Nanohydroxyapatite Electrodeposition onto Electrospun Nanofibers: Technique Overview and Tissue Engineering Applications

Nanocomposite scaffolds based on the combination of polymeric nanofibers with nanohydroxyapatite are a promising approach within tissue engineering. With this strategy, it is possible to synthesize nanobiomaterials that combine the well-known benefits and advantages of polymer-based nanofibers with the osteointegrative, osteoinductive, and osteoconductive properties of nanohydroxyapatite, generating scaffolds with great potential for applications in regenerative medicine, especially as support for bone growth and regeneration. However, as efficiently incorporating nanohydroxyapatite into polymeric nanofibers is still a challenge, new methodologies have emerged for this purpose, such as electrodeposition, a fast, low-cost, adjustable, and reproducible technique capable of depositing coatings of nanohydroxyapatite on the outside of fibers, to improve scaffold bioactivity and cell–biomaterial interactions. In this short review paper, we provide an overview of the electrodeposition method, as well as a detailed discussion about the process of electrodepositing nanohydroxyapatite on the surface of polymer electrospun nanofibers. In addition, we present the main findings of the recent applications of polymeric micro/nanofibrous scaffolds coated with electrodeposited nanohydroxyapatite in tissue engineering. In conclusion, comments are provided about the future direction of nanohydroxyapatite electrodeposition onto polymeric nanofibers.

Porous Carbonated Hydroxyapatite-Based Paraffin Wax Nanocomposite Scaffold for Bone Tissue Engineering: A Physicochemical Properties and Cell Viability Assay Analysis

Porosity is one of the parameters of scaffold pore structure that must be developed using paraffin wax as a synthetic polymer for making porous bioceramics carbonated hydroxyapatite (CHA). This study fabricated CHA based on abalone mussel shells (Halioitis asinina); CHA/paraffin wax nanocomposite scaffolds were synthesized using paraffin wax with concentration variations of 10, 20, and 30 wt.%. The energy-dispersive X-ray spectroscopy (EDS) results showed that the Ca/P molar ratio of CHA was 1.72, which approaches the natural bone. The addition of paraffin wax in all concentration variation treatments caused the crystallographic properties of the CHA/paraffin wax nanocomposite scaffolds to decrease. The results of pore analysis suggest that the high concentration of paraffin wax in the CHA suspension is involved in the formation of more pores on the surface of the scaffold, but only CHA/paraffin wax 30 wt.% had a scaffold with potential to be used in media with a cellular growth orientation. The micropore analysis was also supported by the cell viability assay results for CHA/paraffin wax 30 wt.% nanocomposite scaffold, where serial doses of scaffold concentrations to mouse osteoblast cells were secure. Overall, based on this analysis, the CHA/paraffin wax scaffold can be a candidate for bone tissue engineering.

Nano Iron Oxide-PCL Composite as an Improved Soft Tissue Scaffold

Iron oxide nanoparticles were employed to fabricate a soft tissue scaffold with enhanced physicochemical and biological characteristics. Growth promotion effect of L-lysine coated magnetite (Lys@Fe3O4) nanoparticles on the liver cell lines was proved previously. So, in the current experiment these nanoparticles were employed to fabricate a soft tissue scaffold with growth promoting effect on the liver cells. Lys@Fe3O4 nanoparticles were synthesized via co-precipitation reaction. Resulted particles were ~7 nm in diameter and various concentrations (3, 5, and 10 wt%) of these nanoparticles were used to fabricate nanocomposite PCL fibers. Electrospinning technique was employed and physicochemical characteristics of the resulted nanofibers were evaluated. Electron micrographs and EDX-mapping analysis showed that nanoparticles were well dispersed in the PCL fibers and no bead structure were formed. As expected, incorporation of Lys@Fe3O4 to the PCL nanofibers resulted in a reduction in hydrophobicity of the scaffold. Nanocomposite scaffolds were shown increased tensile strength with increasing concentration of employed nanoparticles. In contrast to PCL scaffold, nearly 150% increase in the cell viability was observed after 3-days exposure to the nanocomposite scaffolds. This study indicates that incorporation of magnetite nanoparticles in the PCL fibers make them more prone to cell attachment. However, incorporated nanoparticles can provide the attached cells with valuable iron element and consequently promote the cells growth rate. Based on the results, magnetite enriched PCL nanofibers could be introduced as a scaffold to enhance the biological performance for liver tissue engineering purposes.

Repair of Osteoporotic Bone Defects Using Adipose-Derived Stromal Cells and Umbilical Vein Endothelial Cells Seeded in Chitosan/Nanohydroxyapatite-P24 Nanocomposite Scaffolds

Background. The cell regeneration and blood supply of bone defect lesions are restricted under osteoporotic pathological conditions, which make the healing of bone defect of osteoporosis still a great challenge. The current therapeutic strategies that mainly inhibit bone resorption are not always satisfactory for osteoporotic bone defects, which make the development of new therapies an urgent need. Methods. Previously, we prepared chitosan/nanohydroxyapatite (CS/nHA) biomimetic nanocomposite scaffolds for controlled delivery of bone morphogenetic protein 2-derived peptide (P24). In this study, we determined the effect of coculturing adipose-derived stromal cells (ADSCs) and human umbilical vein endothelial cells (HUVECs) with the CS-P24/nHA nanocomposite scaffolds on osteoporotic bone defect healing. In vitro mixed coculture models were employed to assess the direct effects of coculture. Results. ADSCs cocultured with HUVECs showed significantly greater osteogenic differentiation and mineralization compared with ADSCs or HUVECs alone. The CS-P24/nHA scaffold cocultured with ADSCs and HUVECs was more effective in inducing osteoporotic bone repair, as demonstrated by micro-computed tomography and histology of critical-sized calvariae defects in ovariectomized rats. Calvariae defects treated with the CS-P24/nHA nanocomposite scaffold plus ADSC/HUVEC coculture had a greater area of repair and better reconstitution of osseous structures compared with defects treated with the scaffold plus ADSCs or the scaffold plus HUVECs after 4 and 8 weeks. Conclusion. Taken together, coculture of ADSCs and HUVECs with the CS-P24/nHA nanocomposite scaffold is an effective combination to repair osteoporotic bone defects.

In-vitro Evaluation of Chitosan - Hydroxyapatite Nanocomposite Scaffolds as Bone Substitutes with Antibiofilm Properties

An opaque, white chitosan/ Hydroxyapatite nanocomposite was prepared by a simple blend method. Morphology, pore size and dispersion of nano-hydroxyapatite in chitosan matrix were visualized using SEM images. The FTIR and SEM with EDX analysis confirmed the bony apatite layer was formed on the outside of the composite. Porosity measurements and water uptake studies of the nanocomposite were evaluated which revealed the maximum porosity of 80% to 92% in the chitosan: hydroxyapatite nanocomposite at the ratio of 20:80. The results also showed that water absorption ability was inversely proportional to the hydroxyapatite present in the nanocomposite. The porosity of prepared nanocomposite was corresponding to the cancellous bone porosity of 50% to 90% suggesting possible applications in bone transplantation. The nanocomposite exhibited antibacterial activity towards the tested Gram-negative and Gram-positive species of bacteria and reduced the bacterial adhesion in biofilm formation.