Coating of certain matrix cores with aqueous-based systems of acrylate methacrylate, a water-insoluble copolymer and drug release profiles

Stimuli-responsive hydrogels in drug delivery and tissue engineering

Hydrogels are the three-dimensional network structures obtained from a class of synthetic or natural polymers which can absorb and retain a significant amount of water. Hydrogels are one of the most studied classes of polymer-based controlled drug release. These have attracted considerable attention in biochemical and biomedical fields because of their characteristics, such as swelling in aqueous medium, biocompatibility, pH and temperature sensitivity or sensitivity towards other stimuli, which can be utilized for their controlled zero-order release. The hydrogels are expected to explore new generation of self-regulated delivery system having a wide array of desirable properties. This review highlights the exciting opportunities and challenges in the area of hydrogels. Here, we review different literatures on stimuli-sensitive hydrogels, such as role of temperature, electric potential, pH and ionic strength to control the release of drug from hydrogels.

WITHDRAWN: An overview on stimuli responsive hydrogels as drug delivery system

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Monitoring of dissolution induced changes in film coat composition by 1H NMR spectroscopy and SEM

In our study we investigated the release mechanisms of coated oral dosage forms more deeply. The aim of the study was to monitor the buffer induced leaching out of water soluble compounds from Kollicoat SR films and to relate this process to the film properties and the release kinetics. Propranolol HCl tablets were coated with different amounts and ratios of polyvinyl acetate (Kollicoat SR) and poly(vinyl alcohol)-poly(ethylene glycol)-graft-copolymer (Kollicoat IR). Polyvinyl pyrrolidone (Kollidon 30) was added as a second water soluble polymer and triacetin as a plasticizer. In addition to kinetics of the drug release, the films were studied by SEM and 1H NMR spectroscopy. SEM micrographs revealed morphological changes of the tablet surface that were related to an alteration in film coat composition. The described 1H NMR method provided the opportunity to quantify the leaching of Kollicoat IR, Kollidon 30 and triacetin. Drug release kinetics were related to dissolution induced changes in coating composition. Permeability of the film coat increased, when about 90% of the water soluble polymers and plasticizer triacetin were leached out of the film coat.