Akio Ohashi

A long-term lifetime amperometric glucose sensor with a perfluorocarbon polymer coating

We have developed an amperometric glucose sensor whose electrodes are coated with a four-layered membrane: 3-aminopropyltriethoxysilane (gamma-APTES), Nafion, glucose oxidase (GOX), and perfluorocarbon polymer (PFCP). Tests demonstrate the sensors ability to accurately and successively determine glucose concentrations ranging from 2.8 to 167 mM, over a 66 day period with no increase in response time, while remaining imperviousness to the effects of interference species (2.8 mM ascorbic acid, 0.3 mM uric acid, 0.3 mM p-acetaminophen). Furthermore, tests on diabetic urine samples showed an excellent correlation coefficient of 0.985 (y=1.04x+4.73, n=30) between sensor results and those of Glucose-Dehydrogenase clinical laboratory analyses.

A novel approach for toxicity sensing using hepatocytes on a collagen-patterned plate

Abstract This paper shows a hepatocyte culture on finely patterned plates by collagen as a novel approach for toxicity sensing. Collagen, which is a substratum, is patterned by a photolithography method. Patterned collagen has the inherent activity of adhering hepatocytes in spread shape. Almost all hepatocytes adhered are observed on the patterned collagen, namely, hepatocyte adhesion location control is achieved on the collagen-patterned plate. Hepatocyte morphology is also controlled in an elongated shape on a plate with collagen stripes. These results provide the possibility of achieving a toxicity sensing device, based on cultured hepatocytes.

Development of CCD-based direct observation equipment for biological samples

Equipment for the direct observation of biological samples has been developed. The equipment comprises a charge coupled device (CCD) unit and a light-emitting diode (LED), which is placed above the light-sensing face of the CCD. The biological sample is positioned just onto the CCD with no lens system interposed. Because of its small size, the equipment can be operated in an incubator, allowing the continuous observation of biological samples under appropriate temperature, humidity and gas concentration conditions. The equipment is operated periodically at 5-minute periods to reduce the influence of heat generated by the equipment and to maintain a constant sample temperature. E. coli colony formation is observed continuously for 70 hours without any adverse effects occurring during the observation. Hepatocyte morphological change and hepatocyte pattern formation are also observed.

4.24 – Toxicity Sensing Using a Hepatocyte Pattern Formed on a Photolithographic Plate

This chapter discusses a study analyzing the toxicity sensing using a hepatocyte pattern formed on a photolithographic plate. A novel toxicity sensing method was investigated, based on a formed hepatocyte pattern. This method uses hepatocytes cultured with a toxic sample on a collagen-patterned plate prepared by photolithography. The developed toxicity sensing method is discussed. At first, a collagen-patterned culture plate was settled in a polystyrene culture dish. The culture plate had about 50 μm wide collagen stripes at 50 μm intervals. It was fabricated by means of partial collagen adsorption on a quartz plate surface by photolithography. Next, hepatocytes, human hepatocellular carcinoma cell lines (Hep G2), minimum essential medium (MEM) supplemented with 10% fetal bovine serum, and various concentrations of carbon tetrachloride (CCl 4 ) as a toxic sample was put into the dish. Without CCl 4 addition, hepatocytes covered the entire culture plate, because the collagen stripe interval was comparable with hepatocyte size. However, when 5 mM of CCl 4 was added, hepatocyte stripe pattern was observed because almost all of the hepatocytes adhered only on the collagen stripe.

DEVELOPMENT OF DIRECTLY-SENSING EQUIPMENT FOR IN-SITU HEPATOCYTES OBSERVATION

Cultured hepatocytes are widely studied as a model liver, because they maintain most of the liver functions. Continuous observation in primary hepatocytes culture is useful for hepatocyte research. However, it is difficult to maintain culture conditions. This paper shows a direct sensing equipment for in situ hepatocytes observation, composed of a Charge Coupled Device (CCD) and a simple light source without a lens system. Observation of hepatocytes and microorganisms are achieved by this equipment.