Evaluation of water properties in HEA–HEMA hydrogels swollen in aqueous-PEG solutions using thermoanalytical techniques

Hydrogels are polymeric materials used in many pharmaceutical and biomedical applications due to their ability to form 3D hydrophilic polymeric networks, which can absorb large amounts of water. In the present work, polyethylene glycols (PEG) were introduced into the hydrogel liquid phase in order to improve the mechanical properties of hydrogels composed of 2-hydroxyethylacrylate and 2-hydroxyethylmethacrylate (HEA–HEMA) synthesized with different co-monomer compositions and equilibrated in water or in 20 % water–PEG 400 and 600 solutions. The thermoanalytical techniques [differential scanning calorimetry (DSC) and thermogravimetry (TG)] were used to evaluate the amount and properties of free and bound water in HEA–HEMA hydrogels. The internal structure and the mechanical properties of hydrogels were studied using scanning electron microscopy and friability assay. TG “loss-on-drying” experiments were applied to study the water-retention properties of hydrogels, whereas the combination of TG and DSC allowed estimating the total amount of freezable and non-freezing water in hydrogels. The results show that the addition of viscous co-solvent (PEG) to the liquid medium results in significant improvement of the mechanical properties of HEA–HEMA hydrogels and also slightly retards the water loss from the hydrogels. A redistribution of free and bound water in the hydrogels equilibrated in mixed solutions containing 20 vol% of PEGs takes place

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700

pH-sensitive polyvinylpyrrolidone-acrylic acid hydrogels: Impact of material parameters on swelling and drug release

In this study, we fabricated pH-sensitive polyvinylpyrrolidone/acrylic acid (PVP/AA) hydrogels by a free-radical polymerisation method with variation in the content of monomer, polymer and cross-linking agent. Swelling was performed in USP phosphate buffer solutions of pH 1.2, 5.5, 6.5 and 7.5 with constant ionic strength. Network structure was evaluated by different parameters and FTIR confirmed the formation of cross-linked hydrogels. X-ray crystallography showed molecular dispersion of tramadol HCl. A drug release study was carried out in phosphate buffer solutions of pH 1.2, 5.5 and 7.5 for selected samples. It was observed that swelling and drug release from hydrogels can be modified by changing composition and degree of cross-linking of the hydrogels under investigation. Swelling coefficient was high at higher pH values except for the one containing high PVP content. Drug release increased by increasing the pH of the medium and AA contents in hydrogels while increasing the concentration of cross-linking agent had the opposite effect. Analysis of the drug release mechanism revealed non-Fickian transport of tramadol from the hydrogels

SOLUBILIZACÍON DE HOMOPOLÍMEROS POR MICELAS DE COPOLIMEROS DE BLOQUE EN LÍQUIDOS ORGÁNICOS. SEMI-TEORIA

RESUMEN En este artículo se presenta una semi-teoría la cual se ajusta de forma satisfactoria a los resultados experimentales del comportamiento del fenómeno de solubilización de homopolímeros por micelas de copolímeros de bloque en líquidos orgánicos. Esta semi-teoría basada en parte en relaciones empíricas predice la respectiva relación de solubilización homopolímero/copolímero. También se presenta el factor o índice de solubilización (a), el cual es una forma de cuantificar la solubilización y está definido como el logaritmo decimal del peso molecular máximo de homopolímero para el cual un sistema (copolímero/disolvente) es capaz de solubilizar una determinada cantidad de homopolímero, la cual es expresada como capacidad de solubilización (relación H/C, en peso). ABSTRACT This article presents a semi-theory that satisfactorily matches the experimental results of the behavior of the solubilization phenomenon of homopolymers by block-copolymer micelles in organic liquids. This semi-theory, partially based on empirical relationships, forecasts the respective relationship of solubilization homopolymer/copolymer. It also presents the factor or index of solubilizationi (a), which is a way of quantifying the solubilization and is defined as the decimal logarithm of the maximum molecular weight of homopolymer for which a system (copolymer/solvent) can solubilize a specific amount of homopolymer, which is expressed as the capacity of solubilization (relation H/C, in weight). Key words: Solubilization, Micelles, Block-copolymers

SOLUBILIZACÍON DE HOMOPOLÍMEROS POR MICELAS DE COPOLIMEROS DE BLOQUE EN LÍQUIDOS ORGÁNICOS. SEMI-TEORIA

RESUMEN En este artículo se presenta una semi-teoría la cual se ajusta de forma satisfactoria a los resultados experimentales del comportamiento del fenómeno de solubilización de homopolímeros por micelas de copolímeros de bloque en líquidos orgánicos. Esta semi-teoría basada en parte en relaciones empíricas predice la respectiva relación de solubilización homopolímero/copolímero. También se presenta el factor o índice de solubilización (a), el cual es una forma de cuantificar la solubilización y está definido como el logaritmo decimal del peso molecular máximo de homopolímero para el cual un sistema (copolímero/disolvente) es capaz de solubilizar una determinada cantidad de homopolímero, la cual es expresada como capacidad de solubilización (relación H/C, en peso). ABSTRACT This article presents a semi-theory that satisfactorily matches the experimental results of the behavior of the solubilization phenomenon of homopolymers by block-copolymer micelles in organic liquids. This semi-theory, partially based on empirical relationships, forecasts the respective relationship of solubilization homopolymer/copolymer. It also presents the factor or index of solubilizationi (a), which is a way of quantifying the solubilization and is defined as the decimal logarithm of the maximum molecular weight of homopolymer for which a system (copolymer/solvent) can solubilize a specific amount of homopolymer, which is expressed as the capacity of solubilization (relation H/C, in weight). Key words: Solubilization, Micelles, Block-copolymers

Solution properties of PMMA-II. θ-Temperature and unperturbed dimensions of isotactic PMMA

The unperturbed dimensions of isotactic PMMA have been obtained by the application of various theoretical treatments to laser light scattering measurements carried out in a good solvent (ethyl acetate). A mean value for 〈s02〉/M of 7.25·10-18 cm2 mol g-1 was obtained. This value is shown to be in good agreement with that obtained from viscosity data in a theta solvent (acetonitrile θ = 27.5°). © 1977.Peer reviewe

Functionalized core-shell polymers prepared by microemulsion polymerization

In this work we present a novel process for the preparation of latex with high solid content, but maintaining the characteristics of microemulsion polymerization latex, small particle size (106). With the polystyrene latex obtained by microemulsion polymerization as seed, core-shell, styrene-butyl acrylate polymers functionalized with itaconic acid were prepared. Materials were characterized by DSC, DMTA and TEM. These polymers have better mechanical properties than the non functionalized or those prepared by emulsion polymerization

Functionalized core-shell polymers prepared by microemulsion polymerization

In this work we present a novel process for the preparation of latex with high solid content, but maintaining the characteristics of microemulsion polymerization latex, small particle size (<50 nm) and polymer with high molecular weight (>106). With the polystyrene latex obtained by microemulsion polymerization as seed, core-shell, styrene-butyl acrylate polymers functionalized with itaconic acid were prepared. Materials were characterized by DSC, DMTA and TEM. These polymers have better mechanical properties than the non functionalized or those prepared by emulsion polymerization