Space radiation resistant transparent polymeric materials

A literature search in the field of ultraviolet and charged particle irradiation of polymers was utilized in an experimental program aimed at the development of radiation stable materials for space applications. The rationale utilized for material selection and the synthesis, characterization and testing performed on several selected materials is described. Among the materials tested for ultraviolet stability in vacuum were: polyethyleneoxide, polyvinylnaphthalene, and the amino resin synthesized by the condensation of o-hydroxybenzoguanamine with formaldehyde. Particularly interesting was the radiation behavior of poly(ethyleneoxide), irradiation did not cause degradation of optical properties but rather an improvement in transparency as indicated by a decrease in solar absorptance with increasing exposure time

A highly-selective chloride microelectrode based on a mercuracarborand anion carrier.

The chloride gradient plays an important role in regulating cell volume, membrane potential, pH, secretion, and the reversal potential of inhibitory glycine and GABAA receptors. Measurement of intracellular chloride activity, [Formula: see text], using liquid membrane ion-selective microelectrodes (ISM), however, has been limited by the physiochemical properties of Cl- ionophores which have caused poor stability, drift, sluggish response times, and interference from other biologically relevant anions. Most importantly, intracellular [Formula: see text] may be up to 4 times more abundant than Cl- (e.g. skeletal muscle) which places severe constraints on the required selectivity of a Cl- - sensing ISM. Previously, a sensitive and highly-selective Cl- sensor was developed in a polymeric membrane electrode using a trinuclear Hg(II) complex containing carborane-based ligands, [9]-mercuracarborand-3, or MC3 for short. Here, we have adapted the use of the MC3 anion carrier in a liquid membrane ion-selective microelectrode and show the MC3-ISM has a linear Nernstian response over a wide range of aCl (0.1 mM to 100 mM), is highly selective for Cl- over other biological anions or inhibitors of Cl- transport, and has a 10% to 90% settling  time of 3  sec. Importantly, over the physiological range of aCl (1 mM to 100 mM) the potentiometric response of the MC3-ISM is insensitive to [Formula: see text] or changes in pH. Finally, we demonstrate the biological application of an MC3-ISM by measuring intracellular aCl, and the response to an external Cl-free challenge, for an isolated skeletal muscle fiber

Zinc(II) coordination polymers with pseudopeptidic ligands

Two new phenyl-bridged pseudopeptidic ligands have been prepared and structurally characterised. The nature of the ligands’ substituents play an important role in the nature of the solid state structure yielding either hydrogen bonded linked sheets of molecules or infinite hydrogen bonded networks. Both these ligands were reacted with a range of zinc(II) salts with the aim of synthesising coordination polymers and networks and exploring the role that anions could play in determining the final structure. The crystal structures of four of these systems (with ZnSO4 and ZnBr2) were determined; in one case, a 3D coordination network was obtained where zinc–ligand coordination bonds generated the 3D arrangements. Three other 3D networks were obtained by anion-mediated hydrogen bonding of coordination 1D chains or 2D sheets. These four very different structures highlight the important role played by the ligands’ substituents and the counteranions present in the system

Role of surface charge and oxidative stress in cytotoxicity of organic monolayer-coated silicon nanoparticles towards macrophage NR8383 cells

Background - Surface charge and oxidative stress are often hypothesized to be important factors in cytotoxicity of nanoparticles. However, the role of these factors is not well understood. Hence, the aim of this study was to systematically investigate the role of surface charge, oxidative stress and possible involvement of mitochondria in the production of intracellular reactive oxygen species (ROS) upon exposure of rat macrophage NR8383 cells to silicon nanoparticles. For this aim highly monodisperse (size 1.6 ± 0.2 nm) and well-characterized Si core nanoparticles (Si NP) were used with a surface charge that depends on the specific covalently bound organic monolayers: positively charged Si NP-NH2, neutral Si NP-N3 and negatively charged Si NP-COOH. Results - Positively charged Si NP-NH2 proved to be more cytotoxic in terms of reducing mitochondrial metabolic activity and effects on phagocytosis than neutral Si NP-N3, while negatively charged Si NP-COOH showed very little or no cytotoxicity. Si NP-NH2 produced the highest level of intracellular ROS, followed by Si NP-N3 and Si NP-COOH; the latter did not induce any intracellular ROS production. A similar trend in ROS production was observed in incubations with an isolated mitochondrial fraction from rat liver tissue in the presence of Si NP. Finally, vitamin E and vitamin C induced protection against the cytotoxicity of the Si NP-NH2 and Si NP-N3, corroborating the role of oxidative stress in the mechanism underlying the cytotoxicity of these Si NP. Conclusion - Surface charge of Si-core nanoparticles plays an important role in determining their cytotoxicity. Production of intracellular ROS, with probable involvement of mitochondria, is an important mechanism for this cytotoxicit

Study of the effects of ethylene oxide-freon 12 upon properties of polymers and metallic surfaces Final report, 10 Oct. 1964 - 31 Mar. 1966

Physical, mechanical, and electrical tests to determine the effects on polymeric products after exposure to ethylene oxide-Freon 1

Recent advances in smart biotechnology: Hydrogels and nanocarriers for tailored bioactive molecules depot

Over the past ten years, the global biopharmaceutical market has remarkably grown, with ten over the top twenty worldwide high performance medical treatment sales being biologics. Thus, biotech R&D (research and development) sector is becoming a key leading branch, with expanding revenues. Biotechnology offers considerable advantages compared to traditional therapeutic approaches, such as reducing side effects, specific treatments, higher patient compliance and therefore more effective treatments leading to lower healthcare costs. Within this sector, smart nanotechnology and colloidal self-assembling systems represent pivotal tools able to modulate the delivery of therapeutics. A comprehensive understanding of the processes involved in the self assembly of the colloidal structures discussed therein is essential for the development of relevant biomedical applications. In this review we report the most promising and best performing platforms for specific classes of bioactive molecules and related target, spanning from siRNAs, gene/plasmids, proteins/growth factors, small synthetic therapeutics and bioimaging probes.Istituto Italiano di Tecnologia (IIT)COST Action [CA 15107]People Program (Marie Curie Actions) of the European Union's Seventh Framework Program under REA [606713 BIBAFOODS]Portuguese Foundation for Science and Technology (FCT) [PTDC/AGR-TEC/4814/2014, IF/01005/2014]Fundacao para a Ciencia e Tecnologia [SFRH/BPD/99982/2014]Danish National Research Foundation [DNRF 122]Villum Foundation [9301]Italian Ministry of Instruction, University and Research (MIUR), PRIN [20109PLMH2]"Fondazione Beneficentia Stiftung" VaduzFondo di Ateneo FRAFRAinfo:eu-repo/semantics/publishedVersio

Antimicrobial wafers as a novel technology for infection control in chronic wounds.

Bacterial contamination and persistent infection is a common cause of impaired wound healing. Generally, non-healing wounds display similar physiological features with regards to mixed bacterial flora, ischemia and production of exudate. The application of topical, broad spectrum antimicrobial compounds embedded in absorbent dressings has been shown to control bioburden and improve healing. Lyophilised, biopolymeric antimicrobial wafers can offer a contemporary, user-friendly, self-adhesive and effective approach for the management of suppuration and polybacterial contamination in a wide range of non-healing wounds. Cohesive, non-friable, porous, disc shape wafers were successfully produced with sodium alginate (SA) (18.17 plusminus 0.70 Pa.s), guar gum (GG) (82.21 plusminus 5.41 Pa.s; 95.87 plusminus 2.31 Pa), xanthan gum (XG) (2.86 plusminus 0.12 Pa.s; 23.61 plusminus 0.68 Pa), karaya gum (KAG) (12.89 plusminus 0.93 Pa.s) and an original gel consisting of a blend of a synergistic SA-KAG (7.75 plusminus 0.64 Pa.s; 86.34 plusminus 5.19 Pa) (1:1 ratio). Clinical concentrations of the broad spectrum, topical, antimicrobial compounds, neomycin sulphate (0.5 % w/v NS), chlorhexidine digluconate (0.5 % v/v CHD), povidone iodine (1.0 % v/v PVP-I) and silver sulfadiazine (1.0 % w/v SS) were mixed with compatible biopolymers and appeared to alter the rheological properties of the biopolymers. Rheological analysis of pre-lyophilised gels was undertaken to quantify the flow properties of the gels. The necessity of producing sterile wafers was investigated by exposing all biopolymer-antimicrobial combinations to 25 and 40 kGy of gamma irradiation. Gamma-rays caused total degradation of GG, KAG, SA and SA-KAG, while XG appeared to withstand irradiation. A novel free standing dissolution raft (FSDR) was designed and used to quantify the CHD released from both gels and wafers. CHD released from wafers ranged from 3.5 plusminus 0.01 to 17.4 plusminus 0.39 %. Gels and wafers released CHD in a sustained manner and the release profile of wafers was similar to the respective gels, with the exception of GG. Neither gels nor wafers released 100% of the incorporated antimicrobial indicating that drug-polymer interactions governed the general performance of antimicrobial wafers, in terms of adhesion, expansion ratio (ER), inhibition ratio (IR), water uptake capacity (WUC) and antimicrobial delivery. Molecular modelling studies undertaken for KAG-antimicrobial complexes demonstrated an unusual Z-shape geometry for cationic CHD. The charge and geometry of CHD was plausibly responsible for the antimicrobials entrapment within biopolymeric networks. The efficacy of antimicrobial wafers was demonstrated in vitro under simulated conditions of an exuding wound using modified disc diffusion and an original antimicrobial diffusion cell (ADC). All wafers were effective in vitro against common chronic wound pathogens of such as methicillin-resistant Staphylococcus aureus (MRSA), methicillin-sensitive Staphylococcus aureus (MSSA), E. coli and P. aeruginosa. Antimicrobial activity depended on the sensitivity of the microorganisms to a specific antimicrobial compound and the presence of organic material. Data obtained demonstrated that the presence of protein (BSA) in the pseudo-exudate inhibited the antimicrobial activity of CHD and PVP-I, while enhancing the antimicrobial activity of SS and NS against MRSA. The general findings summarised in this thesis conclude that factors such as protein content, electrolyte content and pH of exudate play a key role in the efficacy of self-adhesive, absorbent formulations intended for the topical delivery of antimicrobial compounds to non-healing, infected wounds. Drug-polymer interactions developed between biopolymers and incorporated antimicrobial compounds have a profound effect on the general performance of lyophilised antimicrobial wafers