nanochannels of porous anodic alumina (PAA), a nanochannel platform for microRNA (miRNA) detection has been proposed. Significant steric and electrostatic hindrance of the miRNA-initiated DNA-nanoflower growth may also amplify the signal readout for miRNA detection to give excellent sensitivity, selectivity and reproducibility.

Multifunctional nanocatalyst-based ultrasensitive detection of human tissue transglutaminase 2.

Tissue transglutaminase 2 (TGM2) is a novel tumor marker, which can be used as the complementary marker for alpha-fetoprotein to improve overall diagnostic performance of hepatocellular carcinoma at the clinical level. In this work, we have developed a multifunctional nanocatalyst-based electrochemical method for TGM2 assay with an ultrahigh sensitivity. Here we firstly functionalize carboxyl-modified graphene oxide with poly-lysine and copper ion to form an electrochemical nanocatalyst. On the one hand, the nanocatalyst can function as the substrate of TGM2. On the other, the nanocatalyst can be applied for signal amplification to enable high sensitivity of the detection. With the specific glutamine-donor-peptide of TGM2 modified on the electrode, the exertion of the transamidation activity by TGM2 can lead to the tethering of the nanocatalyst with the peptide on the electrode, inducing obvious changes of the electrochemical signals. Therefore, simple and sensitive detection of TGM2 can be achieved. Moreover, TGM2 is also detected effectively in complex serum samples, suggesting potential diagnostic applications of the new method proposed in this work.

A simple and visible colorimetric method through Zr(4+)-phosphate coordination for the assay of protein tyrosine phosphatase 1B and screening of its inhibitors.

Inhibitors of protein tyrosine phosphatase 1B (PTP1B) are promising agents for the treatment of type 2 diabetes and obesity, so a colorimetric method has been developed in this work for PTP1B assay and screening of its inhibitors. The method is based on the chelation effect of zirconium (Zr(4+)) ions on the phosphate group, which may induce aggregation of 4-aminophenylphosphate-functionalized gold nanoparticles (APP/AuNPs) and the corresponding color change of the testing solution. Owing to the dephosphorylation of PTP1B, the aggregation of AuNPs will be influenced by PTP1B since there is no coordination reactivity between Zr(4+) ions and 4-aminophenol, the hydrolyzed product of APP catalyzed by the enzyme. Therefore, a simple colorimetric method for the assay of PTP1B activity can be developed. Under the optimized experimental conditions, the ratios of absorbance at a wavelength of 650 nm to that at 522 nm vary linearly with the PTP1B activity in the range from 0.005 to 0.18 U mL(-1) with the lowest detection limit of 0.0017 U mL(-1). Moreover, using this proposed method, the inhibition effect of 6-chloro-3-formyl-7-methylchromone, betulinic acid, ursolic acid, and sodium orthovanadate on PTP1B activity can be tested with IC50 values of 10, 13, 9, and 1.1 µM, respectively. Therefore, this new method has great potential not only for the detection of PTP1B activity but also for the screening of the inhibitors.

Photodynamic effect of hypericin on the conformation and catalytic activity of hemoglobin.

Hypericin, extracted from H. perforatum, can induce the generation of reactive oxygen species by visible light irradiation, which may consequently induce the conformational change of hemoglobin. We have not only employed UV-vis spectroscopy to observe the changes of UV-vis spectra of the protein, which reveals the conformational changes of the protein, but also employed electrochemical method to obtain its enhanced peroxidase activity. The photodynamic effect of hypericin on the conformation and catalytic activity of the protein has also been proven to be strongly dependent on the irradiation time, the hypericin concentration and the presence of oxygen. This work is beneficial not only to the fabrication of more sensitive hydrogen peroxide biosensor, but also to the guidance of the usage of this medicinal herb molecule, since the conformational change of the protein and the enhanced peroxidase can be easily obtained only by visible light irradiation on hypericin, the process of which is so common to happen.

Electrochemical sensing DNA damage with nano-titanium dioxide and repair with a medicinal herb species resveratrol.

We have developed a simple electrochemical method to detect DNA damage caused by the photovoltaic effect of nano-TiO(2). Meanwhile, we have found that resveratrol, a Chinese Traditional Medicinal Herb species, can have a repairing effect to the oxidized DNA, which can also be detected with the proposed technique in this paper.

Electrochemistry of sinapine and its detection in medicinal plants.

Sinapine (O-sinapoyl choline) is a crucial component, with much medicinal value, of many dietary and medicinal plants. It has been found that sinapine gives an electrochemical response at a pyrolytic graphite electrode. The electrochemical properties of sinapine have been investigated. The peak current in the cyclic voltammogram is linear in the concentration range 1.9 x 10(-6)-2.5 x 10(-4) mol L(-1) and the limit of detection is 9.9 x 10(-7) mol L(-1). These properties can be applied to the determination of sinapine in extracts from three kinds of medicinal plant. The electrochemical method reported here is highly selective, sensitive, and stable.

The electrochemistry and determination of Ligustrazine hydrochloride.

Ligustrazine is one of the active ingredients contained in Ligusticum chuanxiong Hort. (Umbelliferae), which is widely used in traditional Chinese medicine for the treatment of cardiovascular problems. In this work, the electrochemistry of Ligustrazine hydrochloride (LZC) and its determination are investigated. The detection limit is estimated to be 8.0 x 10(-8) M, with three linear ranges from 1.0 x 10(-6) to 1.0 x 10(-4) M, 1.0 x 10(-4) to 5.0 x 10(-4) M, and 6.5 x 10(-4) to 1.6 x 10(-3) M. The method has been proved to be highly sensitive, selective, and stable, and has been successfully applied to determining LZC in LZC injections.

Electrochemical investigations of baicalin and DNA-baicalin interactions.

Baicalin is an anti-HIV drug purified from the traditional Chinese medicinal plant Scutellaria Baicalensis Georgi. Baicalin has proven to be electroactive at pyrolytic graphite (PG) electrodes. We thus studied its interaction with DNA via the electrochemical approach. We observed that the peak currents corresponding to the baicalin reduction-oxidation (redox) reaction significantly decrease upon the addition of DNA. With complementary ultraviolet/visible (UV/Vis) spectroscopic evidence, we suggest that baicalin binds to DNA through intercalation. This feature has enabled baicalin to discriminate between double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA).

An easy and rapid method to determine aristolochic acids I and II with high sensitivity.

Aristolochic acid (AA), a natural component in some Chinese medicinal plants, is nephrotoxic and carcinogenic, and is involved in a specific type of renal fibrosis, called Chinese herbs nephropathy (CHN). In this paper, we report the electrochemistry of AA and a novel method to detect the species based on the electrochemical studies. The detection limit is estimated to be 1.0x10(-8) M with a linear range from 5.0x10(-8) M to 1.3x10(-6) M. Meanwhile, this method is applicable in detection in real samples, such as Caulis Aristolochiae Manshuriensis (CAM), Radix Aristolochiae (RA), Fructus Aristolochiae (FA) and Radix Stephaniae Tetrandrae (RST). The concentration of AA in the CAM sample was 3.50 +/- 0.12x10(-4) M. Consistent results have been obtained from both the electrochemical approach described here and the previously reported HPLC method.

Isolation and determination of p-hydroxybenzoylcholine in traditional Chinese medicine Semen sinapis Albae.

A special component is isolated from Semen sinapis Albae (white mustard seed), a traditional Chinese medicine. According to the physical and chemical investigation and spectroscopic identification, this component can be known as p-hydroxybenzoylcholine bisulfate, a choline base. This component in the drug is also determined by RP-HPLC. A reversed-phase C(18) column is used to separate the p-hydroxybenzoylcholine with an eluent of methanol-0.05 mol/L monopotassium phosphate solution (30:70) (adjusted by phosphoric acid to pH 3.6) at the flow rate of 0.5 mL/min. Detection is carried out with a UV detector operated at 285 nm, and the column temperature is 25 degrees C. It reveals that there is 0.021% (w/w) of p-hydroxybenzoylcholine bisulfate in Semen sinapis Albae and 0.037% (w/w) in stir-baked Semen sinapis Albae.