Comparison of the performance of natural latex membranes prepared with different procedures and PTFE membrane in guided bone regeneration (GBR) in rabbits.

This work assessed the performance of membranes made of natural latex extracted from Hevea brasiliensis prepared with three different methods: polymerized immediately after collection without the use of ammonia (L1); polymerized after preservation in ammonia solution (L2); and polymerized after storage in ammonia, followed by Soxhlet technique for the extraction of substances (L3). Polytetrafluoroethylene (PTFE) membrane was used as control. Two 10-mm diameter bone defects were surgically made in the calvaria of thirty adult male New Zealand rabbits. Defects (total n = 60) were treated with guided bone regeneration (GBR) using L1, L2, L3 or PTFE membranes (n = 15 for each membrane). Ten animals were euthanized after 7, 20 and 60 days postoperatively so that five samples (n = 5) of each treatment were collected at each time, and bone regeneration was assessed microscopically. The microscopic analysis revealed defects filled with blood clot and new bone formation at the margins of the defect in all 7-day samples, while 20-day defects were mainly filled with fibrous connective tissue. After 60 days defects covered with L1 membranes showed a significantly larger bone formation area in comparison to the other groups (P < 0.05, ANOVA, Tukey). Additionally, bone tissue hypersensitization for L1 and PTFE membranes was also investigated in six additional rabbits. The animals were subjected to the same surgical procedure for the confection of one 10-mm diameter bone defect that was treated with L1 (n = 3) or PTFE (n = 3). Fifty-three days later, a second surgery was performed to make a second defect, which was treated with the same type of membrane used in the first surgery. Seven days later, the animals were euthanized and samples analyzed. No differences among L1 and PTFE samples collected from sensitized and non-sensitized animals were found (P > 0.05, Kruskal-Wallis). Therefore, the results demonstrated that latex membranes presented performance comparable to PTFE membranes, and that L1 membranes induced higher bone formation. L1 and PTFE membranes produced no hypersensitization in the bone tissue.

Biocompatibility studies of natural rubber latex from different tree clones and collection methods.

Natural rubber latex (NRL) has several features that make it an excellent biomaterial to promote the growth and repair of tissues, skin and bones. Most of the research with NRL membranes uses a mixture of different clones and chemical preservatives in the collection process. In this study, we compared five clones that produce NRL, seeking to identify their differences in biocompatibility. The clones studied were RRIM 600, PB 235, GT1, PR 255 and IAN 873 commonly found in plantations in Brazil. We did also study the effect of ammonia used during latex collection. NRL membranes were prepared aseptically and sterilized. In the in vitro tests, the membranes remained in direct contact with mouse fibroblasts cells for three periods, 24, 48 and 72 h. In the in vivo tests, the membranes were implanted subcutaneously in rabbits. The results indicated the biocompatibility of the membranes obtained from all clones. Membranes from the clones RRIM 600 and IAN 873 induced greater cell proliferation, suggesting greater bioactivity. It was found that the membranes made from latex that was in contact with ammonia during collection, showed cytotoxic and genotoxic effects in cultures, as well as necrosis, and increased inflammatory cells in the rabbit's tissues close to the implant.

Date fruit melanin is primarily based on (-)-epicatechin proanthocyanidin oligomers.

Plant-based melanin seems to be abundant, but it did not receive scientific attention despite its importance in plant biology and medicinal applications, e.g. photoprotection, radical scavenging, antimicrobial properties, etc. Date fruit melanin (DM) has complex, graphene-like, polymeric structure that needs characterization to understand its molecular properties and potential applications. This study provides the first investigation of the possible molecular composition of DM. High performance size-exclusion chromatography (HPSEC) suggested that DM contains oligomeric structures (569-3236 Da) and transmission electron microscopy (TEM) showed agglomeration of these structures in granules of low total porosity (10-1000 Å). Nuclear magnetic resonance (NMR) spectroscopy provided evidence for the presence of oligomeric proanthocyanidins and electron paramagnetic resonance (EPR) spectroscopy revealed a g-factor in the range 2.0034-2.005. Density functional theory (DFT) calculations suggested that the EPR signals can be associated with oligomeric proanthocyanidin structures having 4 and above molecular units of (-)-epicatechin. The discovery of edible melanin in date fruits and its characterization are expected to open a new area of research on its significance to nutritional and sensory characteristics of plant-based foods.

Exploring the Charge Transport of a Natural Eumelanin for Sustainable Technologies.

Eumelanin, the main quinone-based biomaterial of the melanin family of compounds, is emerging as a model for medical and sustainable electronic interfaces due to its biocompatibility, biodegradability, and transducing abilities. The study utilizes current-voltage measurements and impedance/dielectric spectroscopy under a controlled hydration atmosphere to investigate the charge transport of eumelanin produced from the S. parvus BSB49 strain. We show no differences in the electrical response in highly hydrated conditions compared to the standard synthetic eumelanin. Hence, our findings provide the groundwork to assess the potential use of this natural eumelanin in sustainable organic (bio)electronic applications.

Structural changes of conjugated Pt-containing polymetallaynes exposed to gamma ray radiation doses.

The effect of (60)Co gamma rays irradiation on the polymetallayne [-Pt(PBu(3))-C≡C-C(6)H(4)-C(6)H(4)-C≡C-](n) (Pt-DEBP) of defined chain length corresponding to 10 repeat units, has been studied in detail. The UV-vis absorption spectra of Pt-DEBP have been recorded in solution upon exposure of the polymetallayne at increasing radiation doses in the range up to 90 Gy, with special care to the features related to low doses. Complex modifications of the chemical structure of Pt-DEBP could be accessed through NMR, FTIR, GPC, and XPS characterizations, which support the attack of Cl and H radicals coming from the radiolysis of the solvent, CHCl(3), to the triple C≡C bonds of the backbone, leading to the formation of chlorinated double and single C-C bonds, with a concomitant increase of the molecular weight due to a recombinant effect of oligomer fragments upon irradiation. The presence of vinyl and single chlorinated moieties has been sustained from the simulation of the UV-vis spectra based on theoretical calculations.

Introduction to celebrating Latin American talent in chemistry.

In celebration of the excellence and breadth of Latin American research achievements across the chemical sciences, we are delighted to present an introduction to the themed collection, Celebrating Latin American talent in chemistry.

Reactivity of eumelanin building blocks: A DFT study of monomers and dimers.

Melanins are natural pigments with important biological properties and have been considered promising materials for several bio-electronic applications. In spite of it, until now there is no satisfactory understanding of the macromolecular structure of these compounds. In this work, we have employed electronic structure calculations to evaluate the local reactivity on monomeric building blocks of eumelanin and on a varied combination of these units (dimers). The reactivity studies were accomplished by Condensed-to-Atoms Fukui Indexes in a DFT approach. The results have evidenced a dominance order in the reactivity of the building units that guides the polymerization process of melanin. In addition, from the differences of the local reactivities it was possible to better understand the reactions that can take place during eumelanin synthesis and estimate how they could be influenced by experimental conditions.

Photoinduced hole-transfer in semiconducting polymer/low-bandgap cyanine dye blends: evidence for unit charge separation quantum yield.

Power-conversion efficiencies of organic heterojunction solar cells can be increased by using semiconducting donor-acceptor materials with complementary absorption spectra extending to the near-infrared region. Here, we used continuous wave fluorescence and absorption, as well as nanosecond transient absorption spectroscopy to study the initial charge transfer step for blends of a donor poly(p-phenylenevinylene) derivative and low-band gap cyanine dyes serving as electron acceptors. Electron transfer is the dominant relaxation process after photoexcitation of the donor. Hole transfer after cyanine photoexcitation occurs with an efficiency close to unity up to dye concentrations of approximately 30 wt%. Cyanines present an efficient self-quenching mechanism of their fluorescence, and for higher dye loadings in the blend, or pure cyanine films, this process effectively reduces the hole transfer. Comparison between dye emission in an inert polystyrene matrix and the donor matrix allowed us to separate the influence of self-quenching and charge transfer mechanisms. Favorable photovoltaic bilayer performance, including high open-circuit voltages of approximately 1 V confirmed the results from optical experiments. The characteristics of solar cells using different dyes also highlighted the need for balanced adjustment of the energy levels and their offsets at the heterojunction when using low-bandgap materials, and accentuated important effects of interface interactions and solid-state packing on charge generation and transport.

Identification of Common Resonant Lines in the EPR Spectra of Melanins.

Melanins are natural pigments with promising bioelectronic applications. Among their unique properties, the existence of a persistent paramagnetic signal can be considered one of the most intriguing and controversial features. Additionally, the possible influence of such centers on charge transport accentuates the need for a better understanding of their origin and specific characteristics. In this report, electron paramagnetic resonance spectra of melanin samples obtained at different experimental conditions were systematically studied. From the fitting procedure, three distinct resonant lines are proposed, two associated with carbon-centered radicals and one with semiquinone free radicals.

K-band EPR dosimetry: small-field beam profile determination with miniature alanine dosimeter.

The use of small-size alanine dosimeters presents a challenge because the signal intensity is less than the spectrometer sensitivity. K-band (24 GHz) EPR spectrometer seems to be a good compromise between size and sensitivity of the sample. Miniature alanine pellets were evaluated for small-field radiation dosimetry. Dosimeters of DL-alanine/PVC with dimensions of 1.5 mm diameter and 2.5 mm length with 5 mg mass were developed. These dosimeters were irradiated with 10 MV X-rays in the dose range 0.05-60 Gy and the first harmonic (1h) spectra were recorded. Microwave power, frequency and amplitude of modulation were optimized to obtain the best signal-to-noise ratio (S/N). For beam profile determination, a group of 25 dosimeters were placed in an acrylic device with dimensions of (7.5 x 2.5 x 1)cm3 and irradiated with a (3 x 3)cm2 10 MV X-rays beam field size. The dose at the central region of the beam was 20 Gy at a depth of 2.2 cm (build up for acrylic). The acrylic device was oriented perpendicular to the beam axis and to the gantry rotation axis. For the purposes of comparison of the spatial resolution, the beam profile was also determined with a radiographic film and 2 mm aperture optical densitometer; in this case the dose was 1 cGy. The results showed a similar spatial resolution for both types of dosimeters. The dispersion in dose reading was larger for alanine in comparison with the film, but alanine dosimeters can be read faster and more directly than film over a wide dose range.

K-band ESR spectra of calcite stalagmites from southeast and south Brazil.

Samples of calcite stalagmites from Caverna Santana (Sao Paulo State) and Caverna Botuvera (Santa Catarina State), southeastern and southern Brazil, respectively, were studied by electron spin resonance (ESR). The more common microwave frequency (X-Band, 9.5 GHz) as well as higher frequency K-band, 24 GHz were employed for the determination of the age of the samples. Even after extensive signal averaging, the dosimetric signal is not very well defined in the X-band (9.5 GHz). Using the K-band spectrometer it was possible to clearly identify the 6 hyperfine lines of Mn2+ and other paramagnetic centers in the g=2 region: SO2- and CO2- radicals. The use of high microwave frequency gives better S/N and spectral resolution making the identification of the dosimetric signal easier. The total dose (TD) or equivalent dose (ED) deposited in the samples was 2.3+/-0.3 Gy and 1.7+/-0.4 Gy for Caverna Botuvera samples and 2.6+/-0.7 Gy for the sample of Caverna Santana, giving an age of 2.9+/-0.7 ky, 2.1+/-0.8 ky and 3+/-1 ky, respectively. These first results are compatible with U/Th analysis. Due to the low S/N precision, measurements were possible only with the use of secondary standard composed on Mn2+ lines, naturally present in this sample.

ESR dating at K and X band of northeastern Brazilian megafauna.

The archaeological dose (AD) was measured in three tooth samples of giant mammals that belonged to Brazilian megafauna using electron spin resonance (ESR) spectroscopy at X-band (nu approximately 9.5 GHz) and K-band (nu approximately 24 GHz). Samples were collected in Lagoa de Dentro, Puxinanã city in Paraiba, a northeast state in Brazil and were identified as Haplomastodon waringi (Holland) (two teeth) and one tooth sample of Xenorhinotherium bahiense (Cartele and Lessa). The average AD led to an age for the Haplomastodon samples of 11.6 ky bp. For one sample (Haplomastodon) K-band was also employed to evaluate the AD. The K-band spectrum had three components, determined using spectral simulation as follows: a wide isotropic line with g factor 2.0048, an orthorhombic line with g(x)=2.0034, g(y)=2.0022 and g(z)=1.9974, and another isotropic line with g factor 2.0008. The amplitude of these three signals increase with the added dose and the average dose found was 26+/-5 Gy. This result is compatible with the AD determined with X-band 21+/-3 Gy.

Preliminary evaluation of second harmonic direct detection scheme for low-dose range in alanine/EPR dosimetry.

The usefulness of a direct detection scheme of the second harmonic (2h) overmodulated signal from irradiated alanine in EPR dosimetry was studied. For this purpose, a group of DL-alanine/paraffin cylindrical pellets was produced. The dosimeters were irradiated with a 60Co radiotherapy gamma source with doses of 0.05, 0.1, 0.5, 1 and 5 Gy. The EPR measurements were carried out in a VARIAN-E4 spectrometer operating in X-band with optimized parameters to obtain highest amplitude signals of both harmonics. The 2h signal was detected directly at twice the modulation frequency. In preliminary results, the 2h showed some advantages over the 1 h such as better resolution for doses below 1 Gy, better repeatability results and better linear behaviour in the dose range indicated.

Eumelanin thin films: solution-processing, growth, and charge transport properties.

Eumelanin pigments show hydration-dependent conductivity, broad-band UV-vis absorption, and chelation of metal ions. Solution-processing of synthetic eumelanins opens new possibilities for the characterization of eumelanin in thin film form and its integration into bioelectronic devices. We investigate the effect of different synthesis routes and processing solvents on the growth, the morphology, and the chemical composition of eumelanin thin films using atomic force microscopy and X-ray photoelectron spectroscopy. We further characterize the films by transient electrical current measurements obtained at 50% to 90% relative humidity, relevant for bioelectronic applications. We show that the use of dimethyl sulfoxide is preferable over ammonia solution as processing solvent, yielding homogeneous films with surface roughnesses below 0.5 nm and a chemical composition in agreement with the eumelanin molecular structure. These eumelanin films grow in a quasi layer-by-layer mode, each layer being composed of nanoaggregates, 1-2 nm high, 10-30 nm large. The transient electrical measurements using a planar two-electrode device suggest that there are two contributions to the current, electronic and ionic, the latter being increasingly dominant at higher hydration, and point to the importance of time-dependent electrical characterization of eumelanin films.

Subcutaneous tissue reaction and cytotoxicity of polyvinylidene fluoride and polyvinylidene fluoride-trifluoroethylene blends associated with natural polymers.

Cytotoxicity and subcutaneous tissue reaction of innovative blends composed by polyvinylidene fluoride and polyvinylidene fluoride-trifluoroethylene associated with natural polymers (natural rubber and native starch) forming membranes were evaluated, aiming its applications associated with bone regeneration. Cytotoxicity was evaluated in mouse fibroblasts culture cells (NIH3T3) using trypan blue staining. Tissue response was in vivo evaluated by subcutaneous implantation of materials in rats, taking into account the presence of necrosis and connective tissue capsule around implanted materials after 7, 14, 21, 28, 35, 60, and 100 days of surgery. The pattern of inflammation was evaluated by histomorphometry of the inflammatory cells. Chemical and morphological changes of implanted materials after 60 and 100 days were evaluated by Fourier transform infrared (FTIR) absorption spectroscopy and scanning electron microscopy (SEM) images. Cytotoxicity tests indicated a good tolerance of the cells to the biomaterial. The in vivo tissue response of all studied materials showed normal inflammatory pattern, characterized by a reduction of polymorphonuclear leukocytes and an increase in mononuclear leukocytes over the time (p < 0.05 Kruskal-Wallis). On day 60, microscopic analysis showed regression of the chronic inflammatory process around all materials. FTIR showed no changes in chemical composition of materials due to implantation, whereas SEM demonstrated the delivery of starch in the medium. Therefore, the results of the tests performed in vitro and in vivo show that the innovative blends can further be used as biomaterials.

Optical behavior of conjugated Pt-containing polymetallaynes exposed to gamma-ray radiation doses.

The effect of (60)Co γ irradiation on the absorption and emission spectra of the organometallic polymer [-Pt(PBu(3))(2)-C≡C-C(6)H(4)-C(6)H(4)-C≡C-](n) (Pt-DEBP) in chloroform and toluene solutions for dosimetry applications has been studied. The system Pt-DEBP/chloroform can be used for dosimetric applications in two different ways: (i) monitoring of absorption spectra changes for higher doses (higher than 1 Gy), and (ii) monitoring of emission spectra changes for low doses (below 1 Gy). The response of the polymer solution to γ ray doses has been interpreted with the aid of theoretical studies based on time dependent density functional theory (TD-DFT) calculations on the absorption bands of a model complex and of the possible fragments coming from the degradation of the polymer backbone. It has been proposed that the observed changes are promoted by the attack of radicals, from the radiolysis of the solvent, on the polymer triple bonds.

Latex use as an occlusive membrane for guided bone regeneration.

Latex extracted from Hevea brasiliensis was used as an occlusive membrane for guided bone regeneration. Twenty-four rabbits were divided in two groups: treated and control group. Critical size bone defects (2 cm × 1 cm) were surgically made in the rabbit calvarium. Two latex membranes were implanted in each animal of the treated group, whereas the control defect was filled only with autogenous blood clot. After 15, 30, 60, and 120 days, animals from each group were euthanized, and the samples with regenerated bone were removed. No signs of allergy or rejection were noticed around the calvarial bone defect of the treated group. In the histological analysis, no foreign body inflammatory reaction was observed in the adjacent tissues in contact with the membranes demonstrating that latex can be used at injured sites as an aid in the healing process. Histological analysis, digital radiography, and electron spin resonance were used to evaluate the progress of bone repair. The results show significant differences between groups (p < 0.05) suggesting that latex membranes accelerates healing in critical bone defects.

Produção científica na Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto - USP: aplicação do índice de Hirsch / Scientific bibliographic productivity at FFCLRP-USP (undergraduate courses and graduate programs): an application of the h-index

O objetivo do presente trabalho foi analisar/quantificar a produtividade cientifica dos docentes pertencentes à Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo (FFCLRP-USP) vinculados aos oito cursos de graduação e seis programas de pós-graduação. Métodos: Os índices analisados para cada professor foram: 1) número total de artigos (na plataforma Lattes), 2) número de artigos indexados pela Thomson ISI Web ofScience, e 3) o índice-h. Aplicamos os testes ANOVA, Kruskall-Wallis e o Post Hoc (Bonferrroni) para identificar possíveis diferenças entre os cursos de graduação e os programas de pósgraduação.

In this work, an analysis of scientific bibliographic productivity was made using the Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo (FFCLRPUSP) as example. It is a special Institution in the Brazilian University system which encompasses four important areas of knowledge (fields of concentration) in natural, biological, humanities, and social areas. It is composed by four departments which offer altogether eight undergraduate courses:1) Psychology, 2) Pedagogy, 3) Chemistry, 4) Biology, 5) Medical Physics, 6) Biomedical Informatics,7) Sciences of Information and Documentation and 8) Mathematics Applied to Business and sixgraduate programs leading to M.S. and Ph.D. degrees. Moreover, when analyzing the different courses of FFCLRP, they represent typical academic organization in Brazil and Latin America and could be taken as a model for analyzing other Brazilian research institutions.