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Biomineralized polysaccharide-coated alginate beads containing PNIPAAM were prepared. The resulting beads can be used as carriers for sustained pH/temperature-sensitive drug delivery. Characterizations using SEM, EDS, FTIR, and POM revealed that the beads were covered by the calcium-phosphate-mineralized alginate/chitosan membrane. The drug-release behavior was examined using indomethacin as a model drug, and the release profile of the developed materials was found to be responsive to pH and temperature. The release profile could be sustained under neutral conditions, indicating that the mineralized polysaccharide membrane could prevent the permeability of the encapsulated drug and reduce the drug release rate.

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In order to obtain dual-stimuli-responsive (temperature/pH) alginate beads that exhibit LCST close to human body temperature for sustained drug release applications, poly (NIPAAm-co-AAm) hydrogel (with LCST 37.5-C) were selected and associated with calcium alginate to prepare inorganic--organic hybrid biomineralized polysaccharide alginate beads via a one-step method in this paper. Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) results demonstrated that calcium phosphate could not only be found in the surface but also in the cross-section of biomineralized polysaccharide beads. Both equilibrium swelling and indomethacin release behavior were found to be pH-and thermo-responsive. In addition, indomethacin release profile could be sustained with a inorganic--organic hybrid membrane: the release amount reached 96% within 4 hr for the unmineralized beads, while a drug release of only 64% obtained after subjecting the biomineralized polysaccharide beads to the same treatment. These results indicate that the biomineralized polysaccharide membrane could prevent the permeability of the encapsulated drug and reduce the drug release rate effectively. The studied system has the potential to be used as an effective smart sustainable delivery system for biomedical applications.

To improve the mechanical strength of natural hydrogels and to obtain a sustained drug-delivery device, temperature-/pH-sensitive hydrogel beads composed of calcium alginate (Ca-alginate) and poly(N-isopropylacrylamide) (PNIPAAm) were prepared in the presence of poly(sodium acrylate) (PAANa) with ultrahigh molecular weight (M g ! 1.0 Â 10 7 ) as a strengthening agent. The influence of PAANa content on the properties, including the beads stability, swelling, and drug-release behaviors, of the hydrogels was evaluated. Scanning electron microscopy and oscillation experiments were used to analyze the structure and mechanical stability of the hydrogel beads, respectively. The results show that stability of the obtained Ca-alginate/PNIPAAm hydrogel beads strengthened by PAANa the alginate/ poly(N-isopropyl acrylamide) hydrogel bead (SANBs) was significantly improved compared to that of the beads without PAANa (NANBs) at pH 7.4. The swelling behavior and drug-release capability of the SANBs were markedly dependent on the PAANa content and on the environmental temperature and pH. The bead sample with a higher percentage of PAANa exhibited a lower swelling rate and slower drug release. The drug release profiles from SANBs were further studied in simulated intestinal fluid, and the results demonstrated here suggest that SANBs could serve as a potential candidate for controlled drug delivery in vivo.