Self-assembly, antimicrobial activity, and membrane interactions of arginine-capped peptide bola-amphiphiles

The self-assembly and antimicrobial activity of two novel arginine-capped bola-amphiphile peptides, namely RA6R and RA9R (R, arginine; A, alanine) are investigated. RA6R does not self-assemble in water due to its high solubility, but RA9R self-assembles above a critical aggregation concentration into ordered nanofibers due to the high hydrophobicity of the A9block. The structure of the RA9R nanofibers is studied by cryogenic transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS). Circular dichroism spectroscopy shows that both RA6R and RA9R adopt coil conformations in water at low concentration, but only RA9R adopts a β-sheet conformation at high concentration. SAXS and differential scanning calorimetry are used to study RA6R and RA9R interactions with a mixed lipid membrane that models a bacterial cell wall, consisting of multilamellar 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol/1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine vesicles. Cytotoxicity studies show that RA6R is more cytocompatible than RA9R. RA6R has enhanced activity against the Gram-negative pathogen P. aeruginosa at a concentration where viability of mammalian cells is retained. RA9R has little antimicrobial activity, independently of concentration. Our results highlight the influence of the interplay between relative charge and hydrophobicity on the self-assembly, cytocompatibility, and bioactivity of peptide bola-amphiphiles

Tailoring block copolymer nanoporous thin films with acetic acid as a small guest molecule

Block copolymers offer the fabrication of mesoporous thin films with distinct nanoscale structural features. In this contribution, we present the use of acetic acid (CH3COOH) as a low‐molecular‐weight guest molecule to tune the supramolecular assembly of poly[styrene‐block‐(4‐vinylpyridine)] (PS‐b‐P4VP), offering a versatile and straightforward method to obtain tailored nanostructured films with controlled topography and pore size. Spin‐coating toluene solutions of PS‐b‐P4VP, with a variable amount of CH3COOH, leads to micellar thin films, where the micelles contain the carboxylic acid as a guest molecule. The size can be conveniently modified in these films (from 48 to 75 nm) by varying the amount of organic acid in the starting solutions. Subsequent surface reconstruction of micellar films using ethanol leads to ring‐shaped copolymer nanoporous films with modulated diameter. Controlling the micelle reconstruction process, cylindrical porous films are also obtained. Interestingly, changing the type of aliphatic carboxylic acid leads to a modification of the observed film morphology from micelles to out‐of‐plane P4VP cylinders (or lamellae) in a PS matrix

Aggregation and phase equilibria of fluorinated ionic liquids

Grant SFRH/BD/100563/2014. IF/00190/2014 . IF/00210/2014. PTDC/EQU-EQU/29737/2017. PTDC/QEQ-FTT/3289/2014. IF/00210/2014/CP1244/CT0003. UID/QUI/50006/2019. POCI-01-0145-FEDER - 007265.In this work a specific family of ionic liquids, denominated fluorinated ionic liquids, with fluorine tags equal or longer than four carbon atoms, are fully characterized in order to understand their solubility and self-aggregation in aqueous solutions. The numerous combinations between cations and anions make these compounds a feasible option for the replacement of traditional and toxic surfactants used in the industrial and biomedical field. In this work, the increment of both hydrogenated and fluorinated side chain lengths, the influence of the cation headgroup (imidazolium and cholinium)as well as the difference between perfluorobutanesulfonate and perfluoropentanoate anions were studied. The liquid-liquid phase equilibria of fluorinated ionic liquids based on the perfluorobutanesulfonate anion with water were carried out. The self-aggregation behaviour of the different fluorinated ionic liquids in aqueous solutions was also determined using conductimetric titration, surface tension measurements and transmission electron microscopy. Several thermodynamic and surface parameters were obtained and used to discuss the aggregation process. These novel characterized fluorinated ionic liquids demonstrate an improved surface activity and aggregation behaviour, driven essentially by the increment of both hydrogenated and fluorinated chain lengths.authorsversionpublishe

Tuning ordered pattern of Pd species through controlled block copolymer self-assembly

We report a method for the preparation of ordered patterns of Pd species on a substrate based on the use of polystyrene-block-poly(ethylene oxide) copolymer (PS-b-PEO) templates and selective inclusion of palladium (Pd) species in the PEO domains. PS-b-PEO samples of different total molecular masses self-assemble in a cylindrical microphase-separated morphology, in which vertically aligned PEO cylinders, with different diameters depending on the molecular mass, are organized in a hexagonal array of different lateral spacings. The cylindrical nanostructure is maintained after the selective inclusion of Pd species (Pd acetate and Pd nanoparticles (NPs) after reduction of Pd ions of the salt) in the PEO cylinders so that the characteristic sizes (diameters and lateral spacings) of the included Pd species are tuned by the characteristic sizes of the block copolymer (BCP) template, which are regulated by molecular mass. Treatment of nanocomposites at elevated temperatures in air removes the polymer matrix and leads to the formation of arrays of palladium oxide (PdO) NPs covering a solid support. The patterns of PdO NPs are characterized by different particle diameters and gap distances, mirroring the patterns and characteristic nanodimensions of the parent BCPs used as templates

A dynamic supramolecular polyurethane network whose mechanical properties are kinetically controlled

We report the synthesis and characterization of a kinetically controlled, thermoreversible supramolecular polyurethane whose mechanical properties depend unusually strongly on the processing history. Materials were prepared by solution casting, quenching and annealing of quenched material, allowing pronounced micro-structural evolution, which leads to rapid increases in modulus as determined by rheological analysis. Tensile tests showed that the quenched material is soft, weak and ductile (shear modulus ~ 5 MPa, elongation ~ 250 %), but after annealing, at 70 °C for one hour, it becomes stiffer, stronger and more brittle (~ 20 MPa, ~ 20 %). FTIR and NMR spectroscopic analysis, coupled with MDSC and SAXS, were performed to investigate the network’s dynamic structural changes. SAXS results suggest the presence of a lamellar structure in the sample when solution cast at high temperature, or annealed. This ordering is unique when compared to structurally-related supramolecular bisurethane and bisurea polymers, and may be the cause of the observed path dependence. These mechanical properties, which can be switched repeatedly by simple thermal treatments, coupled with its adhesion properties as determined from peel and tack tests, make it an excellent candidate as a recyclable material for adhesives and coatings

Role of age and comorbidities in mortality of patients with infective endocarditis

Purpose: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. Methods: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015. Patients were stratified into three age groups:<65 years, 65 to 80 years, and = 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. Results: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 = 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients =80 years who underwent surgery were significantly lower compared with other age groups (14.3%, 65 years; 20.5%, 65-79 years; 31.3%, =80 years). In-hospital mortality was lower in the <65-year group (20.3%, <65 years;30.1%, 65-79 years;34.7%, =80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%, =80 years; p = 0.003).Independent predictors of mortality were age = 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI = 3 (HR:1.62; 95% CI:1.39–1.88), and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared, the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. Conclusion: There were no differences in the clinical presentation of IE between the groups. Age = 80 years, high comorbidity (measured by CCI), and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

Combined gelatin-chondroitin sulfate hydrogels with graphene nanoparticles

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Combined Gelatin-Chondroitin Sulfate Hydrogels with graphene nanoparticles

10 pages, 5 figures, 3 tablesCreating flexible, high-strength hydrogels from harmless, low-cost natural polymers is an area of intense research today due to their potential applications in the biomedical field, which demands materials with ambivalent physicochemical features. In particular, great efforts were devoted to the preparation of sustainable biohydrogels, composed of hydrophilic networks of renewable, biocompatible, biodegradable, and low-cost biopolymers. Bionanocomposites are a promising synthetic approach to combine specific multifunctional materials with targeted physicochemical properties. Novel bionanocomposite hydrogels were designed by combining both chondroitin sulfate (CS) as well as gelatin (GE) obtained from the waste generated by the fish industries to form double fibre networks with tailored properties. In addition, hybrid bionanocomposites were achieved by introducing graphene nanoparticles (xGnP) into the double fibrillar network (GE/CS) to enhance the physicochemical properties. The bionanocomposite nanostructures were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC) while their rheological properties and thermal stability were determined by rheological and thermogravimetric analyses (TGA), respectively. The likely interactions between CS and gelatin in the GE/CS hydrogel network were proved by ATR-FTIR spectroscopy. The incorporation of xGnP improved the mechanical properties of the GE/CS fibrillary network by an order of magnitude in the shear storage modulus. Eventually, the generated bionanocomposites hydrogels and bionanocomposite hybrid hydrogels have promising potential for applications in many biomedical fields, including drug delivery and tissue engineering by mimicking tissue extracellular matrix components such as the gelatin for collagen and the CS in the cartilageThe authors acknowledge the financial support received from Project KET4F-Gas-SOE2/P1/P0823, which is co-financed by the European Regional Development Fund within the framework of Interreg Sudoe Programme and project PID2019-105827RB-I00–Agencia Estatal de Investigación, SpainPeer reviewe

Biocompatibility enhancement of PLA by the generation of bionanocomposites with fish collagen derivatives

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