[Preparation, characterization and biological assessment of polycaprolactone/starch composites for bone tissue engineering applications]

Biodegradable polycaprolactone/starch composites can be used for bone tissue engineering applications. The effect of the ratio of components on composite properties is of tremendous importance. Polycaprolactone/starch composite of 80/20 and 70/30 ratios were fabricated by dissolving them in chloroform followed by evaporation of the solvent. The composites were characterized by fourier transform infrared spectroscopy. Their bioactivity was evaluated by studying the apatite formation ability after immersing the specimens in simulated body fluid. The results of compressive test on samples showed that the composite's modulus and strength approximated that of human trabecular bone. Mass loss in distilled water and starch degradation rate in PBS was evaluated, which showed that the starch ratio was effective in composite degradation. MTT analysis and alkaline phosphatase levels showed that this composite had no toxicity and could increase G-299 cell line osteoblastic activities. The increase in cellular osteoblastic activities and the ability for apatite formation on the composite surface, in addition to the polycaprolactone/starch samples' mechanical properties shows their capability to be used as substitutes for bone. Because this composite degradation rate is controlled by changing the starch ratio, it has the potential for use in bone tissue engineering applications. Samples that have a 70/30 ratio are considered optimal due to their enhanced cellular response and better mechanical properties

Synthesis and characterization of fiber reinforced polymer scaffolds based on natural fibers and polymer for bone tissue engineering application

A wide range of materials and scaffolding fabrication methods for bone tissue engineering have been explored recently. Fiber reinforced polymers [FRP] system appears to be a suitable system. By the exclusive use of biocompatible or bio-absorbable polymers and fibers, novel generation of scaffolds for applications in tissue engineering can be prepared. Mulberry Silk as highlighted natural fiber with its specific economic, mechanical and biological properties has been used for fabrication FRP scaffolds. In this study FRP scaffolds prepared by a combination of silk fibroin polymer, which is another configuration of silk fibers as a porous matrix and silk fibers as the reinforcement element. FRP scaffolds have been fabricated by the freeze-drying method. Microstructure has been analyzed by scanning electron microscopy and the results show an integrative structure. Mechanical properties have been evaluated by universal testing machine. Compressive mechanical modules as well as strength of FRP scaffolds increased about three times in magnitude in comparison with pure fibroin scaffolds. FRP scaffolds had a compressive module of -3.6 MPa. Osteoblast viability and attachment on FRP scaffolds were investigated in vitro by MTT assay, which showed no cytotoxic response. Additionally, based on SEM results it is concluded that FRP scaffolds provide a good environment for osteoblast attachment

Fabrication and characterization of regenerated silk/bioglass composites for bone tissue engineering

One of the major issues in bone tissue engineering is the design and fabrication of bioactive, bioresorbable porous 3D scaffolds capable of maintaining their structure and integrity over a predictable period of time. One such approach is the fabrication of composite scaffolds. In this study we present fabrication and characterization of novel silk/bioglasscomposite scaffolds. Regenerated fibroin was constructed from mulberry silk cocoons and calcium silicophosphate bioactive glass was made by sol-gel processing. For fabrication of a homogenous composite, grained bioglass particles were modified with 3- aminopropyltriethoxysilane coating. Fibroin/bioglass composite scaffolds were fabricated by the freeze-dry technique at different concentrations. Silk protein extract was evaluated by FTIR and XRD methods. FTIR spectrum showed sharp amide peaks at 1655 cm-1 and 1530 cm-1 wave lengths, which confirmed the existence of fibroin. XPS analysis demonstrated that the amino groups were established on the surface of the glass powder. The fabricated 3D scaffolds were morphologically analyzed by scanning electron microscopy, which showed uniformly dispersed bioglass particles in all structures. Scaffolds were seeded with human mesenchymal stem cells for 21 days. Considering the cytocompatibility of the scaffolds and osteogenic differentiation during three weeks, it could be concluded that the appropriate combination of structural and biological properties make the silk/bioglass composite scaffold a probable choice for potential use in bone tissue engineering

Study of Collagen Immobilization on a Novel Nanocomposite to Enhance Cell Adhesion and Growth

Surface properties of a biomaterial could be critical in determining biomaterial's biocompatibility due to the fact that the first interactions between the biological environment and artificial materials are most likely occurred at material's surface. In this study, the surface properties of a new nanocomposite [NC] polymeric material were modified by combining plasma treatment and collagen immobilization in order to enhance cell adhesion and growth. Methods: NC films were plasma treated in reactive O[2] plasma at 60 W for 120 s. Afterward, type I collagen was immobilized on the activated NC by a safe, easy, and effective one-step process. The modified surfaces of NC were characterized by water contact angle measurement, water uptake, scanning electron microscopy [SEM], and Fourier transformed infrared spectroscopy in attenuated total reflection mode [ATR-FTIR]. Furthermore, the cellular behaviors of human umbilical vascular endothelial cells [HUVEC] such as attachment, growth and proliferation on the surface of the NC were also evaluated in vitro by optical microscopy and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide test. Results: The outcomes indicated that plasma treatment and collagen immobilization could improve hydrophilicity of NC. SEM micrograph of the grafted film showed a confluent layer of collagen with about 3-5 jum thicknesses. In vitro tests showed that collagen-grafted and plasma-treated surfaces both resulted in higher cell adhesion and growth state compared with untreated ones. Conclusion: Plasma surface modification and collagen immobilization could enhance the attachment and proliferation of HUVEC onto NC, and the method would be usefully applied to enhance its biocompatibility

[Bioactivity enhancement of hydroxyapatite by silicon substitution]

Silicon is an effective element in bone biomineralization; hence Si-substituted hydroxyapatite can be a relevant bioceramic as bone materials substitution. Stoichiometric hydroxyapatite [HA] and Si-substituted hydroxyapatite [Si-HA] with different contents of Si substitution were synthesized successfully by a hydrothermal method using Ca [NO3] 2, [NH4] 3PO4 or [NH4] 2HPO4 and Si [OCH2CH3] 4 [TEOS] as starting materials. Crystalline Phases, chemical composition, microstructure and morphology of synthesized powders were investigated using X-ray diffraction [XRD], Fourier transform IR spectroscopy [FTIR], inductively coupled plasma AES [ICP-AES] and scanning electron microscopy [SEM] techniques. The results proved silicon substitution in hydroxyapatite structure and revealed that the substitution of phosphate groups by silicate groups caused some OH-loss to maintain charge balance and the lattice parameters slightly changed with respect to stoichiometric HA. Si-incorporation reduces the crystallites size of Si-HA and crystallinity, thus the solubility of Si-HA powders increases, and as a result Si-substitution has improved bioactivity behavior of HA. Based on in-vitro tests; soaking and incubating the specimens in simulated body fluid [SBF] and MTT assays [Dimethylthiazol assay], Si-substituted hydroxyapatite is more bioactive than pure hydroxyapatite

Preparation and characterization of hydroxyapatite coating on Ti6Al4V cylinders by combination of alkali-heat treatments and biomimetic method

Biomimetic method was used to apply hydroxyapatite [HA] coating onto Ti6Al4V cylinders. This process is a physicochemical method in which a substrate is soaked in a solution simulating the physiological conditions, for a period of time enough to form a desirable layer of the calcium phosphate on the substrate. In the present study, specimens were soaked in 5, 10 M solutions of NaOH at temperatures of 60 or 80°C for 24 and 72 h. Surface of samples were characterized using scanning electron microscopy [SEM] and thin film X-ray diffraction [TF-XRD]. The optimum condition was found to be 72 h of soaking in 5 M NaOH at 80§C. Specimens treated under these optimum conditions were subsequently heat-treated at 500, 600, and 700°C for 1h in order to consolidate the sodium titanate hydrogel layer. Under the heat treatment condition of 600°C for 1h and subsequent soaking in simulated body fluid [SBF], apatite formed within 3 days. It was observed that, apatite formation increased significantly, which is an indication of the materials ability for use as a load bearing implant