Jungtae Kim

Electropolymerized Molecularly Imprinted Polypyrrole Film for Sensing of Clofibric Acid

Piezoelectric quartz crystals and analogous gold substrates were electrochemically coated with molecularly imprinted polypyrrole films for pulsed amperometric detection (PAD) of clofibric acid, a metabolite of clofibrate. Cyclic voltammetry data obtained during polymerization and deposited weight estimations revealed a decrease of the polymerization rate with increasing clofibric acid concentration. XPS measurements indicated that clofibric acid could be removed after imprinting with an aqueous ethanol solution, which was further optimized by using PAD. Zeta potential and contact angle measurements revealed differences between molecularly imprinted (MIP) and non-imprinted polymer (NIP) layers. Binding experiments with clofibric acid and other substances showed a pronounced selectivity of the MIP for clofibric acid vs. carbamazepine, but the response of MIP and NIP to 2,4-dichlorophenoxyacetic acid was higher than that for clofibric acid. A smooth surface, revealed by AFM measurements, with roughness of 6–8 nm for imprinted and non-imprinted layers, might be a reason for an excessively low density of specific binding sites for clofibric acid. Furthermore, the decreased polymerization rate in the presence of clofibric acid might not result in well-defined polymer structures, which could be the reason for the lower sensitivity.

A Cytochrome P450 3A4 Biosensor Based on Generation 4.0 PAMAM Dendrimers for the Detection of Caffeine

Cytochromes P450 (CYP, P450) are a large family of heme-active-site proteins involved in many catalytic processes, including steroidogenesis. In humans, four primary enzymes are involved in the metabolism of almost all xenobiotics. Among these enzymes, CYP3A4 is responsible for the inactivation of the majority of used drugs which makes this enzyme an interesting target for many fields of research, especially pharmaceutical research. Since the late 1970s, attempts have been made to construct and develop electrochemical sensors for the determination of substrates. This paper is concerned with the establishment of such a CYP3A4-containing biosensor. The sensor was constructed by adsorption of alternating layers of sub-nanometer gold particle-modified PAMAM (poly-amido-amine) dendrimers of generation 4.0, along with the enzyme by a layer-by-layer assembly technique. Atomic force microscopy (AFM), quartz crystal microbalance (QCM), and Fourier-transformed infrared spectroscopy (FTIR) were employed to elucidate the sensor assembly. Additionally, the biosensor was tested by cyclic voltammetry using caffeine as a substrate.

Development of a novel micro immune-magnetophoresis cell sorter

In this paper, we present a novel method to separate T-cell using immune-magnetophoresis (IMP) cell sorting chip. Our novel micro cell sorter utilizing the immune-affinity and the high gradient magnetic field is aiming for the separation of target T lymphocytes from biological suspensions such as whole blood. This micro IMP cell sorter also overcomes several weaknesses of existing micro magnetic-activated cell sorting (micro MACS) systems with novel functionalities, such as continuous operation, fully automated one step cell sorting, micro sized simple chip design, no sheath flow requirement and minimum waste of reagent. Furthermore, the labeling process, which is performed by either a manual work process or by additional integrated micro mixers as the pre-process, has been simplified without mixing of media. We expect that our novel micro IMP cell sorter can be used widely in biomedical applications, e.g. as a chip array system for an automated laboratory device, as a muTAS (micro Total Analysis System) or as an implantable micro medical system, etc.

Uniform magnetic mobility in a curved magnetophoretic channel

This paper reports a curved channel design of an immune-magnetophoretic cell sorter for uniform magnetic mobility which provides an advanced capture process between the target cells and magnetic particles. Furthermore the design prevents unwanted immobilization of magnetic particles and cell-particle complexes on the channel walls. The curved channel has been designed for avoiding magnetic field gradient vectors reversible to flow direction that result immobilization as well as slow speed of the particles. Consequently, S-shape curved magnetophoretic channel has been fabricated along the circumferences of 2 axial-poled magnets in PMMA substrate. The cell sorter has been demonstrated for T lymphocyte sorting from a cell mixture. The results showed more than 3 times higher recovery rate of the target cell in comparison with a straight micro channel and competitive cell sorting performances over conventional manual process.

Simulation and optimization of the Microklystrode

The Microklystrode which has hybrid form of klystron and triode microwave tube has been developed. Because of its micro-scaled components and assemblies, in the realization, the fabricated tube has characteristic differences from basic analytic design. Also, specific parameters of output/feedback antenna were not enough in the cavity design and gap field evaluation of design process. Using the fabricated real part model, the optimal design of output/feedback antenna has been simulated. From the simulation results, the comparison of frequency characteristic and power efficiency between analytic model and real model are presented in this paper. And the optimized efficiency models of antennas are also presented.