Physicochemical characterization of halloysite/alginate bionanocomposite hydrogel

Bionanocomposite beads of halloysite/alginate have been recently studied as a medium for drug delivery and adsorption or absorption due to their biocompatibility, renewability and ease of preparation. However, there is no dedicated work on extensive characterization of this bionanocomposite material to provide further understanding on the material properties. In this work, the mechanical, chemical, and mass transfer properties of halloysite/alginate bionanocomposite are investigated. The incorporation of halloysite nanotubes has no effect on the size and on the shape of the alginate beads. Fourier transform infrared spectroscopy (FTIR) spectra show no chemical interaction between the halloysite nanotubes and the alginate polymers. Energy dispersive X-ray analyzer (EDX) shows that the halloysite nanotubes are embedded within the layers of Ca-alginate hydrogel networks but they are not present in the pores between the matrices. This finding is confirmed by the field emission scanning electron microscopy (FESEM) images which further show that the halloysite nanotubes are well dispersed within the alginate matrix. The Youngʹs modulus of the halloysite/alginate bionanocomposite beads, determined using uni-axial compression test and Hertzʹs model, increased by 35% at 100 g/L halloysite nanotube loading compared to that of blank alginate beads. Despite this, the elastic limit of the beads with halloysite nanotubes is only slightly lower than the blank beads. Moreover, the diffusion coefficient of glucose molecules into the halloysite/alginate bionanocomposite beads is in the same order of magnitude with that of the blank alginate beads. The enhanced mechanical properties without severely compromising other physicochemical properties make halloysite/alginate bionanocomposite a more promising material for a variety of applications including bioprocessing and tissue engineering.