A miniaturized biosensor for rapid detection of tetracycline based on a graphene field-effect transistor with an aptamer modified gate.

Tetracycline is a broad-spectrum antibiotic for human, poultry and livestock that may cause health damage when enriched in humans. Therefore, it is essential to create a rapid tetracycline assay with high sensitivity, specificity and portability. In this study, a miniaturized tetracycline biosensor based on aptamer-modified graphene field-effect transistor (Apt-SGGT) was fabricated and two detection strategies using transfer characteristic curves and real-time channel current were established for different circumstances. The detection limits of the two strategies were 2.073 pM and 100 pM, respectively. The biosensor also demonstrated outstanding stability, anti-interference and specificity ability. Finally, the biosensor was employed to detect the content of tetracycline in Skim Milk with outstanding recovery rate. We believe that the miniaturized Apt-SGGT biosensor with appropriate detection strategies will provide an ideal portable sensing platform for many important analytes in food with superior selectivity and sensitivity.

Breath alcohol sensor based on hydrogel-gated graphene field-effect transistor.

The inspection of drunk driving has become an effective measure to reduce the occurrence of traffic accidents. In this work, we constructed a breath alcohol biosensor based on a hydrogel-gated graphene field-effect transistor (HGGT) with chlorella derived layered carbon nanosheets (CNs) and alcohol oxidase (AOx) embedded in the hydrogel. The sensing mechanism of the AOx/CNs functionalized sensor lies in the oxidation reaction of alcohol by AOx and the electrocatalytic oxidation reaction of the generated H2O2. The HGGT based alcohol sensor exhibited an excellent sensitivity with a very low detection limit down to 1 µM (i.e. 0.046 ppm), and has been successfully applied to breath alcohol test after drinking. Compared with normal solution-gated graphene transistors, employment of hydrogel as a source of electrolytes greatly enhances the portability of the sensor, and facilitates functionalization with enzymes and nanomaterials. Due to the advantages of real-time, high portability and accuracy of the functionalized HGGT sensor, it demonstrates a promising platform for constructing biosensors for many other analytes.

[Expression of osteoclast differentiation factor and intercellular adhesion molecule-1 of bone marrow mesenchymal stem cells enhanced with osteogenic differentiation].

OBJECTIVE: To investgate whether the expression of osteoclast differentiation factor (ODF), intercellular adhesion molecule-1 (ICAM-1) depended on the stage of osteoblastic differentiation from rat bone marrow mesenchymal stem cells (BMSC). METHODS: BMSC (4 passage) were selected for osteogenic differentiation by treated with osteogenic supplements (OS). Cells were harvested by day 0, 3, 6, 9, 12, 18 respectively after osteogenic inducement. In each experiment, control and OS-treated cells were processed in parallel. ODF and ICAM-1 mRNA were analyzed by semiquantitave RT-PCR assay. RESULTS: Expression of ODF was enhanced with osteogenic differentiation guadully. whereas, expression of ICAM-1 was activated at OS-treated day 6, then keeping at a stable level. CONCLUSION: This study indicated that BMSC undergoing osteogenic inducement was an ideal model for studying the differentiation and maturation of osteoblasts. During the early stage of differentiation along osteoblasts from stem cells to osteocytes, BMSC or osteoprogenitor react somewhat differently from osteoblasts, suggesting the ability of osteoblasts to regulating differentiation and maturation of osteoclasts have been improved with osteogenic culture.