Preparation, Characterization and Intracellular Imaging of 2,4-Dichlorophenoxyacetic Acid Conjugated Gold Nanorods.

Visualizing the biodistribution of pesticides inside living cells is great importance for enhancing targeting of pesticides. Here we reported for the first time that gold nanorods (Au NRs) with size of 39.4 nm x 11.3 nm could be used as a fluorescent tracer to examine the distribution of a typical herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), in tobacco bright yellow 2 (BY-2) cells. The nanostructures of hybrid materials were analyzed by using Raman spectra and X-ray photoelectron spectroscopy (XPS), including spectra assignments and electronic property. These data revealed 2,4-D has successfully conjugated MP-Au NRs according to Raman and XPS. The biodistribution of the conjugates inside BY-2 cells was directly examined at 12 and 24 h by the two-photon microscopy. The intensity of two-photon luminescence (TPL) inside cells demonstrated that the conjugates could be localized and excluded by BY-2 cells. Thus, this labeling approach opens up new avenues to the facile and efficient labeling of pesticides.

[Study on molecular spectrum of fried linseed oil].

In order to ensure security of fried food and find out regularity of frying oil, the change of linseed oil fried in different time was investigated by three dimensional fluorescence and UV. The experiment results showed that the property of fried oil has not changed obviously in first two hours, but with the prolongation of frying time, the fluorescence spectra and UV spectra of fried linseed oil changed immensely after frying for six hours, which indicates that more harmful substances were produced after linseed oil was fried more than six hours.

[Quality research on Epimedium cut crude drug processed with oil].

OBJECTIVE: To study internal quality of 14 batches Epimedium cut crude drug processed with oil, and to provide informations for quality specification in Chinese Pharmacopeia of 2010 edition. METHODS: 14 batches Epimedium cut crude drug processed with oil were investigated impurity, moisture content, total ash, acid-insoluble ash, extractum and assaying to analyze and evaluate their quality condition. RESULTS: It is suggested that, in Epimedium cut crude drug processed with oil, the moisture content should not pass 8.0%, total ash should not pass 8.0%, acid-insoluble ash should not pass 2.0%, extractum content should not lower than 12.0%, total flavonoids content should not lower than 5.0%, icariin content should not lower than 0.6%, and Baohuoside I content should not lower than 0.1%. CONCLUSION: Quality evaluation system of Epimedium cut crude drug processed with oil has been constructed initially, it will offer scientific basis for instituting quality specification in Chinese Pharmacopeia of 2010 edition.

Ultrasensitive electrochemical immunosensor for ochratoxin A using gold colloid-mediated hapten immobilization.

A convenient, specific, and highly sensitive electrochemical immunosensor based on an indirect competitive assay format was developed for the determination of ochratoxin A (OTA), a common toxic contaminant in various kinds of agricultural products. The sensing substrate was prepared using a gold electrode modified with a self-assembled monolayer of 1,6-hexanedithiol that mediated the assembly of a gold colloid layer, which could enhance the surface loading of OTA-ovalbumin conjugate and improve the sensitivity in electrochemical readouts. After competition of the limited anti-OTA mouse monoclonal antibody between immobilized hapten and OTA analyte in sample solution, alkaline phosphatase (ALP)-labeled horse anti-mouse immunoglobulin G (IgG) antibody was selectively bound onto the surface of the electrode, affording an indicator for OTA concentration in the sample. Electrochemical response arising from the oxidation of enzymatic product of 1-naphthyl phosphate was observed to be inversely proportional to OTA concentration in the range from 10 pg/ml to 100 ng/ml with a detection limit as low as 8.2 pg/ml. Furthermore, a negligible matrix effect and good recoveries were obtained in the determination of corn samples, evidencing the feasibility of the proposed method for accurate determination of OTA in corn samples.

2,4-Dichlorophenoxyacetic acid functionalized gold nanoparticles: synthesis, characterization and biological effects.

Understanding and visualizing the biodistribution of agricultural chemicals inside cells and living plants is very important for enhancing targeting and changing the application approaches of chemicals. Here, a novel material was synthesized through 2,4-dichlorophenoxyacetic acid functionalized small gold nanoparticles (2,4-D-MP-Au NPs). The successful modification of Au NPs (4.46 ± 0.70 nm) was ascertained by UV-vis, TEM, FTIR and XPS. TGA data revealed about 1197 molecules of 2,4-D were coupled to the surface of one Au nanoparticle, which was sufficient for bioapplications. The optical imaging of 2,4-D-MP-Au NPs inside BY-2 cells was directly examined, revealing that 2,4-D-MP-Au NPs could be internalized in BY-2 cells by the two-photo microscopy and endocytosis, as the internalization mechanism was energy dependent for 2,4-D-MP-Au NPs. Furthermore, the biodistribution of 2,4-D-MP-Au NPs in Ricinus cotyledons was measured, revealing that 2,4-D-MP-Au NPs could enter into mesophyll cells of Ricinus cotyledons; the cell recognition was enhanced after 2,4-D conjugated Au NPs. These results indicate that the conjugates have great potential for applications on bioimaging and biolabeling for agricultural chemicals in plant physiology.

Sensitive and selective DNA detection based on the combination of hairpin-type probe with endonuclease/GNP signal amplification using quartz-crystal-microbalance transduction.

In order to develop a highly sensitive and selective piezoelectric transducer for the detection of DNA, the bio-recognizing probe is for the first time designed by introducing a hairpin structure and a recognition site for EcoRI into an oligonucleotide sequence and signal amplifiers are prepared by modifying gold nanoparticles (GNPs) with biomolecules, deepening the application and understanding of biomaterials. The piezoelectric transducer is prepared by immobilizing designed hairpin recognition probe onto the quartz-crystal-microbalance (QCM). In the absence of target DNA, the hairpin probe is removed from the QCM surface after exposure to endonuclease, inhibiting the subsequent signaling reaction. In contrast, introduction of target DNA can open the hairpin probe due to the probe/target hybridization, dissociating the cleavable double-stranded portion. In this case, even if being treated with endonuclease, the integrated hairpin probe is maintained. Subsequent introduction of GNPs modified with detection probes that can hybridize to the terminal sequence of hairpin probe results in a many-folds increase of the frequency response. Utilizing the proposed transduction scheme, the reliable target DNA detection can be accomplished. The detection limit of 2 pM and dynamic response range for target DNA from 2 to 300 pM are obtained. Furthermore, single-base mismatched DNAs can be easily identified. The developed proof-of-principle of a novel piezoelectric transduction scheme is expected to establish a potential platform for the disease-associated mutation analysis and DNA hybridization detection in biotechnology and medical diagnostics.

An ultrasensitive electrochemical "turn-on" label-free biosensor for Hg2+with AuNP-functionalized reporter DNA as a signal amplifier.

A highly selective electrochemical biosensor for the ultrasensitive detection of Hg2+ in aqueous solution has been developed based on the strong and specific binding of Hg2+ by two DNA thymine bases (T-Hg2+-T) and the use of AuNP-functionalized reporter DNA to achieve signal amplification.