Presence Of Hydroxyapatite Nanoparticles Research Articles

Mechanical properties of (poly(L‐lactide‐co‐glycolide))‐based fibers coated with hydroxyapatite layer

AbstractThis article presents the results of the experimental study on manufacturing and mechanical evaluation of poly(L‐lactide‐co‐glycolide) (PLGA)‐based fibers modified with ceramic nanoparticles. Study was conducted to establish the effect of biomimetic formation of apatite layers on polymeric fibers on their mechanical properties. The tensile tests were performed to determine the influence of polymer crystallinity and the presence of hydroxyapatite nanoparticles (nanoHAp) on mechanical properties of PLGA fibers coated with hydroxyapatite (HAp) layer. HAp deposits on the surfaces of the fibers precipitated from simulated body fluid (SBF). Three types of fibers coated with HAp layers were compared in mechanical tests. The results indicated that by using a biomimetic fiber coating method the mechanical properties of the fibers are affected by their crystallinity. The nanoHAp modified polymer fibers after incubation in SBF were found to have a continuous HAp layer. The layer affected the mechanical behavior (force–strain function) of the fibers from nonlinear to linear, typical of ceramic materials. The tensile modulus of the fibers with a continuous layer was found to increase with the apatite layer thickness, whereas the tensile strength decreases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Fibrous Composites With Anisotropic Distribution of Mechanical Properties After Layer‐by‐Layer Deposition of Aligned Electrospun Fibers

AbstractNanofibers and composite nanofibers have been used as mechanical reinforcement in a bulk matrix, but there is little research done on bulk nanocomposites made out of nanofibers. In the current study, in situ grown composite fibers of poly(DL‐lactide) (PDLLA) and hydroxyapatite (HA) were obtained with uniaxial distribution, which were deposited by layer‐by‐layer with different interlayer angles, and hot‐pressed into fibrous composites with anisotropic distribution of mechanical properties. Composite fibrous mats with the HA loading of 25.2 ± 2.1% and orientation degree of 75.4 ± 3.6% were obtained. Orthogonal experiments design was employed to qualitatively analyze effects of the hot‐pressing parameters on the mechanical properties. The holding temperature, pressure, and duration were optimized as 60 °C, 2 MPa, and 10 min, respectively, to maintain the fibrous structure, strengthen the interfiber bondings, and eliminate the dimensional shrinkage of the hot‐pressed fibrous composites. The ultimate tensile strength along the axial direction was 36.2 ± 2.2 MPa, which was significantly higher than that along the transverse direction. Furthermore, the aligned composite fibers were deposited by layer‐by‐layer with different interlayer angles, and the quantitative equations of the ultimate tensile strength along the axial and transverse directions were drafted as a function of the interlayer deposition angles. The results of cell culture indicated that the presence of HA nanoparticles in the fibrous composites improved the hydrophilicity and provided favorable conditions for cell proliferation and osteogenic differentiation. It is suggested that hot‐pressed fibrous composites with anisotropic distribution of mechanical properties be potential as bone substitutes and repairing devices.

Electrocodeposition of hydroxyapatite nanoparticles with zinc–iron alloys

We report on the preparation of composite films consisting of ultrafine hydroxyapatite (HAp) nanoparticles in a zinc–iron (ZnFe) matrix. The films have been prepared by electrocodeposition from an alkaline electrolyte containing pyrophosphate as complexing agent. The HAp nanoparticles, synthesized by chemical precipitation, feature a needle-like shape with a diameter of ~ 10 nm and a length ~ 100 nm. The effects of a variety of deposition conditions, viz. current density, pH, temperature and composition of the plating bath on the codeposition of HAp nanoparticles with ZnFe-alloys were investigated by evaluating the alloy composition, nanoparticle content, structure and microhardness of the composite coatings. The presence of HAp nanoparticles in the bath was found to increase the iron content in the alloy and decrease the current efficiency of the cathodic deposition. Furthermore, a distinct increase in the Vickers microhardness appeared as a result of the nanoparticle incorporation.

Biomimetic patterning of polymer hydrogels with hydroxyapatite nanoparticles

We report here an in situ process to produce nano-composite polymer hydrogels having surfaces patterned with hydroxyapatite (HA) nanoparticles (100 nm). Poly (vinyl alcohol) (PVA) has been used as a hydrogel forming medium. A three step process, comprising precipitation of HA nanoparticles in presence of PVA molecules and freeze thawing of obtained PVA-HA emulsion, followed by critical point drying, has been devised to produce three dimensional nanocomposite hydrogels. Interaction of Ca 2+ with oxygen atoms of PVA and the hydrogen bonding characteristic of the polymer have been exploited to have controlled size distribution of HA in a continuous and macroporous network of PVA. A systematic variation in the polymer concentration could be correlated with microstructural features of the hydrogel.