Application of multi-way analysis to UV-visible spectroscopy, gas chromatography and electronic nose data for wine ageing evaluation.

In this study, a multi-way method (Tucker3) was applied to evaluate the performance of an electronic nose for following the ageing of red wines. The odour evaluation carried out with the electronic nose was combined with the quantitative analysis of volatile composition performed by GC-MS, and colour characterisation by UV-visible spectroscopy. Thanks to Tucker3, it was possible to understand connections among data obtained from these three different systems and to estimate the effect of different sources of variability on wine evaluation. In particular, the application of Tucker3 supplied a global visualisation of data structure, which was very informative to understand relationships between sensors responses and chemical composition of wines. The results obtained indicate that the analytical methods employed are useful tools to follow the wine ageing process, to differentiate wine samples according to ageing type (either in barrel or in stainless steel tanks with the addition of small oak wood pieces) and to the origin (French or American) of the oak wood. Finally, it was possible to designate the volatile compounds which play a major role in such a characterisation.

A multiway chemometric and kinetic study for evaluating the thermal stability of edible oils by ¹H NMR analysis: comparison of methods.

The degradation process of edible oils of different nature, submitted to heating at 170°C, 190°C and 210°C with aeration, was studied by means of (1)H nuclear magnetic resonance spectroscopy (NMR). In this study, secondary products such as aldehydes were detected and monitored over time. Two complementary analytical approaches were adopted to characterize the kinetics of the appearance of aldehydes in the heated oils. This first was a classical kinetic approach based on the assumption that the overall degradation reaction to form aldehydes follows a rate law of order 1. This approach allowed us to calculate a thermal stability criterion for classifying the oils according to their heat stability. A second approach was to use the spectral fingerprint corresponding to aldehydes in a multivariate data analysis procedure in order to give the major trend in the studied phenomena, taking into account the multiway nature of recorded data. The application of different 3-way and 4-way Tucker3 models led to a better understanding of the chemical stability of the oils studied and was used to determine the order of stability of these oils. This multiway approach provides additional information that 2-way processing (PCA) does not provide clearly, such as the overall contribution of the heating time factor on the chemical evolution of oils. In conclusion, this work shows that a fully chemometric study of NMR spectra allows to order the oils according to their thermal stability and to achieve a result in good agreement with existing analytical and kinetic studies in the literature.

Poloxamer 407 as a solubilising agent for tolfenamic acid and as a base for a gel formulation.

A solubility phase study was carried out to investigate the ability of Poloxamer 407 (P407) to solubilise tolfenamic acid. P407 considerably enhanced the solubility of this anti-inflammatory agent, by increasing its concentration in aqueous solution at least 2000-fold (up to C=4mM), when present at 12% (w/w) at 25 degrees C. The solubilisation process was spontaneous and exothermic, as indicated by thermodynamic parameters. A mixture experimental design was used to investigate the physical and release properties of P407-based gel formulations. The experimental design allowed verifying that drug release, occurring through a Fickian diffusion mechanism, was independent of the bulk viscosity of the system. The sustained release of tolfenamic acid towards the receptor phase constituted by isopropyl myristate was accompanied, in its early stage, by the concomitant release of ethanol and tetrahydrofurfuryl alcohol (THFA) used as cosolvents to obtain a drug loading of 0.6% (w/w). The poloxamer micellar phase was directly involved in the late stage of drug release, thus indicating that a strong interaction occurred in the gel between the poloxamer and tolfenamic acid. Results point out the possibility of both the systemic and topical administration of tolfenamic acid by means of aqueous solutions or gels containing P407 at an adequate concentration.

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 nanoparticles made of chitosan or N-trimethyl chitosan and a cisplatin-alginate complex.

In this work, nanoparticles with a negative or positive surface charge were prepared through electrostatic interaction of an anionic cisplatin-alginate complex with a cationic polyelectrolyte, namely chitosan or N-trimethyl chitosan (substitution degree of 85%). Statistical experimental design allowed the study of the influence of component amounts on the characteristics of nanoparticles. Mean particle diameter ranged from 180 nm to 350 nm. After 24 h, while the cisplatin-alginate complex released almost all the drug in saline-buffered solution at pH 7.4, approximately 40% w/w of total cisplatin was released from negative nanoparticles and roughly 50% w/w from positive ones. The same cumulative amounts of released drug were found after 48 h, with a progressive reduction to lower values up to 6 days. Drug loading of nanoparticles with a positive zeta potential (43 mV-60 mV) ranged from 13% w/w to 21% w/w and particle yield, referred to total polymers, was about 15% w/w (50% w/w if referred to cisplatin-alginate complex). Nanoparticles with a negative zeta potential (-34 mV) were obtained with a yield of 40% w/w and a drug loading of 18% w/w. These nanoparticles were the least active on all cell lines tested, while the cytotoxic activity of the positive nanoparticles was similar to or lower than that of cisplatin, probably depending on the combination of sizes and zeta potential values, on P388 murine and A2780 human cells. On A549 human cells, the nanoparticles with the smallest size and the lowest positive zeta potential were more active than cisplatin and showed a similar capability in inducing apoptosis in A2780 human cells. These results indicate that cisplatin complexes with polycarboxylate polymers can be transformed into cisplatin particulate carriers of high potential interest.

A composite sensor array impedentiometric electronic tongue Part II. Discrimination of basic tastes.

An impedentiometric electronic tongue based on the combination of a composite sensor array and chemometric techniques aimed at the discrimination of soluble compounds able to elicit different gustative perceptions is presented. A composite array consisting of chemo-sensitive layers based on carbon nanotubes or carbon black dispersed in polymeric matrices and doped polythiophenes was used. The electrical impedance of the sensor array was measured at a frequency of 150 Hz by means of an impedance meter. The experimental set-up was designed in order to allow the automatic selection of a test solution and dipping of the sensor array following a dedicated measurement protocol. Measurements were carried out on 15 different solutions eliciting 5 different tastes (sodium chloride, citric acid, glucose, glutamic acid and sodium dehydrocholate for salty, sour, sweet, umami and bitter, respectively) at 3 concentration levels comprising the human perceptive range. In order to avoid over-fitting, more than 100 repetitions for each sample were carried in a 4-month period. Principal component analysis (PCA) was used to detect and remove outliers. Classification was performed by linear discriminant analysis (LDA). A fairly good degree of discrimination was obtained.

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.