In vitro cytotoxicity of binary TI alloys for bone implants

Interest in using titanium (Ti) alloys as load-bearing implant materials has increased due to their high strength to weight ratio, lower elastic modulus, and superior biocompatibility and enhanced corrosion resistance compared to conventional metals such as stainless steel and Co-Cr alloys. In the present study, the in vitro cytotoxicity of five binary titanium alloys, Ti15Ta, Ti15Nb, Ti15Zr, Ti15Sn and Ti15Mo, was assessed using human osteosarcoma cell line, SaOS-2 cells. The Cell proliferation and viability were determined, and cell adhesion and morphology on the surfaces of the binary Ti alloys after cell culture were observed by SEM. Results indicated that the Ti binary alloys of Ti15Ta, Ti15Nb and Ti15Zr exhibited the same level of excellent biocompatibility; Ti15Sn alloy exhibited a moderate biocompatibility while Ti15Mo alloy exhibited a moderate cytotoxicity. The SaOS-2 osteoblast-like cells had flattened and spread across the surfaces of the Ti15Ta, Ti15Nb, Ti15Zr and Ti15Sn groups; however, the cell shapes on the Ti15Mo alloy was shrinking and unhealthy. These results indicated that the Mo contents should be limited to a certain level in the design and development of new Ti alloys for implant material applications.

Ti6Ta4Sn alloy and subsequent scaffolding for bone tissue engineering

Porous titanium (Ti) and titanium alloys are promising scaffold biomaterials for bone tissue engineering, because they have the potential to provide new bone tissue ingrowth abilities and low elastic modulus to match that of
natural bone. In the present study, a new highly porous Ti6Ta4Sn alloy scaffold with the addition of biocompatible alloying elements (tantalum (Ta) and tin (Sn)) was prepared using a space-holder sintering method. The
strength of the Ti6Ta4Sn scaffold with a porosity of 75% was found to be significantly higher than that of a pure Ti scaffold with the same porosity. The elastic modulus of the porous alloy can be customized to match that of
human bone by adjusting its porosity. In addition, the porous Ti6Ta4Sn alloy exhibited an interconnected porous structure, which enabled the ingrowth of new bone tissues. Cell culture results revealed that human SaOS₂
osteoblast-like cells grew and spread well on the surfaces of the solid alloy, and throughout the porous scaffold. The surface roughness of the alloy showed a significant effect on the cell behavior, and the optimum surface
roughness range for the adhesion of the SaOS2 cell on the alloy was 0.15 to 0.35 mm. The present study illustrated the feasibility of using the porous Ti6Ta4Sn alloy scaffold as an orthopedic implant material with a special
emphasis on its excellent biomechanical properties and in vitro biocompatibility with a high preference by osteoblast-like cells.

Bioactive hydroxyapatite coating on titanium-niobium alloy through a sol-gel process

Hydroxyapatite (HA) was coated on the surface of a titanium-niobium (Ti-Nb) alloy by a sol-gel process. Triethyl phosphite and calcium nitrate were used as the phosphorus (P) and calcium (Ca) precursors respectively to prepare a Ca/P sol solution. The Ti-Nb alloy was dip-coated in the sol and heated at 600°C for 30 minutes. X-ray diffraction (XRD) analysis indicated the major phase constituent of the coating after heat treatment was HA. Scanning electron microscopy (SEM) observation showed that a few cracks were distributed on the HA coating. The in-vitro bioactivity of the HA coated Ti-Nb alloy was assessed using a cell culture of SaOS-2 osteoblast-like cells. The density of cell attachment was determined by MTT assay; the cell morphology was observed by SEM. Results indicated that the density of cell attachment on the surface of the Ti-Nb alloy was significantly increased by HA coating. Cell morphology observation showed that cells attached, spread and grew well on the HA coated surface. It can be concluded that the HA coating improved the in-vitro bioactivity of Ti-Nb alloy effectively.

Biomimetic modification of porous TiNbZr alloy scaffold for bone tissue engineering

Porous titanium (Ti) and Ti alloys are important scaffold materials for bone tissue engineering. In the present study, a new type of porous Ti alloy scaffold with biocompatible alloying elements, that is, niobium (Nb) and zirconium (Zr), was prepared by a space-holder sintering method. This porous TiNbZr scaffold with a porosity of 69% exhibits a mechanical strength of 67MPa and an elastic modulus of 3.9GPa, resembling the mechanical properties of cortical bone. To improve the osteoconductivity, a calcium phosphate (Ca/P) coating was applied to the surface of the scaffold using a biomimetic method. The biocompatibility of the porous TiNbZr alloy scaffold before and after the biomimetic modification was assessed using the SaOS2 osteoblast–like cells. Cell culture results indicated that the porous TiNbZr scaffold is more favorable for cell adhesion and proliferation than its solid counterpart. By applying a Ca/P coating, the cell proliferation rate on the Ca/P-coated scaffold was significantly improved. The results suggest that high-strength porous TiNbZr scaffolds with an appropriate osteoconductive coating could be potentially used for bone tissue engineering application.

Lactoferrin and cancer in different cancer models

Lactoferrin (Lf) is a multifunctional protein and an essential element of innate immunity. Cancer is a major killer in today's world accounting for around 13% of all deaths according to the World Health Organisation (W.H.O.). The five most common forms of cancer include lung, colorectal, stomach, liver and breast cancer. Lactoferrin is a natural forming iron-binding glycoprotein with antibacterial, antioxidant and anti-carcinogenic effects. It is produced in exocrine glands and is secreted in many external fluids as a first line of defence. Lactoferrin also has the capacity to induce apoptosis and inhibit proliferation in cancer cells as well as restore white and red blood cell levels after chemotherapy. This review focuses on the therapeutic effect bovine sourced lactoferrin has on various forms of cancer in various models. It also focuses on the benefits of 3D in vitro cell culture. 3D cell culture has vast advantages over 2D models including demonstration of realistic therapeutic results and heightened resistance that 2D models fail to display.

Three-dimensional tissue scaffolds from interbonded poly(e-caprolactone) fibrous matrices with controlled porosity

In this article, we report on the preparation and cell culture performance of a novel fibrous matrix that has an interbonded fiber architecture, excellent pore interconnectivity, and controlled pore size and porosity. The fibrous matrices were prepared by combining melt-bonding of short synthetic fibers with a template leaching technique. The microcomputed tomography and scanning electron microscopy imaging verified that the fibers in the matrix were highly bonded, forming unique isotropic pore architectures. The average pore size and porosity of the fibrous matrices were controlled by the fiber/template ratio. The matrices having the average pore size of 120, 207, 813, and 994 mm, with the respective porosity of 73%, 88%, 96%, and 97%, were investigated. The applicability of the matrix as a three-dimensional (3D) tissue scaffold for cell culture was demonstrated with two cell lines, rat skin fibroblast and Chinese hamster ovary, and the influences of the matrix porosity and surface area on the cell culture performance were examined. Both cell lines grew successfully in the matrices, but they showed different preferences in pore size and porosity. Compared with two-dimensional tissue culture plates, the cell number on 3D fibrous matrices was increased by 97.27% for the Chinese hamster ovary cells and 49.46% for the fibroblasts after 21 days of culture. The fibroblasts in the matrices not only grew along the fiber surface but also bridged among the fibers, which was much different from those on two-dimensional scaffolds. Such an interbonded fibrous matrix may be useful for developing new fiber-based 3D tissue scaffolds for various cell culture applications.

In vitro studies of cells grown on the superconductor PrOxFeAs

The recent discovery of arsenic-based high temperature superconductors has reignited interest in the study of superconductor: biological interfaces. However, the new superconductor materials involve the chemistry of arsenic and their toxicity remains unclear [Hand, E., 2008. Nature 452 (24), 922]. In this study the possible adverse effects of this new family of superconductors on cells have been examined. Cell culture studies in conjunction with microscopy and viability assays were employed to examine the influence of arsenic-based superconductor PrO_xFeAs (x = 0.75) material in vitro. Imaging data revealed that cells were well adhered and spread on the surface of the superconductor. Furthermore, cytotoxicity studies showed that cells were unaffected during the time-course of the experiments, providing support for the biocompatibility aspects of PrO_xFeAs-based superconductor material.

In vitro behavior of human osteoblast-like cells (SaOS2) cultured on surface modified titanium and titanium–zirconium alloy

In this study, titanium (Ti) and titanium-zirconium (TiZr) alloy samples fabricated through powder metallurgy were surface modified by alkali-heat treatment and calcium (Ca)-ion-deposition. The alteration of the surface morphology and the chemistry of the Ti and TiZr after surface modification were examined. The bioactivity of the Ti and TiZr alloys after the surface modification was demonstrated. Subsequently, the cytocompatibility of the surface modified Ti and TiZr was evaluated via in vitro cell culture using human osteoblast-like cells (SaOS2). The cellular attachment, adhesion and proliferation after cell culture for 14 days were characterized by scanning electron microscopy (SEM) and MTT assay. The relationship between surface morphology and chemical composition of the surface modified Ti and TiZr and cellular responses was investigated. Results indicated that the surface-modified Ti and TiZr alloys exhibited excellent in vitro cytocompatibility together with satisfactory bioactivity. Since osteoblast adhesion and proliferation are essential prerequisites for a successful implant in vivo, these results provide evidence that Ti and TiZr alloys after appropriate surface modification are promising biomaterials for hard tissue replacement.

8-modified-2'-deoxyadenosine analogues induce delayed polymerization arrest during HIV-1 reverse transcription

The occurrence of resistant viruses to any of the anti-HIV-1 compounds used in the current therapies against AIDS underlies the urge for the development of new drug targets and/or new drugs acting through novel mechanisms. While all anti-HIV-1 nucleoside analogues in clinical use and in clinical trials rely on ribose modifications for activity, we designed nucleosides with a natural deoxyribose moiety and modifications of position 8 of the adenine base. Such modifications might induce a steric clash with helix αH in the thumb domain of the p66 subunit of HIV-1 RT at a distance from the catalytic site, causing delayed chain termination. Eleven new 2′-deoxyadenosine analogues modified on position 8 of the purine base were synthesized and tested in vitro and in cell-based assays. In this paper we demonstrate for the first time that chemical modifications on position 8 of 2′-deoxyadenosine induce delayed chain termination in vitro, and also inhibit DNA synthesis when incorporated in a DNA template strand. Furthermore, one of them had moderate anti-HIV-1 activity in cell-culture. Our results constitute a proof of concept indicating that modification on the base moiety of nucleosides can induce delayed polymerization arrest and inhibit HIV-1 replication.

Enzyme-assisted self-assembly under thermodynamic control

The production of functional molecular architectures through self-assembly is commonplace in biology, but despite advances^{1, 2, 3}, it is still a major challenge to achieve similar complexity in the laboratory. Self-assembled structures that are reproducible and virtually defect free are of interest for applications in three-dimensional cell culture^{4, 5}, templating⁶, biosensing⁷ and supramolecular electronics⁸. Here, we report the use of reversible enzyme-catalysed reactions to drive self-assembly. In this approach, the self-assembly of aromatic short peptide derivatives^{9, 10} provides a driving force that enables a protease enzyme to produce building blocks in a reversible and spatially confined manner. We demonstrate that this system combines three features: (i) self-correction—fully reversible self-assembly under thermodynamic control; (ii) component-selection—the ability to amplify the most stable molecular self-assembly structures in dynamic combinatorial libraries^{11, 12, 13}; and (iii) spatiotemporal confinement of nucleation and structure growth. Enzyme-assisted self-assembly therefore provides control in bottom-up fabrication of nanomaterials that could ultimately lead to functional nanostructures with enhanced complexities and fewer defects.

On corrosion behaviour of magnesium alloy AZ31 in simulated body fluids and influence of ionic liquid pretreatments

This paper reports on the corrosion of Mg alloy AZ31 in simulated body fluid (SBF) using static immersion tests and electrochemical impedance spectroscopy. A preliminary study on the effect of flowing SBF on the corrosion behaviour of AZ31 has also been carried out. Low toxicity ionic liquids (ILs) trimethyl(butyl)phosphonium diphenyl phosphate P1444DPP and trihexyl(tetradecyl)-phosphonium bis-2,4,4trimethylpentyl-phosphinate [P66614][ i(C8) 2PO2] have been used to provide corrosion protection for AZ31 in SBF. Time dependent immersion tests indicate that under static conditions, AZ31 suffers severe localised corrosion in SBF, with pits developing predominantly beside the Al-Mn intermetallic phase in the α matrix. At longer immersion times, the corrosion product eventually precipitates and covers the entire specimen surface. When exposed to SBF under flowing conditions with a shear stress of 0·88 Pa, more uniform corrosion was observed. The optical profilometry results and electrochemical impedance spectroscopy analysis suggest that both P
1444DPP and [P66614][i(C8)2PO2] pretreatments can increase the corrosion resistance of AZ31 in SBF, in particular by decreasing the number of deeper pits found on the alloy surface. Cytotoxic test shows that the presence of the ILs P
1444DPP and [P66614][i(C8)2PO2] in cell culture media slightly inhibits the growth of human coronary artery endothelial cells in comparison with the good cell viability around the treated specimen. A pretreatment with IL is used in order to improve the corrosion resistance of this alloy in SBF. © 2012 Institute of Materials, Minerals and Mining.

An impaired mitochondrial electron transport chain increases retention of the hypoxia imaging agent diacetylbis(4-methylthiosemicarbazonato)copper II

Radiolabeled diacetylbis(4-methylthiosemicarbazonato)copper^II [Cu^II(atsm)] is an effective positron-emission tomography imaging agent for myocardial ischemia, hypoxic tumors, and brain disorders with regionalized oxidative stress, such as mitochondrial myopathy, encephalopathy, and lactic acidosis with stroke-like episodes (MELAS) and Parkinson’s disease. An excessively elevated reductive state is common to these conditions and has been proposed as an important mechanism affecting cellular retention of Cu from Cu^II(atsm). However, data from whole-cell models to demonstrate this mechanism have not yet been provided. The present study used a unique cell culture model, mitochondrial xenocybrids, to provide whole-cell mechanistic data on cellular retention of Cu from Cu^II(atsm). Genetic incompatibility between nuclear and mitochondrial encoded subunits of the mitochondrial electron transport chain (ETC) in xenocybrid cells compromises normal function of the ETC. As a consequence of this impairment to the ETC we show xenocybrid cells upregulate glycolytic ATP production and accumulate NADH. Compared to control cells the xenocybrid cells retained more Cu after being treated with Cu^II(atsm). By transfecting the cells with a metal-responsive element reporter construct the increase in Cu retention was shown to involve a Cu^II(atsm)-induced increase in intracellular bioavailable Cu specifically within the xenocybrid cells. Parallel experiments using cells grown under hypoxic conditions confirmed that a compromised ETC and elevated NADH levels contribute to increased cellular retention of Cu from CuII(atsm). Using these cell culture models our data demonstrate that compromised ETC function, due to the absence of O2 as the terminal electron acceptor or dysfunction of individual components of the ETC, is an important determinant in driving the intracellular dissociation of Cu^II(atsm) that increases cellular retention of the Cu.

A controllable simple method for production of polymeric nanofiberous composite via single nozzle jet electrospinning

A special Micro-Nano fiberous composite structure composed of nano- and micro-scale fiber of Polycaprolactone (PCL) and Gelatin produced by using single nozzle electrospinning instrument. By controlling the solution (polymer concentration and polymer composition percent) and processing parameters of electrospinning (feed rate and electrostatic field), different portion of nano and micro fibers in the structure is achieved. This method can result a one-stage method of fabrication of Micro-Nano fiberous composite structure instead of previously used twostage process or using additional facility to produce structure near-similar to this composite structure. The resulting materials finely mingle nano- and micro fibers together, rather than simply juxtaposing them, as is commonly found in the literature. The results obtained from SEM, Flow Porosimetry, and DMA led the authors to confirm that the structure has very versatile and improved properties for many applications like cell culture scaffolds. These favourable mechanical and structural properties can provide easier opening of spaces for cell penetration to deeper levels of the scaffold and withstand to tensions during to clinical handling.

Carbon Nanotube Biofiber Formation in a Polymer-Free Coagulation Bath

A novel solution spinning method to produce highly conducting carbon nanotube (CNT) biofibers is reported. In this process, carbon nanotubes are dispersed using biomolecules such as hyaluronic acid, chitosan, and DNA, and these dispersions are used as spinning solutions. Unlike previous reports in which a polymer binder is used in the coagulation bath, these dispersions can be converted into fibers simply by altering the nature of the coagulation bath via pH control, use of a crosslinking agent, or use of a biomolecule-precipitating solvent system. With strength comparable to most reported CNT fibers to date, these CNT biofibers demonstrate superior electrical conductivities. Cell culture experiments are performed to investigate the cytotoxicity of these fibers. This novel fiber spinning approach could simplify methodologies for creating electrically conducting and biocompatible platforms for a variety of biomedical applications, particularly in those systems where the application of an electrical field is advantageous?for example, in directed nerve and/or muscle repair.