New core-shell hydroxyapatite/Gum-Acacia nanocomposites for drug delivery and tissue engineering applications.

Core-shell hydroxyapatite (HAP) - gum acacia (GA) nanocomposite, in which the HAP acts as a core while the GA serves as a shell, was synthesized by precipitation techniqueusing Ca(NO3 )2 .4H2 O and NH4 H2 PO4 as precursors for Ca and P, respectively. The crystallite size and morphology of the synthesized core-shell HAP-GA nanocomposite was evaluated by X-ray diffraction measurement and transmission electron microscopy. The crystallite size of GA-HAP nanocomposite is markedly decreased from 89 nm to 63 nm when the concentration of GA in the reaction mixture is increased from 0 to 10%. Transmission electron micrographs confirm encapsulation of GA over the HAP particles, leading to the formation of GA shell-HAP core assembly, which is quite evident for 10% GA-HAP composites. The nature of functional groups present in HAP was identified using FT-IR and Raman spectroscopies while its chemical composition was analyzed by energy dispersive X-ray analysis. The Ca/P ratio of the synthesized HAP's was found to be 1.67. The elemental composition of the HAP samples was evaluated by X-ray photoelectron spectroscopy. The peaks at binding energies 286.5 and 289.3 eV of C 1S and the peaks at 530.6 eV and 532.1 eV of the O 1S spectra further substantiate encapsulation of GA over the HAP particles, resulting in the formation of GA-HAP nanocomposite. Pellet samples of HAP were immersed in simulated body fluid to ascertain their bioactivity using scanning electron micrographs. The drug, naringenin, was loaded within the core of HAP by pellet pressing method. The drug-loaded core-shell HAP composites were subjected to microbial studies, hemolytic studies and MTT assay to assess their biocompatibility.