Single-walled carbon nanotubes loaded hydroxyapatite–alginate beads with enhanced mechanical properties and sustained drug release ability

Single-walled carbon nanotubes (SWCNTs) containing biomaterial with enhanced mechanical properties for the potential orthopedic application were synthesized and investigated. X-ray diffraction and X-ray fluorescence analysis were indications of the formation of calcium-deficient (Ca/P = 1.65) hydroxyapatite (HA) with a small carbonate content under influence of microwave irradiation. The investigated mechanical properties (maximal relative deformation, compressive strength and Young’s modulus) of SWCNT loaded HA–alginate composites confirm their dependence on SWCNTs content. The compressive strength of HA–alginate–SWCNT and the HA–alginate control (202 and 159 MPa, respectively) lies within the values characteristic for the cortical bone. The addition of 0.5% SWCNT, in relation to the content of HA, increases the Young's modulus of the HA–alginate–SWCNT (645 MPa) compared to the SWCNT-free HA–alginate sample (563 MPa), and enhances the material shape stability in simulated physiological conditions. Structural modeling of HA–alginate–SWCNT system showed, that physical adsorption of SWCNT into HA–alginate occurs by forming triple complexes stabilized by solvophobic/van der Waals interactions and H-bonds. The high-performance liquid chromatography demonstrated the influence of SWCNTs on the sustained anaesthesinum drug (used as a model drug) release (456 h against 408 h for SWCNT-free sample). Cell culture assay confirmed biocompatibility and stimulation of osteoblast proliferation of 0.05% and 0.5% SWCNT-containing composites during a 3-day cultivation. All these facts may suggest the potential possibility of using the SWCNT-containing materials, based on HA and alginate, for bone tissue engineering.