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Abstract
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The aim of this work was to prepare pH-sensitive drug carriers for colon specific drug delivery through a
completely green and environmentally friendly route (without using any organic solvents, hazardous
chemicals and even a harsh procedure). To achieve this, natural biopolymers (sodium alginate, chitosan
and carboxymethylcellulose sodium) were used. Naproxen (as a model drug) and magnetic nanoparticles
were encapsulated into the alginate microcapsules by formation of an alginate–Ca2+ complex. To
overcome the drawbacks of the alginate microcapsules like porosity and burst drug release, they were
coated with chitosan and carboxymethylcellulose sodium by a layer-by-layer technique that led to the
formation of polyelectrolyte complexes through inter-ionic interactions between oppositely charged
biopolymers. After coating with these natural polymers, porosity was reduced and burst drug releases
were modified. The prepared magnetic microcapsules were characterized by FT-IR, DSC and SEM to
study their structures and the roles that each polymeric layer plays. The swelling ratios and in vitro drug
release profiles of the microcapsules were studied in both enzyme-free simulated gastric (SGF, pH 1) and
simulated colonic fluids (SCF, pH 7.4). These microcapsules could be driven by means of an external
magnet and also the results show that these coated microcapsules are completely pH-sensitive and
potentially can be used as stimuli responsive carriers for colon specific drug delivery.
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