Molecularly imprinted electrochemical aptasensor based on functionalized graphene and nitrogen-doped carbon quantum dots for trace cortisol assay.

This paper proposes a novel electrochemical aptasensor that integrates molecular imprinting techniques for trace analysis of cortisol. This sensor is based on functionalized graphene and nitrogen-doped carbon quantum dots. The morphology and structure of the modified electrode were characterized by scanning electron microscopy and Raman spectroscopy. The functional monomer aptamer and the template molecule cortisol were adsorbed on the electrode by electrostatic adsorption to construct an imprinted sensing platform. Under the optimal conditions, such as the concentration of template molecule, the ratio of template to functional monomer, the elution and adsorption time, the sensor exhibits linearity and a low detection limit of 10-12-10-8 M and 3.3 × 10-13 M, which is more sensitive than other reported cortisol analysis methods. In addition, this sensor can realize the determination of cortisol in salivary samples with high recovery values, showing great development potential in the field of life sciences.

A sensitive molecularly imprinted electrochemical aptasensor for highly specific determination of melamine.

An electrochemical aptamer sensor based on gold nanoparticles (AuNPs) was developed for highly specific sensing of melamine (MEL), which combines molecularly imprinted polymers (MIPs) and aptamers. AuNPs were synthesized by simple reduction of sodium citrate and characterized by transmission electron microscopy. The MIP membranes with particular recognition sites were formed by electropolymerization of dopamine (DA) with polythymine (poly T) aptamers as functional monomers and melamine as template molecules. Under optimal experimental conditions, this molecularly imprinted electrochemical aptamer sensor (MIEAS) exhibits a linear relationship between 10-12 M and 10-4 M for detecting MEL with the detection limit of 6.7 × 10-13 M. Moreover, this sensor displays excellent selectivity, reproducibility and stability. The milk samples analysis has confirmed the potential application of this MIEAS to quantitative detection of melamine.

Fabrication of poly-sulfosalicylic acid film decorated pure carbon fiber as electrochemical sensing platform for detection of theophylline.

In this work, we integrated the superiority of good conductivity, large surface area of carbon fibers and the catalytic property, good biocompatibility of polymer sulfosalicylic acid to construct a novel electrochemical sensor to detect theophylline in drug analysis. The morphology of nanocomposite was characterized by scanning electron microscopy (SEM). The polymerization between monomers was observed by Fourier transform infrared spectroscopy (FTIR). The composite between carbon material and polymer was verified by Raman spectrum. Under the optimal experimental conditions, the concentration of theophylline (0.6∼137 µM) and the peak current value revealed a good linear relationship and the limit of detection as low as 0.2 µM. In addition, the proposed sensor exhibits repeatability, stability and ease of selectivity.

A Fluorescent "Turn-off" Probe for the Determination of Curcumin Using Upconvert Luminescent Carbon Dots.

This work established a novel and simple method for quantitative determination of curcumin by developing a "turn-off" fluorescence probe based on upconvert luminescent carbon dots (p-CDs). The carbon dots were synthesized with p-aminobenzoic acid (PABA) and ethanol by solvothermal method and had specific up-conversion luminescence properties which could be applied in other sensing fields. The sensing mechanism of this fluorescent probe was based on the inter filter effect (IFE) between p-CDs and curcumin. As the concentration of curcumin increased, the fluorescence of p-CDs could be selectively quenched. Under the optimal conditions, the fluorescence quenching intensity of p-CDs had a good linear relationship with curcumin in the range of 0.4-45 µΜ and the detection limit was 0.133 µM. In addition, the fluorescent "turn-off" probe constructed with p-CDs exhibited high accuracy and recovery in the analysis of real sample curry powder, indicating that the fluorescence "turn-off" probe had potential application for the detection of curcumin in the complex matrixes.

[Clinical significance of venous return disturbance in patients with osteonecrosis of femoral head].

OBJECTIVE: To evaluate the correlation of venous return disturbance (VRD), bone marrow edema (BME) and the amount of joint fluid with clinical symptoms in osteonecrosis of the femoral head (ONFH). METHODS: Twenty patients (25 hips) with ONFH proved by pathology were parallelly examined by 1.5 T MR and medullograph. RESULT: In total 25 hips VRD was observed in 16 hips with medullograph and 13 hips with the clinical symptoms (P <0.05). BME was found in 17 with MRI (P <0.01), and the was found in 15 hips with MRI (Spearman=0.949). VRD were found in 16 hydrarthrus. CONCLUSION: ONFH patients with clinical symptoms have VRD, BME and the hydrarthrus. The medullograph is of value in monitoring the development of ONFH.