Akira Yamamura

An organic pollution sensor based on surface photovoltage

Abstract A surface photovoltage (SPV) device, which is sensitive to surface pH, was applied to the fabrication of an organic pollution sensor. Trichosporon cutaneum, designated for use as a biochemical oxygen demand (BOD) sensor by the Japanese Industrial Standard, was employed as the immobilized biocatalyst. A flow cell of the system consists of an SPV device and a microbial membrane immobilized with T. cutaneum between membrane filters. The pH measurement by the SPV device and fabrication of SPV-based sensor is discussed and characterized by comparison with the 5 day BOD test (BOD5) and sensors used in the measurement of BOD (BODs). Response time was 25 min, and a microbial membrane can be used more than 14 weeks. Though there is a different substrate specificity, the system was applicable to BOD measurement of some real waste water and shows good agreement with BODS and BOD5.

A rapid BOD sensing system using luminescent recombinants of Escherichia coli

A biochemical oxygen demand (BOD) sensing system based on bacterial luminescence from recombinant Escherichia coli containing lux A-E genes from Vibrio fischeri has been developed. It was possible to use frozen cells of luminescent recombinants of E. coli as the bacterial reagents for measurement. Steady bioluminescence was observed during the incubation time between 90 and 150 min in the presence of a sole carbon source such as glucose, acetate, L-glutamate and BOD standard solution (GGA solution). This disposable bacterial reagent was applied to measure and detect organic pollution due to biodegradable substances in various wastewaters. The obtained values of this study showed a similar correlation with that of the conventional method for BOD determination (BOD5). Bacterial luminescence that was visualized with an imaging system using a charge coupled device (CCD) camera and a photomulti-counter demonstrated that this method could also be used for multi-sample detection of organic pollution due to biodegradable substances by using a microtiter plate. These results suggested for successful achievement of high-though-put detection of BOD in practical.

Application of micromachine techniques to biotechnological research

Abstract Novel methods to construct a multianalyte biosensing chip are described. A method is two-step immobilization in which materials are not immobilized directly but indirectly via small support materials. Biomaterials are immobilized on a certain support particle in the first step. The particles are placed or stuck on a chip in the second step. The other method is random fluidic self-assembly of the microsupports for reducing the complication in the second step on the chip. The combination of the methods enables us to immobilize various kinds of biomaterials densely on a chip. The ways to avoid possible problems due to random distribution are discussed. Several examples are also described.

Fabrication of New DNA Chip Microarrays Using Hydrophobic Interaction

Abstract We report here a new approach for an arrangement of many kinds of DNAs on transducers to construct a multifunctional DNA chip. The particles were arranged on the chip pattern by the random fluidic self-assembly method, using a hydrophobic interaction for a assembly. The immobilization of DNAs was evaluated by fluorescence.

Random distribution of biomaterials as a handling method on microarray applied to PCR, biosensors and high through-put screening

Describes a random distribution method to bring biomaterials into an array of sites on a chip. A mixture of biomolecules or a mixed suspension of particles immobilized with biomaterials was simply poured on an array and the components were randomly distributed. A microchamber array for PCR was developed by semiconductor microfabrication techniques. Amplification of pGFP was confirmed using a technique based on energy transfer of fluorescent dyes. Addition of BSA in PCR mixture enhances PCR efficiency. Furthermore, employing a special membrane made it possible to pick up the PCR products, Random distribution method is also applied to the construction of biosensor arrays. The authors first employed a two-step immobilization in which materials are not immobilized directly but indirectly via small support materials. In this case random distribution is called random fluidic self-assembly. This arranges the microparticles reducing the complication in the second step on the chip.