A pH-responsive composite hydrogel beads based on agar and alginate for oral drug delivery

To improve the mechanical strength of calcium alginate hydrogel and obtain sustained drug delivery, the pH-sensitive composite gel beads composed of agar and alginate were prepared in the presence of agar as a modifying agent. All the obtained gel beads were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The influence of the content of agar on the properties of the hydrogel including mechanical strength, swelling and drug release behavior was evaluated in simulated intestinal fluid (pH 7.4) and gastric fluid (pH 2.1) at 37 °C. Results illustrated that mechanical strength of agar/alginate beads (AALB) was significantly improved compared with the native alginate beads (NALB) without agar. The swelling and drug release behavior of AALB was markedly dependent on the content of agar. The gel beads with higher content of agar exhibited a lower rate of swelling and drug release within 720 min. Drug release behavior of AALB was further studied in simulated intestinal fluid and gastric fluid, and results showed that AALB could serve as a potential candidate for controlled drug delivery.

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