Compositionally Modified Hydroxyapatite Nanocrystals for Polymer/Ceramic Scaffold Applications

Abstract

The polymer/bioceramic composite materials attract much attention for the development of bioresorbable implants and tissue engineering scaffolds. Hydroxyapatite (HA) is the most commonly used bioceramic material due to its similarity to the major mineral component of the hard tissue. We synthesized carbonated and Mg-substituted HA nanocrystals with various concentrations of CO32− and Mg2+ ions by chemical precipitation in the range of the process temperatures from 25 °C to 100 °C.The HA nanocrystals were mixed with several polymeric materials (PCL, PLA, PVA, collagen) to fabricate bulk and nanofiber polymer/HA nanoparticle composites with the HA loading up to 80 % by weight. The HA nanocrystals and polymer/HA composites were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron and atomic force microscopy. Mechanical properties of the composites were investigated using nanoindentation technique.

Electrospinning Induced Orientation of Protein Fibrils

“…The scattering-derived average cross-sectional radius of fibrils from composite fibers after removal of PEO was approximately a third of that reported for ovalbumin fibrils 36 and slightly smaller than model determinations of cylindrical radii from randomly aligned insulin fibrils in solution. 57 The broad distribution of observed radii could be ascribed to individual and bundled protein fibrils, as evidenced from TEM micrographs (Figure 4).…”

“…Incorporation of protein fibrils significantly increased elastic moduli of electrospun fibers, making them comparable to or stiffer than fibers composed of other proteins 35,36,38 or synthetic polymers, 41,43,66 as highlighted in Figure 8c. Elastic moduli of the electrospun fibers were also comparable to values for whey protein fibrils, which have an elastic modulus of 1−4 GPa.…”

“…Nanoindentation measurements to identify the elastic moduli of electrospun fibers revealed a dependence on indentation depth (Figure 8a) that is typical for nanoindentation studies of polymeric materials. 36 While it is desirable to utilize depths at which elastic moduli are independent of depth to avoid errors from surface adhesion, such independence was not observed prior to exceeding a depth equivalent to 10% of the fiber diameter. Indentations exceeding 10% of sample thickness are not recommended so as to avoid substrate-related contributions.…”

An electrospun triphasic nanofibrous scaffold for bone tissue engineering

“…Collagen/HA scaffolds prepared with up to 20 wt% HA having a 100-150 nm particle size and 500-700 nm average fiber diameter have previously been reported using a co-electrospinning technique [25]. Recently, we have used sol-gel methods to incorporate nano-HA particles (15-80 nm particle size) into the solution mixture for coelectrospinning [26]. In this study, we report on triphasic fibrous nanocomposite scaffolds with average fiber diameter below 200 nm.…”

“…In a previous FTIR study comparing 'bulk' collagen with electrospun collagen scaffolds, Stanishevsky et al [36] reported a shift to lower wavenumbers in electrospun collagen of the major peak in the amide I band from 1667 cm −1 (fibers) to 1642 cm −1 (bulk), as well as the peak of amide II band from 1574 cm −1 (fibers) to 1544 cm −1 (bulk). We also observe similar amide I and amide II peak shifts for our collagen/HA and triphasic scaffolds.…”