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Properties and Mechanism of Hydroxyapatite Coating Prepared by Electrodeposition on a Braid for Biodegradable Bone Scaffolds.

ABSTRACT: Hydroxyapatite (HA) coating is successfully prepared by electrodeposition on the surface of polyvinyl alcohol (PVA)/polylactic acid (PLA) braid which serves as a potential biodegradable bone scaffold. The surface morphology, element composition, crystallinity and chemical bonds of HA coatings at various deposition times (60, 75, 90, 105 and 120 min) are characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively. Average Surface roughness (Ra) of HA coating is observed by confocal microscopy. The results reveal that the typical characteristic peaks of the FTIR spectrum confirm that HA coating is successfully prepared on the rugged surface of the PVA/PLA braid. The XRD results indicate that the crystallinity of HA can be improved by increasing deposition time. In the 90 min-deposition, hydroxyapatite has a dense and uniform coating morphology, Ca/P ratio of 1.7, roughness of 0.725 ?m, which shows the best electrodeposition performance. The formation mechanism of granular and plate-like hydroxyapatite crystals is explained by the structural characteristics of a hydroxyapatite unit cell. This study provides a foundation for a bone scaffold braided by biodegradable fibers.

SUBMITTER: Li TT

PROVIDER: S-EPMC6567105 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Project description:Polylactic acid (PLA) has been widely used as filaments for material extrusion additive manufacturing (AM) to develop patient-specific scaffolds in bone tissue engineering. Hydroxyapatite (HA), a major component of natural bone, has been extensively recognized as an osteoconductive biomolecule. Here, inspired by the mussel-adhesive phenomenon, in this study, polydopamine (PDA) coating was applied to the surface of 3D printed PLA scaffolds (PLA@PDA), acting as a versatile adhesive platform for immobilizing HA nanoparticles (nHA). Comprehensive analyses were performed to understand the physicochemical properties of the 3D-printed PLA scaffold functionalized with nHA and PDA for their potent clinical application as a bone regenerative substitute. Scanning electron microscopy (SEM) and element dispersive X-ray (EDX) confirmed a successful loading of nHA particles on the surface of PLA@PDA after 3 and 7 days of coating (PLA@PDA-HA3 and PLA@PDA-HA7), while the surface micromorphology and porosity remain unchanged after surface modification. The thermogravimetric analysis (TGA) showed that 7.7 % and 12.3% mass ratio of nHA were loaded on the PLA scaffold surface, respectively. The wettability test indicated that the hydrophilicity of nHA-coated scaffolds was greatly enhanced, while the mechanical properties remained uncompromised. The 3D laser scanning confocal microscope (3DLS) images revealed that the surface roughness was significantly increased, reaching Sa (arithmetic mean height) of 0.402 μm in PLA@PDA-HA7. Twenty-eight days of in-vitro degradation results showed that the introduction of nHA to the PLA surface enhances its degradation properties, as evidenced by the SEM images and weight loss test. Furthermore, a sustainable release of Ca2+ from PLA@PDA-HA3 and PLA@PDA-HA7 was recorded, during the degradation process. In contrast, the released hydroxyl group of nHA tends to neutralize the local acidic environments, which was more conducive to osteoblastic differentiation and extracellular mineralization. Taken together, this facile surface modification provides 3D printed PLA scaffolds with effective bone regenerative properties by depositing Ca2+ contents, improving surface hydrophilicity, and enhancing the in-vitro degradation rate.

Project description:Our long-term goal is to develop smart biomaterials that can facilitate regeneration of critical-size craniofacial lesions. In this study, we tested the hypothesis that biomimetic scaffolds electrospun from chitosan (CTS) will promote tissue repair and regeneration in a critical size calvarial defect. To test this hypothesis, we first compared in vitro ability of electrospun CTS scaffolds crosslinked with genipin (CTS-GP) to those of mineralized CTS-GP scaffolds containing hydroxyapatite (CTS-HA-GP), by assessing proliferation/metabolic activity and alkaline phosphatase (ALP) levels of murine mesenchymal stem cells (mMSCs). The cells' metabolic activity exhibited a biphasic behavior, indicative of initial proliferation followed by subsequent differentiation for all scaffolds. ALP activity of mMSCs, a surrogate measure of osteogenic differentiation, increased over time in culture. After 3 weeks in maintenance medium, ALP activity of mMSCs seeded onto CTS-HA-GP scaffolds was approximately two times higher than that of cells cultured on CTS-GP scaffolds. The mineralized CTS-HA-GP scaffolds were also osseointegrative in vivo, as inferred from the enhanced bone regeneration in a murine model of critical size calvarial defects. Tissue regeneration was evaluated over a 3 month period by microCT and histology (Hematoxylin and Eosin and Masson's Trichrome). Treatment of the lesions with CTS-HA-GP scaffolds induced a 38% increase in the area of de novo generated mineralized tissue area after 3 months, whereas CTS-GP scaffolds only led to a 10% increase. Preseeding with mMSCs significantly enhanced the regenerative capacity of CTS-GP scaffolds (by ?3-fold), to 35% increase in mineralized tissue area after 3 months. CTS-HA-GP scaffolds preseeded with mMSCs yielded 45% new mineralized tissue formation in the defects. We conclude that the presence of HA in the CTS-GP scaffolds significantly enhances their osseointegrative capacity and that mineralized chitosan-based scaffolds crosslinked with genipin may represent a unique biomaterial with possible clinical relevance for the repair of critical calvarial bone defects.

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Properties and Mechanism of Hydroxyapatite Coating Prepared by Electrodeposition on a Braid for Biodegradable Bone Scaffolds.

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