Marco Cesar Cunegundes Guimarães

Regulatory T Cell as a Target for Cancer Therapy

Advances in our understanding of CD4+CD25+Foxp3+ regulatory T cells (TRegs) enabled the characterization of their activities in maintaining peripheral tolerance, preventing autoimmune diseases, and limiting chronic inflammatory diseases. Ironically, an effective action of these cells during tumor development can limit beneficial responses by suppressing immunity and limiting antitumor resistance, whereas one of the main functions of the immune system is to eliminate malignant cells. During the last years, the immunological role, mechanism of action, and clinical importance of these cells were profoundly characterized and the relationship between this subset of lymphocytes and cancerous cells arises as a key factor that influences tumor development. Recent insights obtained from clinical studies and experimental mouse models expand our perception of the potential role of TRegs in cancer treatment. In this review we describe the basic mechanisms of TReg origin and differentiation, their potential role in cancer, as well as the future perspectives concerning the modulation of these cells as a potential approach for anticancer strategies.

Evaluation of PvuII and XbaI polymorphisms in the estrogen receptor alpha gene (ESR1) in relation to menstrual cycle timing and reproductive parameters in post-menopausal women

OBJECTIVE To evaluate the association of -397T>C and -351A>G single nucleotide polymorphisms (SNPs) - also called PvuII and XbaI, respectively - located on estrogen receptor alpha (ERS1) gene with age at menarche, menopause onset, fertility and miscarriage in a population of post-menopausal women. STUDY DESIGN Cross-sectional study with 273 healthy, high miscegenated, post-menopausal women (mean age of 63.1±9.7 years old). Subjects were genotyped for PvuII and XbaI SNPs by PCR-RFLP and confirmed by automatic sequencing. Reproduction informations (age at menarche, age at menopause, number of pregnancies, fertility rate and miscarriages) were obtained by retrospective study using a questionnaire. RESULT(S) Age at menarche, menopause onset, number of pregnancies, total fertility rate, and parity did not seem to be influenced by any of the studied genotypes (chi-square, p>0.05). However, women carrying the xx genotype showed a 44% higher chance of miscarriage, whereas this value did not trespass 16% for any other genotype analyzed. It has been also observed a higher occurrence of miscarriage in association with combined xxpp genotype of ERS1 gene (chi-square, p<0.01). CONCLUSION(S) The present data indicate that the studied SNPs on ERS1 gene do not influence the menstrual cycle timing and parity but there is a strong relationship between the xx ERS1 SNP genotype and the incidence of miscarriage in the post-menopausal population analyzed.

Extracellular biosynthesis of silver nanoparticles using the cell-free filtrate of nematophagous fungus Duddingtonia flagrans

The biosynthesis of metallic nanoparticles (NPs) using biological systems such as fungi has evolved to become an important area of nanobiotechnology. Herein, we report for the first time the extracellular synthesis of highly stable silver NPs (AgNPs) using the nematophagous fungus Duddingtonia flagrans (AC001). The fungal cell-free filtrate was analyzed by the Bradford method and 3,5-dinitrosalicylic acid assay and used to synthesize the AgNPs in the presence of a 1 mM AgNO3 solution. They have been characterized by UV–Vis spectroscopy, X-ray diffraction, transmission electron microscopy, dynamic light scattering, Zeta potential measurements, Fourier-transform infrared, and Raman spectroscopes. UV–Vis spectroscopy confirmed bioreduction, while X-ray diffractometry established the crystalline nature of the AgNPs. Dynamic light scattering and transmission electron microscopy images showed approximately 11, 38 nm monodisperse and quasispherical AgNPs. Zeta potential analysis was able to show a considerable stability of AgNPs. The N–H stretches in Fourier-transform infrared spectroscopy indicate the presence of protein molecules. The Raman bands suggest that chitinase was involved in the growth and stabilization of AgNPs, through the coating of the particles. Our results show that the NPs we synthesized have good stability, high yield, and monodispersion.

Virtual Reconstruction and Three-Dimensional Printing of Blood Cells as a Tool in Cell Biology Education

The cell biology discipline constitutes a highly dynamic field whose concepts take a long time to be incorporated into the educational system, especially in developing countries. Amongst the main obstacles to the introduction of new cell biology concepts to students is their general lack of identification with most teaching methods. The introduction of elaborated figures, movies and animations to textbooks has given a tremendous contribution to the learning process and the search for novel teaching methods has been a central goal in cell biology education. Some specialized tools, however, are usually only available in advanced research centers or in institutions that are traditionally involved with the development of novel teaching/learning processes, and are far from becoming reality in the majority of life sciences schools. When combined with the known declining interest in science among young people, a critical scenario may result. This is especially important in the field of electron microscopy and associated techniques, methods that have greatly contributed to the current knowledge on the structure and function of different cell biology models but are rarely made accessible to most students. In this work, we propose a strategy to increase the engagement of students into the world of cell and structural biology by combining 3D electron microscopy techniques and 3D prototyping technology (3D printing) to generate 3D physical models that accurately and realistically reproduce a close-to-the native structure of the cell and serve as a tool for students and teachers outside the main centers. We introduce three strategies for 3D imaging, modeling and prototyping of cells and propose the establishment of a virtual platform where different digital models can be deposited by EM groups and subsequently downloaded and printed in different schools, universities, research centers and museums, thereby modernizing teaching of cell biology and increasing the accessibility to modern approaches in basic science.

Electrochemical and Morphological Investigations of Ga Addition to Pt Electrocatalyst Supported on Carbon

This paper is consisted in the synthesis of platinum-based electrocatalysts supported on carbon (Vulcan XC-72) and investigation of the addition of gallium in their physicochemical and electrochemical properties toward ethanol oxidation reaction (EOR). PtGa/C electrocatalysts were prepared through thermal decomposition of polymeric precursor method at a temperature of 350°C. Six different compositions were homemade: Pt50Ga50/C, Pt60Ga40/C, Pt70Ga30/C, Pt80Ga20/C, Pt90Ga10/C, and Pt100/C. These electrocatalysts were electrochemically characterized by cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), and electrochemical impedance spectroscopy (EIS) in the presence and absence of ethanol 1.0 mol L−1. Thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were also carried out for a physicochemical characterization of those materials. XRD results showed the main peaks of face-centered cubic Pt. The particle sizes obtained from XRD and TEM analysis range from 7.2 nm to 12.9 nm. The CV results indicate behavior typical of Pt-based electrocatalysts in acid medium. The CV, EIS, and CA data reveal that the addition of up to 31% of gallium to the Pt highly improves catalytic activity on EOR response when compared to Pt100/C.

Raman Spectroscopy and Electrochemical Investigations of Pt Electrocatalyst Supported on Carbon Prepared through Plasma Pyrolysis of Natural Gas

Physicochemical and electrochemical characterisations of Pt-based electrocatalysts supported on carbon (Vulcan carbon, C1, and carbon produced by plasma pyrolysis of natural gas, C2) toward ethanol electrooxidation were investigated. The Pt20/C180 and Pt20/C280 electrocatalysts were prepared by thermal decomposition of polymeric precursors at 350°C. The electrochemical and physicochemical characterisations of the electrocatalysts were performed by means of X-ray diffraction (XRD), transmission electron microscope (TEM), Raman scattering, cyclic voltammetry, and chronoamperometry tests. The XRD results show that the Pt-based electrocatalysts present platinum metallic which is face-centered cubic structure. The results indicate that the Pt20/C180 electrocatalyst has a smaller particle size (10.1–6.9 nm) compared with the Pt20/C280 electrocatalyst; however, the Pt20/C280 particle sizes are similar (12.8–10.4 nm) and almost independent of the reflection planes, which suggests that the Pt crystallites grow with a radial shape. Raman results reveal that both Vulcan carbon and plasma carbon are graphite-like materials consisting mostly of sp2 carbon. Cyclic voltammetry and chronoamperometry data obtained in this study indicate that the deposition of Pt on plasma carbon increases its electrocatalytic activity toward ethanol oxidation reaction.

Surface-Enhanced Raman Plasmon in Self-Assembled Sulfide-Coated Gold Nanoparticle Arrays

This paper investigates the surface-enhanced Raman plasmon in self-assembled gold nanoparticle arrays. The self-assembly process reported in this paper is triggered by the addition of sulfide in a sample of citrate-stabilized gold nanoparticles (AuNPs). The characterization of gold nanoparticle arrays was carried out by UV-visible absorption spectrum, transmission electron microscopy (TEM), and Raman map. Results demonstrate an aggregation of AuNPs with a peculiar physical docking resembling nanowires. Moreover, these nanostructures exhibited intense Raman scattering signal when compared with regular AuNPs. This simple technique is a candidate for future applications such as sensors for detecting sulfide compounds and nanosystem fabrication.

Ultrasensitive nanosensor based on silver nanoparticles to detect hydrogen peroxide

Studies to determine the concentration of hydrogen peroxide (H2O2) are important in biological system due to cellular damages provoked by reative oxygen species that include H2O2. An alternative to detect H2O2 is through an optical nanosensors based on silver nanoparticles, which have great potential for chemical and biological sensing applications. Here we demonstrate that attenuated total reflectance (ATR) from interaction of silver nanoparticles and hydrogen peroxide were able to detect very low levels of H2O2 around 0,001mM.

Quantification of Inter-particle Spacing Caused by Thiol Self-Assembled Monolayers Using Transmission Electron Microscopy

AbstractNano-surface modification techniques have been increasingly reported in a multitude of applications. However, the metal-ligand interface can be difficult to characterize, mainly due to the inadequacy of analytical methodologies. Here, we analyze this interface using transmission electron microscopy, which can determine the thickness of the linkers. This work presents a comprehensive physical characterization of gold nanoparticles with modified surfaces using conventional transmission electron microscopy. We have successfully demonstrated a simple and reliable protocol for the quantification of inter-particle spacing caused by SAM thiol ligands bound onto AuNPs. This approach is based on the linear correlation of the distance between the gold nanoparticles and the length of 3-mercaptopropionic acid (MPA), 11-mercaptoundecanoic acid (MUA), and 16-mercaptohexadecanoic acid (MHA). Graphical Abstract

Virola oleifera-capped gold nanoparticles showing radical-scavenging activity and low cytotoxicity

The development of effective nanoparticle therapeutics has been hindered by their surface characteristics, such as hydrophobicity and charge. Therefore, the success of biomedical applications with nanoparticles is governed by the control of these characteristics. In this article, we report an efficient green capping method for gold nanoparticles (AuNPs) by a reduction with sodium citrate and capping with Virola oleifera (Vo), which is a green exudate rich in polyphenols and flavonoids. The Vo-capped AuNPs were characterized by UV, DLS, FTIR, Raman, TEM, DPPH, FRAP and their cytotoxicity was evaluated on the viability of Murine macrophage cell. The AuNPs had an average particle size of 15 nm and were stable over a long time, as indicated by their unchanged SPR and zeta potential values. These nanoparticles were assessed for their antioxidant potential using DPPH and FRAP and demonstrated the highest antioxidant activities and low cytotoxicity. We propose that the Virola oleifera-capped AuNPs have potential biomedical applications.