Abstract
Magnetic nanofibrous scaffolds of poly(caprolactone) (PCL) incorporating magnetic nanoparticles (MNP) were produced, and their effects on physico-chemical, mechanical and biological properties were extensively addressed to find efficacy for bone regeneration purpose. MNPs 12 nm in diameter were citrated and evenly distributed in PCL solutions up to 20% and then were electrospun into nonwoven nanofibrous webs. Incorporation of MNPs greatly improved the hydrophilicity of the nanofibers. Tensile mechanical properties of the nanofibers (tensile strength, yield strength, elastic modulus and elongation) were significantly enhanced with the addition of MNPs up to 15%. In particular, the tensile strength increase was as high as ∼25 MPa at 15% MNPs vs. ∼10 MPa in pure PCL. PCL-MNP nanofibers exhibited magnetic behaviors, with a high saturation point and hysteresis loop area, which increased gradually with MNP content. The incorporation of MNPs substantially increased the degradation of the nanofibers, with a weight loss of ∼20% in pure PCL, ∼45% in 10% MNPs and ∼60% in 20% MNPs. Apatite forming ability of the nanofibers tested in vitro in simulated body fluid confirmed the substantial improvement gained by the addition of MNPs. Osteoblastic cells favored the MNPs-incorporated nanofibers with significantly improved initial cell adhesion and subsequent penetration through the nanofibers, compared to pure PCL. Alkaline phosphatase activity and expression of genes associated with bone (collagen I, osteopontin and bone sialoprotein) were significantly up-regulated in cells cultured on PCL-MNP nanofibers than those on pure PCL. PCL-MNP nanofibers subcutaneously implanted in rats exhibited minimal adverse tissue reactions, while inducing substantial neoblood vessel formation, which however, greatly limited in pure PCL. In vivo study in radial segmental defects also signified the bone regeneration ability of the PCL-MNP nanofibrous scaffolds. The magnetic, bone-bioactive, mechanical, cellular and tissue attributes of MNP-incorporated PCL nanofibers make them promising candidate scaffolds for bone regeneration.
Highlights
Scaffolds for tissue engineering play important roles in providing sites for anchorage of stem/progenitor cells and their self-renewal and possible lineage specific differentiation [1,2,3]
magnetic nanoparticles (MNP) produced by the citric acid functionalization were characterized (Fig. 1)
The average diameter of MNPs was determined from the X-ray diffraction (XRD) pattern according to Scherrer’s equation: D = kl/b cosh [30], where l is X-ray wavelength of Cu Ka radiation 1.54 Au, k is the shape factor that can be assigned a value of 0.89 if the shape is unknown, h is Bragg angle, and b is the full width at half maximum in radians
Summary
Scaffolds for tissue engineering play important roles in providing sites for anchorage of stem/progenitor cells and their self-renewal and possible lineage specific differentiation [1,2,3]. Designing magnetic scaffolds has been proposed for the regeneration and repair of tissues in damage and disease [10,11,12,13,14,15]. Scaffolds coated with magnetic NPs (MNPs) more avidly attract growth factors and other biomolecules in vitro [10,11,12,13,14,15]. The incorporation of MNPs into scaffolds is believed to increase the rate of bone cell growth and differentiation due to the bone tissue ability to recognize the mechano-electrical conversion (i.e., mechanical stress converted from or into a magnetism-induced voltage) leading to an increased cellular proliferation and expression levels of multiple genes related with bone differentiation [16,17]
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