Abstract
Due to its excellent bone-like mechanical properties and non-toxicity, magnesium (Mg) and its alloys have attracted great interest as biomaterials for orthopaedic applications. However, their fast degradation rate in physiological environments leads to an acute inflammatory response, restricting their use as biodegradable metallic implants. Endowing Mg-based biomaterials with immunomodulatory properties can help trigger a desired immune response capable of supporting a favorable healing process. In this study, electrospun poly(ε-caprolactone) (PCL) fibers loaded with coumarin (CM) and/or zinc oxide nanoparticles (ZnO) were used to coat the commercial AZ31 Mg alloy as single and combined formulas, and their effects on the macrophage inflammatory response and osteoclastogenic process were investigated by indirect contact studies. Likewise, the capacity of the analyzed samples to generate reactive oxygen species (ROS) has been investigated. The data obtained by attenuated total reflection Fourier-transform infrared (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) analyses indicate that AZ31 alloy was perfectly coated with the PCL fibers loaded with CM and ZnO, which had an important influence on tuning the release of the active ingredient. Furthermore, in terms of degradation in phosphate-buffered saline (PBS) solution, the PCL-ZnO- and secondary PCL-CM-ZnO-coated samples exhibited the best corrosion behaviour. The in vitro results showed the PCL-CM-ZnO and, to a lower extent, PCL-ZnO coated sample exhibited the best behaviour in terms of inflammatory response and receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated differentiation of RAW 264.7 macrophages into osteoclasts. Altogether, the results obtained suggest that the coating of Mg alloys with fibrous PCL containing CM and/or ZnO can constitute a feasible strategy for biomedical applications.
Highlights
Mg and its alloys have gained more and more attention as potential candidates for orthopaedic applications due to their good biodegradability, biocompatibility and favourable mechanical properties [1,2,3]
FTIT-ATR technique is used to point out the presence of different functional groups which can be found in PCL, CM or zinc oxide nanoparticles (ZnO), components that were used to coat the Mg alloy
The results showed that the Mg-PCL-CM sample released 15 μg mL−1 as compared with 26 μg mL−1 released from the Mg-PCL-CM-ZnO sample, which highlights the possibility of tailoring the CM release
Summary
Mg and its alloys have gained more and more attention as potential candidates for orthopaedic applications due to their good biodegradability, biocompatibility and favourable mechanical properties [1,2,3]. The M2d macrophage subset, known as tumor associated macrophages (TAM), is capable of secreting the vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP), molecules essential in new blood vessel formation and tissue remodelling during the bone repair process [30]. In terms of implantable devices, the presence of the anti-inflammatory mediators and the response following tissue remodeling, aids the vascularization process of the biomaterial through the suppression of the fibrous encapsulation [31]. Due to their involvement in the immune response modulation, the M2 macrophage prove their important role in tissue repair and bone remodelling process. A favourable macrophage phenotype switch can lead to an effective bone tissue regeneration
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