Enhancement of ion dynamics in PMMA-based gels with addition of TiO2 nano-particles

Solvent and ion dynamics in PMMA based gels have been investigated as a function of the loading of nanosized TiO₂ particles. The gels have a molar ratio of 46.5:19:4.5:30 of ethylene carbonate (EC), propylene carbonate (PC), lithium perchlorate and PMMA, respectively. A series of samples with 0, 4, 6 and 8 wt.% TiO₂ filler were investigated. The diffusion coefficients for the lithium ions and for the two solvents (EC and PC) were investigated by pfg-NMR. It was shown that the addition of filler to the gel electrolytes enhances the diffusion of the cations, while the diffusion of the solvents remains constant. Raman measurements show no significant changes in ion–ion interactions with the addition of fillers, while the ionic conductivity is seen to decrease. However, the sample with 8 wt.% TiO₂ had a conductivity close to that of the unfilled sample.

The enhancement of lithium ion dissociation in polyelectrolyte gels on the addition of ceramic nano-fillers

Nano-particle oxide fillers including TiO₂, SiO₂ and Al₂O₃ have previously been shown to have a significant affect on the properties of both polymer and polymer gel electrolytes. In some cases, conductivity increases of one order of magnitude have been reported in crystalline PEO–base complexes. In this work, we report the effects of TiO₂ and SiO₂ on a poly(Li-AMPS)-based gel polyelectrolyte. Impedance spectroscopy and pfg-NMR spectroscopy indicates an increase in the number of available charge carriers with the addition of filler. An ideal amount of ceramic filler has been identified, with additional filler only saturating the system and reducing the conductivity below that of the pristine polyelectrolyte system. SEM micrographs suggest a model whereby the filler interacts readily with the sulfonate group; the surface area of the filler being an important factor.

Enhancement of ion dissociation in polyelectrolyte gels

High conductivity in single ion conducting polymer electrolytes is still the ultimate aim for many electrochemical devices such as secondary lithium batteries. Achieving effective ion dissociation in these cases remains a challenge since the active ion tends to remain in close proximity to the backbone charge as a result of a low degree of ion dissociation. A unique aspect of this dissociation problem in polyelectrolytes is the repulsion between the backbone charges created by dissociation. One way of enhancing ion dissociation in polyelectrolyte systems is to use copolymers in which only a fraction (<20%) of the mer units are charged and where the comonomer is itself chosen to be polar and preferably to be compatible with potential solvents. We have also found that certain dissociation enhancers based on ionic liquids or boroxine ring compounds can lead to high ionic conductivity. In the cases where an ionic liquid is used as the solvent in a polyelectrolyte gel, the viscosity of the ionic liquid and its hydrophilicity are critical to achieving high conductivity. Compounds based on the dicyanamide anion appear to be very effective ionic solvents; polyelectrolyte gels incorporating such ionic liquids exhibit conductivities as high as 10⁻² S/cm at room temperature. In the case of boroxine ring dissociation enhancers, gels based on poly(lithium-2-acrylamido-2-methyl-1-propanesulfonate) and ethylene carbonate produce conductivities approaching 10⁻³ S/cm. This paper will discuss these approaches for achieving higher conductivity in polyelectrolyte materials and suggest future directions to ensure single ion transport.

Ionic conductivity of polymer gels deriving from alkali metal ionic liquids and negatively charged polyelectrolytes

We have prepared polymer gel electrolytes with alkali metal ionic liquids (AMILs) that inherently contain alkali metal ions. The AMIL consisted of sulfate anion, imidazolium cation, and alkali metal cation. AMILs were mixed directly with poly(3-sulfopropyl acrylate) lithium salt or poly(2-acrylamido-2-methylpropanesulfonic acid) lithium salt to form polymer gels. The ionic conductivity of these gels decreased with increasing polymer fraction, as in general ionic liquid/polymer mixed systems. At low polymer concentrations, these gels displayed excellent ionic conductivity of 10⁻⁴ to 10⁻³ S cm⁻¹ at room temperature. Gelation was found to cause little change in the ⁷Li diffusion coefficient of the ionic liquid, as measured by pulse-field-gradient NMR. These data strongly suggest that the lithium cation migrates in successive pathways provided by the ionic liquids.

Zwitterion effect in polyelectrolyte gels based on lithium methacrylate-N,N-dimethyl acrylamide copolymer

Zwitterionic compounds such as those based on 1-butylimidazolium-3-(n-butanesulfonate) have previously been shown to have positive effects on the transport properties of polyelectrolytes. The addition of the zwitterion has been found to, in some cases, increase the dissociation of the lithium ion and enhance the conductivity by almost an order of magnitude. In this work, we report the effects of adding the above-mentioned zwitterion into the polyelectrolyte gel system poly(lithium methacrylate-co-N,N-dimethyl acrylamide); the anionic group being a stronger base leads to different behaviour for this copolymer compared to previous work. Polyelectrolyte gels based on dimethyl sulfoxide and polyether solvents were investigated to determine the breadth of applicability of the zwitterion in improving lithium ion transport. Impedance spectroscopy and pulse field gradient-NMR diffusion indicate an increase in the number of available charge carriers with zwitterion addition in some gel systems, however, the effect is not universal.

Architecture of fiber network : from understanding to engineering of molecular gels

A new approach of engineering of molecular gels was established on the basis of a nucleation-initiated network formation mechanism. A variety of gel network structures can be obtained by regulating the starting temperature of the sol−gel transition. This enables us to tune the network from the spherulitic domains pattern to the extensively interconnected fibrillar network. As the consequence of fibrous network structure turning, desirable rheological and other in-use properties of the materials can be obtained accordingly. This approach of micro-/nanostructural fabrication may open up a new route for micro-/nanofunctional materials engineering in general.

Engineering of small-molecule gels based on the thermodynamics and kinetics of fiber formation

In this chapter, we will give an overview of our work on manipulating the micro/nano structure and macroscopic properties of SMGs. Firstly, it will cover the analysis of the thermodynamics of fiber formation in SMGs and the classification and characterization of the topological and micro/nano structures of fiber networks, followed by the analysis of the formation kinetics of these networks. The criteria of engineering of the SMGs will be summarized according to the latest understanding of the formation mechanisms of fiber networks. On the basis of this understanding, approaches that have been developed to engineer the micro/nanometer structures and macroscopic properties of typical SMGs will be presented.

Molecular gels for controlled formation of micro-/nano-structures

The preparation of nano structured materials such as nanoparticles, nanofiber and nanowires have been a focus of research in the last two decades. Due to their large surface-to-volume ration and superior properties compared to the conventional macroscopic materials, these materials promise to revolutionize many fields such as electronics, catalysis, and biomedicine. Hence, controlling the growth of these nanostructures has been a global interest. Although controlling the formation of macroscopically sized inorganic materials can be easily achieved, it is a challenge if the size of a material is reduced to a micrometer or nanometer scale. Synthesis of structures using organic templates has been demonstrated to be a simple and convenient approach, since the organic matter can be easily removed by calcination or suitable solvents. These organic templates include colloidal particles and fibers of polymers, aggregates of surfactants, carbon materials such as carbon nanotubes, organic crystals and fibers in small-molecule gels (SMGs) and polymer gels.

Highly conductive and thermally stable ion gels with tunable anisotropy and modulus

A new liquid-crystalline ion gel exhibits unprecedented properties: conductivity up to 8 mS cm(-1) , thermal stability to 300 °C, and electrochemical window to 6.1 V, as well as adjustable transport anisotropy (up to 3.5×) and elastic modulus (0.03-3 GPa). The combination of ionic liquid and magnetically oriented rigid-rod polyanion provides widely tunable properties for use in diverse electrochemical devices.

Controlling the supramolecular architecture of molecular gels with surfactants

Manipulating molecular assembly is significant for achieving materials with desirable performances. In this paper, two nonionic surfactants, Span 20 and Triton X-100, are used to tune the nucleation and fiber growth of a molecular gelator 2,3-di-n-decyloxyanthracene (DDOA). Confocal microscopic images show that Span 20 induces elongation of DDOA spherulites, and promotes fiber side branching. In contrast, Triton X-100 enhances the primary nucleation of DDOA leading to the formation of smaller DDOA spherulites, and promotes fiber tip branching. (1)H NMR investigation demonstrates strong interactions between the hydrophobic tails of the surfactants and the alkyl chains of DDOA molecules.The interactions significantly reduce the diffusion of DDOA molecules. The different effects of the two surfactants could be attributable to their different alkyl hydrophobic tails. The hydrophobic tail of Span 20 is similar to the alkyl chain of DDOA, which could promote the adsorption of Span 20 on the fiber side surface rich in alkyl chains of DDOA.While the benzene ring in the hydrophobic tail of Triton X-100 could facilitate the primary nucleation of DDOA and the adsorpion of Triton X-100 on the fiber tip surface rich in aromatic structure of DDOA. The observations of this work will help the development of a convenient approach to tune the fiber network structure of molecular gels.

The textural properties and microstructure of konjac glucomannan - tungsten gels induced by DC electric fields

Konjac glucomannan - tungsten (KGM-T) gels were successfully prepared under DC electric fields, in the presence of sodium tungstate. The textural properties and microstructure of the gels were investigated by Texture Analyzer, Rheometer and SEM. Based on the response surface methodology (RSM) results, the optimum conditions for KGM-T gel springiness is 0.32% sodium tungstate concentration, 0.54% KGM concentration, 24.66V voltage and 12.37min treatment time. Under these conditions, the maximum springiness value of KGM-T gel is 1.21mm. Steady flow measurement indicated that KGM-T gel showed characteristic non-Newtonian pseudoplastic behaviour, with low flow behaviour indexes in the shear thinning region. SEM demonstrated the porosity of the freeze-dried samples. These findings may pave the way to use DC electric fields for the design and development of KGM gels and to apply KGM gels for practical applications.

Alterations in the proportions of skeletal muscle proteins following a unilateral lesion to the substantia nigra pars compacta of rats

It is well established that mammalian skeletal muscles exhibit a considerable degree of plasticity and one of the main determining factors of this plasticity is the activity pattern and duration of motoneurone discharge. Lesions to the right substantia nigra pars compacta (SNpc) of six adult rats were made to determine whether altered output from the SNpc ultimately leads to a change in the expression of proteins in contralateral skeletal muscles. After 4 months, altered motor performance was identified by the administration of amphetamine. After 7 months, 30–70% of dopaminergic cells in the SNpc had been destroyed. The protein content of muscles was then quantified from densitometric scans of gels, and expressed as a % of the amount of actin (the protein used as a reference in this study). The lesion affected the expression of different protein isoforms in the fast- and slow-twitch muscles. In slow-twitch soleus muscles, the lesion decreased the proportion of α-tropomyosin and increased the proportion of β-tropomyosin. In the fast-twitch extensor digitorum longus muscles, the lesion increased the proportion of the fast isoform of troponin-T_1f, and decreased the proportions of the two isoforms of myosin light chain. This study establishes a connection between the chronic effects of a lesion to the SNpc, with a loss of dopaminergic neurones, impaired motor performance, and altered expression of proteins in skeletal muscle. The implication of these results is that the altered motor function observed in Parkinson’s disease may be associated with alterations to the expression of skeletal muscle proteins.

Sol-gel derived HA/TiO2 double coatings on Ti scaffolds for orthopaedic applications

Hydroxyapatite/titania (HA/TiO₂) double layers were coated onto Ti scaffolds throughout for orthopaedic applications by sol-gel method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and X-ray diffractometry (XRD) were used for the characterisation of the phase transformations of the dried gels and coated surface structures. Scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS) was used for the observation and evaluation of the morphology and phases of the surface layers and for the assessment of the in vitro tests. The in vitro assessments were performed by soaking the HA/TiO₂ double coated samples into the simulated body fluid (SBF) for various periods. The TiO₂ layer was coated by a dipping-coating method at a speed of 12 cm/min, followed by a heat treatment at 600 °C for 20 min. The HA layer was subsequently dipping-coated on the outer surface at the same speed and then heat-treated at difference temperatures. The results indicat that the HA phase begins to crystallize after a heat treatment at 560 °C. The crystallinity increases obviously at 760 °C. SEM observations find no delamination or crack at the interfaces of HA/TiO₂ and TiO₂/Ti. The HA/TiO₂ coated Ti scaffolds displays excellent bone-like apatite forming ability when it is soaked into SBF. Ti scaffolds after HA/TiO₂ double coatings can be anticipated as promising implant materials for orthopaedic applications

Phospholipase activity in human mesenteric ischaemia and infarction

Currently, diagnostic tests for mesenteric ischaemia and infarction are inadequate due to poor sensitivity and specificity. In addition, many potential markers appear too late to be clinically useful. At present, definitive diagnosis can only be made at the time of surgery, which is not ideal as surgery is often to be avoided in critically ill and elderly patients. A clinically useful, minimally invasive test is likely to decrease the currently very high mortality rate and allow monitoring of 'at risk' patients during their hospital stay. A two-dimensional electrophoresis based proteomic approach was undertaken to assess plasma protein differences between patients with surgically confirmed bowel infarction and control Intensive Care patients. The major protein differences were found to be members or variants of acute phase proteins. Serum amyloid A showed the largest difference between the two patient groups, and this protein was investigated in greater depth. An analysis was performed to compare the diagnostic ability of several commonly used indicators of critical illness and bowel infarction with serum amyloid A and phospholipase A2. Although none of the variables were ideal for clinical use, plasma phospholipase A2 activity showed the best discriminatory power, as determined by Receiver Operating Characteristic curves. From a review of the literature, phospholipase AI (PLA2) appeared to be increased in the bowel as a result of ischaemia and infarction. In one patient, matched tissues were obtained, and PLA2 activity was found to be significantly higher in infarcted bowel tissue compared to ischaemic bowel tissue. PLA2 activity was significantly greater in bowel lumen than tissue, suggesting that the protein was being released, and may enter the circulation. PLA2 activity was increased in the plasma of bowel infarction patients compared with control patients, though the difference was not significant. The phospholipase activity exhibited a number of similarities to typical phospholipase A2 proteins, but also showed a number of inconsistent characteristics. For this reason, we wished to identify the protein responsible for the increased phospholipase activity in infarcted human bowel. The PLA2 activity in human bowel could not be abolished by immunoprecipitation of the PLA2 isoforms IIA (well described in bowel) and V (a closely related isoform). To investigate these proteins, a native urea protein gel devised for snake venom phospholipase A2 was modified for use with mammalian phospholipase AI. The modified gel was used to show that the protein with phospholipase activity from infarcted gut was different from normal gut PLA2 and type IIA PLA2. A number of extensions were devised for these native gels and were found to be useful both in this investigation and for venom investigations. Protein purification was undertaken to identify the protein responsible for the increased phospholipase activity in infarcted bowel. Protein was purified from infarcted human bowel using a number of techniques that exploited unusual characteristics of the protein. The purification techniques each retained the native activity of the protein and the purification could therefore be monitored with a phospholipid hydrolysis assay at each stage. The protein identified by mass spectrometry was an excellent match for cyclophilin B, an inflammatory protein that had previously been identified in rat bowel at the mRNA level (Hasel et al, 1991, Kainer & Doris, 2000). As the purification progress had been monitored throughout with a phospholipid hydrolysis assay, cyclophilin B was an unexpected identification, as it is not known to have phospholipase activity. Cyclophilin B was removed from the highly purified samples via immunoprecipitation and this process abolished all phospholipase activity. The addition of cyclosporin A, (the pharmaceutical ligand of cyclophilin B), did not effect the phospholipase activity. Cyclophilin B protein was found in normal and infarcted human bowel using Western blotting. Cyclophilin B protein also appeared to be present in the bowel lumen and plasma of several patients with bowel infarction, but not in control patients. Immunohistochemistry confirmed the ubiquitous nature of cyclophilin B that had been reported by other groups. This project has investigated the use of two dimensional gel electrophoresis based proteomics to identify proteins present in the plasma of patients with confirmed bowel infarction and control intensive care patients. The major protein classes observed were members of the acute phase proteins, which highlights the need for pre-fractionation of plasma to identify lower abundance, disease associated proteins. A series of potential plasma markers were compared using Receiver Operating Characteristic Curves. Although no ideal marker was clear from this analysis, phospholipase activity appeared to warrant further investigation. Phospholipase activity was investigated in human infarcted bowel. Protein purification identified cyclophilin B as a bowel protein that showed unusual phospholipid hydrolysing activity. Cyclophilin B is a ubiquitous protein in intestinal cell types in both normal and infarcted tissue. There appears to be release of cyclophilin B into bowel lumen and plasma under conditions of mesenteric ischaemia and infarction.

The effects of treating male hypogonadism on couples' sexual desire and function

Introduction: Hypogonadism is a common endocrine condition characterized by low levels of testosterone (T) and marked by numerous symptoms, one of which is low sexual desire. Studies comparing T delivery systems have suggested that hypogonadal men’s partners may be at risk from exposure to T gels. Little other mention is found of the impact of hypogonadism and its treatment on a man’s partner and the couple’s sexual function.

Aim: To assess sexual desire and sexual function in hypogonadal men and their woman partners before and after treatment with T replacement therapy.

Methods: Twenty-one hypogonadal men and 18 partners were recruited from a   tertiary endocrine clinic, and were compared with a control group of 20 eugonadal age-matched men and their partners. All men had baseline blood tests to confirm their status as hypogonadal or eugonadal, and hypogonadal men repeated tests at 3-month intervals. All participants completed the Sexual Desire Inventory (SDI) and sexual function questionnaires at baseline and at 3-month intervals until the hypogonadal men attained normal T levels.

Main Outcome Measures: Pre- and post-treatment SDI and sexual function questionnaires were compared once T normalization was achieved. Between- and within-group comparisons were carried out.

Results: Pretreatment hypogonadal men recorded lower levels of sexual desire and function than controls, but significantly improved once hypogonadism was corrected. Eugonadal controls recorded no significant changes in either sexual desire or function during the study. Partners of the hypogonadal men reported no changes on the SDI, but significant improvements in sexual function as their partners recovered.

Conclusion: SDI and sexual function measures reflect sexual changes that  accompany rising serum T levels during correction of male hypogonadism. Women partners reported more satisfaction, less pain, and improved sexual function following the men’s treatment. Treatments affecting one partner potentially have important effects on the other.