On the design and development of foamed GO-hydrogel nanocomposite surfaces by ultra-short laser processing.

Graphene oxide (GO) and reduced graphene oxide have outstanding qualities that could be exploited as reinforcement and antibacterial agents in a plethora of biomedical applications. In this contribution, it is reported the deployment of a polyacrylamide GO-hydrogel composite (GO@pAAm) which was photo-converted and structured by ultra-short laser irradiation using a direct laser writing (DLW) approach. The materials were characterized by Fourier Transform Infrared spectroscopy, scanning electron microscopy and confocal microscopy. The laser structure generates a multi-photo-induced effect: surface foaming and patterning, microdomains with enhanced selective water-swelling and effective GO photo-reduction. A first laser scan seems likely to induce the photo-reduction of GO and subsequent laser pulses trigger the structure/foaming. The photo-reduction of GO is evidenced by Raman spectroscopy by the relatively changing intensities of the D to G signals. Macroscopically by an increase in conductivity (decrease in sheet resistance fromRS-GO@pAAm= 304 ± 20 kΩ sq-1toRS-rGO@pAAm-DLW= 27 ± 8 kΩ sq-1) suggesting a reduction of the material measured by 4-Point-Probe.

Templated CaCO3 Crystallization by Submicrometer and Nanosized Fibers.

Electrospun submicrometer-sized poly(ε-caprolactone) (PCL) meshes and nanosized multiwalled carbon nanotubes (MWCNTs) were used as a template for preparing porous and interconnected inorganic-organic hybrid materials composed of CaCO3. Herein, we describe the proportion and incorporation method of submicrometer-sized plasma-treated PCL meshes over areas >1 mm(2) with CaCO3 using three crystallization methods including the use of poly(acrylic acid) (PAA). We found that flexible and rigid acid-functionalized MWCNTs showed a clear capacity and effects to penetrate calcite particles. MWCNTs interacted differently with the individual growth planes of CaCO3, indicating that fibers can undergo changes depending on sulfonate or carboxylate groups, adopt different orientations in solution, and thereby elicit changes in CaCO3 morphology. In summary, the use of PCL and acidic MWCNT fibers as an additive for substrate templates and experimental crystallization provides a viable approach for studying various aspects of biomineralization, including the production of controlled particles, control of porosities, and defined morphologies at microscale and nanoscale levels.

Visible-light-mediated Diels-Alder reactions under single-chain polymer confinement: investigating the role of the crosslinking moiety on catalyst activity.

Macromolecular scaffolds are rapidly emerging in catalysis owing to the ability to control catalyst placement at precise locations. This spatial proximity allows for enhanced catalyst activity that may not be observed using small molecules. Herein, we describe a triphenylpyrylium (TPT)-based visible-light active single-chain polymer nanoparticle (SCNP) that facilitates the radical cation [4 + 2]-cycloaddition. We find that the catalytic activity is highly dependent on the styrylarene comonomer used, wherein it can act as a redox mediator under confinement, increasing the catalytic turnover (TON) by up to 30 times in comparison to free TPT in solution. Mechanistic studies indicate that TPT excited states are quenched by the acene, with the resultant radical cation formed from naphthalene-based SCNPs able to proceed in oxidizing the dienophile in the elementary step of the reaction, while leading to near quantitative yields of the cycloadduct. The TPT-SCNP demonstrates enhanced photocatalyst efficiency compared to molecular TPT, and is able to be recycled and reused in three iterations of the reaction prior to decreased performance from photobleaching. Our results overall suggest that the confined nature of the SCNP and spatial proximity of acene-based pendants enforces their participation as cocatalytic redox mediators that impart enhanced photoredox catalysis under confinement.

A direct and quantitative three-dimensional reconstruction of the internal structure of disordered mesoporous carbon with tailored pore size.

A new technique that allows direct three-dimensional (3D) investigations of mesopores in carbon materials and quantitative characterization of their physical properties is reported. Focused ion beam nanotomography (FIB-nt) is performed by a serial sectioning procedure with a dual beam FIB-scanning electron microscopy instrument. Mesoporous carbons (MPCs) with tailored mesopore size are produced by carbonization of resorcinol-formaldehyde gels in the presence of a cationic surfactant as a pore stabilizer. A visual 3D morphology representation of disordered porous carbon is shown. Pore size distribution of MPCs is determined by the FIB-nt technique and nitrogen sorption isotherm methods to compare both results. The obtained MPCs exhibit pore sizes of 4.7, 7.2, and 18.3 nm, and a specific surface area of ca. 560 m(2)/g.

Mechanochemical Synthesis of Polyanilines and Their Nanocomposites: A Critical Review.

The mechanochemical synthesis of polyanilines (PANIs), made by oxidative polymerization of anilines, is reviewed. First, previous knowledge of the polymerization reaction in solution is discussed to understand the effect of different parameters: oxidant/monomer ratio, added acid, oxidant, temperature and water content on the properties of the conducting polymers (molecular weight, degradation, doping/oxidation level, conductivity, and nanostructure). The work on mechanochemical polymerization (MCP) of anilines is analyzed in view of previous data in solution, and published data are critically reconsidered to clarify the interpretation of experimental results. A key factor is the production of acids during polymerization, which is often overlooked. The production of gaseous HCl during MCP of aniline hydrochloride is experimentally observed. Since some experiments involves the addition of small amounts of water, the kinetics and heat balance of the reaction with concentrated solutions were simulated. A simple experiment shows fast (<2 min) heating of the reaction mixture to the boiling point of water and temperature increments are observed during MCP in a mortar. The form and sizes of PANI nanostructures made by MCP or solution are compared. The extensive work on the production of nanocomposites by MCP of anilines together with different nanomaterials (porous clays, graphene, carbon nanotubes, metal, and oxide nanoparticles) is also described.

Functionalization of Conductive Polymers through Covalent Postmodification.

Organic chemical reactions have been used to functionalize preformed conducting polymers (CPs). The extensive work performed on polyaniline (PANI), polypyrrole (PPy), and polythiophene (PT) is described together with the more limited work on other CPs. Two approaches have been taken for the functionalization: (i) direct reactions on the CP chains and (ii) reaction with substituted CPs bearing reactive groups (e.g., ester). Electrophilic aromatic substitution, SEAr, is directly made on the non-conductive (reduced form) of the CPs. In PANI and PPy, the N-H can be electrophilically substituted. The nitrogen nucleophile could produce nucleophilic substitutions (SN) on alkyl or acyl groups. Another direct reaction is the nucleophilic conjugate addition on the oxidized form of the polymer (PANI, PPy or PT). In the case of PT, the main functionalization method was indirect, and the linking of functional groups via attachment to reactive groups was already present in the monomer. The same is the case for most other conducting polymers, such as poly(fluorene). The target properties which are improved by the functionalization of the different polymers is also discussed.

Development of micropatterning polyimide films for enhanced antifouling and antibacterial properties.

A commercial biomedical Polyimide (PI) film was topographically and chemically modified by generating micrometric periodic arrays of lines using Direct Laser Interference Patterning (DLIP) in order to improve antifouling and antibacterial properties. DLIP patterning was performed with periods from 1 µm to 10 µm. The physical modification of the surface was characterized by SEM, AFM and contact angle measurements and, the chemical composition of the ablated surfaces was analyzed by ATR-IR and XPS spectroscopies. The antibacterial effects were evaluated through the effect on Pseudomonas aeruginosa colonies growth on the LB (Luria Bertani) broth. The results showed that the laser treatment change the topography and as a consequence the chemistry surface, also that the microstructured surfaces with periods below 2 µm, exhibited a significant bacterial (P. aeruginosa) adhesion decrease compared with non-structured surfaces or with surfaces with periods higher than 2 µm. The results suggest that periodic topography only confer antifouling properties and reduction of the biofilm formation when the microstructure presents periods ranging from 1 µm to 2 µm. On the other hand, the topography that confer strong antifouling superficial properties persists at long incubation times. In that way, polymer applications in the biosciences field can be improved by a surface topography modification using a simple, single-step laser-assisted ablation method.

Gas hydrate versus seabed morphology offshore Lebu (Chilean margin).

Gas-hydrate occurrences along the Chilean margin have been widely documented, but the processes associated with fluid escapes caused by the dissociation of gas hydrates are still unknown. We report a seabed morphology growth related to fluid migration offshore Lebu associated with mud cones by analysing oxygen and deuterium stable water isotopes in pore water, bathymetric, biological and sedimentological data. A relief was observed at - 127 m water depth with five peaks. Enrichment values of δ18O (0.0-1.8‰) and δD (0.0-5.6‰) evidenced past hydrate melting. The orientation of the relief could be associated with faults and fractures, which constitute pathways for fluid migration. The benthic foraminifera observed can be associated with cold seep areas. We model that the mud cones correspond to mud growing processes related to past gas-hydrate dissociation. The integration of (i) the seismic data analysis performed in the surrounding area, (ii) the orientation of our studied relief, (iii) the infaunal foraminifera observed, (iv) the grain size and (v) the total organic matter and isotope values revealed that this area was formerly characterised by the presence of gas hydrates. Hence, this part of the Chilean margin represents a suitable area for investigating fluid-migration processes.

Improving the retention and reusability of Alpha-amylase by immobilization in nanoporous polyacrylamide-graphene oxide nanocomposites.

Alpha-amylase was immobilized inside three different polymeric matrices: polyacrylamide hydrogel (PAAm), polyacrylamide-graphene oxide nanocomposite (PAAm-GO) and alginate in order to study and compare the effect of the matrix on the catalytic performance. The morphology, swelling, mechanical properties, retention efficiency, and the catalytic behavior of these newly supported biocatalysts were studied. Nanocomposite made of PAAm-GO matrix incorporated 98% of the enzyme, likely through a cooperative effect, while alginate gels incorporated only 30%. Moreover, the enzyme retention using PAAm-GO reached a value of 97.5%. Starch hydrolysis catalyzed by the immobilized enzyme in PAAm-GO matrix showed similar kinetics profiles up to 5 cycles suggesting that the enzymatic activity is retained. These results compare very favorably with conventional immobilization in alginate where almost no activity was observed after 3 cycles. All results suggest that the PAAm matrices protect the biocatalyst allowing its reusability. Moreover, the improvements in enzyme catalytic properties via immobilization made this system as an excellent candidate in bio-industrial applications such as bioethanol production. Furthermore, the synthesized catalyst could produce a high yield of bioethanol by using enzymes and yeast immobilized in the same PAAm matrix. In this way, it is possible to produce sequential or simultaneous saccharification and fermentation.

Photothermally enhanced bactericidal activity by the combined effect of NIR laser and unmodified graphene oxide against Pseudomonas aeruginosa.

The manuscript shows the application of unmodified graphene oxide (GO) as a photothermally susceptible material to trigger antibacterial effects. The synthesis and characterization of unmodified GO easily dispersed in aqueous solutions is also shown. High GO concentrations in the dark and low GO concentrations irradiated with near infrared light (NIR) produced death in nosocomial bacterium (Pseudomonas aeruginosa). It is demonstrated that GO dispersion in the dark produced a dose-dependent increase in the antibacterial action at concentrations up to 120 µg/mL. On the other hand, by using much lower concentrations (c.a. 2 µg/mL) of GO (non toxic in the dark) and irradiating with near-infrared radiation during 15 min, a degree of mortality of 98.49% was observed. The P. aeruginosa treated with GO and irradiated exhibited DNA fragmentation due to the physical damage of cell membranes. The GO 2 µg/mL dispersions proved favorable, since they do not induce cell death in the dark, whereas the combination with NIR light triggers the damage to the cell membranes. This characteristic is clearly an advantage in comparison with traditional antibacterial nanomaterials (such as nanoparticles), which induce cell killing due to the nanoparticles toxicity per se. Furthermore, this work provides a novel treatment for combating bacterial nosocomial infections without the use of antibiotics, opening a new area of clinical application via simple photothermal therapy.

Nanocomposites based on pH-sensitive hydrogels and chitosan decorated carbon nanotubes with antibacterial properties.

The present work aimed to study the properties of a novel nanocomposite with promising biomedical applications. Nanocomposites were prepared by the addition of different concentrations of chitosan decorated carbon nanotubes to acrylamide-co-acrylic acid hydrogels. The nanocomposites chemical structure was characterized by Fourier Transform Infrared Spectroscopy (FT-IR). The FT-IR shows the typical bands due to the hydrogel and additionally the peaks at 1750 cm-1 and 1450 cm-1 that correspond to the carbon nanotubes incorporated into the polymer matrix. Mechanical properties and swelling measurements in different buffer solutions were also performed. The nanocomposites showed improved mechanical properties and a stronger pH-response. In order to evaluate antimicrobial activity, the growth and adhesion of Staphylococcus aureus to nanocomposites were studied. Cytocompatibility was also evaluated by MTT assay on MDCK and 3T3 cell lines. The nanocomposites were found to be cytocompatible and showed a reduced bacterial colonization.

Meningoencefalitis por virus Varicella-Zóster posterior a infección por SARS-CoV2: Reporte de dos casos / Meningoencephalitis caused by Varicella-Zoster virus after SARS-CoV2 infection: Two cases report

RESUMEN La meningoencefalitis por el VZV es una patología poco frecuente que se presenta con la reactivación del virus dentro del organismo. OBJETIVO: Describir la presentación clínica de dos pacientes con neuroinfección por VZV posteriormente a infección por SARS-CoV-2. REPORTE DEL CASO: El primer caso corresponde a un hombre de 59 años con antecedente de neumonía moderada por SARS-CoV-2 que después cursó con meningoencefalitis por VZV y, además, desarrolló un síndrome de Ramsay Hunt. El segundo caso es el de una mujer de 37 años con antecedente de infección leve por SARS CoV-2 con un cuadro de cefalea con signos de alarma, en quien se documentó neuroinfección por VZV

ABSTRACT Meningoencephalitis caused by varicella zoster virus is a rare pathology that presents due to the reactivation of the virus in the organism OBJECTIVE: To describe the clinical presentation of two patients with VZV neuroinfection presented after a SARS CoV-2 infection. CASE REPORT: The first case is a 59 year old male with previous moderate SARS CoV-2 infection who presented meningoencephalitis and was diagnosed with Ramsay Hunt's Syndrome. The second case is a 37 year old female with previous SARS CoV-2 infection who presented with an acute onset headache and was documented with VZV neuroinfection.

Facile one-pot exfoliation and integration of 2D layered materials by dispersion in a photocurable polymer precursor.

Efficient exfoliation of graphene and related materials (GRM) and fast and inexpensive integration/assembly are crucial to fulfil their full potential. A high degree of exfoliation in organic media can be achieved with high boiling point liquids that usually leave residues after drying, which is a handicap for many applications. Here, the effective exfoliation and dispersion of GRM in a vinyl monomer, which is subsequently converted to a functional polymer by photopolymerization, is reported. Nanocomposite membranes and three-dimensional objects are produced by the photo-curing process and stereolithography 3D printing, respectively.

Bioethanol production by reusable Saccharomyces cerevisiae immobilized in a macroporous monolithic hydrogel matrices.

Performance of yeasts on industrial processes can be dramatically improved by immobilization of the biocatalyst. The immobilization of Saccharomyces cerevisiae inside monolithic macroporous hydrogels were produced by in-situ polymerization of acrylamide around a live yeast suspension under cryogelation conditions. Preculture of the yeasts was not necessary and this innovative and simple procedure is amenable to scaling-up to industrial production. The yeasts were efficiently retained in monolithic hydrogels, presenting excellent mechanical properties and high cell viability. Macroporous hydrogels showed a fast mass transport allowing the hydrogel-yeast complexes achieved similar ethanol yield and productivity than free yeasts, which is larger than those reached with yeasts immobilized in compact hydrogels. Moreover, the same yeasts were able to maintain its activity by up to five reaction cycles with a cell single batch during fermentation reactions.

Biosorption of aluminum through the use of non-viable biomass of Pseudomonas putida.

Living and non-living biomass of Pseudomonas putida A (ATCC 12633) was used as biosorbent for the removing of Al(3+) from aqueous solutions. The process was stable with time, efficient at pH 4.3 and between 15°C and 42°C. Two isotherms models were applied to describe the interaction between the biosorbent and Al(3+). Non-living biomass of P. putida A (ATCC 12633) was found to be the most efficient at adsorbing Al(3+) with a maximum sorption capacity of 0.55mg Al(3+)/gr adsorbent and with 36×10(5) binding sites of Al(3+)/microorganisms. Infrared spectroscopy analysis shows that the biosorbent present some vibrational band of functional groups that change in presence of Al(3+): hydroxyl, carboxyl and phosphate. Considering that Al(3+) binds to the phosphate group of phosphatidylcholine, non-viable biomass of P. putida PB01 (mutant lacking phosphatidylcholine) was used. Aluminum adsorption of the parental strain was 30 times higher than values registered in P. putida PB01 (36×10(5) sites/microorganism vs 1.2×10(5) sites/microorganism, respectively). This result evidenced that the absence of phosphatidylcholine significantly affected the availability of the binding sites and consequently the efficiency of the biomass to adsorb Al(3+).

IgY against enterotoxigenic Escherichia coli administered by hydrogel-carbon nanotubes composites to prevent neonatal diarrhoea in experimentally challenged piglets.

In previous studies, the applicability of polymeric hydrogels for the protection of egg yolk immunoglobulin (IgY) against simulated gastric conditions was established. Thereafter, the performance of the hydrogels was improved with the addition of chitosan wrapped carbon nanotubes and the in vitro toxicity for porcine intestinal cells of these nanocomposites was assessed. The objective of the present study was to evaluate in vivo the protective efficacy of the nanocomoposite matrix for IgY when the immunoglobulin is used against enterotoxigenic Escherichia coli (ETEC) in challenged piglets. Groups of piglets orally challenged with 10(11)CFU/mL of ETEC were treated with non-protected and protected IgY. The clinical response of each group was monitored and evaluated in terms of dehydration, rectal temperature, faecal consistency score and body weight gain. Blood parameters and histological aspects were also studied. The results showed that treatment of infected piglets with protected IgY reduced significantly the severity of diarrhea. Non-protected IgY group show a lower recovery rate. Blood parameters and histological aspects were normal in both groups. Collectively, these results support previous in vitro studies showing that the nanocomposites can be an effective method of IgY protection against gastric inactivation.

Hybrid biomaterials based on calcium carbonate and polyaniline nanoparticles for application in photothermal therapy.

Inorganic materials contain remarkable properties for drug delivery, such as a large surface area and nanoporous structure. Among these materials, CaCO3 microparticles (CMPs) exhibit a high encapsulation efficiency and solubility in acidic media. The extracellular pH of tumor neoplastic tissue is significantly lower than the extracellular pH of normal tissue facilitating the release of drug-encapsulating CMPs in this area. Conducting polyaniline (PANI) absorbs light energy and transforms it into localized heat to produce cell death. This work aimed to generate hybrid CMPs loaded with PANI for photothermal therapy (PTT). The hybrid nanomaterial was synthesized with CaCO3 and carboxymethyl cellulose in a simple, reproducible manner. The CMP-PANI-Cys particles were developed for the first time and represent a novel type of hybrid biomaterial. Resultant nanoparticles were characterized utilizing scanning electron microscopy, dynamic light scattering, zeta potential, UV-vis, FTIR and Raman spectroscopy. In vitro HeLa cells in dark and irradiated conditions showed that CMP-PANI-Cys and PANI-Cys are nontoxic at the assayed concentrations. Hybrid biomaterials displayed high efficiency for potential PTT compared with PANI-Cys. In summary, hierarchical hybrid biomaterials composed of CMPs and PANI-Cys combined with near infrared irradiation represents a useful alternative in PTT.

Cysteine modified polyaniline films improve biocompatibility for two cell lines.

This work focuses on one of the most exciting application areas of conjugated conducting polymers, which is cell culture and tissue engineering. To improve the biocompatibility of conducting polymers we present an easy method that involves the modification of the polymer backbone using l-cysteine. In this publication, we show the synthesis of polyaniline (PANI) films supported onto Polyethylene terephthalate (PET) films, and modified using cysteine (PANI-Cys) in order to generate a biocompatible substrate for cell culture. The PANI-Cys films are characterized by Fourier Transform infrared and UV-visible spectroscopy. The changes in the hydrophilicity of the polymer films after and before the modification were tested using contact angle measurements. After modification the contact angle changes from 86°±1 to 90°±1, suggesting a more hydrophylic surface. The adhesion properties of LM2 and HaCaT cell lines on the surface of PANI-Cys films in comparison with tissue culture plastic (TCP) are studied. The PANI-Cys film shows better biocompatibility than PANI film for both cell lines. The cell morphologies on the TCP and PANI-Cys film were examined by florescence and Atomic Force Microscopy (AFM). Microscopic observations show normal cellular behavior when PANI-Cys is used as a substrate of both cell lines (HaCaT and LM2) as when they are cultured on TCP. The ability of these PANI-Cys films to support cell attachment and growth indicates their potential use as biocompatible surfaces and in tissue engineering.

Electroanalysis using modified hierarchical nanoporous carbon materials.

The role of the electrode nanoporosity in electroanalytical processes is discussed and specific phenomena (slow double layer charging, local pH effects) which can be present in porous electrode are described. Hierarchical porous carbon (HPC) materials are synthesized using a hard template method. The three dimensional carbon porosity is examined using scanning electron microscopy on flat surfaces cut using a focused ion beam (FIB-SEM). The electrochemical properties of the HPC are measured using cyclic voltammetry, AC impedance, chronoamperometry and Probe Beam Deflection (PBD) techniques. Chronoamperometry measurements of HPC seems to fit a transmission line model. PBD data show evidence of local pH changes inside the pores, during double layer charging. The HPC are modified by in situ (chemical or electrochemical) formation of metal (Pt/Ru) or metal oxide (CoOx, Fe3O4) nanoparticles. Additionally, HPC loaded with Pt decorated magnetite (Fe3O4) nanoparticles is produced by galvanic displacement. The modified HPC materials are used for the electroanalysis of different substances (CO, O2, AsO3(-3)). The role of the nanoporous carbon substrate in the electroanalytical data is evaluated.

Trombosis del seno venoso cerebral durante el puerperio / Cerebral venous sinus thrombosis during puerperium

Resumen: ANTECEDENTES La trombosis del seno venoso cerebral es un trastorno cerebrovascular caracterizado por obstrucción parcial o total de uno o más senos venosos o venas cerebrales. OBJETIVO Conocer la incidencia y las causas de la trombosis del seno venoso cerebral en el puerperio. MATERIAL Y MÉTODO Estudio retrospectivo, observacional y descriptivo en el que se revisaron expedientes de pacientes obstétricas ingresadas en el servicio de Medicina Interna del Hospital Dr. Aurelio Valdivieso en un periodo de cinco años (2009-2014) que manifestaron clínica y radiológicamente el diagnóstico de trombosis del seno venoso cerebral. RESULTADOS Se encontraron seis pacientes con promedio de edad de 23 años con el diagnóstico de trombosis del seno venoso cerebral, las seis cursaban en periodo de puerperio. Las causas ocasionales fueron: tres por síndrome de anticuerpos antifosfolipídicos primario; una tenía trombofilia primaria por deficiencia de proteína C, un caso se debió a administración de hormonal oral y un caso fue idiopático. En relación con el tratamiento, todas recibieron anticoagulación con buena respuesta. CONCLUSIÓN Encontramos que la trombosis del seno venoso cerebral se observa en nuestro medio por lo menos una vez al año, la causa más frecuente es autoinmunitaria del tipo síndrome de anticuerpos antifosfolipídicos.

Abstract: BACKGROUND Cerebral venous sinus thrombosis is a cerebrovascular disorder characterized by partial or complete blockage of one or more venous sinuses or cerebral veins. MATERIAL AND METHOD A retrospective, observational and descriptive study was done in which records of obstetric patients admitted to the Internal Medicine service of Hospital Dr. Aurelio Valdivieso, Oaxaca, Mexico, were reviewed in a period of five years (2009-2014), who had a clinical and radiological diagnosis of cerebral venous sinus thrombosis. RESULTS Six patients were found, with an average age of 23 years with the diagnosis of cerebral venous sinus thrombosis, six were enrolled in the postpartum period. Occasional causes were: three primary antiphospholipid antibodies syndrome, one had protein C deficiency, one case was receiving oral hormonal and one case of idiopathic etiology. In relation to treatment, all received anticoagulation with good response. CONCLUSION Cerebral venous sinus thrombosis presented in our midst at least once a year, the most common cause is autoimmune antiphospholipid antibodies syndrome/cerebral venous sinus thrombosis type.