Sonnur Isik

Acrylic Acid-Based Copolymers as Immobilization Matrix for Amperometric Biosensors

Abstract Libraries consisting of acrylic acid-based polymer resins were synthesized by copolymerizing acrylic acid with different alkyl acrylates and 1-vinyl imidazole concomitantly varying the relative concentrations and the number of monomers present in the reaction mixture. The obtained polymer resins are suitable for electrochemically-induced precipitation on electrode surfaces caused by the protonation of acidic side groups at the polymer chains induced by a local electrochemical formation of protons in the diffusion zone in front of the electrode. Addition of suitable biological recognition elements such as glucose oxidase to suspensions of these electrodeposition paints (EDP) led to the entrapment of the enzyme within the slowly precipitating polymer film, and hence to the nonmanual fabrication of amperometric biosensors. The suitability of the obtained copolymers was screened with respect to the performance of the resulting glucose sensors. It could be demonstrated that the chemical composition of the used EDP significantly influences the properties of the sensors in terms of sensitivity and linear range of their response to glucose. †This article is dedicated to Prof. Dr. Pierre Coulet on the occasion of his retirement.

Odorant-Dependent Generation of Nitric Oxide in Mammalian Olfactory Sensory Neurons

The gaseous signalling molecule nitric oxide (NO) is involved in various physiological processes including regulation of blood pressure, immunocytotoxicity and neurotransmission. In the mammalian olfactory bulb (OB), NO plays a role in the formation of olfactory memory evoked by pheromones as well as conventional odorants. While NO generated by the neuronal isoform of NO synthase (nNOS) regulates neurogenesis in the olfactory epithelium, NO has not been implicated in olfactory signal transduction. We now show the expression and function of the endothelial isoform of NO synthase (eNOS) in mature olfactory sensory neurons (OSNs) of adult mice. Using NO-sensitive micro electrodes, we show that stimulation liberates NO from isolated wild-type OSNs, but not from OSNs of eNOS deficient mice. Integrated electrophysiological recordings (electro-olfactograms or EOGs) from the olfactory epithelium of these mice show that NO plays a significant role in modulating adaptation. Evidence for the presence of eNOS in mature mammalian OSNs and its involvement in odorant adaptation implicates NO as an important new element involved in olfactory signal transduction. As a diffusible messenger, NO could also have additional functions related to cross adaptation, regeneration, and maintenance of MOE homeostasis.