Electrospinning of Liquefied Banana Stem Residue in Conjugation with Hydroxyapatite Nanocrystals: Towards New Scaffolds for Bone Tissue Engineering

Electrospun fibers have high structural similarity to the extracellular matrix (ECM) of natural bone. Some researchers have tried to fabricate cellulose nanofibers using electrospinning method, although the fabricated fibers usually exhibited a non-uniform texture. Moreover, the fabricated mats always suffer from low biological, mechanical and structural properties. Thus, the objective of this study was first to produce a naturally occurring cellulose from banana pseudo-stem through the combination of liquefaction and bleaching processes. The native cellulose was then tried to electrospun in order to determine how a systematic approach based on a Taguchi L9 orthogonal array can be used to fabricate a defect-free fibrous mat. Finally, the electrospun cellulose mats incorporated with hydroxyapatite (HA) nanoparticles were fabricated to generate a new fibrous nanocomposite with enhanced biological and mechanical characteristics. The results revealed that among the electrospinning parameters, cellulose concentration of solution and applied voltage had the greatest effect on the morphology of the fibers. The morphological characterization of the fibrous nanocomposites showed that fibrous cellulose/HA mats had a uniform fiber texture without any significant bead, splashing or particle agglomeration. According to the mechanical tests, the samples containing the higher concentration of HA had a significantly higher elastic modulus and tensile strength. The results obtained from bioactivity analysis indicated an interesting morphological transformation into a flake-like structure which confirmed the high bioactivity of the scaffolds. Accordingly, encapsulation of HA nanoparticles inside the cellulose in the fibrous form can be promising for bone regeneration applications.

PMMA Bone Cements Modified with Silane-Treated and PMMA-Grafted Hydroxyapatite Nanocrystals: Preparation and Characterization

In this study, vinyltrimethoxysilane-treated hydroxyapatite (vHAP) and PMMA-grafted HAP (gHAP) were successfully prepared from original HAP (oHAP). Three kinds of HAP (oHAP, vHAP and g HAP) were used as additives for the preparation of three groups of HAP-modified PMMA bone cements (oHAP-BC, vHAP-BC and gHAP-BC). The setting, bending and compression properties of the bone cements were conducted according to ISO 5833:2002. The obtained results showed that the maximum temperature while curing the HAP-modified bone cements (HAP-BCs) decreased from 64.9 to 60.8 °C and the setting time increased from 8.1 to 14.0 min, respectively, with increasing HAP loading from 0 to 15 wt.%. The vHAP-BC and gHAP-BC groups exhibited higher mechanical properties than the required values in ISO 5833. Electron microscopy images showed that the vHAP and gHAP nanoparticles were dispersed better in the polymerized PMMA matrix than the oHAP nanoparticles. FTIR analysis indicated the polar interaction between the PO4 groups of the HAP nanoparticles and the ester groups of the polymerized PMMA matrix. Thermal gravimetric analysis indicated that mixtures of ZrO2/HAPs were not able to significantly improve the thermal stability of the HAP-BCs. DSC diagrams showed that the incorporation of gHAP to PMMA bone cement with loadings lower than 10 wt.% can increase Tg by about 2.4 °C.

Hydroxyapatite-poly(d,l-lactide) Nanografts. Synthesis and Characterization as Bone Cement Additives

This paper reports the creation of hydroxyapatite/polyester nanografts by “graft-from” polymerization of d,l-lactide with [Ca5(OH)(PO4)3]2 as the initiator and tin(II)-2-ethylhexanoate as the catalyst. Model polymerizations were performed with cyclooctanol as initiator to confirm the grafting on the surface of the hydroxyapatite nanocrystals. Polymers with the highest molecular mass (Mn) between 4250 Da (cyclooctanol) and 6100 Da (hydroxyapatite) were produced. In both cases the molecular mass distributions of the polymers formed were monomodal. The materials obtained were characterized by size-exclusion chromatography, NMR and FT-IR spectroscopy, and thermal methods. Their suitability as additives for commercial bone cement (Simplex P Speedset, Stryker Orthopaedics) has been confirmed by thermal analysis techniques and mechanical testing. The results obtained show that addition of the hydroxyapatite/ polyester nanografts improved both thermal and mechanical properties of the bone cement.

Rapid Collagen-Directed Mineralization of Calcium Fluoride Nanocrystals with Periodically Patterned Nanostructure

Collagen fibrils present periodic structures, which provide space for intrafibrillar growth of oriented hydroxyapatite nanocrystals in bone and contribute to the good mechanical properties of bone. However, there are not...

Growth of mineralized collagen films by oriented calcium fluoride nanocrystals assembly with enhanced cell proliferation

Bone is a highly calcified tissue with 60 wt% inorganic components. It is made up of mineralized collagen fibrils, where the platelet-like hydroxyapatite nanocrystals orientally deposit within collagen fibrils. Inspired...

Introductory of Scherrer’s Equation in Laminated Plate-Shaped Hexagonal Hydroxyapatite Nanocrystals System

Since, hydroxyapatite (HAP) crystal system is hexagonal and its crystalline size in the longitudinal directions of various (a,b,c) axes, which are depending on the thickness of the laminated plate-shaped HAP crystals. Hence, by applying of Scherrer’s equation D100 = Kλ / (β cos ) we calculated their crystallite size as perpendicular to the (100) plane as well as to comparing the thickness of synthesized needle or laminated thin plate shaped HAP nanocrystals of CALPHOS or CONTROL and SUC or Suc-20 samples under hydrothermal condition via organically modified apatite based octacalcium phosphate (OCP) at 180 for 3h. The pH of solution adjusted to 5.5 with incorporating dicarboxylate or succinate ions having Ca/P molar ratio is expected to be 1.56±0.02, where the morphology of OCP are retained. During incorporating of succinate ions in OCP crystals, the hydrogen phosphate (HPO42-) ions in the hydrated layers of OCP are being substituted by succinate ions. These organically modified OCP which generated to HAP with unique nanocrystallite structure have been characterized by using of SEM, FTIR and X-ray diffraction analysis.