Kewei Zhang

Magnetostrictive Microcantilever as an Advanced Transducer for Biosensors

The magnetostrictive microcantilever (MSMC) as a high-performance transducer was introduced for the development of biosensors. The principle and characterization of MSMC are presented. The MSMC is wireless and can be easily actuated and sensed using magnetic field/signal. More importantly, the MSMC exhibits a high Q value and works well in liquid. The resonance behavior of MSMC is characterized in air at different pressures and in different liquids, respectively. It is found that the Q value of the MSMC in water reaches about 40. Although the density and viscosity of the surrounding media affect the resonance frequency and the Q value of MSMC, the density has a stronger influence on the resonance frequency and the viscosity has a stronger influence on the Q value, which result in that, for MSMC in air at pressure of less than 100 Pa, the resonance frequency of MSMC is almost independent of the pressure, while the Q value increases with decreasing pressure. MSMC array was developed and characterized. It is experimentally demonstrated that the characterization of an MSMC array is as simple as the characterization of a single MSMC. A filamentous phage against Salmonella typhimurium was utilized as bio-recognition unit to develop an MSMC based biosensor. The detection of S. typhimurium in water demonstrated that the MSMC works well in liquid.

Magnetostrictive particle based biosensors for in situ and real-time detection of pathogens in water

Biosensors for in situ detection of pathogenic bacteria in liquid are developed using magnetostrictive particles (MSP) as the sensor platform. The sensing elements used are phage E2 against Salmonella typhimurium, monoclonal antibody against Listeria monocytogenes, polyclonal antibody against Escherichia coli, and polyclonal antibody against Staphylococcus aureus, respectively. These biosensors were characterized in cultures with different populations ranging from 5 × 101 to 5 × 108 cfu/mL. It is found that the MSP‐based biosensors work well in water and have a rapid response with a response time in minutes, which makes the MSP‐based sensors suitable for in situ and real‐time detection of pathogenic bacteria in liquid. The experimental results show that all MSP‐phage and MSP‐antibody biosensors in size of 1.0 mm × 0.3 mm × 15 µm exhibit a detection limit better than 100 cfu/mL. Based on the Hill plot, it is concluded that each bacterial cell is bound onto the sensor surface through about four‐to‐five sites. When the cultures with low population (<106 cfu/mL) are tested, both MSP‐phage and MSP‐antibody sensors exhibit the similar response. However, the phage‐MSP sensors exhibit a higher capability in the capture of target bacterial cell. Biotechnol. Bioeng. 2014;111: 2229–2238.

Development of highly sensitive handheld device for real-time detection of bacteria in food

To ensure the safety of food, a detection device, which can detect/monitor the present of bacteria in a real-time manner and can be easily used for in-field tests, is highly desirable. Recently, magnetostrictive particles (MSPs) as a new type of high-performance biosensor have been developed. The detection of various bacteria and spores in food with high sensitivity has already been experimentally demonstrated. To fully use the technique for food safety, two miniaturized interrogation systems based on frequency-domain and time-domain technique are developed to fabricate a handheld detection device. The detection of Salmonella typhimurium (S. typhimurium) in liquid using a time-domain based interrogation system was demonstrated.

Detection of Bacillus anthracis spores in water using biosensors based on magnetostrictive microcantilever coated with phage

Microcantilevers (MCs) as state-of-art sensor platforms have been widely investigated. We recently introduced a new type of MC, magnetostrictive microcantilever (MSMC), as high performance sensor platform. The MSMC is a remote/wireless sensor platform and exhibits a high quality merit factor in liquid. In this paper, a MSMC-based biosensor is developed for detecting B. anthracis spores in liquid, a potential biothreaten agent. The results demonstrated the advantages of MSMCs as a sensor platform. MSMCs with different sizes were fabricated and utilized in the experiments. The MSMCs were coated with the filamentous phage as a bio-recognition element to capture the B. anthracis spores. The phage-coated MSMCs as biosensors were exposed to cultures containing target spores with concentrations ranging from 5 * 104 spores/mL to 5 * 108 spores/mL. The resonance frequency of the MSMC sensors in cultures was monitored in a real-time manner. The results showed that for MSMCs of 2.8 mm * 1.0 mm * 35 &mgr;m and with 1.4 mm * 0.8 mm * 35 &mgr;m have a detection limit of 105 and 104 spores/mL, respectively.

Detection of Bacillus Anthracis Spores Using Magnetostrictive Microcantilever-Based Biosensor

Recently, the magnetostrictive microcantilever (MSMC) as a high performance biosensor platform was introduced. The MSMC is a wireless acoustic wave (AW) sensor and exhibits a high Q value. More importantly, the MSMC works well in liquid. In this paper, the detection of Bacillus anthracis spores using MSMCs with filamentous phage as the bioprobe is reported. The phage-coated MSMC biosensors were exposed to cultures containing target spores with increasing concentrations ranging from 5 x 10 4 to 5 x 10 8 spores/mL. By monitoring the shift in the resonance frequency of the MSMCs, the spores were detected in a real-time manner and a detection limit of 10 5 spores/mL was obtained for the MSMCs used in this research. Higher sensitivity is expected for the MSMCs with smaller size.

Biosensor for direct detection of pathogens on fresh produce

A type of biosensor is recently developed using magnetostrictive particle (MSP) resonator as sensor platform and phage/antibody as bio-probe. The MSP sensors have following unique features: wireless, concentration and separation of the target species from the analytes and in-situ detection capability. The MSP sensors are very inexpensive and sensitive. All the advantages of the MSP sensors are demonstrated by the in-situ detection of pathogens in water and liquid food. To fully utilize the advantages of the MSP sensors, the direct detection of pathogens on the surface of fresh produce was demonstrated.