Patricia Fernanda Andrade

Fabrication of transparent and ultraviolet shielding composite films based on graphene oxide and cellulose acetate.

Graphene oxide (GO) has been considered a promising filler material for building polymeric nanocomposites because of its excellent dispersibility and high surface area. In this work, we present the fabrication and characterization of transparent and ultraviolet (UV) shielding composite films based on GO and cellulose acetate (CA). GO sheets were found to be well-dispersed throughout the CA matrix, providing smooth and homogeneous composite films. Moreover, the GO sheets were completely embedded within the CA matrix and no presence of this nanomaterial was found at the surface. Nevertheless, CAGO composite films offered an improved high energy light-shielding capacity when compared to pristine CA films. Particularly for UVC irradiation, the CAGO film containing 0.50wt% GO displayed a UV-shielding capacity of 57%, combined with 79% optical transparency under visible light. These CAGO composite films can be potentially applied as transparent UV-protective coatings for packing biomedical, pharmaceutical, and food products.

Structural and morphological investigations of β-cyclodextrin-coated silver nanoparticles.

This paper describes the synthesis of silver nanoparticles using an aqueous silver nitrate solution in the presence of glucose as a reducing agent, sodium hydroxide as a reaction catalyst and β-CD as a stabilizer. The structure and the morphology associated to the stabilizing layer around the silver nanoparticles were investigated. Raman spectroscopy confirmed the nanoparticle surface modification by β-CD, demonstrating the interaction between the β-CD rim hydroxyl groups and the AgNP surface. Transmission electron microscopy images showed an average 28.0nm diameter pseudo-spherical nanoparticles. Apart from this, a novel characterization of the β-CD layer surrounding the nanoparticles was carried out by using complementary analytical electron microscopy based on electron spectroscopy imaging in the transmission microscope. Mapping images revealed the presence of carbon and oxygen, demonstrating the existence of a uniform and interacting β-CD layer covering the nanoparticles. The antibacterial activity was also investigated and the β-CD-coated silver nanoparticles showed a promising bactericidal activity against the microorganism Escherichia coli.

Cellulose acetate membrane embedded with graphene oxide-silver nanocomposites and its ability to suppress microbial proliferation

Abstract Bacterial adhesion and consequent biofilm formation are one the biggest hurdles in membrane-based technologies. Due to numerous problems associated with bacterial colonization on membrane surfaces, the development of new approaches to prevent microbial growth has been encouraged. Graphene oxide, produced by the chemical exfoliation of graphite, is a highly water-dispersible nanomaterial which has been used as a platform for the anchoring of nanoparticles and bioactive molecules. In this present study, we propose the fabrication of antimicrobial membranes through the incorporation of graphene oxide-silver nanocomposites into a cellulose acetate polymeric matrix. Transmission electron microscopy, Raman, and UV–visible diffuse reflectance spectroscopy measurements confirmed the presence of graphene oxide-silver sheets in the modified membranes. In comparison to pristine membranes, membranes containing graphene oxide-silver nanocomposites showed larger surface pores and increased pure water flux. In addition, membranes embedded with graphene oxide-silver presented strong antibacterial activity, being able to inactivate adhered bacteria at a rate of 90% compared to pristine cellulose acetate membranes. Our results strongly suggest that the incorporation of graphene oxide-silver nanocomposites to cellulose acetate is a promising strategy to produce membranes that are able to minimize bacterial attachment and growth.Graphical Abstract

Silver nanoparticles/silver chloride (Ag/AgCl) synthesized from Fusarium oxysporum acting against Klebsiella pneumouniae carbapenemase (KPC) and extended spectrum beta-lactamase (ESBL)

Silver nanoparticles/silver chloride (Ag/AgCl) biogenically synthesized acted efficiently on all the bacteria that produced beta-lactamases (Extended Spectrum beta-lactamase-ESBL or Klebsiella pneumoniae carbapenemase-KPC). The presence of imipenem (IPM)/Ag/AgCl showed synergism between the IPM antibiotic and Ag/AgCl nanoparticles. The results obtained with E. coli wild type and beta-lactamases producing bacteria reinforced the potentiality of silver nanoparticles on beta-lactamase enzymes, since E. coli is free of any beta-lactamase enzymatic mechanism, and it was not observed any alteration in the IPM zone inhibition with the silver nanoparticles. The study of biogenic nanoparticles efficacy against resistant microorganism is very important due to progressive increase of antibiotic resistant bacteria. Introduction Klebsiella pneumoniae carbapenemase (KPC)-producing bacteria are a group of emerging highly drug-resistant Gram-negative bacilli causing infections associated with significant morbidity and mortality. Although there are new agents within existing classes of antimicrobials, currently there are no new classes of antimicrobials in the later phases of development with activity against multi drug resistant Gramnegative bacteria [1]. The worldwide spread of KPC-producing K. pneumoniae strains (KPC-KP) has revealed the successful dissemination of a major clone defined as sequence type 258 (ST258). Since 2006, KPC-KP has arisen in South America, particularly in countries bordering Uruguay, Argentina and Brazil [2]. The enzymes beta-lactamases are distributed in the planet and have the capacity of degrade the beta-lactamic antibiotics, a class of pharmaceutical widely used in a severe bacterial infection. Among these enzymes is the ESBL (Extended Spectrum beta-lactamase) and KPC (Klebsiella pneumoniae carbapenemase) that exhibited different action spectra on beta-lactamic antibiotics [3-5]. Many efforts in these last years have dedicated in the development of new drugs or materials due to the emergence and increase of microbial organisms resistant to multiple antibiotics. The most new promising nanomaterials with antibacterial properties are the metallic nanoparticles such as silver nanoparticles [6]. Silver nanoparticles are from a long time known for many researchers, and in this direction were published excellent reviews in the last two years [7-15]. Few reviews were reported on biogenic AgCl nanoparticles [16]. Since, silver nanoparticles as also AgCl nanoparticles showed excellent activity against bacteria, it was interesting to evaluate the affectivity against resistant bacteria. Then, the aim of this work was to evaluate the antibacterial activities of Ag/AgCl nanoparticles combined with imipenem (IPM) against bacteria with resistance mechanism for beta-lactamase. Experimental part Biosynthesis of silver nanoparticles: The Fusarium oxysporum (F. oxysporum) strain used was the following: 07 SD, from ESALQ-USP Genetic and Molecular Biology Laboratory-Piracicaba, S.P., Brazil. The fungal inoculates were prepared in a malt extract 2% and yeast extract Correspondence to: ENelson Durán, Institute of Chemistry, University of Campinas, CP 13083-970, Campinas, SP, Brazil, Tel: +55-19-35213149; E-mail: duran@iqm.unicamp.br Simone U. Picoli, Institute of Health Sciences, Biomedicine Laboratory, Universidade FEEVALE, Novo Hamburgo, RS, Brazil, E-mail: simonepi@terra.com.br

Development of double emulsion nanoparticles for the encapsulation of bovine serum albumin

In the present work, a double emulsion was developed for the encapsulation of Bovine Serum Albumin (BSA) as a model protein for the future encapsulation of viral proteins. The first emulsion polydispersity index (PDI) was studied with increasing concentrations of poly (ε-caprolactone) (PCL) as stabilizer (from 16% w/v to 5% w/v) and polyvinyl alcohol (PVA) as the surfactant in the second emulsion at 1.5% w/v. Results suggest that at decreasing concentrations of PCL the PDI of the emulsion also decrease, indicating that viscosity of the emulsion is crucial in the homogeneity of the resultant size distribution of the nanoparticles. When PVA concentration in the second emulsion was increased from 1.5% w/v to 2.5% w/v the PDI also increased. To study the relationship between the structure of the surfactant in the second emulsion and the resultant BSA encapsulation, emulsions were prepared with Pluronic F68 and PVA both at 1.5% w/v and PCL in the first emulsion at 5% w/v. Results indicated that Pluronic F68 was a better stabilizer because at the same experimental conditions encapsulation of BSA was 1.5 higher than PVA. FTIR studies confirmed the presence of BSA in the nanoparticles. SEM and TEM microscopies showed a size distribution of 300nm-500nm size of nanoparticles. Circular dichroism studies demonstrated that the secondary structure of the protein was conserved after the encapsulation into the nanoparticles.

Polymeric film of 6-arm-poly(ethylene glycol) amine graphene oxide with poly (ε-caprolactone): Adherence and growth of adipose derived mesenchymal stromal cells culture on rat bladder

Nanotechnology has been more present in different fields related to health. The need to find a durable material, of easy use, and which does not interfere significantly in the growth and differentiation of stem cells for the construction of a scaffold for use in urologic surgery, with the purpose of reducing infections, regeneration times and even graft rejection during reconstitution in patients with urethral stricture was conducted a broad survey of information about this and came to the consensus of this project: using graphene oxide, a widely studied nanomaterials which has been presenting numerous beneficial results when in contact with the adipose-derived stem cells. Advanced techniques for the growth, differentiation and proliferation of adipose-derived stem cells were used, as well as the characterization of graphene oxide sheets. For this study, it was prepared the graphene oxide/6 ARM-Poly (ethylene glycol) amine films with poly (e-caprolactone). The graphene suspension in organic solvent was prepared by using an ultrasonicator bath and subsequently, the film was formed by solvent evaporation. Total characterization of graphene oxide/6 ARM-PEG-amine/ poly (e-caprolactone) film was carried out. It was tested growth and adhesion of adipose-derived stem cells on the film, as well as, were verified the histopathological effects of this scaffold when implanted in the urinary bladder to repair the lesion. Our results demonstrated that this scaffold with adipose-derived stem cells enhanced the repair in rat urinary bladder defect model, resulting in a regular bladder. Improved organized muscle bundles and urothelial layer were observed in animals treated with this scaffold with adipose-derived stem cells compared with those treated only suture thread or scaffold. Thus, our biomaterial could be suitable for tissue engineered urinary tract reconstruction.

Additive interaction of carbon dots extracted from soluble coffee and biogenic silver nanoparticles against bacteria

It is known the presence of carbon dots (CDs) in carbohydrate based foods. CDs extracted from coffee grounds and instant coffee was also published. CDs from soluble coffee revealed an average size of 4.4 nm. CDs were well-dispersed in water, fluorescent and we have characterized by XPS, XRD analysis, fluorescence and by FTIR spectra. The MIC value by serial micro-dilution assays for CDs on S. aureus ATCC 25923 was 250 μg/mL and E. coli ATCC 25922 >1000 ug/mL. For silver nanoparticles biogenically synthesized was 6.7 μg/mL. Following the checkerboard assay with combining ½ MIC values of the MICs of 125 μg/mL of carbon dots and 3.4 μg/mL of silver nanoparticles, following the fractionated inhibitory concentration (FIC) index methodology, on S. aureus gave a fractionated inhibitory concentration (FIC) value of 1.0, meaning additive interaction. In general, the unfunctionalized CDs showed to be inefficient as antibacterial compounds, however the CDs extracted from Coffee powder and together silver nanoparticles appeared interesting as antibacterial association.

Graphene oxide sheets-based platform for induced pluripotent stem cells culture: toxicity, adherence, growth and application

It was prepared the graphene oxide (GO) sheets by suspension of GO in ultrapure deionized water or in Pluronic F-68 using a ultrasonicator bath. Total characterization of GO sheets was carried out. The results on suspension of GO in water showed excellent growth and cell adhesion. GO/Pluronic F-68 platform for the growth and adhesion of adipose-derived stem cells (ASCs) that exhibits excellent properties for these processes. GO in water suspension exhibited an inhibition of the cell growth over 5 μg/mL In vivo study with GO suspended in water (100 μg/mL) on Fisher 344 rats via i.p. administration showed low toxicity. Despite GO particle accumulates in the intraperitoneal cavity, this fact did not interfere with the final absorption of GO. The AST (aspartate aminotransferase) and ALT (alanine aminotransferase) levels (liver function) did not differ statistically in all experimental groups. Also, creatinine and urea levels (renal function) did not differ statistically in all experimental groups. Taking together, the data suggest the great potential of graphene oxide sheets as platform to ACSs, as well as, new material for treatment several urological diseases.