Mariselma Ferreira

Angiogenic Properties of Natural Rubber Latex Biomembranes and The Serum Fraction of Hevea brasiliensis

The angiogenic properties of natural rubber were evaluated in this work. We have used the chick chorioallantoic membrane assay (CAM) as a model to investigate the influence of the heating on biological activity in rubber membranes and in non rubber fraction as well. Results showed that natural rubber membranes can induce vascularization. It was observed that angiogenesis activity was maximum when membranes were heated in temperatures between 65oC and 85oC, considering a range from 55oC to 105oC. The same behavior was observed for non rubber fraction and it indicates that this serum fraction may be responsible for angiogenesis. When infrared spectroscopy was performed in the cast films of non rubber fraction samples, as a function of heating, no structural changes was observed. The results obtained shown that natural rubber latex films produced by casting induce the vessel growth in the CAM and it can be considered as a potential biomaterial.

Synergy between polyaniline and OMt clay mineral in Langmuir-Blodgett films for the simultaneous detection of traces of metal ions.

We report on Langmuir-Blodgett (LB) films made with emeraldine salt polyaniline (PAni-ES) and organophilic montmorillonite clay mineral (OMt), where synergy between the components was reached to yield an enhanced performance in detecting trace levels of cadmium (Cd(2+)), lead (Pb(2+)) and copper (Cu(2+)). Detection was carried out using square wave anodic stripping (SWAS) voltammetry with indium tin oxide (ITO) electrodes modified with LB films of PAni-ES/OMt nanocomposite, whose data were compared to those obtained with electrodes coated with neat PAni-ES and neat OMt LB films. The enhanced performance in the nanocomposite may be attributed to the stabilizing and ordering effect promoted by OMt in PAni-ES Langmuir films, which then led to more homogeneous LB films. According to X-ray diffraction data, the stacking of OMt layers was preserved in the LB films and therefore the PAni-ES chains did not cause clay mineral exfoliation. Instead, OMt affected the polaronic state of PAni-ES as indicated in UV-vis, Raman and FTIR spectra, also consistent with the changes observed for the Langmuir films. Taken together these results do indicate that semiconducting polymers and clay minerals may be combined for enhancing the electrical properties of nanostructures for sensing and related applications.

22 – The use of curaua fibers as reinforcements in composites

: Nowadays, there is growing worldwide interest in the use of natural renewable materials to replace synthetic polymers or improve the properties of current materials. Natural fibers seem to offer a great opportunity in this respect, and among them curaua (Ananas erectifolius L. B. Smith) fiber has unique properties, such as high strength, low density, a fine structure and high cellulose content. Due to its mechanical properties and recyclability, it is of great interest for developing composite materials. In addition, because of its high cellulose content, curaua fiber is one of the most potentially important sources of raw material for producing nanocellulose for use in the manufacture of nanocomposites.

Evaluation of cell interaction with polymeric biomaterials based on hyaluronic acid and chitosan

Tissue engineering involves the development of new materials or devices capable of specific interactions with biological tissues, searching the use of biocompatible materials as scaffolds for in vitro cell growth, and functional tissue development, that is subsequently implanted into patient. The aim of the current study was to evaluate the initial aspects of cell interaction with the polymeric biomaterials blends based on hyaluronic acid with chitosan. The hypothesis approach involves synthesis and analysis of swelling and thermal degradation (thermal gravimetric analysis) of the polymer blend; and Vero cell interaction with the biomaterial, through analysis of cytotoxicity, adhesion and cell morphology. The blend resulted in a biomaterial with a high swelling ratio that can allow nutrient distribution and absorption. The thermal gravimetric analysis results showed that the blend had two stages of degradation at temperatures very close to those observed for pure polymers, confirming that the physical mixing of hydrogels occurred, resulting in the presence of both hyaluronic acid and chitosan in the blend. The evaluation of indirect cytotoxicity showed that the blend was non cytotoxic for Vero cells, and the quantitative analysis performed with the MTT could verify a cell viability of 98%. The cells cultured on the blend showed adhesion, spreading and proliferation on this biomaterial, distinguished from the pattern of the control cells. These results showed that the blends produced from hyaluronic acid and chitosan hydrogels are promising for applications in tissue engineering, aiming at future cartilaginous tissue.Graphical Abstract

Cell interactions and cytotoxic studies of cellulose nanofibers from Curauá natural fibers

Cellulose nanofibers (CNF) were isolated from Curauá fibers (Ananas erectifolius L. B. Smith) through a mechanical grinder preceded by mild chemical treatment. Morphology and surface characteristics of the fibers were followed until it reaches the nanoscale as long and flexible nanofibers. In aqueous suspensions, SAXS techniques revealed that such nanofibers present a twisted ribbon structure while rheological measurements demonstrate its high viscosity and a thixotropic behavior. These characteristics suggests the potential application of CNF in biomedical field, which, in turn, stimulates the toxicological studies of such materials. The obtained materials do not show any sign of cytotoxicity by direct or indirect assays for cell viability and cell morphology using Vero cells. Moreover, during the adhesion test, the cells demonstrated higher affinity to the CNF surface. It can be related to its surface properties and its obtaining conditions, which did not use any hazardous chemicals.