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Macromol Biosci. 2006 May 23;6(5):358-63.

Drug release of pH/temperature-responsive calcium alginate/poly(N-isopropylacrylamide) semi-IPN beads.

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3B's Research Group - Biomaterials, Biodegradables and Biomimetics, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.


A series of semi-interpenetrating, polymer network (semi-IPN), hydrogel beads, composed of calcium alginate (Ca-alginate) and poly(N-isopropylacrylamide) (PNIPAAM), were prepared for a pH/temperature-sensitive drug delivery study. The equilibrium swelling showed the independent pH- and thermo- responsive nature of the developed materials. At pH=2.1, the release amount of indomethacin incorporated into these beads was about 10% within 400 min, while this value approached to 95% at pH=7.4. The release rate of the drug was higher at 37 degrees C than that at 25 degrees C and increased slightly with increasing PNIPAAM content. These results suggest that the Ca-alginate/PNIPAAM beads have the potential to be used as an effective pH/temperature sustainable delivery system of bioactive agents. [GRAPHS: SEE TEXT] A summary of the temperature- and pH-dependence on the release of the drug over a period of 450 min. The effect of the temperature on the swelling of the beads is shown in the inset.

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