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.

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%.

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.