The effects of nanostructured hydroxyapatite coating on the biodegradation and cytocompatibility of magnesium implants

Abstract

Magnesium (Mg) alloys, a novel class of degradable, metallic biomaterials, have attracted growing interest as a promising alternative for medical implant and device applications due to their advantageous mechanical and biological properties. Although its biodegradability is an attractive property, rapid degradation of Mg in the physiological environments imposes a major obstacle that limits the translation of Mg-based implants to clinical applications. Therefore, the objective of this study was to develop a nanostructured hydroxyapatite (nHA) coating on polished Mg substrates to mediate the rapid degradation of Mg while improving its integration with bone tissue for orthopedic applications. The nHA coatings were deposited on polished Mg using the patented transonic particle acceleration (Spire Biomedical) process. Surface morphology, elemental compositions, and crystal structures were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction (XRD) analysis, respectively. The degradation of nHA-coated and non-coated Mg samples was investigated by incubating the samples in phosphate buffered saline and revised simulated body fluid, under standard cell culture conditions. Rat bone marrow stromal cells (BMSCs) were harvested and cultured with nHA-coated and non-coated Mg samples to determine cytocompatibility. The degradation results suggested that the nHA coatings decreased Mg degradation. Improved BMSC adhesion was observed on the surfaces of the nHA-coated and non-coated Mg samples, in comparison with the cells on the culture plate surrounding the Mg samples. In conclusion, nHA coatings showed promise for improving the biodegradation and cytocompatibility properties of Mg-based orthopedic implants and should be further studied.

Cardiovascular Applications of Magnesium Alloys

“…With impurities as well as alloying or coating elements, it is important to keep in mind the tolerable upper intake levels of these elements in humans so that improved strength or corrosion resistance does not come at the expense of biocompatibility. Pure Mg alloys for biomedical applications have mostly been replaced by other alloys, though some studies still contain pure magnesium, often as a control [102][103][104][105].…”

Testing the in vitro performance of hydroxyapatite coated magnesium (AZ91D) and titanium concerning cell adhesion and osteogenic differentiation

“…Even if an extended culture period can be achieved and further parameter such as osteogenic induction can be evaluated [9], drawback of this method is the missing evaluation of direct cell-material interactions. A direct cell-material contact was performed in the study by Iskandar et al [41]. They used polished pure (99.9%) Mg that was modified by nanostructured HA via a transonic particle acceleration deposition process.…”

Nanostructured Hydroxyapatite Coating on Bioalloy Substrates: Current Status and Future Directions

“…Using a patented method, which is described as "transonic particle acceleration deposition process" (Spire Biomedical, Inc., Bedford, MA, USA) with pure (99.9%) Mg substrate, 1) the nanoHA coating positively mediated Mg degradation both in phosphate buffered saline (PBS) and revised SBF solutions; and 2) significantly fewer rat bone marrow stromal cells adhered to both coated and uncoated specimens, in comparison to the case for the control (polystyrene cell culture plates) [1]. Each of these results points to the coated Mg specimen having improved properties.…”

“…Desirable properties for a coating on the surface of any biomedical implant include biocompatibility, nontoxicity, high resorption rate, high homogeneity, low porosity, adequate mechanical strength (in particular, high adhesive strength), and ease of deposition on a variety of implant shapes in a conformal manner [1]. In addition, for coatings on orthopaedic implants, such as the femoral stem of a total hip joint replacement (THJR), the coating should be osteoconductive, be osteoinductive, facilitate osseointegration, have excellent facilitation of bone-forming-cell functions (high osteoblast density), promote bone cell adhesion and proliferation, and promote bone mineralization [2][3][4][5].…”

“…There are two focal aspects in the second section, Coating Deposition and Characterization Methods. The first involves steps used in and key process variables of each of the popular deposition methods, such as electrophoretic deposition [15,17,18,[23][24][25][26][27][28] and sol-gel [29,30]; the less popular deposition methods, such as aerosol deposition [31] and radiofrequency magnetron sputtering [32]; and proprietary deposition methods, such as a patented "transonic particle acceleration deposition process" [1]. The second focal aspect involves expositions on the influence of process variables on a large collection of properties of the coating and of the coating-bioalloy substrate system, for a given coating deposition method.…”