A systematic review of the interaction and effects generated by antimicrobial metallic substituents in bone tissue engineering.

Metallic elements are one of the key components of human physiology, which are required for basic cellular and extracellular functions. Herein, we provide insight into the bioactive metallic dopants silver (Ag), zinc (Zn), copper (Cu), magnesium (Mg) and ceria (Ce), which provide resistance against human pathogenic bacteria, and summarise the pathways for their generated effects crucial for osteogenic activity in an antibacterial environment and bone regeneration. Although most of these elements interact with genetic material, resulting in denaturation to produce apoptosis of pathogenic cells, some create adverse effects in the cellular matrix, which interfere with normal cellular metabolism and inhibit cellular activity, reducing the further growth and formation of bacterial colonies. Furthermore, although remarkable antibacterial activity has been recorded, bacterial cells have developed pathways and transporter proteins that remove the excess of these antibacterial elements from the cellular matrix. Thus, a discussion of these reported pathways as limitations is presented to find more novel modes of administration of these elements since they show good biocompatibility and are non-cytotoxic at certain release concentrations. As a cofactor of several enzymes, it is worth noting that some of these elements not only help in the metabolism of bone, but also activate the genetic pathways that regulate the formation of and maintain the factors that support new bone. The choice of incorporating these materials in ionic or nanoparticle form depends on the target substrate since they exhibit different mechanisms of action and even produce selective effects depending on their physical properties.

Structural phase formation and in vitro bioactivity evaluations of strontium phosphosilicate for orthopedic applications.

Structural features of apatites make them one of the most promising candidates for bone tissue regenerative applications. The unique structure and availability of mobile Metal ion as well as other components help interaction with biological fluids and can promote as well as stimulate bone regeneration with correct components. The present study focusses on Strontium phosphosilicate, an apatite analogue to Calcium phosphate-based HAP only loaded with better composition replacing Calcium with stimulatory Strontium and co-existent Silicate alongside phosphate both known to stimulate osteogenesis. Bulk particles were synthesized as powders with Acidic medium as well as the Basic medium of reaction mixture via Sol-Gel and Co-precipitation techniques respectively and phase formation was studied with respect to temperature further detailed by TGA-DSC studies. Secondary phases were also indexed based on which Acidic medium samples sintered at 800°C were comparatively better from the Basic medium on account of the presence of silicate phase forming agglomerated Strontium phosphosilicate. Hemolysis assay and MG-63 based cytotoxicity assay were carried out to study biocompatibility and antibacterial properties were also elucidated in Gram-positive and Gram-negative bacteria. Apatite seeding and bone mineralization studies were carried out with Simulated body fluid and characterized structurally and morphologically.

SPA enhanced FPIA-based detection of pesticide residue with ppb/ppt level detection limit.

Pesticide residue in fruits & vegetables is one of the key issues affecting the export of rural products in India. Pesticide exposure or intake causes major nervous system problems in children. The solutions to quantitate them in field are rare and the pesticide residue detection in the parts per billion (ppb) ranges is challenging. Except ELISA, none of the existing methods can detect pesticide residues in ppb range in the field. We employed a new approach of concentrating field samples and used sodium polyacrylate (SPA) as water absorbing material. The SPA beads concentrate the field samples and obtained a sub ppb range detection using an existing FPIA system and could improve overall sensitivity by 10-100 fold. The developed assay can be done in few seconds. We have used three pesticides 2,4-D, atrazine and methyl parathion with 0.1, 0.5 and 3 ppb detection limit respectively. We developed a simple field ready FPIA device and used sodium poly acrylate (SPA) in this biochemical FPIA to enhance sensitivity. Our tests with spiked field samples offers a possibility of using SPA concentration assisted FPIA in field. This study will have far reaching applications of both qualitative & quantitative analysis chemical analytes in field samples.

Biocompatibility assessment of SiO2-TiO2 composite powder on MG63 osteoblast cell lines for orthopaedic applications.

The objective of this study is to evaluate the biocompatibility of composite powder consisting of silica and titania (SiO2-TiO2) for biomedical applications. The advancement of nanoscience and nanotechnology encourages researchers to actively participate in reinvention of existing materials with improved physical, chemical and biological properties. Hence, a composite/hybrid material has given birth of new materials with intriguing properties. In the present investigation, SiO2-TiO2 composite powder was synthesised by sol-gel method and the prepared nanocomposite was characterised for its phase purity, functional groups, surface topography by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy. Furthermore, to understand the adverse effects of composite, biocompatibility test was analysed by cell culture method using MG63 osteoblast cell lines as a basic screening method. From the results, it was observed that typical Si-O-Ti peaks in FT-IR confirms the formation of composite and the crystallinity of the composite powder was analysed by XRD analysis. Further in vitro biocompatibility and acridine orange results have indicated better biocompatibility at different concentrations on osteoblast cell lines. On the basis of these observations, we envision that the prepared silica-titania nanocomposite is an intriguing biomaterial for better biomedical applications.

In-situ fabrication of zirconium-titanium nano-composite and its coating on Ti-6Al-4V for biomedical applications.

In this study, nanocomposite powder consisting of zirconia and titania (Zr-Ti) have been synthesised by sol-gel method, with the aim of protecting Ti-6Al-4V surface. A simple and low cost electrophoretic deposition (EPD) technique has been employed for coating the nanocomposite material on Ti-6Al-4V. The prepared nanocomposite powder was characterised for its functional groups, phase purity, surface topography by Fourier transform infrared spectroscopy, powder X-ray diffraction and scanning electron microscopy. Further, the biocompatibility nature of the composite powder was studied by [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] colorimetric assay and fluorescence analysis with MG63 osteoblast cell lines. The electrochemical behaviour of composite coating was investigated by potentiodynamic polarization and electrochemical impedance method. The results obtained from the electrochemical techniques indicate more corrosion resistance behaviour with increase of Rct value with the corresponding decrease in Rdl values. From the above findings, the composite coating acts as a barrier layer against corrosion by preventing the leaching of metal ions from a dense and defect free coating. A scratch test analyser was used to assess the integrity of the coating; the lower traction force value of composite coating with increase in load has confirmed the presence of thick adherent layer on the substrate.