Although Escherichia coli (E. coli) is a commensalism organism in the intestine of humans and warm-blooded animals, it can be toxic at higher density and causes diseases, especially the highly toxic E. coli O157:H7. In this paper a quartz crystal microbalance (QCM) biosensor was developed for the detection of E. coli O157:H7 bacteria. The anti-E. coli O157:H7 antibodies were immobilized on a self-assembly monolayer (SAM) modified 5 MHz AT-cut quartz crystal resonator. The SAMs were activated with 16-mercaptopropanoic acid, in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and ester N-hydroxysuccinimide (NHS). The result of changing frequency due to the adsorption of E. coli O157:H7 was measured by the QCM biosensor system designed and fabricated by ICDREC-VNUHCM. This system gave good results in the range of 102–107 CFU mL−1 E. coli O157:H7. The time of bacteria E. coli O157:H7 detection in the sample was about 50 m. Besides, QCM biosensor from SAM method was comparable to protein A method-based piezoelectric immunosensor in terms of the amount of immobilized antibodies and detection sensitivity.

The development of sensitive and chemically selective MRI contrast agents is imperative for the early detection and diagnosis of many diseases. Conventional responsive contrast agents used in 1H MRI are impaired by the high abundance of protons in the body. 129Xe hyperCEST NMR/MRI comprises a highly sensitive complement to traditional 1H MRI because of its ability to report specific chemical environments. To date, the scope of responsive 129Xe NMR contrast agents lacks breadth in the specific detection of small molecules, which are often important markers of disease. Herein, we report the synthesis and characterization of a rotaxane‐based 129Xe hyperCEST NMR contrast agent that can be turned on in response to H2O2, which is upregulated in several disease states. Added H2O2 was detected by 129Xe hyperCEST NMR spectroscopy in the low micromolar range, as well as H2O2 produced by HEK 293T cells activated with tumor necrosis factor.

In the present work a low cost technique for preparation of gold nanoparticles (AuNPs) using microwave heating was developed. The effect of different elements (precursor reagents, irradiation time, and microwave radiation power) on the final morphology of AuNPs obtained through the microwave assisted technique has been investigated. The characterization of the samples has been carried out by transmission electron microscopy, UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy, and powder x-ray diffraction. The results showed that to some extent the above-mentioned characterizations influenced the size of synthetized nanoparticles and application of microwave heating has many advantages such as low cost, rapid preparation and highly uniform particles. As an application in quartz crystal microbalance (QCM) immunosensor, AuNPs are conjugated with the Escherichia coli (E.coli) O157:H7 antibodies for signal amplification to detect E.coli O157:H7 bacteria residual in QCM system.

In this paper, we report a novel seed-mediated method for the preparation of gold nanostars using microwave irradiation. These gold nanostars are produced in different mixed solutions including anionic and zwitterionic surfactants, AgNO 3 and ascorbic acid as reducing agent at room temperature by seed-mediated method using microwave irradiation. Moreover, microwave irradiation plays an important role in mediating the branched growth of the resultant gold nanostars by inducing anisotropic growth on the surfaces of initially formed spherical gold nanoparticles. The gold nanostars are characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and x-ray powder diffraction. It is shown that the gold nanoparticles were formed with star shape (size ranging from 50 to over 100 nm with different branches and aspect ratios (ratio of branch length to width)) and facecentered-cubic (fcc) crystalline structure. Polyethylene glycol (PEG) is used as capping agent to prevent the aggregation of gold nanostars after removing mixed surfactants.

Gold nanobipyramids (NBPs) have attracted much attention because they have potential for applications in smart sensing devices, such as medical diagnostic equippments. This is due to the fact that they show more advantageous plasmonic properties than other gold nanostructures. We describe a chemical reduction method for synthesizing NBPs using conventional heating with ascorbic acid reduction and cetyltrimethylamonium bromide (CTAB)+AgNO 3 as capping agents. The product was characterized by ultraviolet-visible spectroscopy (UV-vis), Fourier transmission infrared spectroscopy (FTIR), transmission electron microscopy (TEM), x-ray powder diffraction (XRD). The results showed that gold nanoparticles were formed with bipyramid shape (tip-to-tip distance of 88.4±9.4 nm and base length of 29.9±3.2 nm) and face-centered-cubic crystalline structure. Optimum parameters for preparation of NBPs are also found.