Synthesis of stimuli-responsive microgels for in vitro release of diclofenac diethyl ammonium.
ABSTRACT Thermal and dual stimuli-responsive microspheres (pH and temperature) were prepared by free radical polymerization of methacrylate bovine serum albumin (BSA-MA) as cross-linker and sodium methacrylate (NaMA) and/or N-isopropylacrylamide (NIPAAm), as hydrophilic/pH-sensitive and thermo-responsive monomers, respectively. Microgels were characterized by infrared spectroscopy, morphological analysis, particle size distribution and determination of swelling properties. The network density and the shape of the microgels were found to depend on the concentration of the reactive species in the polymerization feed. Thermal analyses were performed to determine lower critical solution temperature values, which become close to the body temperature by increasing the content of the hydrophilic moieties in the network. In order to test the preformed materials as drug carriers, in vitro release studies of Diclofenac diethyl ammonium salt were performed. For all the co-polymers, a predominant drug release in the collapsed state was observed, while below the microgel transition temperature, a drug release through the swollen network occurs. The data recorded during the release tests demonstrated that the pH of the surrounding environment influences the drug release more than the temperature of the imbibing medium.
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ABSTRACT: A star-shaped copolymer, poly(N-isopropylacrylamide-co-itaconamic acid (poly(NIPAAm-co-IAM)), being pH- and thermo-dual-responsive, was synthesized by atomic transfer radical polymerization (ATRP) and characterized in this work. The lower critical solution temperature (LCST) of the star copolymer increases with the molar fraction of IAM. The particle size decreases as the temperature increases but increases as the pH value increases. Transmission electron microscopy (TEM) reveals that the star-shaped copolymer has a near-spherical core-shell structure that favors drug delivery. The star copolymer can be used in drug encapsulation as well as drug release. The star copolymer has different drug release rates in environments of different pH, and thus it can carry drugs in an acidic (gastric) environment and release the drugs in a neutral or less acidic (intestinal) environment.Colloid and Polymer Science 02/2015; 293(2). DOI:10.1007/s00396-014-3436-0 · 2.41 Impact Factor
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ABSTRACT: Thermo-responsive hydrogel films, synthesized by UV-initiated radical polymerization, are proposed as delivery devices for non-steroidal anti-inflammatory drugs (Diclofenac sodium and Naproxen). N-isopropylacrylamide and N,N'-ethylenebisacrylamide were chosen as thermo-sensitive monomer and crosslinker, respectively. Infrared spectroscopy was used to assess the incorporation of monomers into the network, and the network density of hydrogel films was found to strictly depend on both feed composition and film thickness. Calorimetric analyses showed negative thermo-responsive behaviour with shrinking/swelling transition values in the range 32.8-36.1°C. Equilibrium swelling studies around the LCST allowed the correlation between the structural changes and the temperature variations. The mesh size, indeed, rapidly changed from a collapsed to a swollen state, with beneficial effects in applications such as size-selective permeation or controlled drug delivery, while the crosslinking degree, the film thickness, and the loading method deeply influenced the drug release profiles at 25 and 40°C. The analysis of both 3D-network structure, release kinetics and diffusional constraints at different temperatures was evaluated by mathematical modelling. Copyright © 2014 Elsevier B.V. All rights reserved.Materials Science and Engineering C 03/2015; 48:499-510. DOI:10.1016/j.msec.2014.12.045 · 2.74 Impact Factor
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ABSTRACT: The use of biologics, polymers, silicon materials, carbon materials, and metals has been proposed for the preparation of innovative drug delivery devices. One of the most promising materials in this field are the carbon-nanotubes composites and hybrid materials coupling the advantages of polymers (biocompatibility and biodegradability) with those of carbon nanotubes (cellular uptake, stability, electromagnatic, and magnetic behavior). The applicability of polymer-carbon nanotubes composites in drug delivery, with particular attention to the controlled release by composites hydrogel, is being extensively investigated in the present review.01/2014; 2014:825017. DOI:10.1155/2014/825017