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A new type of pH biosensor was developed for biological applications. This biosensor was fabricated using silicon microsystem technology and consists in two platinum microelectrodes. The first microelectrode was coated by an electrosynthesized polymer and acted as the pH sensitive electrode when the second one was coated by a silver layer and was used as the reference electrode. Then, this potentiometric pH miniaturized biosensor based on electrosynthesized polypyrrole or electrosynthesized linear polyethylenimine films was tested. The potentiometric responses appeared reversible and linear to pH changes in the range from pH 4 to 9. More, the responses were fast (less than 1 min for all sensors), they were stable in time since PPy/PEI films were stable during more than 30 days, and no interference was observed. The influence of the polymer thickness was also studied.

We focused our study on the olfactory cells growth on biocompatible polymer films electrodeposited on a silicon microsystem. Several substrates such as polyethyleneimine (PEI), polypropyleneimine (PPI), and polypyrrole (PPy), acting as potentially good candidates for cell culture, were tested in order to allow cells to adhere and proliferate. During their growth, the evolution of their morphology was monitored using both confocal microscope and immunohistochemistry, leading to the conclusion of a normal development. An estimation of the adhesion and proliferation rates of rat neuronal cell cultures indicated that PEI and PPI were the best substrates for cultivating olfactory cells.

The development of a new electrochemical sensor consisting in a glass-sealed metal microelectrode coated by a polyethylenimine film is described. The use of polymers as the entrapping matrix for enzymes fulfils all the requirements expected for these materials without damaging the biological material. Since enzyme immobilization plays a fundamental role in the performance characteristics of enzymatic biosensors, we have tested four different protocols for enzyme immobilization to determine the most reliable one. Thus the characteristics of the potentiometric biosensors assembled were studied and compared and it appeared that the immobilization method leading to the most efficient biosensors was the one consisting in a physical adsorption followed by reticulation with dilute aqueous glutaraldehyde solutions. Indeed, the glutaraldehyde immobilized urease sensor provides many advantages, compared to the other types of sensors, since this type of urea biosensor exhibits short response times (15-30s), sigmoidal responses for the urea concentration working range from 1 x 10(-2.5) to 1 x 10(-1.5) M and a lifetime of 4 weeks.

Up to today, several techniques have been used to maintain cells in culture for studying many aspects of cell biology and physiology. More often, cell culture is dependent on proper anchorage of cells to the growth surface. Poly-l-lysine is commonly used as adhesive molecule. In this study, we present, as an alternative to poly-l-lysine, new polymer film substrates, realized by electropolymerization of different monomers on fluorine-doped tin oxide (FTO) surfaces since electropolymerization is a good method to coat selectively metallic or semiconducting electrodes with polymer films. So, the adhesion, proliferation and morphology of rat neuronal cell lines were investigated on polymer treated surfaces. Several amine-based biocompatible polymers were tested: polyethyleneimine (PEI), polypropyleneimine (PPI), polypyrrole (PPy) and poly(p-phenylenediamine) (PPPD). These polymer films were coated on FTO surfaces by electrochemical oxidation. After 8 h in a culture medium, a high percentage of cells was found to be attached to PEI and PPI compared to the other polymers and to the reference surfaces (glass and FTO uncovered). After 24 and 72 h in the culture medium, cells were found to proliferate faster on PEI and PPI than on other polymers and reference surfaces. Consequently, cells have a greater fold expansion on PEI and PPI than on PPPD, PPy or glass and FTO uncoated. From these results, we deduce that PEI and PPI can be useful as coating surface to cultivate neuronal cells.

Potentiometric pH sensors based on linear polyethylenimine (L-PEI) and linear polypropylenimine(L-PPI), two synthetic enzymes and biocompatible polymers, films were prepared by electropolymerization of three different monomers: ethylenediamine (EDA), 1,3-diaminopropane (1,3-DAP) and diethylenetriamine (DETA) in order to be used in clinical, dermatological and biological applications, such as in vivo analysis. In a first step a biosensor was tested which consisted in a platinum wire protruded from glass sheath. The polymer film coated on these platinum electrodes showed good linear potentiometric responses to pH changes from pH 3 to 10. Resulting electrodes present both good reversibility and good stability versus time. The effect of the different polymer film thicknesses to potentiometric responses was also studied. This study allowed us to develop a miniaturized pH biosensor in the second step. This sensor was fabricated using photo-lithography, followed by sputtering and lift-off processes, and it included an electronic detection system. We have also successfully studied the potentiometric responses to pH changes of this device over a period of 1 month, and so we propose this new pH micro-biosensor as an alternative to classical pH sensors currently used in dermatology.

Potentiometric biosensors based on butyrylcholinesterase are developed by co-reticulation of the enzyme with glutaraldehyde on an electropolymerized polyethyleneimine film at the electrode surface. The BuChE-electrode was tested as biochemical sensor for detection of an organophosphorus pesticide, trichlorfon in liquid, the detection being based on the enzyme inhibition. The enzyme electrode showed a detection limit for trichlorfon below 10(-7) M.

Although the European common lizard, Lacerta vivipara, is among the most common Eurasian reptile species, we know little about how these lizards cope with very low temperatures. In this study we examined microenvironmental conditions, body temperature, behavior, and cold strategies to see whether strategies of freezing and supercooling, while normally considered to be mutually exclusive, may in fact be adopted simultaneously by the common lizard. Following up on an earlier study of a lowland population, this time we used a mountain population (850 m) to discover differences in overwintering strategies between the two populations. Differential scanning calorimetry conducted during the hibernation period (vs. the activity period) showed that the blood of highland lizards had an increased ability to resist ice formation, confirming an ecophysiological effect most likely mediated by physical properties of the blood. Mean blood glucose level of unfrozen L. vivipara in the field increased significantly (about fourfold) from 8.5+/-0.7 mmol l(-1) in September to 33.2+/-5.6 mmol l(-1) in March. The blood glucose level then experienced a significant decline as it fell to 6. 2+/-0.8 mmol l(-1) after hibernation in April. Glucose, in conclusion, seems to play a role of cryoprotectant rather than antifreeze.