Maria Gabriela Nogueira Campos

Sorbitol-Plasticized and Neutralized Chitosan Membranes as Skin Substitutes

Chitosan is soluble in diluted acid solutions and can easily form films by casting. However, residual acid neutralization should be performed for biomedical applications what may compromise physical and mechanical properties of the films. Thus, plasticizers can be added to improve these properties. The aim of this study was to characterize morphological, barrier and mechanical properties, besides evaluate the in vitro cytotoxicity of sorbitol-plasticized and NaOH-Na2CO3 neutralized chitosan membranes for skin substitute application. Scanning electron microscopy, X-ray diffraction, water vapor permeability and mechanical tests were carried out to characterize the obtained membranes. Moreover, Vero cells were used for in vitro cytotoxicity evaluation. In this paper, we report a non-cytotoxic sorbitol-plasticized chitosan membrane with desirable properties for skin substitution, such as flexibility, water vapor permeability and high percentage of elongation.

Non-Cytotoxic Quantum Dot–Chitosan Nanogel Biosensing Probe for Potential Cancer Targeting Agent

Quantum dot (Qdot) biosensors have consistently provided valuable information to researchers about cellular activity due to their unique fluorescent properties. Many of the most popularly used Qdots contain cadmium, posing the risk of toxicity that could negate their attractive optical properties. The design of a non-cytotoxic probe usually involves multiple components and a complex synthesis process. In this paper, the design and synthesis of a non-cytotoxic Qdot-chitosan nanogel composite using straight-forward cyanogen bromide (CNBr) coupling is reported. The probe was characterized by spectroscopy (UV-Vis, fluorescence), microscopy (Fluorescence, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering. This activatable (“OFF”/“ON”) probe contains a core–shell Qdot (CdS:Mn/ZnS) capped with dopamine, which acts as a fluorescence quencher and a model drug. Dopamine capped “OFF” Qdots can undergo ligand exchange with intercellular glutathione, which turns the Qdots “ON” to restore fluorescence. These Qdots were then coated with chitosan (natural biocompatible polymer) functionalized with folic acid (targeting motif) and Fluorescein Isothiocyanate (FITC; fluorescent dye). To demonstrate cancer cell targetability, the interaction of the probe with cells that express different folate receptor levels was analyzed, and the cytotoxicity of the probe was evaluated on these cells and was shown to be nontoxic even at concentrations as high as 100 mg/L.

Magnetic Nanoparticles Obtained by Homogeneous Coprecipitation Sonochemically Assisted

The present work demonstrates preparation of magnetic nanoparticles by a novel method. Magnetic nanoparticles with potential for biomedical and environmental applications were obtained by homogeneous coprecipitation method sonochemically assisted. The effect of ultrasonic cavitation on changing the reaction environment was studied. The chemical reaction media used here was very similar to those used for Sono-Fenton process. The ultrasonic energy has driven the growth of particles; smaller diameter nanoparticles were obtained by applying a higher power. For the first time, it was demonstrated the iron oxide nanoparticles synthesis at pH lower than 6.

Chitosan Associated with the Extract of Unripe Banana Peel for Potential Wound Dressing Application

The authors report the preparation of chitosan membranes associated with the extract of unripe banana peel. Extracts were prepared by decoction, using boiling distilled water. The extraction process was repeated three times. First and third extracts served as solvent to prepare chitosan membranes by solvent evaporation technique. The chitosan membranes associated with the first and third extracts of unripe banana peel exhibit good flexibility, transparency, and uniformity. Scanning Electron Microscopy images showed dense membranes. Brownish color of membranes was observed due to the presence of tannins, which was confirmed by Infrared Spectroscopy analysis. Thermal properties of the membranes were evaluated by Differential Scanning Calorimetry (DSC), which exhibited good thermal stability at physiological temperature (37°C). At this temperature and pH 7.2, membranes were also able to absorb fluids. The hydrophilic character of the membranes was determined by contact angle measurements. The membranes demonstrated their capacity for gaseous exchange and exhibited water-vapor permeability (WVP) rates comparable to injured skin one. Finally, high number of viable dermal fibroblasts was observed by indirect cytotoxicity assay suggesting potential application of these membranes as skin wound dressing.

Evaluation of Antibacterial Activity of Chitosan Membranes Associated to Unripe Banana Peel

The treatment of skin wounds is a worldwide problem due to possible complications of healing process, such as infections, sepsis and even death. Current treatment strategies involves the use of dressings, bandages and topical application of antibiotic to the wound. An ideal dressing should protect against bacterial contamination, while covering the wound. The aim of this study was to investigate the antibacterial activity of chitosan membranes associated to banana peel for potential wound dressing application, since both materials have previously demonstrated antimicrobial properties. The active principles of banana peel were extracted by two methods: decoction and drying. Membranes were prepared by chitosan association with the extracts of first and third days of decoction and with different concentrations of dried extract, by the casting/solvent evaporation techniques. All obtained membranes were uniform, flexible and easily unmolded. Antibacterial activity studies were performed by the Surface Plating technique. Inhibition of bacterial growth was evaluated against two bacteria Escherichia coli and Staphylococcus aureus, usually present in skin wounds. All membranes were able to inhibit S. aureus e E. coli growth by contacting. In addition to contacting inhibition of E. coli growth, an inhibition halo of 0.5 cm diameter was also observed around the chitosan-unripe banana peel membrane prepared with the extract of first day of decoction.

Processing of Pet-Silver Nanocomposite Filaments

Nanoparticles play a fundamental role on nanocomposite properties, as they significantly increase the contact area and allow a homogeneous distribution in comparison to microparticles. Silver nanoparticles (AgNP) have been extensively used in biomedical and engineering applications due to their interesting properties, such as antibacterial activity. Polyethylene terephthalate (PET) is a semi-crystalline polymer and has excellent chemical resistance and thermal stability. Because of its remarkable properties, PET has been used in several industrial applications, such as packaging, electrical, automotive, construction and textile. The aim of this study was to prepare potential antimicrobial PET-AgNP nanocomposite filaments for textile applications. Therefore, AgNP were incorporated in the PET matrix at different concentrations (0.05; 0.10; 0.15; 0.20; 0.25; 0.30; 0.35 and 0.40%) by extruding the PET resin with specific amounts of a 10% (w/w) AgNP/PET master batch. Then, rheological characterization was carried out and filaments were produced for mechanical, optical and thermal analyses. The incorporation of up to 0.20% (w/w) of AgNP in the polymeric matrix has not significantly altered overall properties of PET nanocomposites. Moreover, the nanocomposite incorporated with 0.05% of AgNP demonstrated suitable intrinsic viscosity for fiber processing and PET-like mechanical, thermal and optical properties.

Morphological and mechanical characterization of chitosan-calcium phosphate composites for potential application as bone-graft substitutes

Bone diseases, aging and traumas can cause bone loss and lead to bone defects. Treatment of bone defects is challenging, requiring chirurgical procedures. Bone grafts are widely used for bone replacement, but they are limited and expensive. Due to bone graft limitations, natural, semi-synthetic, synthetic and composite materials have been studied as potential bone-graft substitutes. Desirable characteristics of bone-graft substitutes are high osteoinductive and angiogenic potentials, biological safety, biodegradability, bone-like mechanical properties, and reasonable cost. Herein, we prepared and characterized potential bone-graft substitutes composed of calcium phosphate (CP) - a component of natural bone, and chitosan (CS) - a biocompatible biopolymer. Methods CP-CS composites were synthetized, molded, dried and characterized. The effect of drying temperatures (38 and 60 °C) on the morphology, porosity and chemical composition of the composites was evaluated. As well, the effects of drying temperature and period of drying (3, 24, 48 and 72 hours) on the mechanical properties - compressive strength, modulus of elasticity and relative deformation-of the demolded samples were investigated. Results Scanning electron microscopy and gas adsorption-desorption analyses of the CS-CP composites showed interconnected pores, indicating that the drying temperature played an important role on pores size and distribution. In addition, drying temperature have altered the color (brownish at 60 °C due to Maillard reaction) and the chemical composition of the samples, confirmed by FTIR. Conclusion Particularly, prolonged period of drying have improved mechanical properties of the CS-CP composites dried at 38 °C, which can be designed according to the mechanical needs of the replaceable bone.

Contaminants Recovery from Acid Mine Drainage

In some mines where sulfide minerals can occur in form of pyrite acid mine drainage (AMD) may occur, and it constitutes one of the main environmental impact. In order to prevent that AMD compromises aquifers layers and reaches mine surroundings, a treatment that consists in its neutralization with the use of a hydrated lime suspension is usually conducted. Contaminants that are soluble in AMD are precipitated, remaining in the solid phase. The work here presented aims recover uranium and rare earths found in one of these precipitates, which consists of calcium diuranate and metal hydroxides in a calcium sulfate matrix. This material contains approximately 0.25% of triuranium octoxide (U3O8) and 2.5% of rare earth oxides (TR2O3). The recovery of uranium and rare earths contained in the precipitate was performed through a hydrometallurgical process. The test resulted in a leaching with sulfuric acid presented solubilization of 96% for uranium and 90% for rare earths. A percentage yield of 99.7% and 99.9% was obtained in the steps of uranium extraction and re-extraction from the leachate, respectively.

Investigation of Microstructural Changes after Solution Annealing Treatment in a Duplex Stainless Steel

This work investigates the microstructural changes developed during the solution annealing treatment under different conditions for the steel UNS S31803. The studied material was submitted to solution anneal at 1100°C for 30, 120 and 240 min, followed by cooling in water, air and furnace. The results evaluation was based on micrographic analysis and the results showed the influence of treatment period and cooling rates in distribution and morphology of austenitic phase. It was observed the same morphology of austenitic phase in all treatment conditions, however, the volume fraction of this phase increased with the treatment period increase, and further refinement with lower cooling rates. It was found that the solution treatment by longer period with the lower cooling rate significantly enhanced the intermetallic phases transformation. The intermetallic phases precipitation could be detected when the samples were solution-treated for 120 and 240 min and cooled at furnace.

Emprego de membrana de quitosana em feridas cutâneas induzidas experimentalmente em equinos

The aim of this study was to evaluate the effects of chitosan film on wound repair in horse distal limb. Skin wounds were induced on metacarpus and metatarsus region of four adults horses. On treat group, eight wounds were covered with chitosan film and on control group sodium chlorid 0.9% was used. During the experimental period, it was evaluated the wound diameter, exuberant granulation tissue formation, kind of exudat, histological analyzes, and some characteristics of the chitosan film (plasticity during handling and presence or absence of film on each change). The chitosan film had not interfered on healing time, might serving to cover skin wounds, with potential advantages, if it is used as a conductive of substances that interfere positively in the healing process, opening a field to news studies.