Graphene inks for printed flexible electronics: Graphene dispersions, ink formulations, printing techniques and applications

Graphene inks have recently enabled the dramatic improvement of printed flexible electronics due to their low cost, ease of processability, higher conductivity and flexibility. In this review, we discuss the state-of-the-art of the fundamental formulation of graphene inks and the current printing techniques used for inks deposition, followed by recent practical applications for printed flexible electronics. The progression of science and technology for the dispersion of graphene using variety of solvents and the characteristics of the resulting conductive inks have been highlighted, with specific emphasis focused on the challenges to be resolved. The printing techniques discussed here include screen printing, gravure printing, inkjet printing and other emerging printing technologies. Each approach's pros and cons are discussed in correlation with the ink formulations and the operating principles. We also discuss the challenges and outlook of graphene ink for its future development in the world of printed flexible devices.

The anti-inflammatory non-antibiotic helper compound diclofenac: an antibacterial drug target

Diclofenac sodium (Dc) was found to possess antibacterial activity against both drug-sensitive and drug-resistant clinical isolates of Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Mycobacterium spp., in addition to its potent anti-inflammatory activity. The time-kill curve study indicates that this non-steroidal drug exhibits bactericidal activity against Listeria, E. coli, and M. tuberculosis. The antibacterial activity of Dc comes, in part, from its ability to inhibit the DNA synthesis of E. coli and L. monocytogenes. Dc could protect murine listeriosis, salmonellosis, and tuberculosis at doses ranged within its maximum recommended human or non-toxic ex-vivo dose. Dc possesses anti-plasmid activity and acts as a 'helper compound' in synergistic combination with streptomycin against E. coli and Mycobacterium or gentamicin against Listeria. This review focuses on the possible use of Dc, a non-antibiotic helper compound, in infections and inflammatory conditions, rationalized on the basis of the activities of the compounds.

Studies on the antibacterial potentiality of isoflavones

The isoflavonoid compounds 'YS11-YS21' were screened for possible antimicrobial property against 12 known Gram-positive and Gram-negative sensitive bacteria. YS11 and YS16 failed to show antimicrobial activity and YS12, 13, 14, 15, 17, 18 and 20 had moderate antimicrobial action. Compounds YS19 and YS21 showed pronounced antimicrobial property. YS19 and YS21 were then tested in vitro against 214 strains of bacteria from one Gram-positive and six Gram-negative genera. The minimum inhibitory concentration (MIC) of YS19 and YS21 was determined by agar dilution method and ranged from 25 to 200 mg/l in most strains. At concentrations of 30 and 60 microg/mouse these compounds offered significant protection to mice challenged with 50 median lethal dose (MLD) of a virulent strain of Salmonella Typhimurium.

Tough Photocrosslinked Silk Fibroin/Graphene Oxide Nanocomposite Hydrogels

The development of protein-based hydrogels for tissue engineering applications is often limited by their mechanical properties. Herein, we present the facile fabrication of tough regenerated silk fibroin (RSF)/graphene oxide (GO) nanocomposite hydrogels by a photochemical cross-linking method. The RSF/GO composite hydrogels demonstrated soft and adhesive properties during initial stages of photocrosslinking (<2 min), which is not observed for the pristine RSF hydrogel, and rendered a tough and nonadhesive hydrogel upon complete cross-linking (10 min). The composite hydrogels exhibited superior tensile mechanical properties, increased β-sheet content, and decreased chain mobility compared to that of the pristine RSF hydrogels. The composite hydrogels demonstrated Young's modulus as high as ∼8 MPa, which is significantly higher than native cartilage (∼1.5 MPa), and tensile toughness as high as ∼2.4 MJ/m³, which is greater than that of electroactive polymer muscles and at par with RSF/GO composite membranes fabricated by layer-by-layer assembly. Small-angle scattering study reveals the hierarchical structure of photocrosslinked RSF hydrogels to comprise randomly distributed water-poor (hydrophobic) and water-rich (hydrophilic) regions at the nanoscale, whereas water pores and channels exhibiting fractal-like characteristics at the microscale. The size of hydrophobic domain (containing β-sheets) was observed to increase slightly with GO incorporation and/or alcohol post-treatment, whereas the size of the hydrophilic domain (intersheet distance containing random coils) was observed to increase significantly, which influences/affects water uptake capacity, cross-link density, and mechanical properties of hydrogels. The presented results have implications for both fundamental understanding of the structure-property relationship of RSF-based hydrogels and their technological applications.

Potential role of the cardiovascular non-antibiotic (helper compound) amlodipine in the treatment of microbial infections: scope and hope for the future

The appearance of multiresistant bacterial strains coupled with the globally ongoing problem of infectious diseases point to the imperative need for novel and affordable antimicrobial drugs. The antibacterial potential of cardiovascular non-antibiotics such as amlodipine (AML), dobutamine, lacidipine, nifedipine and oxyfedrine has been reported previously. Of these drugs, AML proved to have the most significant antibacterial activity against Gram-positive and Gram-negative bacteria. Time-kill curve studies indicate that this Ca(2+) channel blocker exhibits bactericidal activity against Listeria monocytogenes and Staphylococcus aureus. AML could protect against murine listeriosis and salmonellosis at doses ranging within its maximum recommended human or non-toxic ex vivo dose. AML acts as a 'helper compound' in synergistic combination with streptomycin against several Gram-positive and Gram-negative bacterial strains in vitro as well as in the murine salmonellosis model in vivo. The present review focuses on the possible use of cardiovascular non-antibiotics such as AML as auxiliary compound targets for synergistic combinations in infections and hypertension conditions, rationalised on the basis of the activities of the compounds.

Berberine in toxin-induced experimental cholera

1. Oral administration of berberine to infant rabbits 18-24 h before the intraintestinal administration of choleragenic toxins, arrests diarrhoea or significantly prolongs the survival time.2. The use of berberine in the treatment of clinical cholera is further justified.3. Berberine is an antidiarrhoeal drug and the host tissues play a major part in the control of diarrhoeal symptoms.

The anti-inflammatory drug Diclofenac retains anti-listerial activity in vivo

AIMS

The interactions between nonsteroidal anti-inflammatory drugs (NSAID) and Listeria monocytogenes have not been sufficiently documented to date. The aim of this study was to investigate the possible effects of Diclofenac (Dc) in a murine listerial infection model.

METHODS AND RESULTS

Dc was administered orally at 2.5 mug g(-1) to female albino strain of laboratory mouse (BALB/c) thrice postinfection (1 x 10(8) CFU ml(-1) oral challenge with L. monocytogenes ATCC 51774), which resulted in significantly (P < 0.01) reduced bacterial counts in liver and spleen, decreased (10-fold, P < 0.05) hepatic colonization and necrosis, and caused up-regulation of the expression of inflammatory cytokines (interferon-gamma, interleukin-1beta, tumour necrosis factor-alpha), compared with drug-free control.

CONCLUSIONS

Dc may be useful as a promising adjuvant to the existing therapies in controlling systemic listerial infection. Further, quantitative structure-activity relationship studies might contribute in manipulating it as a lead compound for the synthesis of new, more effective nonantibiotics, perhaps, devoid of side-effects that could be recommended as a compassionate therapy for listeriosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first in vivo study designed to evaluate the antilisterial effect of the NSAID Dc with special emphasis on the immunological mechanism of action of the drug.

Facile Fabrication of Polymerizable Ionic Liquid Based-Gel Beads via Thiol-ene Chemistry

Multipurpose gel beads prepared from natural or synthetic polymers have received significant attention in various applications such as drug delivery, coatings, and electrolytes because of their versatility and unique performance as micro- and nanocontainers.1 However, comparatively little work has been done on poly(ionic liquid)-based materials despite their unique ionic characteristics. Thus, in this contribution we report the facile preparation of polymerizable ionic liquid-based gel beads using thiol-ene click chemistry. This novel system incorporates pentaerythritol tetra (3-mercaptopropionate) (PETKMP) and 1,4-di(vinylimidazolium) butane bisbromide in a thiol-ene-based photopolymerization to fabricate the gel beads. Their chemical structure, thermal and mechanical properties have been investigated using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The gel beads possess low Tg and their ionic functionalities attribute self-healing properties and their ability to uptake small molecules or organic compounds offers their potential use as pH sensing material and macrocontainers.

Antimicrobial potentiality of a new non-antibiotic: the cardiovascular drug oxyfedrine hydrochloride

Ten cardiovascular drugs, having diverse pharmacological action, were screened for possible antimicrobial property against known eight sensitive bacteria, belonging to Gram positive and Gram negative types. Although five drugs failed to show antimicrobial activity and three had moderate antimicrobial action, oxyfedrine HCl and dobutamine were seen to possess pronounced antimicrobial property. Oxyfedrine was further tested in vitro against 471 strains of bacteria from two Gram positive and fourteen Gram negative genera. The minimum inhibitory concentration (MIC) of oxyfedrine was determined by agar dilution method, which ranged from 50-200 microg/ml in most of the strains, while some strains were inhibited at even lower concentrations. In animal experiments, this compound was capable of offering significant protection to Swiss strain of white mice, challenged with 50 median lethal dose (MLD) of a virulent strain of Salmonella typhimurium at concentrations of 15, 30 and 60 microg/mouse. The in vivo results were highly significant according to chi-square test.

Polymeric Ionic Liquid Nanoparticle Emulsions as a Corrosion Inhibitor in Anticorrosion Coatings

In this contribution, we report the facile preparation of cross-linked polymerizable ionic liquid (PIL)-based nanoparticles via thiol-ene photopolymerization in a miniemulsion. The synthesized PIL nanoparticles with a diameter of about 200 nm were fully characterized with regard to their chemical structures, morphologies, and properties using different techniques, such as Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. To gain an in-depth understanding of the physical and morphological structures of the PIL nanoparticles in an emulsion, small-angle neutron scattering and ultra-small-angle neutron scattering were used. Neutron scattering studies revealed valuable information regarding the formation of cylindrical ionic micelles in the spherical nanoparticles, which is a unique property of this system. Furthermore, the PIL nanoparticle emulsion was utilized as an inhibitor in a self-assembled nanophase particle (SNAP) coating. The corrosion protection ability of the resultant coating was examined using potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that the PIL nanoparticle emulsion in the SNAP coating acts as an inhibitor of corrosion and is promising for fabricating advanced coatings with improved barrier function and corrosion protection.

Perspective on Constructing Cellulose-Hydrogel-Based Gut-Like Bioreactors for Growth and Delivery of Multiple-Strain Probiotic Bacteria

The current perspective presents an outlook on developing gut-like bioreactors with immobilized probiotic bacteria using cellulose hydrogels. The innovative concept of using hydrogels to simulate the human gut environment by generating and maintaining pH and oxygen gradients in the gut-like bioreactors is discussed. Fundamentally, this approach presents novel methods of production as well as delivery of multiple strains of probiotics using bioreactors. The relevant existing synthesis methods of cellulose hydrogels are discussed for producing porous hydrogels. Harvesting methods of multiple strains are discussed in the context of encapsulation of probiotic bacteria immobilized on cellulose hydrogels. Furthermore, we also discuss recent advances in using cellulose hydrogels for encapsulation of probiotic bacteria. This perspective also highlights the mechanism of probiotic protection by cellulose hydrogels. Such novel gut-like hydrogel bioreactors will have the potential to simulate the human gut ecosystem in the laboratory and stimulate new research on gut microbiota.

4D Printing of Hydrogels: Innovation in Material Design and Emerging Smart Systems for Drug Delivery

Advancements in the material design of smart hydrogels have transformed the way therapeutic agents are encapsulated and released in biological environments. On the other hand, the expeditious development of 3D printing technologies has revolutionized the fabrication of hydrogel systems for biomedical applications. By combining these two aspects, 4D printing (i.e., 3D printing of smart hydrogels) has emerged as a new promising platform for the development of novel controlled drug delivery systems that can adapt and mimic natural physio-mechanical changes over time. This allows printed objects to transform from static to dynamic in response to various physiological and chemical interactions, meeting the needs of the healthcare industry. In this review, we provide an overview of innovation in material design for smart hydrogel systems, current technical approaches toward 4D printing, and emerging 4D printed novel structures for drug delivery applications. Finally, we discuss the existing challenges in 4D printing hydrogels for drug delivery and their prospects.

Osteonecrosis of hyoid bone and thyroid cartilage

A 55-year-old man with carcinoma of the right pyriform fossa was treated with cobalt therapy. Subsequently, osteonecrosis of the right greater horn and the right superior horn of the thyroid cartilage developed, followed by pathologic fractures of the processes and spontaneous expulsion of the sequestrae.

In vitro and in vivo efficacies of amlodipine against Listeria monocytogenes

Listeria monocytogenes causes suppurative gastritis in BALB/c mice. We investigated the effect of the antihypertensive drug amlodipine (Aml) on the growth of L. monocytogenes in vitro and in vivo. Aml showed noteworthy inhibitory action (minimum inhibitory concentration, MIC(90) 32 microg/ml) against Listeria strains and demonstrated cidal (minimum bactericidal concentration, MBC 64 microg/ml) activity. Aml administered orally at 2.5 microg/g in female BALB/c mice for 7 days, commencing 4 days before oral challenge (1 x 10(8) CFU/ml with L. monocytogenes ATCC 51774), significantly reduced bacterial counts in the stomach (P < 0.01), liver (P < 0.01), and spleen (P < 0.05), and decreased (P < 0.05) gastric lesions, neutrophilic infiltration, edema, vascular degeneration, and necrosis of gastric tissues. It caused the down-regulation of expression of inflammatory cytokines (IFN-gamma, IL-1 beta, and TNF-alpha) compared to drug-free control. Aml may be used in the presence of an antibiotic as adjunct therapy that boosts the host immunity against Listeria. Further, QSAR studies might contribute in manipulating it as a lead compound for the synthesis of new, more effective non-antibiotics (helper compounds), perhaps devoid of side-effects, that could be recommended as compassionate therapy for listeriosis.

In vitro synergistic effect of gentamicin with the anti-inflammatory agent diclofenac against Listeria monocytogenes

AIMS

A total of nine Listeria monocytogenes strains (seven serotypes) were studied to ascertain whether the non-steroidal anti-inflammatory drug diclofenac (Dc) used in combination with the conventional antilisterial antibiotic gentamicin (Gm) or ampicillin (Am) synergistically augments the efficacy of the antibiotic in vitro.

METHODS AND RESULTS

The effect of combination was evaluated by the checkerboard method to obtain a fractional inhibitory concentration (FIC) index followed by kill curves. Dc was synergistic with Gm (FIC 0.37) and there was indifference with Am (FIC 1) against L. monocytogenes ATCC 51774. The magnitude of the differences between killing by a single agent and the combination observed at 24 h was significant (P < 0.05) for Dc plus Gm but not Dc plus Am.

CONCLUSIONS

Thus, the ability of extended antibiotic therapy may be improved with the help of this synergistic drug pair in listeriosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Such findings may indicate parallel administration of anti-inflammatory and anti listeriosis drugs.

Water-Reprocessable, Reformable, and Ecofriendly Sustainable Material Based on Disulfide-Cross-Linked Polyethyleneimine

A reformable polymer gel material has been developed based on the disulfide cross-linking of low-molecular-weight polyethylenimine (PEI) that can be synthesized through a facile thiolation method and reprocessed through an aqueous method without the use of solvents or additional chemicals. Despite being made with water-soluble PEI, the cross-linked gel shows good mechanical integrity and its properties can be controlled through the fabrication parameters, maintaining the hydrophilic nature of PEI while being sufficiently robust to form a free-standing film that does not dissolve in water. The properties of the gel have been characterized by Fourier transform infrared spectroscopy, thermogravimetry, and dynamic mechanical analyses, showing the effect of parameters such as the degree of thiolation and thermal curing. The reformability of the gel comes from the disulfide cross-links, which can be disrupted and reformed through a simple, aqueous processing method utilizing ultrasonication, creating an aqueous dispersion, which can be recast multiple times with minimal loss in physical properties.

High speed all-optical PRBS generation based on quantum-dot semiconductor optical amplifiers

A scheme to generate return-to-zero on-off keying (RZ-OOK) high speed all-optical pseudo random bit sequence (PRBS) based on quantum-dot semiconductor optical amplifiers (QD SOA) has been studied. By analyzing the performance of the core functional unit of this system, which is composed of QD SOA-based logic XOR and AND gates, as well as considering the saturation effect of the QD device and noise level of the system, we demonstrated the system's capability of producing stable high speed optical PRBS signals. Results show that the performance of the system depends on a number of parameters, including relaxation lifetime from QD excited state to ground state, injected current density, bit repetition rate, signal pulse width and single pulse energy. For devices with relaxation time approximately 1.0 ps, injected current density >1.8 kA/cm(2), single pulse energy <1.0 pJ with pulse width around 1.0 ps, the system is capable of PRBS generation at speeds of approximately 250 Gb/s.