ÁLVARO ANTONIO ALENCAR  DE QUEIROZ

ÁLVARO ANTONIO ALENCAR DE QUEIROZ

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Higher electrical conductivity of functionalized graphene oxide doped with silver and copper (II) ions
2023 - PEREIRA, NELSON G.A.; GONZALEZ, MARIA E.L.; QUEIROZ, ALVARO A.A. de; OLIVEIRA, ADHIMAR F.; WANDERLEY NETO, ESTACIO T.
This study presents a new methodology for graphene oxide (GO) synthesis through electrochemical exfoliation of graphite, followed by phthalic anhydride functionalization (PhA-GO) and doping with Cu2+ and Ag+ ions. The synthesis of GO involved the use of an electrochemical cell with H2 SO4 as the electrolyte, with a gradual increase in potential from 2.3 V to 10 V. Extensive characterization techniques confirmed the successful incorporation of oxygen-containing functional groups, verifying the oxidation of graphite. PhA-GO functionalization was confirmed by thermogravimetric analysis, Differential Scanning Calorimetry, Fourier-transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDX), which confirmed the presence of Cu2+ and Ag+ ions. The Scherrer equation determined a grain size of 75.85 nm for GO. The electrical properties exhibited semiconductor and semimetal behavior, particularly in PhA-GO/Ag+ composites, making them suitable for electronic devices over a wide temperature range, presenting a promising pathway for advanced materials in electronic applications.
Poly(vinyl alcohol)/poly(glycerol) dendrimer hydrogel mediated green synthesis of silver nanoparticles
2022 - MARCONDES, POLLYANA; ROSAS, GISELA H.; GONZALEZ, MARIA E.L.; QUEIROZ, ALVARO A.A. de; MARQUES, PAULO S.
In this paper, we report the synthesis and evaluation of a poly(vinyl alcohol)/poly(glycerol) dendrimer hydrogel incorporated with green synthesized silver nanoparticles (PVA/PGLD-AgNPs) using Cinnamomum verum extract as the reducting agent (Cz-extract). The Cz-extract was prepared using ultrasonic technique. UV-visible (UV-vis) spectra of Cz-extract confirmed the presence of cinnamaldehyde. PVA/PGLD-AgNPs films were prepared using 5, 10 and 20 mL of Cz-extract and characterized by UV-vis, Fourier transform infrared spectroscopy, Thermogravimetric analysis and X-ray diffraction (XRD). The surface plasmon resonance band in the UV-vis spectra confirmed the formation of AgNPs. XRD pattern confirmed the presence of silver, with average crystallite sizes calculated by Scherrer equal to 13.64 nm, 16.63nm and 20.27 nm for AgNPs prepared with 5 mL, 10 mL and 20 mL of Cz-extract, respectively. AgNPs release kinetic was studied by Korsmeyer– Peppas model. The antimicrobial results revealed that the PVA/PGLD-AgNPs hydrogels showed good antibacterial activity behavior against Escherichia coli.
Physicochemical and biological properties of nanohydroxyapatite grafted with star-shaped poly(ε-caprolactone)
2022 - KAIRALLA, ELENI C.; BRESSIANI, JOSE C.; BRESSIANI, ANA H. de A.; RIBELA, MARIA T. de C.P.; HIGA, OLGA Z.; QUEIROZ, ÁLVARO A.A. de
To overcome the disadvantages generated by the lack of interfacial bonding between hydroxyapatite nanocrystals (HAPN) and agglomeration of particles in the development of biodegradable nanocomposites a chemical grafting method was applied to modify the surface of HAPN through grafting of the three-arms star-shaped poly(ε-caprolactone) (SPCL) onto the nanoparticles. The chemical grafting of SPCL onto HAPN (SPCL-g-HAPN) has been investigated using Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy (TEM), photoelectron spectroscopy, X-ray diffraction, zeta potential (ZP) and contact angle (CA). TEM micrographs of the SPCL-g-HAPN revealed the existence of hybrid organic/inorganic (O/I) nanoscale domains. The results of albumin (HSA) and fibrinogen (HFb) adsorption indicate resistance to HFb adsorption by SPCL-g-HAPN relatively to unmodified HAPN. The ZP and CA measurement suggest a heterogeneous topology for SPCL-g-HAPN likely due to the existence of hydrophobic-hydrophilic regions on the nanocomposite surface. The enzyme degradation by cholesterol esterase and lipase indicates that the rates of hydrolysis for SPCL-g-HAPN were very slow relative to the SPCL/HAPN blends. The in vitro biological studies showed that the human osteoblast-like cells (MG-63) cells had normal morphology and they were able to attach and spread out on SPCL-g-HAPN surfaces. A higher overall cellular proliferation was observed on SPCL-g-HAPN scaffolds compared to pure HAPN or SPCL materials.
In vitro cytotoxic data on Se-methylselenocysteine conjugated to dendritic poly(glycerol) against human squamous carcinoma cells
2022 - CORREA, NICOLI D.G.; SILVA, FELIPE D.; VIEIRA, DANIEL P.; SOARES, CARLOS R.J.; QUEIROZ, ALVARO A.A. de
Polymeric nanoparticles acting as sources of selenium (Se) are currently an interesting topic in cancer chemotherapy. In this study, polyglycerol dendrimer (DPGLy) was functionalized with seleno-methyl-selenocysteine (SeMeCys) by means of Steglich esterification with 4-dimethylaminopyridine/(l-ethyl-3-(3-dimethylaminopropyl)carbodiimide) (EDC/DMAP) and cerium chloride as cocatalyst in acetonitrile at quantitative yields of 98 ± 1%. The SeMeCys coupling DPGLy efficiency vs. time were determined by Fourier Transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV–Vis) spectroscopy. The cytotoxic effects of SeMeCys–DPGLy on the Chinese Hamster ovary cell line (CHO-K1) and head and neck squamous cell carcinoma (HNSCC) cells line were assessed by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. No signs of general toxicity of SeMeCys–DPGLy against CHO-K1 cells were detectable at which cell viability was greater than 98%. MTS assays revealed that SeMeCys–DPGLy reduced HNSCC cell viability and proliferation at higher doses and long incubation times.
Fabrication of hyperbranched polyglycerols microcapsules from microfluidics guided by artificial neural networks
2021 - ALVES, ANDRESSA A.; QUEIROZ, ÁLVARO A.A. de; QUEIROZ, ALFREDO A.A.E. de
In recent years, the microfluidic approach has received a lot of attention from the scientific community due to the simple and efficient synthesis of highly monodisperse microcapsules used in a variety of applications in biotechnology and medicine such as, for example, materials synthesis, drug encapsulation, among others [1,2]. Thus, in this work, hyperbranched polyglycerol microcapsules (HPGM) were developed using microfluidic technology. Artificial neural network (ANN) feed-forward using multilayer perceptron architecture was trained and applied to model and predict the microfluidic process. The HPGM produced were characterized by scanning electron microscope (SEM), attenuated total reflection-Fourier transform infrared (ATR-FTIR) and thermogravimetric analysis (TGA). The fabricated HPGM showed spherical size and monomodal distribution with an average diameter of 29 μm. The developed ANN proved to be efficient predictor, showing well agreement with the experimental data (R2=0.9983). Based on these results in this research, it was found that the microfluidic device for producing HPGM was successfully developed since it was possible to synthesize microcapsules with targeted properties, monodispersed with high stability and low porosity. In this way, microfluidic technology guided by ANN can be used to synthesize HPGM for biotechnology processes.
Biophysical properties of electrospun chitosan-grafted poly(lactic acid) nanofibrous scaffolds loaded with chondroitin sulfate and silver nanoparticles
2022 - JUNIOR, ALEXANDRE F.; RIBEIRO, CHARLENE A.; LEYVA, MARIA E.; MARQUES, PAULO S.; SOARES, CARLOS R.J.; QUEIROZ, ALVARO A.A. de
The aim of this work was to study the biophysical properties of the chitosan-grafted poly(lactic acid) (CH-g-PLA) nanofibers loaded with silver nanoparticles (AgNPs) and chondroitin-4-sulfate (C4S). The electrospun CH-g-PLA:AgNP:C4S nanofibers were manufactured using the electrospinning technique. The microstructure of the CH-g-PLA:AgNP:C4S nanofibers was investigated by proton nuclear magnetic resonance (1H-NMR), scanning electron microscopy (SEM), UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), and Fourier transform infrared (ATR-FTIR) spectroscopy. ATR-FTIR and 1H-NMR confirm the CH grafting successfully by PLA with a substitution degree of 33.4%. The SEM measurement results indicated apparently smooth nanofibers having a diameter range of 340 ± 18 nm with porosity of 89 ± 3.08% and an average pore area of 0.27 μm2. UV-Vis and XRD suggest that silver nanoparticles with the size distribution of 30 nm were successfully incorporated into the electrospun nanofibers. The water contact angle of 12.8 ± 2.7° reveals the hydrophilic nature of the CH-g-PLA:AgNP:C4S nanofibers has been improved by C4S. The electrospun CH-g-PLA:AgNP:C4S nanofibers are found to release ions Ag+ at a concentration level capable of rendering an antimicrobial efficacy. Gram-positive bacteria (S.aureus) were more sensitive to CH-g-PLA:AgNP:C4S than Gram-negative bacteria (E. coli). The electrospun CH-g-PLA:AgNP:C4S nanofibers exhibited no cytotoxicity to the L-929 fibroblast cells, suggesting cytocompatibility. Fluorescence microscopy demonstrated that C4S promotes the adhesion and proliferation of fibroblast cells onto electrospun CH-g-PLA:AgNP:C4S nanofibers.
Microfluidic caging lipase in hyperbranched polyglycerol microcapsules for extracorporeal treatment of enzyme pancreatic insufficiency
2021 - ALVES, ANDRESSA A.; QUEIROZ, ALFREDO A.A.E. de; SOARES, CARLOS R.J.; QUEIROZ, ALVARO A.A. de
Lipase cartridges are currently the mainstay of treatment to improve fat absorption related to pancreatic insufficiency (PI) in patients receiving enteral nutrition feedings. Enzyme immobilization is an essential prerequisite for designing lipase cartridges systems for efficient enzymatic fat hydrolysis. A microfluidic approach has been adopted to produce lipase (LIP) caged in hyperbranched polyglycerol microcapsules (HPGly). The resulting HPGly-LIP microcapsules are spherical and had an average diameter of 29 µm with monomodal size distribution. The optimum conditions determined by artificial neural networks were HPGly concentration of 10 wt.%, LIP loading of 20% (wt) and total flow rate in microfluidic cell of 1.0 mL/h. Under these conditions, the maximum capacity of the LIP that can be microencapsulated is around 85% with respect to the HPGly concentration of 10 wt.% and total flow rate in microfluidic cell of 1.0 mL/h. This resultant HPGly-LIP exhibited Michaelis–Menten coefficients of 1.138,14 mM (Km) and 0.49 U/mg (Vmax) showing higher activity compared to free LIP. Finally, the robust HPGly-LIP microcapsules showed excellent recyclability. The in vitro Analysis of the HPGly-LIP cytotoxicity showed that microcapsules had no cytotoxic effect to L929 fibroblasts cells and behaved very similar to the negative control. These features will be useful for the facile construction of biocatalytic systems with high efficiency, excellent recyclability and adequate biocompatibility for treatment of patients with PI receiving enteral nutrition feedings.
Intelligent optical temperature sensor based on polyglycerol dendrimer microspheres encapsulating hopeites
2021 - OLIVEIRA, MAYARA L.P. de; WANDERLEY NETO, ESTACIO T.; QUEIROZ, ALFREDO A.A.E. de; QUEIROZ, ALVARO A.A. de
Optical thermometry is a growing technological field which exploits the ability of certain materials to change their optical properties with temperature. In this work, poly(glycerol dendrimer) microspheres (PGLyD) encapsulating cobalt-doped hopeite (CoHo) was synthesized for its potential use as optical thermometer. The structure of the CoHo:PGLyD was studied using scanning electron microscopy (SEM), infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). On the basis of SEM images, the CoHo:PGLyD exhibited a spherical shape in which around 80% of the microspheres were within 0.82 µm. A multilayer feed-forward artificial neural network (MLP-ANN) was used to extract the chromaticity profile dependence of the CoHo:PGLyD with temperature. A color change was observed for the CoHo:PGLyD, going from dark blue (490-550 nm) to pale pink (650 nm) when the temperature changed from 20-200 °C, respectively. These results suggest that CoHo:PGLyD is a promising material for temperature sensing applications.
Intelligent electrospun thermochromic composite nanofibers for temperature measurements
2021 - PERES, MAYARA L. de O.; NETO, ESTACIO T.W.; QUEIROZ, ALFREDO A.A.E. de; QUEIROZ, ALVARO A.A. de
Thermochromic nanofibers (NFs) have emerged as an important class of nanostructured materials and have found a broad range of technologic applications. Herein, an optical fiber temperature sensor composed of coating electrospun thermochromic NFs on the end-face of fiber is reported. A composite coating consisting of an aqueous dispersion of a thermochromic material (cobalt-doped zinc phosphate or also called cobalt-doped hopeite -CoHo), in polyglycerol dendrimer (PGD), was directly electrospun onto the end-face surface of multimode optical fiber for the fabrication of temperature optical fiber sensor. Morphological features and optical properties of the resulting electrospun CoHo:PGD NFs were assessed. The diameter of the electrospun CoHo:PGDNFs deposited on the end-face of optical fiber was 500 ± 14 nm. The spectroscopic absorption of the electrospun CoHo:PGDNFs at 630 nm is measured to determine their relationship with temperature. The results under variable temperature from 25 to 250 °C indicate good linearity and show the potential of using CoHo:PGDNFs sensing applications for control in industrial processes that require a steady or changing temperature. To extract the chromaticity profile of the CoHo:PGDNFs and their temperature dependence, a multilayer feed-forward artificial neural network (ANN) was used. ANN has been successfully employed to extract temperature information from the chromatic changes of CoHo:PGDNFs.
Effects of highly porous electrospun hyperbranched polyglycerol scaffolds on the adhesion and spreading fibroblasts in vitro
2014 - BARATELA, FERNANDO J.C.; HIGA, OLGA Z.; PASSOS, ESDRAS D. dos; QUEIROZ, ALVARO A.A. de