Optimization of a glucose biosensor setup based on a Ni/Al HT matrix

An amperometric glucose biosensor was developed using an anionic clay matrix of hydrotalcitic nature (Ni/Al-NO3 HT) as enzyme support, which was electrochemically synthesized at -0.90 V versus SCE, using a rotating disk Pt electrode to assure homogeneity of the electrodeposition suspension. The biorecognition element was glucose oxidase (GOx) immobilized on HT during the electrosynthesis, which was followed by cross-linking with glutaraldehyde vapours to avoid the enzyme release. The performances of the biosensor, in terms of sensitivity to glucose calculated from the slope of the calibration curve, are dependent on parameters related to the electrodeposition. An experimental design was applied to detect the optimal conditions of electrosynthesis in order to optimize the glucose biosensor performance. The factors taken into account were enzyme concentration and Ni/Al molar ratio. A full factorial design was performed to study linear interactions between factors and their quadratic effects and the optimal setup was evaluated by the isoresponse curves. The significant factors were enzyme concentration (linear and quadratic terms) and the interaction between enzyme concentration and Ni/Al molar ratio. Under the optimized electrodeposition conditions, the reproducibility of the biosensor fabrication was very good, being the RSD of the sensitivity about 5%.

Preparation and evaluation of a chitosan salt–poloxamer 407 based matrix for buccal drug delivery

The aim of this work was to prepare and evaluate a matrix for buccal drug delivery composed of a chitosan salt and poloxamer 407. Different chitosan salts were formed by reacting chitosan with acetic, citric, and lactic acid. Various proportions of poloxamer 407 were added to the aqueous solution of chitosan salt, and the residue obtained by lyophilisation was compressed into discs, using a 30 kN compression force. An experimental design (3(2)) was used to study the influence of the type of chitosan salt and of the relative amount of poloxamer on drug release capacity, swelling, erosion, and mucoadhesiveness of matrices. The results showed that matrix properties depended significantly on both relative amount of poloxamer and chitosan salt type. The rank orders of chitosan salts for the four processes evaluated were as follows: drug release: chitosan acetate>chitosan citrate>chitosan lactate; swelling: chitosan lactate>chitosan acetate=chitosan citrate; erosion: chitosan citrate>chitosan lactate>chitosan acetate; mucoadhesion: chitosan lactate>chitosan acetate=chitosan citrate. Mucoadhesion was particularly favoured when poloxamer 407 was present at about 30% (w/w). The matrix composed of chitosan lactate and poloxamer 407 showed the best characteristics for buccal administration.

Application of the principal component analysis (PCA) to the ecological study of an artificial environment: the tunny-fishing net of Camogli (Ligurian Sea)

The management of the marine environment and resource exploitation depend on the knowledge of both water conditions and ecological relationships between organisms. In the framework of fishing problems, an adequate food availability is important in order to allow maintaining and growth of fish stocks. The tunny-fishing of Camogli, owing to the coco-fibre texture of its net, can improve the trophic resources allowing the settlement of organisms eaten by fish. The distribution and composition of settled organisms was studied during the campaign 1988 by microscopical methods. The results have been elaborated by using multivariate (PCA) methods. Foraminifers, ciliates, hydroids, nematodes and copepods were the mainly observed groups. Their variations with season and depth and the relationships with caught fish species are presented. The elaboration of data by PCA allowed an easy and complete interpretation of the obtained complex data set showing the existence of a "rope" and of a "depth" effect.

Design and optimization of the variables in the adsorptive stripping voltammetric determination of rufloxacin in tablets, human plasma and urine

An adsorptive stripping voltammetric method with a hanging mercury drop electrode was developed for the determination of the fluoroquinolone rufloxacin in tablets, human plasma and urine. Measurements were obtained in differential pulse mode and a multivariate strategy was used to optimize the variables involved. Besides the independent effects of the variables, a strong interaction between scan rate and pulse duration has been found. Rufloxacin was analysed at concentrations between 1.7 x 10(-8) and 1.9 x 10(-7) M with a detection limit of 9.2 x 10(-9) M. Diluted tablet solutions and urine samples were analysed directly, while plasma samples needed an extraction procedure before voltammetric analysis. An improved HPLC procedure was used as comparative method.

Heterogeneity of presynaptic muscarinic receptors regulating neurotransmitter release in the rat brain

The existence of multiple muscarinic receptors in the brain was investigated by using neurotransmitter release as a functional parameter and by comparing the effects of agonists and antagonists on three systems of release regulation mediated by presynaptic muscarinic receptors. The receptors selected as models for our experiments were: 1) the muscarinic autoreceptors mediating inhibition of acetylcholine release in the cortex; 2) the muscarinic autoreceptors present in the nerve endings of the hippocampus; and 3) the muscarinic presynaptic receptors mediating potentiation of striatal dopamine release (heteroreceptors). The experiments were performed by using rat brain synaptosomes in superfusion. Acetylcholine, oxotremorine and carbachol inhibited the release of [3H]acetylcholine evoked by 15 mM KCI in cortex and hippocampus and potentiated the K+-evoked [3H]dopamine release in the striatum. The concentration-response curves were similar in the three systems, the rank of potency being: acetylcholine greater than oxotremorine greater than carbachol. The effects of acetylcholine were counteracted by several muscarinic antagonists with different rank of potencies and different potency ratios. In particular, the rank of potencies for the drugs tested was: atropine greater than secoverine greater than stercuronium greater than pirenzepine at the autoreceptors, both in cortex and hippocampus; but it was: atropine greater than pirenzepine = secoverine greater than stercuronium, at the heteroreceptors in the striatum. Pirenzepine was 100 times more potent on heteroreceptors than on autoreceptors. Our results suggest the possibility of a differential activation or blockade of central muscarinic receptors by selective drugs.