Longevinex ® Improves Human Atrophic Aged-related Macular Degeneration (AMD) Photoreceptor / Retinal Pigment Epithelium Mediated Dark Adaptation*

Aim: Gradual photoreceptor/ RPE deterioration/ vision loss in AMD is common, irrespective of US NEI AREDS I/II supplement risk reduction, or intra-vitreal anti-VEGF pharmacology. We evaluated dark adaptation (DA), a broad measure of photoreceptor / RPE health, with / without epigenetic modulation using a resveratrol–based caloric-restriction mimic (Longevinex ®www.longevinex.com). Study Design: Case series, bi-ocular, clinical DA evaluation in deteriorating AMD, before and after supplementation, under medical center compassionate use guidelines. Place and Duration of Study: Captain James A Lovell Federal Health Care Center, Illinois, USA, Optometry/Ophthalmology Departments between 4/2015 and 8/2016. Methods: Baseline clinical DA threshold (log DB), time (min), and fixation (%) were taken for patients with established atrophic AMD (n=14 eyes; 6 M / 1 F; ages 64 - 89 years), using the AdaptDx ® (www.maculogix.com), with pupil dilation and best refraction. Following prescription of Longevinex® 1 capsule qd AM, DA was repeated, with each eye’s response considered independent. Results: All but 2 eyes improved in one or more DA parameters, with 3 cases showing improvement by retinal macula SD OCT. Expected vs. actual (worse vs. same/better), by eye, was significant by Chi Square, P < .01. Additional factors affecting DA: smoking, alcohol, elevated CRP and statins were retrospectively evaluated. Conclusion: These first cases of epigenetic-induced DA stability / improvement are consistent with previous beneficial effects of Longevinex® such as enhanced choriocapillaris circulation. DA is the earliest functional AMD sign and a prime candidate for “AMD prevention”. This work merits expansion to controlled studies

Conventional and Radiation Synthesis of Polymeric Nano- and Microgels and Their Possible Applications

Soft nanomaterials – polymeric nanogels and microgels – have made a fast and brilliant career, from an unwanted by-product of polymerization processes to an important and fashionable topic of interdisciplinary research in the fields of polymer chemistry and physics, materials science, pharmacy and medicine. Together with their larger analogues – macroscopic gels, most known in the form of water-swellable hydrogels – they have a broad field of actual and potential applications ranging from filler materials in coating industry to modern biomaterials.  A multitude of techniques has been described for the synthesis of polymeric nano- and microgels. Most of them can be classified in two groups. The first one are techniques based on concomitant polymerization and crosslinking (where the substrates are monomers or their mixtures), called by some authors "crosslinking polymerization". The second group are methods based on intramolecular crosslinking of macromolecules (where the starting material is not a monomer, but a polymer). The possibilities of employing macroscopic polymer gels as biomaterials, mostly in the form of hydrogels based on synthetic polymers, have been explored since 1960's, when these materials were first synthesized [1]. Since then, a number of products reached the stage of commercial application, soft contact lenses, drug delivery systems and wound dressings being the most widely known examples. Given the number of research groups involved and progress being made in this field, one may anticipate that in the future the number of hydrogel-based biomedical products on the market will be constantly increasing

Dual Stimuli-Responsive Polysaccharide Hydrogels Manufactured by Radiation Technique

Featured Application Stimuli-responsive hydrogels encompassing biobased polymers are anticipated for utilization in various fields, starting from drug delivery systems through temporal actuators and water reservoirs to biodegradable microelements and nutrient delivery depots. This paper describes the results of the radiation-induced crosslinking of polysaccharides modified with hydroxypropyl and carboxymethyl functional groups, hydroxypropylcellulose (HPC) and carboxymethylcellulose (CMC), respectively, without and with poly(ethylene glycol) diacrylate (PEGDA) as a crosslinking agent, to obtain dual stimuli-responsive hydrogels. The gels were characterized in terms of water uptake and gel fraction, parameters that mainly depend on the HPC-CMC compositions, but also on the macromer crosslinker content and the absorbed dose. The swelling of hydrogels is controlled by both the temperature, due to the amphiphilic character of HPC and pH, due to the anionic functional groups of CMC. In spite of a similar degree of substitution in both cellulose derivatives, 1.4 for HPC and 1.2 for CMC, the pH response of hydrogels with an equal content of both polysaccharides is considerably higher-a reduction in swelling of up to 95% with a decrease in the pH to 2 was recorded-than the response to thermal-stimulus-wherein a reduction in swelling of less than 70% with an increasing in temperature to 55 degrees C was found. These biopolymers-based hydrogels of specific, stimuli-responsive swelling properties are anticipated in applications where a combination of two stimuli is essential and biodegradation may be required

Poly(vinyl methyl ether) hydrogels at temperatures below the freezing point of water - molecular interactions and states of water

Water interacting with a polymer reveals a number of properties very different to bulk water. These interactions lead to the redistribution of hydrogen bonds in water. It results in modification of thermodynamic properties of water and the molecular dynamics of water. That kind of water is particularly well observable at temperatures below the freezing point of water, when the bulk water crystallizes. In this work, we determine the amount of water bound to the polymer and of the so-called pre-melting water in poly(vinyl methyl ether) hydrogels with the use of Raman spectroscopy, dielectric spectroscopy, and calorimetry. This analysis allows us to compare various physical properties of the bulk and the premelting water. We also postulate the molecular mechanism responsible for the pre-melting of part of water in poly(vinyl methyl ether) hydrogels. We suggest that above &#8722;60 °C, the first segmental motions of the polymer chain are activated, which trigger the process of the pre-melting

Polymerization reactions and modifications of polymers by ionizing radiation

Ionizing radiation has become the most effective way to modify natural and synthetic polymers through crosslinking, degradation, and graft polymerization. This review will include an in-depth analysis of radiation chemistry mechanisms and the kinetics of the radiation-induced C-centered free radical, anion, and cation polymerization, and grafting. It also presents sections on radiation modifications of synthetic and natural polymers. For decades, low linear energy transfer (LLET) ionizing radiation, such as gamma rays, X-rays, and up to 10 MeV electron beams, has been the primary tool to produce many products through polymerization reactions. Photons and electrons interaction with polymers display various mechanisms. While the interactions of gamma ray and X-ray photons are mainly through the photoelectric effect, Compton scattering, and pair-production, the interactions of the high-energy electrons take place through coulombic interactions. Despite the type of radiation used on materials, photons or high energy electrons, in both cases ions and electrons are produced. The interactions between electrons and monomers takes place within less than a nanosecond. Depending on the dose rate (dose is defined as the absorbed radiation energy per unit mass), the kinetic chain length of the propagation can be controlled, hence allowing for some control over the degree of polymerization. When polymers are submitted to high-energy radiation in the bulk, contrasting behaviors are observed with a dominant effect of cross-linking or chain scission, depending on the chemical nature and physical characteristics of the material. Polymers in solution are subject to indirect effects resulting from the radiolysis of the medium. Likewise, for radiation-induced polymerization, depending on the dose rate, the free radicals generated on polymer chains can undergo various reactions, such as inter/intramolecular combination or inter/intramolecular disproportionation, b-scission. These reactions lead to structural or functional polymer modifications. In the presence of oxygen, playing on irradiation dose-rates, one can favor crosslinking reactions or promotes degradations through oxidations. The competition between the crosslinking reactions of C-centered free radicals and their reactions with oxygen is described through fundamental mechanism formalisms. The fundamentals of polymerization reactions are herein presented to meet industrial needs for various polymer materials produced or degraded by irradiation. Notably, the medical and industrial applications of polymers are endless and thus it is vital to investigate the effects of sterilization dose and dose rate on various polymers and copolymers with different molecular structures and morphologies. The presence or absence of various functional groups, degree of crystallinity, irradiation temperature, etc. all greatly affect the radiation chemistry of the irradiated polymers. Over the past decade, grafting new chemical functionalities on solid polymers by radiation-induced polymerization (also called RIG for Radiation-Induced Grafting) has been widely exploited to develop innovative materials in coherence with actual societal expectations. These novel materials respond not only to health emergencies but also to carbon-free energy needs (e.g., hydrogen fuel cells, piezoelectricity, etc.) and environmental concerns with the development of numerous specific adsorbents of chemical hazards and pollutants. The modification of polymers through RIG is durable as it covalently bonds the functional monomers. As radiation penetration depths can be varied, this technique can be used to modify polymer surface or bulk. The many parameters influencing RIG that control the yield of the grafting process are discussed in this review. These include monomer reactivity, irradiation dose, solvent, presence of inhibitor of homopolymerization, grafting temperature, etc. Today, the general knowledge of RIG can be applied to any solid polymer and may predict, to some extent, the grafting location. A special focus is on how ionizing radiation sources (ion and electron beams, UVs) may be chosen or mixed to combine both solid polymer nanostructuration and RIG. LLET ionizing radiation has also been extensively used to synthesize hydrogel and nanogel for drug delivery systems and other advanced applications. In particular, nanogels can either be produced by radiation-induced polymerization and simultaneous crosslinking of hydrophilic monomers in “nanocompartments”, i.e., within the aqueous phase of inverse micelles, or by intramolecular crosslinking of suitable water-soluble polymers. The radiolytically produced oxidizing species from water, •OH radicals, can easily abstract H-atoms from the backbone of the dissolved polymers (or can add to the unsaturated bonds) leading to the formation of C-centered radicals. These C-centered free radicals can undergo two main competitive reactions; intramolecular and intermolecular crosslinking. When produced by electron beam irradiation, higher temperatures, dose rates within the pulse, and pulse repetition rates favour intramolecular crosslinking over intermolecular crosslinking, thus enabling a better control of particle size and size distribution. For other water-soluble biopolymers such as polysaccharides, proteins, DNA and RNA, the abstraction of H atoms or the addition to the unsaturation by •OH can lead to the direct scission of the backbone, double, or single strand breaks of these polymers

Poly(vinyl methyl ether) hydrogels at temperatures below the freezing point of water - molecular interactions and states of water

Water interacting with a polymer reveals a number of properties very different to bulk water. These interactions lead to the redistribution of hydrogen bonds in water. It results in modification of thermodynamic properties of water and the molecular dynamics of water. That kind of water is particularly well observable at temperatures below the freezing point of water, when the bulk water crystallizes. In this work, we determine the amount of water bound to the polymer and of the so-called pre-melting water in poly(vinyl methyl ether) hydrogels with the use of Raman spectroscopy, dielectric spectroscopy, and calorimetry. This analysis allows us to compare various physical properties of the bulk and the premelting water. We also postulate the molecular mechanism responsible for the pre-melting of part of water in poly(vinyl methyl ether) hydrogels. We suggest that above &#8722;60 °C, the first segmental motions of the polymer chain are activated, which trigger the process of the pre-melting

Temperature and frequency dependence of microwave conductivity of isotropic reticulate doped polymers

Frequency dependence of conductivity for reticulate doped systems is observed at room temperature only around 1 GHz and even so it is relatively weak. The temperature dependence of conductivity is characteristic of the CT complex used and not of the polymer matrix. For the system containing TTF-TCNQ, for which the d.c. conductivity has a maximum at c. 230 K (i.e. metal-like behaviour at higher temperatures), this maximum becomes more pronounced and shifts towards lower temperatures with increasing frequency in the GHz range. The temperature dependence of the microwave conductivity is weaker than that of the d.c. conductivity. Such behaviour can be described by a modified Maxwell-Wagner model if an appropriate shape factor for the conducting inclusions is introduced, and if a relatively high conductivity of the continuous phase is assumed. We conclude that charge-carrier transport in reticulate doped polymers is not controlled by insulating barriers. The disorder within microcrystals plays a fundamental role, while the CT complex crystalline network is continuous in spite of very low concentration

Persistent photoexcitation effect on the poly(3-hexylthiophene) film: Impedance measurement and modeling

International audienceWe report on the equivalent circuit modeling of the relaxation behavior of an optically excited thick poly(3-hexylthiophene) (P3HT) film by means of impedance spectroscopy. Fabricated metal-semiconductor-metal devices with Au electrodes showed a nearly perfect ohmic behavior under ambient conditions. Impedance measurements on illuminated P3HT device showed a dramatical decrease of the impedance modulus under illumination and very slow relaxation to the initial state. Impedance-frequency data obtained during relaxation could not be explained by a simple parallel resistance-capacitance circuit but it could be best fitted by incorporating a constant-phase element instead of a normal capacitance. By observing the variation of the circuit parameters, it is found that the relaxation process is dominated by slow recombination (elimination) of the excess photogenerated carriers, which is confirmed by the time-varying photoconductivity of the device