Novel in situ mucoadhesive gels based on Pluronic F127 and xyloglucan containing metronidazole for treatment of periodontal disease

Novel thermoresponsive in situ-forming hydrogels were prepared from co-solutions of Pluronic F127 (PF; triblock-copolymer of polyethylene oxide, polypropylene oxide and polyethylene oxide) and 0.1 wt% tamarind seed xyloglucan (0.1TSX). Based on test tube inversion method, co-solutions comprising 18 or 20 wt% PF and 0.1TSX (18PF/0.1TSX or 20PF/0.1TSX) gelled at 29 and 26 °C compared with 28 and 25 °C for equivalent concentration of PF solutions. DSC analyses indicated that 18PF/0.1TSX and 20PF/0.1TSX exhibited micellization temperatures of 15.5 and 14.9 °C, respectively, compared with 16.2 and 15.7 °C, respectively, for 18PF and 20PF. The lower micellization temperature but higher gel formation temperature suggests that 0.1TSX assists micelle formation but may interrupt order pack structure of micelle that is necessary for gelling. SEM revealed the cylindrical pore structure of lyophilized gels with diameters around 35 μm for 18PF, 20PF and 42 μm for 18PF/0.1TSX and approximately 78 μm for 20PF/0.1TSX. Extractables, released from PF/0.1TSX gels in phosphate buffered saline, did not reduce the viability of mouse osteoblast-like (MC3T3-E1) cells compared with the control, whereas those from PF gels were very cytotoxic with cell viability of 54–60% compared with the control. Therefore, the addition of 0.1TSX resulted in a significant decrease in cytotoxicity of PF. PF/0.1TSX gels exhibited improved mucoadhesive strength compared with PF gels and sustained the release of incorporated metronidazole antibacterial. These biocompatible systems which are in the liquid state before administration and undergo gelation in situ to form a gel at body temperature may, therefore, be injected into periodontal pockets to achieve sustained local delivery of antibacterials for the treatment of periodontitis.     

Augmentation of heat transfer through passive techniques

The thermal performance of energy preservation systems is greatly improved by increasing miniaturization and boosting. These are imaginative (or Promethean) techniques to enhance heat transfer. Enhancement methods of heat transfer draw great attention in front of the industrial sector because of their ability to provide energy savings and raise the economic efficiency of thermal systems. Three techniques these methods are categorized; those are active, passive, and compound. Different types of components are used in passive methods because of the transfer/working fluid flow path to the enhancement of the heat transfer rate. In this article, the subject of the review was the passive heat transfer enhancement methods including inserts (conical strips, winglets, twisted tapes, baffles), porous materials, coil/helical/spiral tubes, rough surfaces (corrugated/ribbed surfaces), extended surfaces (fins) and nanofluids (mono and hybrid nanofluid). Recent passive heat transfer enhancement techniques are studied in this article as they are cost-effective and reliable, and also comparably passive methods do not need any extra power to promote the energy conversion systems' thermal efficiency than active methods. In the passive approaches, various components are applied to the heat transfer/working fluid flow path to improve the heat transfer rate. The passive heat transfer enhancement methods studied in this article include inserts (twisted tapes, conical strips, baffles, winglets), extended surfaces (fins), porous materials, coil/helical/spiral tubes, rough surfaces (corrugated/ribbed surfaces), and nanofluids (mono and hybrid nanofluid). From the pioneers' research work, it is clear that a lower twist ratio and lower pitch, lesser winglet angles can provide more heat transfer rate and a little bit more friction factor. In the case of nanofluids, a little bit of pumping power is enhanced. Finally, heat transfer enhancement is compared with the thermal performance factor, which is more than unity.     

Wet-electrochemical growth of CdTe layers for photovoltaic applications

Journal of Materials Science: Materials in Electronics - Cadmium telluride (CdTe) thin films have been prepared using a low-cost potentiostatic electrochemical technique from an aqueous...     

A reappraisal on biodegradation of fluoride compounds: role of microbes

Fluorine is a highly reactive gas, rarely occurs in nature, in elemental form. Fluorosis is an excruciating and crippling disease caused by fluoride intake. Microbial degradation is cost‐effective and eco‐friendly method of removing fluoride compounds. The enzymes and genes involved in the fluoride‐degrading pathway have been identified and characterised. The in‐silico studies on degradative enzymes and their molecular interaction can be more advantageous in understanding fluoride toxicity and its degradative efficiency. Microbes exhibiting fluoride degradative potential or fluoride adsorption potential can be used for bioremediation of fluoride‐contaminated water. Large population is affected by fluorosis; both the welfare state and researchers are required to address the problem. The microbial degradation of fluoride provides sustainable, cost‐effective and ecofriendly technology. In the present review, an attempt has been made to compile all the available literature related to biodegradation of fluoride compounds.     

Synthesis of polypyrrole/polythiophene copolymers in supercritical carbon dioxide

Synthesis and processing of polymer-based materials through green friendly methods involving supercritical fluids particularly supercritical carbon dioxide (SCC) has recently received substantial technological importance because of the commercial and industrial benefits involved. In the present work, a SCC assisted green and sustainable process has been developed to synthesize polypyrrole/polythiophene copolymers (PPCs). The process of synthesis has been conducted through ferric chloride-initiated chemical oxidative polymerization in the presence of various molar proportions of pyrrole to thiophene 0:1.0, 1.0:0, 1.0:1.0 and 1.0:2.0 at temperature ranging from 50 to 90 °C, 1,200 psi over 12 h in SCC. Polymerization below 90 °C afforded PPCs in semi-solid products, whereas polymerizations conducted at 90 °C under identical conditions have afforded the end products in complete solid state. The structure and properties of PPCs have been evaluated through ultraviolet–visible absorption and Fourier transform infrared spectra, elemental analysis, atomic force microscopy, simultaneous thermogravimetric–differential thermal analysis–differential thermogravimetry and four-point probe electrical conductivity methods. With molar proportion of thiophene, time and temperature, all the polymerization reactions have been conducted to completion resulting in PPCs with enhanced polymerization yield, rheoviscosity, dispersion of polypyrrole into polythiophene matrix and thermal stability. This has contributed a simultaneous loss in the electrical conductivity of PPCs.     

Progress towards marketable earth-abundant chalcogenide solar cells

Kesterite-related photovoltaic materials are considered a promising alternative to CdTe and Cu(In,Ga)(S,Se)₂ absorbers, primarily because they are not reliant on scarce elements such as indium and tellurium or the heavy metal cadmium. Recently, we reported a performance breakthrough for this materials class, reaching by a simple hydrazine-based deposition technique 9.6% power conversion efficiency for Cu₂ZnSn(S,Se)₄ devices (40% improvement over vacuum-based methods). Here, more detailed characterization for a hydrazine-prepared device shows the potential of this technology for further efficiency improvement. We also present initial device results for Cu₂ZnSn(S,Se)₄ films deposited using a mixed water-hydrazine-based solvent, yielding devices with 8.1% efficiency.     

Direct electrical measurements on single-molecule genomic DNA using single-walled carbon nanotubes

A unique nanoelectronic platform, based on single-walled carbon nanotubes (SWNTs), has been fabricated for measuring electrical transport in single-molecule DNA. We have tested 80 base pairs of single- and double-stranded DNA (ssDNA and dsDNA, respectively) of complex base sequences. About a 25-40 pA current (at 1 V) was measured for the dsDNA molecule covalently attached to the SWNT electrode at its termini. In the absence of base pair stacking, a ssDNA carries a feeble current of approximately 1 pA or less. Gate-voltage-dependent I-V characteristics revealed that the bridging dsDNA molecule acts as a p-type channel between SWNT source and drain electrodes.     

Antibacterial activity of chitosan-based matrices on oral pathogens

Chitosan is a well sought-after polysaccharide in biomedical applications due to its biocompatibility, biodegradability to non-toxic substances, and ease of fabrication into various configurations. However, alterations in the anti-bacterial properties of chitosan in various forms is not completely understood. The objective of this study was to evaluate the anti-bacterial properties of chitosan matrices in different configurations against two pathogens—Gram-positive Streptococcus mutans and Gram-negative Actinobacillus actinomycetemcomitans. Two-dimensional (2-D) membranes and three-dimensional (3-D) porous scaffolds were synthesized by air drying and controlled-rate freeze drying. Matrices were suspended in bacterial broths with or without lysozyme (enzyme that degrades chitosan). Influences of pore size, blending with Polycaprolactone (PCL, a synthetic polymer), and neutralization process on bacterial proliferation were studied. Transient changes in optical density of the broth, adhesion characteristics, viability, and contact-dependent bacterial activity were assessed. 3-D porous scaffolds were more effective in reducing the proliferation of S. mutans in suspension than 2-D membranes. However, no significant differences were observed on the proliferation of A. actinomycetemcomitans. Presence of lysozyme significantly increased the antibacterial activity of chitosan against A. actinomycetemcomitans. Pore size did not affect the proliferation kinetics of either species, with or without lysozyme. NaOH neutralization of chitosan increased bacterial adhesion whereas ethanol neutralization inhibited adhesion without lowering proliferation. Mat culture tests indicated that chitosan does not allow proliferation on its surface and it loses antibacterial activity upon blending with PCL. Results suggest that the chemical and structural characteristics of chitosan-based matrices can be manipulated to influence the interaction of different bacterial species. Aparna R. Sarasam and Phoebe Brown contributed equally     

Silver nanoparticles: Large scale solvothermal synthesis and optical properties

Silver nanoparticles have been successfully synthesized by a simple and modified solvothermal method at large scale using ethanol as the refluxing solvent and NaBH₄ as reducing agent. The nanopowder was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible and BET surface area studies. XRD studies reveal the monophasic nature of these highly crystalline silver nanoparticles. Transmission electron microscopic studies show the monodisperse and highly uniform nanoparticles of silver of the particle size of 5 nm, however, the size is found to be 7 nm using dynamic light scattering which is in good agreement with the TEM and X-ray line broadening studies. The surface area was found to be 34.5 m²/g. UV-visible studies show the absorption band at ∼425 nm due to surface plasmon resonance. The percentage yield of silver nanoparticles was found to be as high as 98.5%.     

International Collaboration in Indian Scientific Papers

Internationally co-authored publications may be regarded as an indicator of scientific co-operation between countries and is of interest in science policy. In this study, the extent of international collaboration in Indian science has been estimated from SCI data in 1990 and 1994. We find an increase in collaboration both in terms of output and the extent of the network and significantly higher impact (IF) associated with internationally co-authored papers in several disciplines. However, there was no significant increase in IF of collaborative papers over time, whereas Indian papers in general showed a statistically significant, though small, increase in average impact from 1990 to 1994. The bulk of Indian scientific co-operation was with the developed Western nations and Japan, but it was often the smaller countries with a few co-authored papers which showed higher average impact. Co-operation with South Asian countries, initially low, has doubled in four years. By a combination of multivariate data analysis techniques the relative positions of India's partners in scientific collaboration have been mapped with respect to the fields of co-operation.