Preparation of DNA–cyclodextrin–silica composite by sol–gel method and its utilization as an environmental material

A DNA–cyclodextrin–silica composite was prepared by the sol–gel method. This composite possessed the bi-functions of double-stranded DNA, such as intercalation into DNA, and cyclodextrin, such as inclusion into its intramolecular cavity. Therefore, we demonstrated the accumulation of harmful compounds from an aqueous multi-component solution using a DNA–cyclodextrin–silica composite column. As a result, the DNA–cyclodextrin–silica composite column can effectively accumulate not only planar structure-containing harmful compounds, such as dioxin and polychlorobiphenyl (PCB) derivatives, but also non-planar structure containing compounds, such as bisphenol A and diethylstilbestrol, from an aqueous multi-component solution. The accumulated amount of these harmful compounds was more than 90%. Additionally, the DNA–cyclodextrin–silica composite column was recycled by the application of methanol. Therefore, the DNA–cyclodextrin–silica composite may have the potential to be used as an environmental material for the accumulation of harmful compounds from industrial or experimental waste.     

Implant surface features as key role on cell behavior

It has been recognized that physical and chemical properties of biomaterial surfaces mediate the quality of extracellular matrix (ECM) that may affect cell behaviors. In nature, ECM is a heterogeneous three-dimensional superstructure formed by three major components, glycosaminoglycan, glycoconjugate, and protein, that anchors cellular compartments in tissues and regulates the function and the behavior of cells. Changes in the biointerface alter the quality of ECM and morphology through cell surface receptors, which, in turn, enable it to trigger specific cell signaling and different cellular responses. In fact, a number of strategies have been used to improve the functionality of surfaces and direct cell behavior through precisely designed environments. Herein, we aimed to discuss, through a science-based viewpoint, the biomaterial surface features on cell behavior and analyze the impact of cell physical modification on dental implant development.     

Green synthesis of silver nanoparticles using Beta vulgaris: Role of process conditions on size distribution and surface structure

The present work reports the green synthesis of silver nanoparticles, using Beta vulgaris peel extract with a subsequent investigation on the size distribution and surface structure of nanoparticles formed under various process conditions. The green-chemical reduction mechanism of silver ions to nanoparticles by the active organic functional groups present in the extract was characterized, using the respective spectroscopic techniques. The effects of various process parameters, including induced intraparticle ripening, were attributed to the controlled formation of anisotropic silver nanoparticles within the supporting matrix of the extract. The plasmon absorption and resonance scattering properties were expected to be favourable for small and larger size nanoparticles (below 25 nm and above 75 nm) respectively, which was considered to be an indicative aspect for synthesizing nanoparticles of narrow size distribution. The zeta potential and dynamic light scattering (DLS) results suggest the good stability and mono-dispersed size distribution of the silver nanoparticles. The transmission electron microscope, selective area electron diffraction (SAED) and X-ray diffraction studies infer that the nanoparticles formed were spherical/quasi-spherical in shape, which primarily exhibited a face centred cubic crystal (FCC) structure. The green-chemical reduction of organic phases in the extract (especially amine (NH₂) groups) as reflected through shifts observed in the Fourier-transform infra red (FTIR) peaks, reveal the possible interaction of the organic molecules with the silver ions in the effective formation, surface modification and stabilization of the silver nanoparticles.     

Heavy metal ions retention by bi-functionalized lignin: Synthesis,applications, and adsorption mechanisms

Bi-functionalized lignin with amino and sulfonic groups (ASL) was synthesized via Mannich reaction and sulfomethylation. It was systematically characterized by FT-IR, element analysis, surface charge and XPS. Effects of initial pH, contact time and initial metal ion concentration on the adsorption of Cu(II) and Pb(II) onto ALS were studied. Results indicated that the biosorbent showed excellent performance for metals even from low pH solutions. The adsorption kinetics and isotherms could be described well with Pseudo-second-order and D–R model, respectively. Further investigation of the metal-loaded ASL by FT-IR and XPS elucidated the amino and sulfonic groups reacted with metals in different way.     

External stimulus-responsive biomaterials designed for the culture and differentiation of ES,iPS, and adult stem cells

The physical and chemical characteristics of biomaterial surface and hydrogels can be altered by external stimuli, such as light irradiation, temperature changes, pH shifts, shear stress forces, electrical forces, and the addition of small chemical molecules. Such external stimulus-responsive biomaterials represent promising candidates that have been developed for the culture and differentiation of embryonic stem (ES) cells, induced pluripotent stem (iPS) cells, and adult stem cells. Biomaterials that are designed to respond in a reversible manner to specific external signals can be formed on micropatterned or non-micropatterned surface, in hydrogels, or on microcarriers. Stem cells and the cells differentiated from them into specific tissue lineages can be cultured and/or differentiated on dishes with immobilized external stimulus-responsive polymers. Cells can be detached from these dishes without using an enzymatic digestion method or a mechanical method when the appropriate external stimulus is generated on the surface. This review discusses the polymers and polymeric designs employed to produce surface and hydrogels for stem cell culture, differentiation, and/or cell detachment using various external stimuli.     

Preparation and characterization of zinc modified calcium silicate/polycaprolactone with graphene oxide composite coating for bone repair applications

The goal of biomaterial interest is the ease of the bone tissue regeneration process or the replacement of damaged bone and other tissues with recently generated bone tissue. Calcium silicate (CaSi) bioceramic is a vital material for bone tissue engineering, predominantly for bone repair. Though, the low toughness of calcium silicate imitates its load-bearing applications. The electrophoretic deposition technique was used to coat various concentrations of Zn²⁺ substituted CaSi on TNT. In this work, a novel as-obtained an appropriate orthopedic implant hybrid material by charged calcium ions of mineralized calcium silicate united with PCL-negatively charged graphene oxide [Zn-CaSi (S₁-S₃)/PCL (P₁-P₃)/GO]. Hence, the effectively as-obtained [Zn-CaSi (S₁-S₃)/PCL (P₁-P₃)/GO] bone-like apatite on the ternary composite coatings on the surface was proven via XRD, FT-IR, FESEM with EDAX spectra, HR-TEM and BET analyses etc., Moreover, the TNT/S₂/P₂@GO ternary composite coatings exhibit better mechanical properties and antibacterial activity. The metal ions released from the coatings were calculated via ICP-AES studies. Moreover, the cell viability and also the live/dead staining of MG63 human osteoblasts cells on the subsequent composite coating material for better cell growth in orthopedic applications.     

In situ tensile deformation of zein films with plasticizers and filler materials

Material deformation is a dynamic process. Visualisation of this deformation can help to understand the local deformation and fracture behaviour. Zein (the prolamin protein from maize) films with different amount of plasticizers (0–25%) and different filler materials (maize oil, Dimodan^®, Vestosint^®, at 25% (w/w) to protein) were deformed under tension and observed at micron scale in real time by a confocal laser scanning microscope (CLSM). The addition of plasticizers increased strain and decreased stress of zein films. At low level of plasticizers (6.25% and 12%), zein films deformed and fracture through micro-crack formation and propagation normal the tensile axis. At high Plasticization, only micro-pores were observed during tensile deformation. The filler material oil and Dimodan^® increased, but Vestosint^® decreased tensile strain in comparison to the control. This shows that the fracture dynamic is affected by the filler materials and is indeed observed by the CLSM. Analysis of local strain by Fluospheres^® as particle tracking showed a good linear correlation with the tensile strain of the plasticized zein films. The local strains of filler materials and zein matrix in the films were different from the overall tensile strain. The combination of CLSM with a fluospheres^® as particle tracking is a good method to study local deformation in biomaterials to understand the deformation and fracture behaviour of biomaterials.     

Production of a functionally graded artificial tooth root by unique sequence of processes

 A unique sequence of processes is used to produce a prototype of a functionally graded artificial tooth root: (1) Dry-jet spraying of the mixture of Ti and Al₂O₃ ultrafine particles (UFPs) produced by radio-frequency plasma onto the surface of a cylindrical Ti rod, where the composition of the UFPs is changed gradually in the outward radial direction from Ti to Al₂O₃; (2) Temperature-gradient sintering of the deposited composite, where the Ti – and the Al₂O₃– rich sides are heated simultaneously at about 1400 K and 1800 K, respectively; (3) Plasma spray coating of hydroxyapatite (HAP) onto the outermost Al₂O₃ surface of the sintered composite. The final product has compressive strength of more than 200 MPa and is durable against fatigue test of 10⁷ stress cycles at 1000 N. The adhesion strength between the Ti substrate and the Ti-Al₂O₃ functionally graded layer exceeds 65 MPa. No contamination with heavy metals is detected throughout the processes and biological cell growth is confirmed to occur on the HAP surface. With these mechanical and biochemical properties the composite produced here is considered to be highly suitable for an artificial tooth root. A series of processes developed here are expected to be applied to the production of various kinds of fine-grained functionally graded materials with complicated forms. Received: 13 October 1997 / Accepted: 27 October 1997     

Re-passivation current of amorphous Zr65Al7.5Ni10Cu17.5 alloy in a Hanks’ balanced solution

To evaluate the repassivation behavior of amorphous phase with chemical and structural homogeneity, time transient of re-passivation current density was measured on amorphous Zr₆₅Al_7.5Ni₁₀Cu_17.5 alloy and crystalline pure Zr with a momentary fracture of a ribbon shaped specimen in an artificial body fluid. Current density abruptly increased to a peak, J_peak, and exponentially decreased to the constant value, J_∞, J_peak and J_∞ on the amorphous specimen were smaller than those on the crystalline specimen, indicating that the amorphous phase would show the smaller dissolution rate from bare metal surface and from a re-passive film than the crystalline specimen, respectively. On the other hand, decrease rate of the current density on the amorphous specimen was smaller than that on the crystalline specimen, indicating the regeneration of passive film on the amorphous specimen was delayed probably because the amount of metal ions dissolved at the initial stage, i.e. the source of re-passive film, was smaller on the amorphous specimen. Consequently, the total charge for the re-passivation of the amorphous specimen was smaller than that of the crystalline specimen, supposing that the amount of dissolved metal ions during re-passivation was smaller on the amorphous specimen than the crystalline specimen.     

Growth and characterization of hydroxyapatite nanorice on TiO2 nanofibers

Hydroxyapatite (HA) coating with nanoparticles like nanorice is fabricated on chemically pretreated titanium (Ti) surface, through an electrochemical deposition approach, for biomaterial applications. The Ti surface was chemically patterned with anatase TiO₂ nanofibers. These nanofibers were prepared by in situ oxidation of Ti foils in a concentrated solution of H₂O₂ and NaOH, followed by proton exchange and calcinations. Afterward, TiO₂ nanofibers on Ti substrate were coated with HA nanoparticles like nanorice. The obtained samples were annealed at high temperature to produce inter diffusion between TiO₂ and HA layers. The resultant layers were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Infrared Spectroscopy (FTIR), corrosion tests in SBF solution, and Electron Probe Micro Analysis (EPMA). It was found that only Ti from the titanium substrate diffuses into the HA coating and a good corrosion resistance in simulated body fluid was obtained.