Chitosan and Poly (Vinyl Alcohol) microparticles produced by membrane emulsification for encapsulation and pH controlled release

© 2015 Elsevier B.V. The Dispersion Cell membrane emulsification technique was used for the production of w/o emulsions with controlled droplet size and narrow size distribution. The influence of the operating parameters of the process was investigated. Varying the dispersed phase flux (10-1250 L h-1 m-2) and the shear stress (2-59 Pa), droplets between 30 and 280 μm were produced with CV's as low as 18%. Nickel and stainless steel membranes were used for the membrane emulsification. Pore geometry influenced the droplet size as well as uniformity and a normally hydrophilic stainless steel membrane with sharp pore openings produced more uniform and smaller drops compared to a PTFE coated hydrophobic nickel membrane with a conical pore surface. For the dispersed phase 15 wt.% PVA or 1-3 wt.% chitosan as well as their blends in water were used. Surfactants PGPR and ABIL EM90 were tested to determine their capability to form stable emulsions in Miglyol 840. PGPR could not be used to stabilize the emulsion with chitosan as the dispersed phase, probably due to the chemical interference between the carboxyl group present in the PGPR and chitosan. Solid microparticles were obtained by chemical crosslinking with glutaraldehyde (GA) at different concentrations (1-50 vol.%). Particles crosslinked using less than 10 vol.% GA were able to swell and release encapsulated compounds. Acid sensitive particles were produced by blending the PVA and chitosan. Up to 80% of Cu2+ and 20% of sodium salicylate was released from the particles under acidic conditions. No significant release was determined under neutral conditions

The use of the Fourier Transform Infrared spectroscopy to determine adulterants in raw milk

The objective of this study was to develop calibrations to determine the concentration of some milk adulterants by using the automated methodology of Fourier Transform Infrared (FTIR). For construction of calibrations, samples were collected from 100 farms in the states of São Paulo and Minas Gerais. Samples were tainted with three different adulterants commonly used in the adulteration of raw milk: sodium bicarbonate (SB), sodium citrate (SC) and cheese whey (W). Each adulterant was used at three different concentrations (SB: 0.05, 0.10 and 0.25%; SC: 0.025, 0.050 and 0.075% and W: 5, 10 and 20%). For validation, 60 samples were collected in other farms, which were not considered at the development stage of calibration. Adulterants were added at the following concentrations: 0.03, 0.06, 0.10 and 0.12% for SB; 0.02, 0.04, 0.06 and 0.08% for SC and 5, 10 and 20% for W. Performance of each calibration was evaluated in terms of accuracy (Se), detection limit (DL) and determination coefficient (R²). All calibrations presented R² higher than 0.91 with DL of 0.015%; 0.017% and 3.9% for SB, SC and W, respectively. Accuracy was 0.005%, 0.009% and 2.26% for SB, SC and W, respectively. Results show that the FTIR methodology can be used for determining the concentration of sodium bicarbonate, sodium citrate and whey in raw milk. Associated with automated equipment, it is a viable option for monitoring these adulterants, having low operational costs and high analytical performance as additional features

Floating microspheres: a review

Gastric emptying is a complex process, one that is highly variable and that makes in vivo performance of drug delivery systems uncertain. A controlled drug delivery system with prolonged residence time in the stomach can be of great practical importance for drugs with an absorption window in the upper small intestine. The main limitations are attributed to the inter- and intra-subject variability of gastro-intestinal (GI) transit time and to the non-uniformity of drug absorption throughout the alimentary canal. Floating or hydrodynamically controlled drug delivery systems are useful in such applications. Various gastroretentive dosage forms are available, including tablets, capsules, pills, laminated films, floating microspheres, granules and powders. Floating microspheres have been gaining attention due to the uniform distribution of these multiple-unit dosage forms in the stomach, which results in more reproducible drug absorption and reduced risk of local irritation. Such systems have more advantages over the single-unit dosage forms. The present review briefly addresses the physiology of the gastric emptying process with respect to floating drug delivery systems. The purpose of this review is to bring together the recent literature with respect to the method of preparation, and various parameters affecting the performance and characterization of floating microspheres.<br>O esvaziamento gástrico é um processo complexo, com elevada variabilidade e responsável pela incerteza do desempenho dos medicamentos in vivo. Dessa forma, os sistemas de liberação modificada de fármacos, com tempo de residência prolongado no estômago, em especial, considerando aqueles fármacos com janela de absorção na porção superior do intestino delgado, apresentam fundamental importância. As principais limitações relativas à absorção do fármaco são, no geral, atribuídas à variabilidade inter e intra-paciente do tempo de trânsito gastro-intestinal (GI) e da não-uniformidade da absorção do fármaco na extensão do canal alimentar. Assim, justifica-se a utilização dos sistemas flutuantes ou hidrodinâmicos de liberação de fármacos. Vários medicamentos gastrorretentivos estão disponibilizados no mercado e incluem comprimidos, cápsulas, pílulas, filmes laminados, microesferas flutuantes, grânulos e pós. As microesferas flutuantes apresentam maior destaque em função da distribuição granulométrica uniforme dessas formulações de dose múltipla. Como resultado, a absorção do fármaco apresenta maior reprodutibilidade e os riscos associados à irritação local são reduzidos. Tais sistemas apresentam maior vantagem quando comparado às formulações de dose única. A presente revisão tem como objetivo apresentar as publicações recentes referentes aos métodos de preparação, os vários parâmetros que afetam o desempenho e a caracterização das microesferas flutuantes. Além disso, o presente trabalho aborda a fisiologia do processo de esvaziamento gástrico no que se refere aos sistemas flutuantes de liberação de fármacos