Dielectrophoretic trapping of nanosized biomolecules on plasmonic nanohole arrays for biosensor applications: simple fabrication and visible-region detection.

Surface plasmon resonance is an optical phenomenon that can be applied for label-free, real-time sensing to directly measure biomolecular interactions and detect biomarkers in solutions. Previous studies using plasmonic nanohole arrays have monitored and detected various biomolecules owing to the propagating surface plasmon polaritons (SPPs). Extraordinary optical transmission (EOT) that occurs in the near-infrared (NIR) and infrared (IR) regions is usually used for detection. Although these plasmonic nanohole arrays improve the sensitivity and throughput for biomolecular detection, these arrays have the following disadvantages: (1) molecular diffusion in the solution (making the detection of biomolecules difficult), (2) the device fabrication's complexities, and (3) expensive equipments for detection in the NIR or IR regions. Therefore, there is a need to fabricate plasmonic nanohole arrays as biomolecular detection platforms using a simple and highly reproducible procedure based on other SPP modes in the visible region instead of the EOT in the NIR or IR regions while suppressing molecular diffusion in the solution. In this paper, we propose the combination of a polymer-based gold nanohole array (Au NHA) obtained through an easy process as a simple platform and dielectrophoresis (DEP) as a biomolecule manipulation method. This approach was experimentally demonstrated using SPP and LSPR modes (not EOT) in the visible region and simple, label-free, rapid, cost-effective trapping and enrichment of nanoparticles (trapping time: <50 s) and bovine serum albumin (trapping time: <1000 s) was realized. These results prove that the Au NHA-based DEP devices have great potential for real-time digital and Raman bioimaging, in addition to biomarker detection.

Selective retrieval of antibody-secreting hybridomas in cell arrays based on the dielectrophoresis.

A cascade of the formation of cell arrays, the discrimination of cells secreting specific molecules, and the selective retrieval of cells has been developed to harvest antibody-secreting hybridomas in heterogeneous cell populations simply and rapidly. The microwell array device consisted of three-dimensional microband electrodes by assembling both upper and lower substrates perpendicularly. Arrays of hybridomas secreting specific antibodies were prepared by aligning hybridomas in each microwell based on the attractive force of positive dielectrophoresis (p-DEP). Antibody secreted by the hybridomas in the microwells was recognized by the antigen immobilized on the microwells or the membrane surfaces of hybridomas to discriminate hybridomas with the secretion ability. Thereafter, a repulsive force of negative dielectrophoresis (n-DEP) was applied to release the target hybridomas from the microwell array. To harvest the target hybridoma, AC signals could be modulated in the n-DEP frequency region and applied to a pair of microband electrodes located above and below each microwell containing target hybridoma. Thus, the cell-based array system described in this study allowed selective retrieval of single target hybridomas by merely switching from p-DEP to n-DEP after selecting the antibody-secreting hybridomas trapped in each microwell. The development of this high-affinity device could be useful to recover hybridomas producing antibodies in large populations of cells rapidly and effectively.

[Evaluation of the Pharmaceutical Properties of Clobetasol Propionate Ointments and Base Stability of the Mixture with Heparinoid Oil Based Creams].

Clobetasol propionate ointment (CLPO) formulations have been classified as members of the "strongest" steroidal efficacy group, with eight of these formulations currently marketed in Japan. Evaluations of pharmaceutical properties of each formulation revealed three classification types: droplet dispersion type containing propylene glycol (PG) and surfactant, type with surfactant but not PG, and other types. These rheological properties were diverse, with no correlation found between viscosity and ointment type. However, when CLPO and six types of heparinoid oil-based cream (HPOC) formulation mixtures were stored at 37℃, a liquid layer was observed starting at 24 h for one CLPO formulation in which polyoxyethylene hydrogenated castor oil 40 was used as a surfactant out of the four droplet-dispersion type ointments and two low-viscosity HPOC formulations. In contrast, one other type of CLPO formulation that contained a surfactant with polysorbate 80, but not PG, exhibited a liquid layer for all of HPOC formulations. This suggests that CLPO formulations that contain a surfactant with a high hydrophilic-lipophilic balance value are likely to generate a liquid layer for mixtures containing HPOC formulation. The present results demonstrate that not only the pharmaceutical properties of the eight CLPO formulations differ from one another, but also that the stabilities of HPOC formulation mixtures are significantly different. Therefore, pharmacists need to focus on inactive as well as active pharmaceutical ingredients to select formulations that patients will want to use, in addition to successfully treating their pathological conditions.

Selective Trapping and Retrieval of Single Cells Using Microwell Array Devices Combined with Dielectrophoresis.

We proposed selective manipulation techniques for retrieving and retaining target cells arrayed in microwells based on dielectrophoresis (DEP). The upper substrate with microband electrodes was mounted on the lower substrate with microwells based on the same design of microband electrodes by 90 degree relative to the lower substrate. A repulsive force of negative dielectrophoresis (n-DEP) was employed to retrieve the target cells from the microwell array selectively. Furthermore, the target cells were retained in the microwells after other cells were removed by n-DEP. Thus, the system described in this study could make it possible to retrieve and recover single target cells from a microwell array after determining the function of cells trapped in each microwell.