Preparation and characterization of a lithium ion conducting electrolyte based on poly(trimethylene carbonate)

In this paper, the results of preliminary studies of two new solvent-free polymer electrolytes based on poly(trimethylene carbonate), p(TMC), with lithium trifluoromethanesulphonate, (triflate), and lithium perchlorate are described. Thin films of these electrolytes were obtained by evaporation of solvent from homogeneous mixtures of known masses of host polymer and salt. Electrolytes with compositions of n between 1.5 and 85, where n represents the molar ratio of (OCOCH2CH2CH2O) units per lithium ion, have been prepared. These solvent-free electrolytes were characterized by measurements of total ionic conductivity, differential scanning calorimetry (DSC) and thermogravimetry (TGA). As expected from previous studies with these salts in poly(ethylene oxide), PEO, the triflate-based system showed superior thermal stability but with a lower total ionic conductivity than that of the perchlorate-containing electrolyte. The highest conductivity (approximately 3×10−4 Ω−1 cm−1) was found at 95°C with the electrolyte composition of (TMC)2LiClO4.Fundação para a Ciência e a Tecnologia (FCT)Shell Chemicals Lt

Characterization of solid polymer electrolytes based on poly(trimethylenecarbonate) and lithium tetrafluoroborate

The results of an investigation of a polymer electrolyte system based on the poly(trimethylene carbonate) host matrix, designated as p(TMC), with lithium tetrafluoroborate guest salt are described in this presentation. Electrolytes with lithium salt compositions with n between 3 and 80 (where n represents the number of (O=COCH2CH2CH2O) units per lithium ion) were prepared by co-dissolution of salt and polymer in anhydrous tetrahydrofuran. The homogeneous solutions obtained by this procedure were evaporated, within a preparative glovebox and under a dry argon atmosphere, to form thin films of electrolyte. The solvent-free electrolyte films produced were obtained as very flexible, transparent, completely amorphous films and were characterized by measurements of total ionic conductivity, cyclic voltammetry, differential scanning calorimetry and thermogravimetry.Shell Chemicals Limited. Fundação para Ciência e Tecnologia. Fundação Calouste Gulbenkian

Study of novel lithium salt-based, plasticized polymer electrolytes

The results of a preliminary investigation of a series of polymer electrolytes based on a novel polymer host, poly(trimethylene carbonate) or p(TMC), with lithium triflate or lithium perchlorate and various plasticizing additives, are described in this presentation. Electrolytes with lithium salt compositions of about n = 10 (where n represents the molar ratio of (O=COCH2CH2CH2O) units per lithium ion) and additive compositions between 5 and 15 wt% (with respect to p(TMC)), were prepared by co-dissolution of salt and polymer in anhydrous solvent with a controlled amount of additive. The homogeneous solutions obtained were evaporated within a preparative glovebox and under a dry argon atmosphere to form thin films of electrolyte. The solvent-free electrolyte films produced were characterized by measurements of total ionic conductivity, differential scanning calorimetry and thermogravimetry. In general the triflate-based electrolytes were found to show moderate ionic conductivity and good thermal stability while perchlorate-based electrolytes showed higher levels of conductivity but lower thermal stability. Electrolytes based on this host polymer, with both lithium salts, were obtained as very flexible, transparent, completely amorphous films.Fundação para a Ciência e a Tecnologia (FCT),Shell Chemicals Lt

Influence of secretory leukocyte protease inhibitor (SLPI) basedeptides on elastase activity and their incorporation into hyaluronic acid hydrogels for chronic wound terapy

Chronic nonhealing skin wounds, such as leg ulcers and pressure sores, represent a major clinical problem and a financial burden for the health care systems. Chronic wounds are characterized by prolonged inflammatory phase that results in high levels of elastase, reactive oxygen species (ROS), and diminished growth factor activity. Under normal physiological conditions, elastase is a powerful host defence and its activity is regulated by endogenous inhibitors. The unrestrained elastase activity in chronic wounds may be tuned by exogenous active materials that inhibit elastase. Secretory leucocyte protease inhibitor, SLPI, is a potent endogenous inhibitor of elastase. Peptide fragments, KRCCPDTCGIKCL (Pep4) and KRMMPDTMGIKML (Pep4M), selected from SLPI primary structure were studied as potential elastase inhibitors. Kinetic studies performed for human neutrophil elastase (HNE) and porcine pancreatic elastase (PPE) in presence of these peptides revealed that both behave as uncompetitive and noncompetitive inhibitors of HNE and PPE, respectively. The influence of ROS and albumin on Pep4 and Pep4M inhibitory activity toward elastase reveals that this mixture increases the inhibitory activity of both peptides. These peptides were incorporated in hyaluronic acid hydrogels to evaluate the possibility of being used as active compounds in a drug delivery system. Assessment of HNE and PPE activity in the presence of these hydrogels formulations revealed a considerable decrease in enzyme activity. Although, only moderated elastase inhibition was observed, these peptides represent potential candidates for chronic wound applications, as there is no need for complete elastase inhibition in the normal wound healing processContract grant sponsor: Portuguese Foundation for Science and TechnologyContract grant number: SFRH/BD/36522/2007Contract grant sponsors: FEDER (European Fund for Regional Development)-COMPETE-QREN-EUContract grant sponsors: COST Action 868The authors greatly acknowledge the European Project Lidwine-Multifunctional medical textiles for wound (e.g., Decubitus) prevention and improved wound healing. The financial support for the Research Centre was given by CQ/UM [PEst-C/QUI/UI0686/2011(FCOMP-01-0124-FEDER-022716]. The divulgation of these results, as an oral communication, was supported by the COST Action 868. The authors thank Professor Ana Campos (Chemistry Department, Minho University, Portugal) for supplying the hyaluronic acid used in this study

Characterization of potential elastase inhibitor-peptides regulated by a molecular switch for wound dressings applications

Elastase plays an important role in wound healing process, degrading damaged tissue and allowing complete tissue recovery. The levels of human neutrophil elastase (HNE) are usually controlled by endogenous inhibitors. However, in the presence of high levels of elastase, like the ones present in chronic wounds, the inhibitors cannot overcome this overproduction and the enzyme starts to degrade the surrounding healthy tissue. In this work we report the development of a molecular switch to control the elastase activity in the exudate of non-healing chronic wounds. A peptide library was generated and screened in a microarray format for protein kinase-mediated phosphorylation. Two peptides were identified as casein kinase Iδ (CKI) substrates: KRCCPDTCGIKCL and its analogous peptide KRMMPDTMGIKML, with cysteine residues replaced by methionine residues. These peptides were studied in solution, both in the phosphorylated and non-phosphorylated forms as potential inhibitors for elastase. The obtained results show that the reversible process of phosphorylation/dephosphorylation results in differential inhibitory activity of the peptides. Thus the reversible process of phosphorylation/dephosphorylation can be used as a kind of molecular switch to control elastase activity. Degradation studies reveal that both the inhibitor-peptides and CKI are degraded by elastase. These results envisage the safe utilisation of these inhibitor-peptides together with CKI in the formulation of wound dressings.This work was supported by the European Project Lidwine - Multifunctional medical textiles for wound (e.g. Decubitus) prevention and improved wound healing. S.C.B. is supported by grants from the Lidwine Project and Foundation for Science and Technology (SFRH/BD/36522/2007). The results divulgation were supported by the COST Action 868. The authors are grateful to Professor Manuel dos Santos and Doutora Laura Carreto (Biology Department, Aveiro University) for use of the DNA microarray readers

NMR and molecular modelling studies on elastase inhibitor-peptides for wound management

Proteases play an important and critical role in the physiological process of wound repair. However, excessive and unregulated release of proteolytic enzymes (e.g., elastase) mediates abnormal degradation of healthy tissues, which leads to inflammatory disorders such as chronic wounds. Thus, it is of therapeutic interest to develop novel synthetic inhibitor-peptides of elastase, which can restore the balance between the free enzyme and the endogenous inhibitors in chronic wounds. In previous works, we have reported two different drug delivery systems to release novel elastase inhibitors to the wound site. In both systems synthetic peptides (KRCCPDTCGIKCL-Pep4 and KRMMPDTMGIKML-Pep4M) based on the primary structure of the endogenous elastase inhibitor, secretory leucocyte protease inhibitor, were used as active material. Phosphorylation of the reported peptides prompts significant structural differences, which reflects in distinct inhibitory capacity towards elastase. These structural modifications were prompted by electrostatic interactions and hydrogen bonds established from the peptide phosphoresidue. The current study was also extended to another synthetic peptide (WCTASVPPQCY-PepBBI) that is based on the reactive loop of another elastase inhibitor, the Bowmen-Birk inhibitor. PepBBI, phosphorylated and non-phosphorylated, displays similar behaviour to Pep4 and Pep4M. The structural modifications reported herein were evaluated by two-dimensional nuclear magnetic resonance and molecular modelling approaches.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (scholarship SFRH/BD/36522/2007 and PEst-OE/EQB/LA0004/2011), FEDER (European Fund for Regional Development)-COMPETE-QREN-EU and the European Project Lidwine - Multifunctional medical textiles for wound (e.g. Decubitus). We acknowledge CERMAX at ITQB-UNL and Rede Nacional de RMN for access to the facilities. Rede Nacional de RMN is supported with funds from FCT, Projecto de Re-equipamento Cientifico contract REDE/1517/RMN/2005, Portugal. Micaelo, N.M. acknowledges the contract research program "Compromisso corn a Ciencia" reference: C2008-UMINHO-CQ-03 and access to the Minho University GRIUM cluster

Di-ureasil ormolytes doped with Mg2+ ions : part 1: morphological, thermal and electrochemical properties

Poly(oxyethylene)(POE/siloxane-based materials incorporating magnesium triflate were prepared by the sol-gel process. The host Class II hybrid matrix (di-ureasil) employed was composed of a siliceous framework to which short POE chains were covalently bonded through urea linkages. Ormolytes with salt composition ranging from 500 to 1 were characterised. The nanohybrid with n = 20, thermally stable up to 360ºC, exhibited the highest ionic conductivity. The electrochemical stability of this material was found to span -3 to +2 volts.Fundação para a Ciência e Tecnologia - POCTI/P/CTM/33653/00; SFRH/BD/13559/03; POCTI/P/CTM/46780/03

Di-urea cross-linked poly(oxyethylene)/siloxane ormolytes for lithium batteries

Poly(oxyethylene)( POE)/siloxane hybrids (di-ureasils) doped with a wide concentration range of lithium triflate were investigated. The host matrix of these materials (d-U(2000)) is a sol-gel derived siliceous network to which POE chains with about 40 repeat units are bonded through urea linkages. Xerogels with n between 500 and 5 (where n is the molar ration of OCH2CH2 repeat units to lithium íons) were obtained as amorphous monoliths thermally stable up to at least 340ºC. A crystalline POE/LiCF3SO3 complex was detected spectroscopically in samples with compositions of n less than 10. Below 90ºC the ormolyte with n = 20 exhibits the highest ionic conductivity of the series characterized. The redox stability of this material is about 4.1 volts

Short chain U(600) di-urea cross-linked poly(oxyethylene)/siloxane ormolytes doped with lanthanum triflate salt

Promising La3+-doped electrolytes based on a hybrid poly(oxyethylene)/siliceous host matrix, U(600), have been produced. The organic and inorganic components of the hybrid structure are covalently bonded through urea linkages. The low molecular weight of the polyether segments of U(600) is thought to be responsible for the total amorphous character and high conductivity at room temperature (1.1×10−4 S cm−1) of these ormolytes.Fundação para a Ciência e a Tecnologia (FCT

Morphological and conductivity studies of di-ureasil xerogels containing lithium triflate

Sol–gel derived poly(oxyethylene)/siloxane hybrids doped with lithium triflate, LiCF3SO3, have been investigated. The host hybrid matrix of these materials, named di-ureasil and represented by U(600), is composed by a siliceous framework to which polyether chains containing 8.5 oxyethylene repeat units are covalently bonded through urea linkages. Xerogel samples U(600)nLiCF3SO3 with n (where n is the molar ratio of oxyethylene moieties per Li+ ion) between ∞ and 0.1 have been examined. X-ray diffraction and differential scanning calorimetry have provided conclusive evidence that the xerogels analyzed are entirely amorphous. The salt-rich material with n=1 exhibits the highest conductivity over the whole range of temperature analyzed (e.g. 4.3×10−6 and 2.0×10−4 Ω−1 cm−1, respectively, at 25 and 94 °C).Fundação para a Ciência e a Tecnologia (FCT