INNOVATIVE CHEMICAL SENSOR TECHNOLOGY sigma factors are synthesized and activated to protect the BASEDN ON INTEGRATION OF cells from environmental stresses. One of the sigma NANOTECHNOLOGY AND BIOTECHNOLOGY factors, RpoS, is triggered to be expressed when the cells Masuo Aizawa enter into the stationary phase, which is followed by the Tokyo Institute of Technology expression of genes required for cell survival. RpoS may Ookayama, Meguro-ku, Tokyo 152-8550, Japan also regulate the expression of various genes in the cellular response to such stresses as starvation, osmotic INTRODUCTION: An explosive progress has been stress, and acid shock, heat shock, and oxidative DNA made on chemical sensors and sensing systems these two damage. decades, resulting in successful commercialization of Non-destructive monitoring system has been developed various gas sensors, biosensors, and ion sensors. It should for evaluating cellular physiological status with the RpoS be pointed that increasing social needs of chemical promoter as stress marker. A reporter plasmid is sensors have recently arisen, and that enormous advanced constructed by inserting green fluorescent protein (GFP) technologies have emerged for development of chemical gene under the rpoS promoter and used to transform sensors. E.coli cells. The fluorescence of the GFP is measured in Current social needs of chemical sensors and sensing intact cells in a non-destructive manner for evaluating the systems may be exemplified as follows; cellular physiological status. 1) Environmental monitoring 2) Environmental assessment LIVING CELL-BASED SENSING SYSTEM AS 3) Safety assessment of chemicals ANIMAL TEST ALTERNATIVE: Biological effects of 4) Safety check of foods chemicals have been assessed in general by animal tests 5) Security check prior to clinical tests. Increasing efforts, however, have 6) High-throughput analyses in drug discovery been concentrated on the development of animal test 7) High-throughput analyses in combinatorial alternatives due to public acceptance. Bioassays based on chemistry cultured cells seem promising, though they suffer from 8) Genome analyses long and tedious procedures. To overcome the drawbacks 9) Point-of-care clinical test of the conventional cell culture bioassays, we have 10) Home health care test developed a novel method for assessing chemicals with a 11) Animal test alternatives cellular biosensing system, in which the cell responses to 12) Artificial nose and tongue chemicals are directly transduced to the sensor output. 13) Chemical sensing under extreme conditions A living cell contains a whole set of intracellular 14) Single molecule detection information networks including gene information 15) Others networks and signal transduction pathways. Molecular Researchers are encouraged to focus the target to these messengers such as hormones, cytokines and social needs to develop chemical sensors by integrating neurotransmitters are recognized by receptors embedded advanced technologies. A special attention should be on the cell membrane surface, resulting in activation of paid on emerging advanced technologies including the intracellular information networks mostly to modulate nanotechnology, nano-biotechnology, genome the gene information networks. The intracellular technology, information technology, bio-informatics, information networks might be perturbed by foreign and others. Most of these social needs are concerned chemical substances, which results in cellular responses. with sensing the molecular interactions with either such The effects of chemicals on the intracellular information information molecule as gene and receptor, or a living networks may thus be assessed by measuring the cellular cell containing a whole set of molecular information responses. networks. A novel category of biosensors and biosensing Two types of cellular sensing systems have been systems are described. developed by implementing either endothelial cell, or macrophage-like cell. A family of nitrogen oxide NEURORECEPTOR-DISPLAYED CELLS ON synthases, cNOS and iNOS, catalyze NO generation from MICROARRAY ELECTRODES FOR SCREENING L-arginine to L-citrulline. The constitutive isoform of PHARMACEUTICALS: A neuroreceptor at the synapse cNOS is steadily expressed in neural and endothelial cells. of a neuron junction may recognize the corresponding In contrast, the inducible isoform of iNOS is temporarily neurotransmitter, and open the ion channel, which is expressed, in macrophages, microglia, and astrocytes, in followed by activating neural information propagation. response to various stimulations. Neuropharmaceuticals such as narcotic agents modulate The endothelial cell-based sensing system with cNOS is the neural information propagation by interacting with effective on assessing pharmaceuticals which concern neuroreceptors. For screening the neuropharmaceuticals with vascular relaxation. The cultured cells are layered on in drug discovery, a high throughput analytical system is a polyion complex film under which a NO detecting essential in assessing the neural effects. electrode is fixed. A novel assessing system has been developed by In a similar fashion, an iNOS-based cellular biosensing implementing neuroreceptor-displayed cells on system is constructed with macrophage-like cells for microarray electrodes. The details are described for a assessing immunomodulating pharmaceuticals. gene engineered glutamate receptor displayed on the surface of an insect cell. ACKNOWLEDGEMENT: The research has been accomplished by collaboration with Dr.E.Kobatake, Dr. NON-DESTRUCTIVE SENSING OF CELLULAR T.Haruyama, Dr. Y.Yanagida, Dr. M.Mie, Dr. Funabashi, STRESS RESPONSES: The physiological status of Mr. K.Kamei, and Mr. P.Sakunan. living cells has been evaluated by measuring respiratory rate, substrate uptake rate and production rate as extracellular variables. In E.coli cells RNA polymerase