Biomimetic fabrication of alginate/CaCO3 hybrid beads for dual-responsive drug delivery under compressed CO2

Alginate/CaCO3 hybrid beads with pH- and thermal-responsive drug release properties were prepared under compressed CO2 using aliphatic poly(urethane-amine)s (PU) as the thermal-responsive component. Polyacrylic acid (PAA) was used as a crystal growth additive to control the structure of the hybrid beads. The hybrid beads were characterized by using scanning electron microscopy, X-ray powder diffraction and thermogravimetric analysis. The interaction between PAA and aliphatic PU contributed to the formation of alginate beads with a compact CaCO3 shell. Indomethacin release behaviour was found to be pH- and thermal-responsive. The release profiles were sustained with CaCO3 microparticles, indicating that the compact CaCO3 shell could hinder the permeability of the encapsulated drug and reduce the drug release effectively. The results suggest that the hybrid alginate beads can be used as “smart” polysaccharide materials for sustained dual-responsive drug delivery.