The vital importance of rapid and accurate detection of food borne pathogens has driven the development of biosensor to prevent food borne illness outbreaks. Electrochemical DNA biosensors offer such merits as rapid response, high sensitivity, low cost, and ease of use. This review covers the following three aspects: food borne pathogens and conventional detection methods, the design and fabrication of electrochemical DNA biosensors and several techniques for improving sensitivity of biosensors. We highlight the main bioreceptors and immobilizing methods on sensing interface, electrochemical techniques, electrochemical indicators, nanotechnology, and nucleic acid-based amplification. Finally, in view of the existing shortcomings of electrochemical DNA biosensors in the field of food borne pathogen detection, we also predict and prospect future research focuses from the following five aspects: specific bioreceptors (improving specificity), nanomaterials (enhancing sensitivity), microfluidic chip technology (realizing automate operation), paper-based biosensors (reducing detection cost), and smartphones or other mobile devices (simplifying signal reading devices).

Smartphone-enabled microfluidic chemiluminescence immunoassay is a promising portable system for point-of-care (POC) biosensing applications. However, due to the rather faint emitted light in such a limited sample volume, it is still difficult to reach the clinically accepted range when the smartphone serves as a standalone detector. Besides, the multiple separation and washing steps during sample preparation hinder the immunoassay's applications for POC usage. Herein, we proposed a novel acoustic streaming tweezers-enabled microfluidic immunoassay, where the probe particles' purification, reaction, and sensing were simply achieved on the same chip at continuous-flow conditions. The dedicatedly designed high-speed microscale vortexes not only enable dynamic trapping and washing of the probe particles on-demand but also enhance the capture efficiency of the heterogeneous particle-based immunoassay through active mixing during trapping. The enriched probe particles and enhanced biomarker capture capability increase the local chemiluminescent light intensity and enable direct capture of the immunobinding signal by a regular smartphone camera. The system was tested for prostate-specific antigen (PSA) sensing both in buffer and serum, where a limit of detection of 0.2 ng/mL and a large dynamic response range from 0.3 to 10 ng/mL using only 10 μL of sample were achieved in a total assay time of less than 15 min. With the advantages of on-chip integration of sample preparation and detection and high sensing performance, the developed POC platform could be applied for many on-site diagnosis applications.

Alfvén's critical ionization velocity observed in high power impulse magnetron sputtering discharges Phys. Plasmas 19, 093505 (2012) Revisiting plasma hysteresis with an electronically compensated Langmuir probe Rev. Sci. Instrum. 83, 093504 (2012) Coded aperture imaging of fusion source in a plasma focus operated with pure D2 and a D2-Kr gas admixture Appl. Phys. Lett. 101, 114104 (2012) EBT2 dosimetry of x-rays produced by the electron beam from a Plasma Focus for medical applications J. Appl. Phys. 112, 054901 (2012) Device convolution effects on the collective scattering signal of the E×B mode from Hall thruster experiments: 2D dispersion relation This paper reports an experimental study of a plasma jet by using optical measurement and spectroscopic method. The plasma jet, composed of an inner electrode with a sharpen end and an outer water-electrode, has a cross-field configuration. A cross-field mode of the plasma jet is realized when the applied voltage is low. However, a different mechanism of plasma plume generation is involved when the applied voltage is high enough, and a linear-field mode of the plasma jet can be realized. The two different modes of the plasma jet are compared by spectroscopic method and results show that electron energy in linear-filed mode is higher than that in cross-field mode.

A novel nucleic acid isothermal amplification method based on saltatory rolling circle amplification (SRCA) for rapid and visual detection of Alicyclobacillus acidoterrestris in apple juice was established. Fourteen A. acidoterrestris strains and 44 non-A. acidoterrestris strains were used to confirm the specificity. The sensitivity of SRCA was 4.5 × 10 1 CFU/mL by observing the white precipitate with the naked eye, while it was 4.5 × 10 0 CFU/mL by fluorescence visualization. The detection limit of SRCA in artificially inoculated apple juice was 7.1 × 10 1 and 7.1 × 10 0 CFU/mL via visualization of the white precipitate and fluorescence, respectively. Compared with the traditional PCR method, SRCA exhibited at least a 100-fold higher sensitivity and 100-fold lower detection limit. Seventy samples were investigated for A. acidoterrestris contamination, and the results showed 100% sensitivity, 97.01% specificity, and 97.14% accuracy compared with those by the conventional microbiological cultivation method. Overall, this method is a potentially useful tool for visual and rapid detection of A. acidoterrestris.

Homogeneous discharge in air is often considered to be the ultimate low-temperature atmospheric pressure plasmas for industrial applications. In this paper, we present a method whereby stable homogeneous discharge in open air can be generated by a simple plasma needle. The discharge mechanism is discussed based on the spatially resolved light emission waveforms from the plasma. Optical emission spectroscopy is used to determine electron energy and rotational temperature, and results indicate that both electron energy and rotational temperature increase with increasing the applied voltage. The results are analyzed qualitatively based on the discharge mechanism.