In situ preparation of nanohydroxyapatite/alginate composites as additives to PVA electrospun fibers as new bone graft materials

Aiming at new fibers containing hydroxyapatite (HAp) nanocrystal composites for bone graft applications, we successfully induced in situ growth of the ceramic phase in alginate gel (HAL) added them as dried materials at 0.1, 0.25 and 0.5% (w/w) to PVA matrices to prepare electrospun fibers. X-ray diffraction pattern and transmission electron microscopy showed rod-like alginate coated hydroxyapatite nanocrystals with diameter and length of (10 +/- 2) nm and (34 +/- 7) nm, respectively. Morphological analysis showed that electrospun composite fibers presented a fiber diameter range of (97-170) nm with a greater homogeneity of size distribution and no grain accumulation in 12% PVA fibers containing 0.1% HAL. All the samples showed mechanical strength limits within those expected for bone graft materials but the best tensile strength response among the electrospun scaffolds [(15.2 +/- 2.5) MPa] was observed for PVA fiber (12%) containing 0.1% HAL. The swelling ratio of all the composite fibers show that the presence of HAL composites induce a homogeneous swelling throughout the 4-week period, compared to bare fibers. We observe that the presence of HAL composites within the PVA fibers induced a greater degradation rate (54-62) % in one month) compared to PVA bare fibers and we attribute this property to the presence of alginate molecules. Biological assays using human gingival fibroblast cells demonstrated that all the fibrous membranes support cell adhesion and proliferation demonstrating their biocompatibility. The fibers and fibrous scaffolds prepared in the present study show very good morphological and mechanical properties as well as biocompatibility, fundamental conditions for applications as bone graft precursor materials.

Automated summary

In this study, electrospun fibers containing hydroxyapatite nanocrystal composites were successfully prepared by inducing in situ growth of the ceramic phase in alginate gel added to PVA matrices. The fibers exhibited excellent morphological and mechanical properties as well as biocompatibility.