Detailed study on cell/materials interaction greatly contributes the molecular design of materials having a regulative effect on cellular functions. In this paper, special emphasis was placed on the molecular design of materials for cell separation. By controlling the distribution mode as well as the protonation degree of amino groups in polyamine graft copolymers, highly selective adsorption of a particular subpopulation of lymphocytes (B cells) on these copolymer surface was achieved, indicating a promising feature of these copolymers as adsorbent for lymphocyte separation. Further, a new cell separation method was established by hybridizing adhesion chromatography and fieldflow fractionation.

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Stimuli-sensitive polymers which change their structure and physical properties in response to external signals have promising potential in the design of drug delivery systems. In particular, self-regulating or auto feedback drug release system so called “intelligent drug delivery”; may be achieved by utilizing stimuli-sensitive polymers. Random copolymers and interpenetrating networks consisting acrylamide derivative showed excellent thermosensitivity to achieve pulsatile drug release. Quick response of the gel surface to temperature changes is utilized as an on-off switch for drug release and permeation. The data represent the first experimental results showing an on-off switching phenomena of thermosensitive hydrogels which are applicable for modulated pulsatile-controlled release systems.

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In 1974, it was found that sintered hydroxyapatite has a good biocompatibility in a dog's femur and mandible bones. Since then, hydroxyapatite has been studied as a biomaterial for artificial bones, cement and tooth roots.
Now, bone fillers made of hydroxyapatite are used clinically worldwide. In 1982, it was clarified that sintered hydroxyapatite has also a good compatibility with skin tissue. Since then, percutaneous devices based on hydroxyapatite have been developed, and the applications have been expanded to CAPD dialysis, blood pressure measurement, blood access for nutrition, and so on.
Hydroxyapatite has various types of crystal faces, including (100), (010), and (001) faces. The surfaces of these faces are very different in atomic elements, numbers, and arrangements. Therefore, their surfaces are also different in biocompatibility. We must design the crystal surfaces of hydroxyapatite according to its functions. In this paper, the crystal and surface structures of hydroxyapatite are described, and the relationship between the surface structure and biocompatibility is discussed.

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In order to develop and bioeleotronic elements of the highly functional artificial organs, the immobilization of redox proteins such as Cytochrome c was examined on the ITO electrode coated with a variety of hydrophilic polymers. It was found that anionic polymers, e. g. polyglutamic acid derivatives are the most available materials to enhance the electron transport between Cytochrome c and the electrode. Various functions such as switching and memory were confirmed with the present redox electrode. Couplings of Cytochrome c-immobilized electrode with other redox proteins e. g. oxidase and dehydrogenase via diaphorase were also found.

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Worldwide reseach on biosensors is growing rapidly, with new advances. Many papers on fundamental and applied aspects are appearing weekly. For the further development of biosensors, especially for the clinical uses, new challenges to microfabrication of biosensors with high performance such as high selectivity, high sensitivity, and satisfactory stability for intelligent, multipurpose clinical autoanalyzers are strongly required. Also a great excitation exists for using in vivo biosensors in connection with the development of artificial organs. For this purpose biomaterials should provide biocompatibility. This article describes the concepts of biosensors and the material science of biosensors from the veiwpoint of effective signal transduction, sensitization and microfabrication. In addition, the importance of surface chemistry is emphasized for the development of biocompatible implantable biosensors.

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The characteristics of biological sensing systems are described on reference to the transformation of stimuli to transmit information, and the behavior of some artifitial membrane systems are discussed to model biosensing and nerve systems. Furthermore, some proposals are presented on the molecular electronic devices in future.

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Effects of adsorption of potassium iodide (KI) on hydrogen content of the plate-type Raney nickel catalyst and its catalytic activity for hydrogenation of alcohol and ketones were investigated. The amounts of K⁺ and I^- were determined by potentiometry and radioactivity measurement. The adsorption isotherms in lower (∼5.5×10^-5mol dm^-3) and higher KI concentration ranges were represented by Freundlich's and BET equations, respectively. The residual hydrogen content of the catalyst and hydrogenation activities of ketones decreased exponentially with an increase in the amount of I^- adsorbed. The surface coverage causing the hydrogenation activity to decrease by 50% was 3% for allyl alcohol and 0.3% for 2-butanone. With respect to allyl alcohol, even such a catalyst as had preadsorbed ca. 5 monolayer amounts of I^-possessed a 33% residual activity.

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The relationship between the reflectivity and the photoacoustic signal magnitude was examined at various solid-liquid interfaces by changing the angle of incidence in total internal reflection photoacoustic spectrometry (TIR-PAS). On the basis of a theory for the photoacoustic signal generation, the relationships could be explained with respect to the glass-dye solution and glass-ITO (Indium-tin oxide) film-dye solution interfaces. In addition, photoacoustic signals arising from surface plasmon-polaritons were observed at the glass-gold film-dye solution interfaces. From these findings, it has been shown that both of optical and thermal properties of the solid-liquid interfaces can be studied by means of TIR-PAS.

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Effects of humidity on the oscillation frequency of a resonating system utilizing a quartz piezoelectric surface acoustic wave (SAW) delay line with a deposited aluminum oxide (AlO_x) thin film have been studied. With exposure to humid air, the frequency of the SAW resonator decreased instantaneously and the change in the frequency was found to be larger than that of the bulk wave resonator. The result obtained shows that the present AlO_z/SAW resonator has a good possibility to be applied to a highly sensitive humidity detector.

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