Heparin as a biomimetic template on nanoapatite rods with tunable aspect ratio: synthesis and biocompatibility

In this study, heparin was used as a natural organic template to prepare nanoscale needle- or rod-like (nanorod) carbonate-based apatite. The characteristic phase and selected area electron diffraction patterns confirmed that the nanorods grew in the preferred crystallographic orientation, that is, the [0001] direction of the c-axis of apatite. As a result of the heparin-templated apatite nanoparticles, the apatite morphological variations revealed that the presence of heparin was potentially incorporated with Ca2+ cations, thereby inhibiting a-axis growth, increasing the aspect length-to-width ratio of the apatite nanorods, and effectively changing the precipitate form into uniform nanoscale rod-like shaped apatite. From the infrared spectra, the hexagonal structure template mediated by heparin was B-type carbonated calcium-deficient hydroxyapatite (CDHA), which indicated that heparin demonstrated regulated growth in the processed template of carbonated CDHA. Cell viability analysis showed that cytotoxicity was caused by the influence of specific nanoscale aspect ratios of the rod-like apatite morphology or by tuning a large aspect ratio of rod-like shaped apatite with a large quantity of heparin incorporation, resulting in fast ion dissolution by rapidly raising the pH. Overdosed heparin used as a template to prepare apatite nanoparticles led to highly negatively charged nanorods that caused cytotoxicity. We propose the optimal group of synthetic HAP@Hep25K within the proper heparin concentration, which showed the intended morphology of apatite nanorods and exhibited biocompatibility.

Automated summary

Heparin was used as a template to prepare nanoscale needle- or rod-like carbonate-based apatite, showing that heparin can regulate the morphology and growth of the nanoapati. The optimal group of synthetic HAP@Hep25K within the proper heparin concentration exhibited the intended morphology of apatite nanorods and biocompatibility.