Monitoring cellular activity: A local redox‐cycling‐based electrochemical chip device (see picture) has been used to entrap three‐dimensional culture cells and evaluate their activity. Deep microwells were incorporated into the chip device for the trapping of embryoid bodies. This chip device is useful for the evaluation of 3D organ tissues.

In this study, we developed a novel method for fabricating microwell arrays constructed from alginate gels, and the alginate gel microwells were used for three-dimensional (3D) cell culture. The alginate gel microwells were fabricated on a patterned ITO electrode using alginate gel electrodeposition. Embryonic stem (ES) cells or hepatocellular carcinoma cells (HepG2) were cultured in the alginate gel microwells containing 3T3 cells. During the culture, embryoid bodies (EBs) or HepG2 spheroids were successfully fabricated in the alginate gel microwells. The oxygen consumption of the EBs indicated that they were successfully cultured. Liver-specific gene expressions of the HepG2 spheroids apparently increased by performing 3D co-culture in the microwell arrays with 3T3 cells. These results show that the alginate gel microwells are a useful 3D culture system.

No abstract

This report describes the electrochemical detection of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device consisting of 256 sensors. The time-course analyses showed that the redox compound in the droplet was dynamically changed during droplet evaporation or mass transfer through a water/oil interface.

We propose a novel electrochemical detection system for alkaline phosphatase (ALP) activity using the difference in water and oil solubilities between the substrate, ferrocene ethyl phosphate ester (FcEtOPO(3)(2-)), and the enzymatic product, ferroceneethanol (FcEtOH). In this system, water droplets containing ALP and FcEtOPO(3)(2-) were placed on a Pt disk microelectrode and surrounded by a mineral oil. By the ALP-catalyzed reaction, FcEtOPO(3)(2-) was converted to FcEtOH, which was then transferred to the mineral oil from the water droplets with FcEtOPO(3)(2-) remaining in the water droplets. After partitioning FcEtOH from the water droplets, FcEtOPO(3)(2-) was detected at the Pt disk microelectrode to estimate the ALP activity. Using this novel system, the ALP activity of embryoid bodies was successfully detected. We believe that the present system will be widely applicable to ALP-based bioassays.