ÁLVARO ANTONIO ALENCAR  DE QUEIROZ

ÁLVARO ANTONIO ALENCAR DE QUEIROZ

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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.
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.
Physicochemical and microbial properties of boron-complexed polyglycerol-chitosan dendrimers
2006 - QUEIROZ, ALVARO A.A. de; ABRAHAM, GUSTAVO A.; CAMILLO, MARIA A.P.; HIGA, OLGA Z.; SILVA, GERALD S.; FERNANDEZ, MARIA DEL M.; ROMAN, JULIO S.
Modeling of ZnS quantum dots synthesis by DFT techniques
2008 - QUEIROZ, ALVARO A.A. de; MARTINS, MAYLER; SOARES, DEMETRIO A.W.; FRANCA, ECIO J.
Controlled release of 5-fluorodine from radiation-crosslinked poly(ethylene-co-vinyl acetate) films
2006 - QUEIROZ, ALVARO A.A. de; ABRAHAM, GUSTAVO A.; HIGA, OLGA Z.