Cristiana Schmidt de Magalhães

Influence of Surface‐Imprinted Nanoparticles on Trypsin Activity

Here, the modulation of enzyme activity is presented by protein-imprinted nanoparticles produced using a solid-phase approach. Using trypsin as target, binding of the nanoparticles to the enzyme results in its inhibition or in stabilization, depending on the orientation of the immobilized enzyme used during imprinting.

Evaluation of a simple and low cost potentiometric biosensor for pharmaceutical and in vivo adrenaline determination.

In this work the polyphenol oxidase (PPO) was the main component of a biosensor for adrenaline determination. The activity of this enzyme was measured in several vegetables. Banana (Musa sp.) extracts presented better results with 974 UA (units of activity). The biosensor was constructed with a polyethylene tube (0.8 mm i.d.) filled with: carbon paste containing 50 UA of the PPO in phosphate buffer (pH=7.00) solution and vaseline as agglutinant. When the biosensor was applied in medicine samples it provided a linear range from 8.00×10(-9) to 8.00×10(-4) mol L(-1); the results obtained with the proposed method and the Brazilian Pharmacopoeia method were in agreement (t-test). When it was applied in blood samples, the matrix-matching calibration was used, and the linear range was from 8.00×10(-7) to 8.00×10(-3) mol L(-1). In vivo studies were also done. The obtained results for those electrodes, which were inserted in the jugular vein of Wistar rats, were very promising.

A Homemade Autosampler/Injector Commutator for Flow Injection Analysis

An autosampler/injector commutator for flow injection analysis (FIA) was constructed with electronic components of used equipments. The apparatus is controlled by commercially available multifunctional interface (PCL711B) connected to a personal computer, and the software was written in Visual Basic language. The system was applied to water analysis and it presented satisfactory results. The low cost and simplicity are the principal characteristics of the autosampler/injector commutator.

The Coffee Protective Effect on Catalase System in the Preneoplastic Induced Rat Liver

This study aimed to evaluate the effect of organic/conventional coffee in liver tissues in the cancer process, taking into account the level and activities of catalase. The experiments were carried out with 8 groups of rats during 12 weeks. They received two injections of ethylenediaminetetraacetic acid solution 1.5% (v/v) prepared in 0.9% NaCl or 1,2-dimethylhydrazine (DMH) subcutaneous dose of 40 mg·kg−1·bw−1 for 2 weeks. The organic/conventional coffee infusions were at 5, 10, and 20% and were incorporated to feed (100 mL of infusion·kg−1 of diet). The catalase activity showed a decrease for livers which received DMH and DMH plus organic coffee at 5% and 10%. However, an increase was observed for those receiving organic 20% and conventional 10% coffee, slowing down and favoring the reversibility of the carcinogenic process. By SDS-PAGE, we observed an intensity decrease of 59 kDa bands, as the percentage of coffee was increased. The iron concentration (by ET-AAS) confirmed the electrophoretic results, suggesting that the DMH influenced the catalase expression conditions, reducing the activity by the loss of iron ions. Thus, the coffee may restore the catalase system in the liver, exerting its chemopreventive effects.

Organic and Conventional Arabica Coffee L: Protective Effects on Liver Under Pre-neoplastic Conditions

Several studies comparing organic and conventional coffee production systems can be found in the literature. Lately, there is an increasing demand for research related to the functional activities of the bioactive constituents of both coffee systems. However, published articles on this topic as well as evidence on the effect of the two types of production linked to anticancer factors in the liver are still scarce. Therefore, the purpose of this chapter is to comparatively evaluate the protective effects of both organic and conventional coffee production in liver tissue neoplasia. The differences in soils and plants were compared, in regards to the coffee compounds and their protective effects on the liver. Finally, we compared how each type of production system (organic or conventional) could influence changes in the protein profile in liver tissue in terms of oxidative damage, suggesting that organic coffee has a more efficient protective action.

Assessment of Cadmium and Lead Adsorption in Organic and Conventional Coffee

Many metals are toxic in human organism, as is the case of cadmium and lead. Therefore, the metal levels in food need to be controlled. In coffee, metals may present risks when they are extracted from the powder to be consumed as beverage. A flow injection analysis (FIA) system is proposed, with atomic absorption detection, to metal adsorption studies in coffee powder. Kinetic study, best isotherms and time, and mass influences were determined. They allowed analyzing the high lead and cadmium adsorption percentage in organic and conventional ground coffee. Metal adsorption occurs in multilayers, following Freundlichs model, and the kinetic model obeyed is the pseudo-second order. The cadmium adsorption suffered higher temperature influence, while the lead retention suffered higher mass influence. This study indicates that the majority of these toxic agents will be retained in the powder and will not be consumed by man, avoiding possible deleterious effects.

CHAPTER 8:Some Aspects of Selenium Determination Employing Solid-Phase Extraction and Atomic Absorption Spectrometry

The selenium determination, as well as selenium speciation, continues to possess drawbacks to be overcome, mainly for complex samples. Inductively coupled plasma mass spectroscopy, which has very good sensitivity, presents limitations for speciation because it provides only total concentration of the selenium. On the other hand, chromatographic techniques also present good performances but, in generally, need a troublesome and slow sample preparation. Preconcentration techniques, such as solid-phase extraction, have been employed due to the low concentrations of selenium species. This text presents an overview about selenium determination, focusing mainly on solid-phase extraction and atomic absorption spectrometry.