Electrochemical detection of carbendazim with mulberry fruit-like gold nanocrystal/multiple graphene aerogel and DNA cycle amplification.

An aptasensor for electrochemical detection of carbendazim is reported with mulberry fruit-like gold nanocrystal (MF-Au)/multiple graphene aerogel (MGA) and DNA cycle amplification. HAuCl4 was reduced by ascorbic acid in a CTAC solution containing KBr and KI and formed trioctahedron gold nanocrystal. The gold nanocrystal underwent structural evolution under enantioselective direction of L-cysteine. The resulting MF-Au shows a mulberry fruit-like nanostructure composed of gold nanocrystals of about 200 nm as the core and many irregular gold nanoparticles of about 30 nm as the shell. The exposure of high-index facets improves the catalytic activity of MF-Au. MF-Au/MGA was used for the construction of an aptasensor for electrochemical detection of carbendazim. The aptamer hybridizes with assistant strand DNA to form duplex DNA. Carbendazim binds with the formed duplex DNA to release assistant strand DNA, triggering one three-cascade DNA cycle. The utilization of a DNA cycle allows one carbendazim molecule to bring many methylene blue-labeled DNA fragments to the electrode surface. This promotes significant signal amplification due to the redox reaction of methylene blue. The detection signal is further enhanced by the catalysis of MF-Au and MGA towards the redox of methylene blue. A differential pulse voltammetric signal, best measured at - 0.32 V vs. Ag/AgCl, increases linearly with the carbendazim concentration ranging from 1.0 × 10-16 to 1.0 × 10-11 M with a detection limit of 4.4 × 10-17 M. The method provides ultrahigh sensitivity and selectivity and was successfully applied to the electrochemical detection of carbendazim in cucumber. This study reports on an ultrasensitive aptasensor for electrochemical detection of carbendazim in cucumber based on mulberry fruit-like gold nanocrystal-multiple graphene aerogel and DNA cycle double amplification.

Colorimetric detection of chlorpyrifos in peach based on cobalt-graphene nanohybrid with excellent oxidase-like activity and reusability.

Cobalt nanocrystal has been widely used as nano-enzyme for sensing and catalysis due to its high stability and low cost, but poor catalytic activity limits its applications in bioanalysis. The study reports one strategy for synthesis of cobalt-graphene nanohybrid. Histidine-functionalized graphene quantum dot (His-GQD) was bound to graphene sheet via π-π stacking and then combined with cobalt ions in the presence of cetyltrimethylammonium chloride to form stable complex and finally reduced under nitrogen to obtain Co-His-GQD-G. The as-synthesized nanohybrid offers well-defined three-dimensional structure and quasi-superparamagnetism. The cobalt nanoparticles were well dispersed on graphene sheets. The unique structure improves oxidase-like activity of Co-His-GQD-G. Further, Co-His-GQD-G was used as the nanozyme for colorimetric detection of chlorpyrifos. Co-His-GQD-G catalyzes oxidization of 3,3',5,5'-tetramethylbenzidine into blue product. Thiocholine produced by hydrolysis of acetylthiocholine under catalysis of acetylcholinesterase inhibits catalytic activity of Co-His-GQD-G and leads to a reduced oxidization rate. Chlorpyrifos inhibits activity of acetylcholinesterase and brings an enhanced absorbance of blue product. The absorbance at 652 nm linearly increases with increasing chlorpyrifos concentration in the range of 2-20 ng mL-1 with detection limit of 0.57 ng mL-1 (S/N = 3). The method was successfully applied in determination of chlorpyrifos in peach by preparing Co-His-GQD-G magnetic gel sheet.

Highly sensitive electrochemical detection of circulating tumor DNA in human blood based on urchin-like gold nanocrystal-multiple graphene aerogel and target DNA-induced recycling double amplification strategy.

Detection of circulating tumor DNA (ctDNA) is important approach to risk stratification and treatment response monitoring of cancer patients, but current method lacks of enough sensitivity and repeatability. The paper repors shape-controlled synthesis of gold nanocrystals via reduction of HAuCl4 with ascorbic acid. The synergy of CTAC, KBr, KI and L-glutathione creates urchin-like gold nanocrystals (U-Au) with more exposed high-index facets. Preparation of electrochemical sensing platform for ctDNA involves modification of U-Au-multiple graphene aerogel for target DNA-induced recycle amplification. DNA probe 1 (P1) with methylene blue (MB) hybridizes with DNA probe 2 with ferrocene (Fc) to form duplex DNA, which was attached to U-Au through Au-S bond. The ctDNA hybridizes with hairpin DNA 1 to open hairpin structure, triggering target DNA-induced recycle. Utilization of target DNA-induced recycling allows one target DNA to approach many MB probes to electrode surface and to leave many Fc probes from electrode surface, promoting significant signal amplification. The detection signal is enhanced by catalyzed redox of Fc and MB. Electrochemical response increases with ctDNA concentration from 0.1 to 1 × 106 fM with detection limit of 0.033 fM. The biosensor provides ultrahigh sensitivity, specificity and stability and was successfully applied in detection of ctDNA in human blood.

Dual amplification in a fluorometric acetamiprid assay by using an aptamer, G-quadruplex/hemin DNAzyme, and graphene quantum dots functionalized with D-penicillamine and histidine.

D-penicillamine and histidine-functionalized graphene quantum dot (DPA-GQD-His) was synthesized and applied in a fluorometric method for determination of acetamiprid using a G-quadruplex DNAzyme. At first DNA probe (probe 1) consists of a target-specific aptamer with two arms of DNA segments. Probe 1 was hybridized with DNA probe 2 composed of a single DNA sequence with two split G-rich DNA sequences. This leads to the formation of a triplex-to-G-quadruplex (TPGQ). Next, acetamiprid was hybridized with the aptamer in the TPGQ to release free DNA probe 2. The released probe 2, in the presence of of K+, undergoes a structural change into a stem-loop structure (by self-complementary hybridization and Hoogsteen hydrogen bonding) that bears a G-quadruplex structure. This is followed by conjugation with hemin to form the G-quadruplex/hemin DNAzyme. The DNAzyme catalyzes the oxidation of o-phenylenediamine by H2O2 to produce a yellow fluorescent product with excitation/emission maxima at 420/560 nm. The oxidation product interacts with DPA-GQD-His to achieve a rapid energy transfer between DPA-GQD-His and oxidation product. This increases the fluorescence of the oxidation product and quenches the fluorescence of DPA-GQD-His. DPA-GQD-His also improves the catalytic activity of DNAzyme towards oxidation of ophenylenediamine oxidization and enhances fluorometric response to acetamiprid. The assay works in the 1.0 fM to 1.0 nM acetamiprid concentration range and has a 0.38 fM detection limit. It was successfully applied to the determination of acetamiprid in tea. Graphical abstractThe study reported one double amplification strategy for ultrasensitive fluorescence detection of acetamiprid in tea with D-penicillamine and histidine-functionalized graphene quantum dots and G-quadruplex/heminDNAzyme. The analtyical method exhibits ultra high sensitivity, selectivity and rapidity of fluorescence response to acetamiprid.

Application of cell culture techniques in cultured meat-a review / 生物工程学报

As one of the top 10 breakthrough and emerging technologies in the world in 2018, cultured meat has attracted extensive attention due to its advantages of traceable origin, food safety and green sustainable development. Europe and the United States have invested a lot of resources to focus on research about cultured meat, which will affect our domestic meat and food market in the future. At present, the challenge of cultured meat production is how to efficiently simulate the growth environment of animal muscle tissue and realize large-scale production in bioreactor. Although cell tissue engineering has been deeply studied and achieved varying successful application, it is still difficult to obtain large-scale cultured meat production due to the high cost and technical requirements. Therefore, the development of efficient and safe cell culture technology is an urgent problem for large-scale cultured meat production, which can effectively reduce costs and achieve industrial application. In this review, we summarize the research progress of animal cell tissue culture technology used for cultured meat, and highlighted the current challenges and possible strategies in further applications.

Electrochemical sensor for detection of cancer cell based on folic acid and octadecylamine-functionalized graphene aerogel microspheres.

Early diagnosis of cancers is critical for prevention of metastasis and early treatment. The study reports an electrochemical sensor for detection of cancer cell based on folic acid (FA) and octadecylamine (OA)-functionalized graphene aerogel microspheres (FA-GAM-OA). Citric acid was mixed with FA and OA and heated at 180 °C for 4 h to form FA and OA-functionalized graphene oxide. The graphene oxide was employed as solid particle surfactant for stabilizing toluene-in-water emulsion. The graphene oxide sheets in the emulsion were self-assembled into graphene oxide gel microspheres on the water/toluene interfaces. Followed by free drying and reduction in H2 at 400 °C for 5 h. The resulted FA-GAM-OA shows a sphere-like structure with an average diameter of 1.2 µm, the rich of open-pores and folic acid groups. Small particle size and good hydrophilicity make FA-GAM-OA can be dispersed in water for sensor preparation. The small size of graphene sheets and their self-assembly avoid a serious agglomeration of graphene sheets. The FA-GAM-OA offers a large surface area (1723.6 m2 g-1) and high electronic conductivity (2978.2 S m-1). The covalent linkage and ordered alignment of folic acid groups at FA-GAM-OA surface achieve to specific cancer cell capture with high capture efficiency. The electrochemical sensor based on FA-GAM-OA exhibits extremely good analytical performances in detection of liver cancer cells with a linear range of 5-105 cell mL-1 giving a low detection limit of 5 cells mL-1 (S/N = 3). The method was successfully applied to electrochemical detection of liver cancer cells in whole blood.

Electrochemical immunosensor for ultrasensitive detection of microcystin-LR based on graphene-gold nanocomposite/functional conducting polymer/gold nanoparticle/ionic liquid composite film with electrodeposition.

The study developed an electrochemical immunosensor for ultrasensitive detection of microcystin-LR in water. Graphene oxide and chloroauric acid were alternately electrodeposited on the surface of glassy carbon electrode for 20 cycles to fabricate graphene-gold nanocomposite. The composite was characterized and its apparent heterogeneous electron transfer rate constant (37.28±0.16 cm s (-1)) was estimated by Laviron's model. To immobilize microcystin-LR antibody and improve the electrical conductivity, 2,5-di-(2-thienyl)-1-pyrrole-1-(p-benzoic acid) and chloroauric acid were electrodeposited on the modified electrode in sequence. The ionic liquid was then dropped on the electrode surface and finally microcystin-LR antibody was covalently connected to the conducting polymer film. Experiment showed the electrochemical technique offers control over reaction parameters and excellent repeatability. The graphene-gold nanocomposite and gold nanoparticles enhance electron transfer of Fe(CN)6(3-/4-) to the electrode. The ionic liquid, 1-isobutyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide, improves stability of the antibody. The sensor displays good repeatability (RSD=1.2%), sensitive electrochemical response to microcystin-LR in the range of 1.0×10(-16)-8.0×10(-15)M and detection limit of 3.7×10(-17)M (S/N=3). The peak current change of the sensor after and before incubation with 2.0×10(-15)M of microcystin-LR can retain 95% over a 20-weeks storage period. Proposed method presents remarkable improvement of sensitivity, repeatability and stability when compared to present microcystin-LR sensors. It has been successfully applied to the microcystin-LR determination in water samples with a spiked recovery in the range of 96.3-105.8%.

A sensitive and highly stable electrochemical impedance immunosensor based on the formation of silica gel-ionic liquid biocompatible film on the glassy carbon electrode for the determination of aflatoxin B1 in bee pollen.

The paper describes a sensitive and highly stable label-free electrochemical impedance immunosensor for the determination of aflatoxin B(1) (AFB(1)), which is based on the formation of silica gel-ionic liquid biocompatible film on the glassy carbon electrode. The electrochemical performances of the sensor were investigated by electrochemical impedance spectroscopy using a Fe(CN)(6)(3-/4-) phosphate buffer solution as base solution for test. As new ionic liquid, 1-amyl-2,3-dimethylimidazolium hexafluorophosphate, offers a very biocompatible microenvironment for AFB(1) antibody, the sensor exhibits good repeatability (RSD=1.2%), sensitive electrochemical impedance response to AFB(1) in the range of 0.1-10 ng ml(-1) and lowers the detection limit of AFB(1) (0.01 ng ml(-1)). The electron-transfer resistance change of the sensor after and before incubation with AFB(1) of 2.0 ng ml(-1) can retain 95% over a 180-day storage period at 4 degrees C. The results present a remarkable improvement of sensitivity (2-fold) and long-term stability (190-fold) when compared to classical silica gel sensor. Moreover, proposed sensor has a high selectivity to AFB(1) alone with no significant response to AFB(2), AFG(1), AFG(2) and AFM(1) as single substrates, it has been successfully applied to the determination of trace AFB(1) in bee pollen samples with a spiked recovery in the range of 96.0-102.5%.

Synergistic contributions of fullerene, ferrocene, chitosan and ionic liquid towards improved performance for a glucose sensor.

The paper describes an ingenious approach for the fabrication of a promising glucose sensor, GOx/C(60)-Fc-CS-IL, that exploits the synergistic beneficial characteristics of fullerene (C(60)), ferrocene (Fc), chitosan (CS) and ionic liquid (IL) for glucose oxidase (GOx). Cyclic voltammetry, impedance spectroscopy and chronoamperometry were used to evaluate performance of the biosensor, respectively. Since efficient electron transfer between GOx and the electrode was achieved, the biosensor exhibits a high sensitivity (234.67 nA nM(-1) cm(-2)), low detection limit (S/N=3) (3x10(-9) M), fast response time (0.752 s), wide calibration range (from 1x10(-8) M to 1x10(-5) M) and excellent long-term stability (30 weeks). The apparent Michaelis-Menten constant (K(M)) of GOx on the composite medium, 0.03 mM, shows high bioelectrocatalytic activity of immobilized enzyme toward glucose oxidation. Due to low operating potential (100 V), the biosensor is relatively insensitive to electroactive interfering species in human blood such as ascorbic acid, and uric acid, which are commonly found in blood samples. Excellent electrochemical reversibility, high sensitivity and stability, technically simple and possibility of preparation at short period of time are of great advantages of these glucose biosensors.

Effect of insulin-like growth factor-1 on intercellular adhesion molecule-1 expression in rat model of congestive heart failure / 中华老年医学杂志

Objective To investigate the effect of insulin-like growth factor-1 (IGF-1) on intercellular adhesion molecule-1 (ICAM-1) expression in rat model with congestive heart failure (CHF). Methods The model of CHF in male Sprague-Dawley rat was established using subcutaneous injection of isoproterenol. The rats were randomized into model group (n = 10),angiotensin converting enzyme inhibitors (ACEI) group ( n=10) and IGF- 1 group ( n = 10). The rats injected with saline were used as normal controls (n=10). The haemodynamic parameters of rats in each group were detected. The concentration of plasma angiotensin Ⅱ (Ang Ⅱ ) and expression of ICAM-1 in rat myocardium were determined by radioimmunoassay and immunohistochemistry,respectively. Results Compared with model group, ACEI and IGF-1 could rescue the diversities of hemodynamic parameters. In addition, ACEI and IGF-1 could also significantly down-regulated concentration of plasma Ang Ⅱ and inhibited ICAM-1 expression. Compared with ACEI, IGF-1 more significantly inhibited ICAM-I expression (0. 804 ± 0. 024 vs. 1. 254 ± 0. 059) and down-regulated concentration of plasma AngⅡ [(369.2±65.0) μg/L vs. (384.4±56.2) μg/L]. Conclusions IGF-1 can suppress ICAM-1 expression in rat model with CHF induced by isoproterenol. This effect may be related to inhibiting activation of RAS system.

Immunosensor Based on Immobilizing Antibody of Aflatoxin B_1 Using Silica Sol-Gel Technology / 分析化学

In the presence of hydrochloric acid, tetraethoxysilicane was hydrolyzed and formed silica sol. Non-labeled immunosensor was fabricated by droping the mixture solution of the silica sol and antibody of aflatoxin B_1 on the surface of glassy carbon electrode. In this work, a Fe(CN)_6~(3-/4-) phosphate buffer solution) was employed as base solution for investigating cyclic voltammetry(CV) and electrochemical impedance spectroscopic(EIS) performances of the sensor, respectively. The experimental results t indicated that because of the complex formed by the immunoreaction hindered the diffusion of Fe(CN)_6~(3-/4-) on the electrode surface, the redox peak current of the immunosensor in CV obviously decreased, and its electron transfer impedance linearly) increased with increasing the concentration of aflantoxin B_1(AFB). When the medium acidit and incubation) time were pH 6.5 and 20 min, respectively, the biggest electron transfer impedance changed value before and after the immunoreaction was obtained. Under the optimal conditions, a linear range to concentration of aflatoxin B_1 was 1-10 μg/L with a detection limit of 0.1 μg/L(S/N=3). Proposed method is of high sensitivity and stability, it has been successfully applied to determine AFB_1 in maize, rice and peanut.

Influence of Acupuncture on Cephalic Acupuncture Points Region Over the Brain-stem Evoked Potential of Patients Suffering Insufficient Blood-Supply of Vertebral Basilar Artery / 中国中医药信息杂志

Objective From the angle of electrophysiology, go further into the mechanism of action of acupuncture treatment to the insufficient blood-supply of vertebral basilar artery and at the same time, make a comparison of the effects between the acupuncture on cephalic meridian points and zonation cephalic acupuncture. Methods Through the contrast before and after adopting the self-acupuncture on the testees of 28 cases (including healthy persons of seven cases and TIA patients of 21 cases), observe the change of immediate effect of all waves latent period values of BAEP. Results The BAEP wave latent period of healthy persons (exclusive of I wave of auditory fainting region) assumes a relative delay within the physiological range and by comparison between points and region, the delay of V-wave Baihui point is evidently higher than that of auditory fainting region. However, the latent period of all waves of TIA patients is relatively moved up, especially there are evident differences before and after the I-wave acupuncture is carried out. Viewing from the comparison between points and region, there is no significant difference. Conclusion The function of acupuncture lies in the adjustment of antagonistic body state and it is most effective under the pathological state. Acupuncture will play the main role of excitation to the auditory nerve conduction of BAEP of TIA patients (from cochlea to midbrain) and the influence over the peripheral nerves is more sensitive than over the center ones. Although points and region have their own relative specificities, there is no significant difference between them.

Preparation of gold-labeled antibody probe and its use in immunochromatography assay for detection of aflatoxin B1.

Preparation of an antibody-colloidal gold probe (conjugate) specific to aflatoxin B1 (AFB1) and its use in developing a rapid AFB1 diagnostic method was presented in this paper. Monodispersional nanogold colloid was synthesized and preparation of nanogold-labeled polyclonal antibody probe to aflatoxin B1 under friendly and optimal condition. Combination of antibody with nanogold particles was also characterized by UV-visible (UV-vis) light absorption spectra, transmission electron microscopy (TEM), fluorescence spectroscopy, titers, cross reactivity and stability measurements. Furthermore, nanogold-labeled probe was used to develop an immunochromatographic (IC) method for aflatoxin B1 analysis. With this method, analysis could be completed in less than 10 min. Detection time was reduced 6-10 times comparative with ELISA. With visual observation, lower test limit was found to be around 2.5 ng/ml aflatoxin B1 standard solution, which was increased to two times of ELISA.

Desensitization of nicotinic receptors / 中国药理学通报

Nicotinic acetylcholine receptors, a ligand-gated ion c hannels,mediates many important physiological processes. Chronic nicotine admini stration could desensitize nicotinic receptors. Many factors which modulate dese nsitization have been described, including different subunits, agonist, signal t ransduction and cellular microenivornment. The important physiological functions of desensitized receptors still remain controversial, may be modulate synaptic transmission,synapse plasticity and mediate self-protection.

Mechanism of delaying aging process with optimal stress / 中华行为医学与脑科学杂志

Objective　 To study the mechanism of delaying aging process under optimal stress . Methods　 Kunming mice swam at the 18℃ water temperature for 15min everyday based upon the model of aging mice induced by D-galactose .After six weeks continuously , the ability of memory and learning , the contents of SOD and MDA were measured, at the same time ,the mitochondria membranous fluidity ,MDA's contents in mitochondria and the activity of ATPase in hippocampus were also determined.Results　 In the aging mice, a significant reduction of learning and memory ability was observed, the contents of SOD decreased , but MDA contents increased markedly, we also found a obvious declining at the ATPase activity and the fluidity of mitochondria membrane . But the optimal swimming stress could effectually antagonize the above-mentioned changes . Conclusions　 The optimal swimming stress could delay the aging process by regulating the balance between the oxidant system and the antioxidant system.