Osvaldo Novais de Oliveira Jr | Universidade de São Paulo (original) (raw)

Newspaper Articles by Osvaldo Novais de Oliveira Jr

O diagnóstico precoce de certos tipos de câncer ou de enfermidades do sistema nervoso, como escle... more O diagnóstico
precoce de certos tipos de câncer ou de enfermidades do sistema nervoso, como esclerose
múltipla ou neuromielite óptica, poderá ser facilitado em breve com o emprego de novo dispositivo de detecção: um sensor de dimensão nanométrica capaz de identificar os
biomarcadores dessas condições patológicas.

Papers by Osvaldo Novais de Oliveira Jr

An investigation has been made of the interaction between chlorpromazine (CPZ) and monolayers of ... more An investigation has been made of the interaction between chlorpromazine (CPZ) and monolayers of 1,2dipalmitoyl-sn-3-glycerophosphatidylcholine (DPPC) and 1,2-dipalmitoyl-sn-3-glycero[phospho-rac-(1glycerol)] (DPPG), both at the air/water interface and in transferred Langmuir-Blodgett films. The Gibbs free energy, ∆G, and the compressibility modulus (C S -1 ), obtained from the surface pressure isotherms, indicated changes in the in-plane interactions of CPZ/DPPG mixed monolayers, with positive values of ∆G. The arrangement of CPZ in the zwitterionic DPPC monolayers causes a weaker interaction in CPZ/DPPC mixed monolayers, with the ∆G fluctuating around zero. IR measurements in transferred monolayers showed that CPZ did not affect the conformational order of the acyl chains, its effects being limited to the bands corresponding to the headgroups. Furthermore, since no shift was observed for the acyl chain bands, the phase transition induced by CPZ is not a liquid expanded (LE) to liquid condensed (LC) transition, as the latter is associated with chain ordering. Taken together, the IR and compressibility results demonstrate that the effect from CPZ cannot be correlated with temperature changes in the subphase for pure monolayers, in contrast to models proposed by other authors.

International Journal of Molecular Sciences, 2013

We report on optimized architectures containing layer-by-layer (LbL) films of natural rubber late... more We report on optimized architectures containing layer-by-layer (LbL) films of natural rubber latex (NRL), carboxymethyl-chitosan (CMC) and magnetite (Fe 3 O 4 ) nanoparticles (MNPs) deposited on flexible substrates, which could be easily bent by an external magnetic field. The mechanical response depended on the number of deposited layers and was explained semi-quantitatively with a fully atomistic model, where the LbL film was represented as superposing layers of hexagonal graphene-like atomic arrangements deposited on a stiffer substrate. The bending with no direct current or voltage being applied to a supramolecular structure containing biocompatible and antimicrobial materials represents a proof-of-principle experiment that is promising for tissue engineering applications in biomedicine.

Thin polymer films produced by alternating bilayers of natural macromolecules, such as humic acid... more Thin polymer films produced by alternating bilayers of natural macromolecules, such as humic acid (HA) and natural rubber latex (NR) extracted from Hevea brasiliensis, were investigated for their cell-attachment interaction with human fibroblast cells. Layer-by-layer (LbL) films with up to 10 bilayers of PAH/HA or PAH/(HA+Latex) were deposited directly on tissue culture polystyrene substrates (TCPS). In control experiments, cast films were fabricated on TCPS using 0.5% (v/v) of fresh latex and 0.5 g/L solutions of HA in different proportions (latex:HA = 10:1, 5:1, 1:1, 1:2). Both PAH/HA and PAH/(HA+Latex) LbL films exhibited good performance on cell adhesion and growth. On the other hand, the cast films were found to be cell resistant and bioinert coatings. The viability for creating cell interactive materials has been demonstrated for these natural macromolecules using the LbL technique.

Journal of Applied Polymer Science, 2012

The recent biomedical applications of natural rubber (NR) latex, mostly in dry membranes, have mo... more The recent biomedical applications of natural rubber (NR) latex, mostly in dry membranes, have motivated research into novel, more noble uses of this low-cost biomaterial. In this article, we provide the first report on the fabrication of layer-by-layer (LbL) films of NR alternated with the polyelectrolytes polyethylenimine (PEI) and polyallylamine hydrochloride (PAH). Stable (PAH/NR) n and (PEI/NR) n LbL films displayed similar physicochemical properties, but differed in terms of film morphology according to atomic force microscopy (AFM) and scanning electron microscopy (SEM) data. Most significantly, (PEI/NR) 5 LbL films were made of smaller and flattened particles, which were not efficient for the growth and proliferation of normal human fibroblasts (NHF). In contrast, efficient NHF proliferation could be obtained with (PAH/NR) n LbL films, with the fibroblasts exhibiting the expected elongated morphology. Furthermore, cell growth did not occur for cast films of NR, thus demonstrating the suitability of the LbL method for this biologically related application. The differences between the two polyelectrolytes illustrate the importance of the film architecture and morphology, which open the way for exploiting the molecular control inherent in the LbL technique for further applications of NR-containing films.

Biophysical Journal, 2012

Colloids and Surfaces B: Biointerfaces, 2010

The capability of self-assembly and molecular recognition of biomolecules is essential for many n... more The capability of self-assembly and molecular recognition of biomolecules is essential for many nanotechnological applications, as in the use of alkyl-modified nucleosides and oligonucleotides to increase the cellular uptake of DNA and RNA. In this study, we show that a lipophilic nucleoside, which is an isomer mixture of 2 -palmitoyluridin und 3 -palmitoyluridin, forms Langmuir monolayers and Langmuir-Blodgett films as a typical amphiphile, though with a smaller elasticity. The nucleoside may be incorporated into dipalmitoyl phosphatidyl choline (DPPC) monolayers that serve as a simplified cell membrane model. The molecular-level interactions between the nucleoside and DPPC led to a remarkable condensation of the mixed monolayer, which affected both surface pressure and surface potential isotherms. The morphology of the mixed monolayers was dominated by the small domains of the nucleoside. The mixed monolayers could be deposited onto solid substrates as a one-layer Langmuir Blodgett film that displayed UV-vis absorption spectra typical of aggregated nucleosides owing to the interaction between the nucleoside and DPPC. The formation of solid films with DNA building blocks in the polar heads may open the way for devices and sensors be produced to exploit their molecular recognition properties.

The use of nanostructured films to modify electrochemical electrodes has allowed a whole host of ... more The use of nanostructured films to modify electrochemical electrodes has allowed a whole host of new systems/devices to be fabricated, with properties that may be tuned upon synergistic interactions between the film components. Films produced with the Layer-by-Layer (LbL) technique, in particular, have opened up the way for new approaches in electrochomism, electrocatalysis, bioelectrochemistry and electroanalysis, for organic and inorganic-organic hybrid nanoarchitectures may be achieved. In addition to the fabrication of novel, optimized materials, with the LbL method fundamental processes such as charge transfer mechanisms involving biomolecules and nanoparticles can be investigated at the molecular level. In this paper we highlight the recent trends in the electrochemistry of LbL films, with emphasis on their promising technological applications in sensing/biosensing and electrochromic devices.

Materials Science and Engineering: C, 2008

Artificial vesicles or liposomes composed of lipid bilayers have been widely exploited as buildin... more Artificial vesicles or liposomes composed of lipid bilayers have been widely exploited as building blocks for artificial membranes, in attempts 13 to mimic membrane interaction with drugs and proteins and to investigate drug delivery processes. In this study we report on the immobilization of 14 liposomes of 1,2-dipalmitoyl-sn-Glycero-3-[Phospho-rac-(1-glycerol)] (Sodium Salt) (DPPG) in layer-by-layer (LbL) films, alternated with poly 15 (amidoamine) G4 (PAMAM) dendrimer layers. The average size of the liposomes in solution was 120 nm as determined by dynamic light 16 scattering, with their spherical shape being inferred from scanning electron microscopy (SEM) in cast films. LbL films containing up to 20 17 PAMAM/DPPG bilayers were assembled onto glass and/or silicon wafer substrates. The growth of the multilayers was achieved by alternately 18 immersing the substrates into the PAMAM and DPPG solutions for 5 and 10 min, respectively. The formation of PAMAM/DPPG liposome 19 multilayers and its ability to interact with BSA were confirmed by Fourier transform infrared spectroscopy (FTIR). The structural features and film 20 thickness were obtained using X-ray diffraction and surface plasmon resonance (SPR). 21

Analytical and Bioanalytical Chemistry, 2011

Recent advances in the control of molecular engineering architectures have allowed unprecedented ... more Recent advances in the control of molecular engineering architectures have allowed unprecedented ability of molecular recognition in biosensing, with a promising impact for clinical diagnosis and environment control. The availability of large amounts of data from electrical, optical, or electrochemical measurements requires, however, sophisticated data treatment in order to optimize sensing performance. In this study, we show how an information visualization system based on projections, referred to as Projection Explorer (PEx), can be used to achieve high performance for biosensors made with nanostructured films containing immobilized antigens. As a proof of concept, various visualizations were obtained with impedance spectroscopy data from an array of sensors whose electrical response could be specific toward a given antibody (analyte) owing to molecular recognition processes. In addition to discussing the distinct methods for projection and normalization of the data, we demonstrate that an excellent distinction can be made between real samples tested positive for Chagas disease and Leishmaniasis, which could not be achieved with conventional statistical methods. Such high performance probably arose from the possibility of treating the data in the whole frequency range. Through a systematic analysis, it was inferred that Sammon's mapping with standardization to normalize the data gives the best results, where distinction could be made of blood serum samples containing 10 −7 mg/mL of the antibody. The method inherent in PEx and the procedures for analyzing the impedance data are entirely generic and can be extended to optimize any type of sensor or biosensor.

Thin Solid Films, 2007

The processing of macrocyclic phthalocyanines (Pc) in the form of thin, nanostructured films has ... more The processing of macrocyclic phthalocyanines (Pc) in the form of thin, nanostructured films has been usually carried out via evaporation techniques, owing to the low solubility exhibited by these compounds. The fabrication of Pc ultrathin films via the Langmuir–Blodgett technique may be advantageous from a technological point of view, since parameters such as film architecture and organization can be achieved

Physical Review E, 2006

The orientational order of liquid crystals (LCs) induced by periodic patterned substrates has bee... more The orientational order of liquid crystals (LCs) induced by periodic patterned substrates has been investigated with cells coated by azopolymer films that could be photoaligned in a controlled way. Two regimes were observed depending on the period of the patterns: (i) above 3.0 microm the LC follows the direction imposed by the patterned substrate since the energy stored in the surface potential minimizes the elastic energy of the LC medium. (ii) For periods smaller than 1.0 microm a homogeneous in-plane state was induced and the LC did not follow the orientation imposed by the surface. This in-plane transition could be explained qualitatively by a theoretical model based on the competition between the Frank-Oseen elastic energy and the phenomenological surface potential. The results also suggest an out-of-plane transition for the LC director as the period was reduced. These results agree with data in the literature for patterned substrates with completely distinct architectures. This indicates that for a particular LC sample the overall behavior depends basically on the texture period instead of the texture architecture. The textures were characterized with a scanning near-field optical microscope (SNOM), which allowed simultaneous morphological and optical images in the submicrometer range.

Journal of Colloid and Interface Science, 2008

The immobilization of enzymes in organized two-dimensional matrices is a key requirement for many... more The immobilization of enzymes in organized two-dimensional matrices is a key requirement for many biotechnological applications. In this paper, we used the Langmuir-Blodgett (LB) technique to obtain controlled architectures of urease immobilized in solid supports, whose physicochemical properties were investigated in detail. Urease molecules were adsorbed at the air-water interface and incorporated into Langmuir monolayers of the phospholipid dipalmitoyl phosphatidyl glycerol (DPPG). Incorporation of urease made DPPG monolayers more flexible and caused the reduction of the equilibrium and dynamic elasticity of the film. Urease and DPPG-urease mixed monolayers could be transferred onto solid substrates, forming LB films. A close packing arrangement of urease was obtained, especially in the mixed LB films, which was inferred with nanogravimetry and electrochemistry measurements. From the blocking effect of the LB films deposited onto indium tin oxide (ITO) substrates, the electrochemical properties of the LB films pointed to a charge transport controlled by the lipid architecture.

The journal of physical chemistry. B, Jan 21, 2005

The fabrication of varied molecular architectures in layer-by-layer (LbL) films is exploited to c... more The fabrication of varied molecular architectures in layer-by-layer (LbL) films is exploited to control the photoluminescence (PL) of poly(p-phenylene vinylene) (PPV) in an unprecedented way. This was achieved by controlling the Förster energy transfer between PPV layers (donors) and layers of a commercial azodye, Brilliant Yellow (BY) (acceptors). Energy transfer was controlled by inserting spacer layers of inert polymers between PPV and BY layers and by photoaligning the BY molecules via trans-cis-trans isomerization. The PPV/BY LbL films displayed polarized PL whose intensity could be varied almost continuously by changing the time of photoalignment, which was carried out by impinging a linearly polarized laser light simultaneously to the PL experiments. For PPV/BY films with no spacer layers, PL was completely quenched, but its intensity increased with the number of spacing layers. Further increase in PL was obtained by photoaligning the BY molecules perpendicularly to the PPV m...

Energy diagrams have been obtained for iron tetrasulfonated phthalocyanine (FeTsPc) and nickel te... more Energy diagrams have been obtained for iron tetrasulfonated phthalocyanine (FeTsPc) and nickel tetrasulfonated phthalocyanine (NiTsPc) from electrochemical and electronic absorption measurements in layer-by-Layer (LbL) films with chitosan in the cationic layers. This was made possible because the chitosan/FeTsPc and chitosan/NiTsPc modified electrodes exhibited a reversible, highly stable electrochemical response, with the voltammetric signal being preserved after several cycles in the range between 0 and 1.0V vs Ag/AgCl. The ionization potential (IP), electroa nity (EA) and energy gap (E g ) were similar for both systems, suggesting that the coordinating metal atom does not play an important role in the elelctronic properties of the immobilized phthalocyanines. Chitosan was found suitable for the cationic layers as it did not affect the electrochemical current appreciably. The anodic peak current varied linearly with the scan rate for chitosan/NiTsPc and chitosan/FeTsPc films, denoting charge transport via electron hopping within the film, typical of a polymer-modified electrode.

Applied Spectroscopy, 2005

The phase transition from the non-polar ␣-phase to the polar ␤phase of poly(vinylidene fluoride) ... more The phase transition from the non-polar ␣-phase to the polar ␤phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous because it is a nondestructive technique. Films of ␣-PVDF were subjected to stretching under controlled rates at 80 ؇C, while the transition to ␤-PVDF was monitored by the decrease in the Raman band at 794 cm Ϫ1 characteristic of the ␣-phase, along with the concomitant increase in the 839 cm Ϫ1 band characteristic of the ␤-phase. The ␣→␤ transition in our PVDF samples could be achieved even for the sample stretched to twice (2؋-stretched) the initial length and it did not depend on the stretching rate in the range between 2.0 and 7.0 mm/min. These conclusions were corroborated by differential scanning calorimetry (DSC) and X-ray diffraction experiments for PVDF samples processed under the same conditions as in the Raman scattering measurements. Poling with negative corona discharge was found to affect the ␣-PVDF morphology, improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, coronainduced effects could not be observed with the other experimental techniques, i.e., X-ray diffraction and infrared spectroscopy.

Advanced Functional Materials, 2007

Biomacromolecules, 2007

Natural gums have been traditionally applied in cosmetics and the food industry, mainly as emulsi... more Natural gums have been traditionally applied in cosmetics and the food industry, mainly as emulsification agents. Due to their biodegradability and excellent mechanical properties, new technological applications have been proposed involving their use with conventional polymers forming blends and composites. In this study, we take advantage of the polyelectrolyte character exhibited by the natural gum Chichá (Sterculia striata), extracted in the Northeastern region of Brazil, to produce electroactive nanocomposites. The nanocomposites were fabricated in the form of ultrathin films by combining a metallic phthalocyanine (nickel tetrasulfonated phthalocyanine, NiTsPc) and the Chichá gum in a tetralayer architecture, in conjunction with conventional polyelectrolytes. The presence of the gum led to an efficient adsorption of the phthalocyanine and enhanced the electrochemical response of the films. Upon combining the electrochemical and UV-vis absorption data, energy diagrams of the Chichá/ NiTsPc-based system were obtained. Furthermore, modified electrodes based on gum/phthalocyanine films were able to detect dopamine at concentrations as low as 10 -5 M.

Nanotoxicology, 2013

Nanomaterials such as carbon nanotubes (CNTs) and nanoparticles have received enormous attention ... more Nanomaterials such as carbon nanotubes (CNTs) and nanoparticles have received enormous attention in analytical areas for their potential applications as new tools for biotechnology and life sciences. Most of these possible applications involve the use of CNTs and related materials as vehicles for drug delivery and/or gene therapy. In this study, we introduce a methodology to evaluate the interactions between CNTs/dendrimers nanoconjugates and phospholipid biomembrane models, using the Langmuir film balance technique. Our main goal was to elucidate the action of engineered nanomaterials in cell membranes, at the molecular level, using a membrane model system. The penetration of single-walled carbon nanotubes (SWCNTs)/polyamidoamine dendrimer nanocomplexes into dipalmitoylphosphatidylcholine monolayers was pronounced, as revealed by adsorption kinetics and surface pressure measurements. These findings suggest that SWCNTs were able to interact even at high surface pressure values, ∼30 mN/m. Therefore, the results confirm that the presence of the nanomaterial affects the packing of the synthetic membranes. We believe the methodology introduced here may be of great importance for further nanotoxicity studies.

Journal of Nanoparticle Research, 2012

Magnetic nanoparticles are promising for a variety of applications, such as biomedical devices, s... more Magnetic nanoparticles are promising for a variety of applications, such as biomedical devices, spin electronics, magnetic data storage media, to name a few. However, these goals may only be reached if stable and organized structures are fabricated. In this article, we report on a single-step synthetic route with the coprecipitation method, in which iron oxide magnetic nanoparticles (Fe 3 O 4 NPs) were stabilized in aqueous media using the poly(diallyldimethylammonium chloride) (PDAC) polyelectrolyte. The Fe 3 O 4 NPs had a diameter of ca. 5 nm, according to transmission electron microscopy (TEM) images, being arranged in an inverse spinel structure typical of magnetite. An investigation with infrared spectroscopy indicated that the mechanisms of stabilization in the polymer matrix were based on the interaction between quaternary amide groups from PDAC and the nanoparticle surface. The Fe 3 O 4 -PDAC NPs exhibited considerable magnetic susceptibility, with a monotonic increase in the magnetization with decreasing temperature. These Fe 3 O 4 -PDAC NPs were immobilized in layer-by-layer (LbL) films, being alternated with layers of poly(vinylsulfonic acid) (PVS). The LbL films were much rougher than typical films made with polyelectrolytes, and Fe 3 O 4 -PDAC NPs have been responsible for the high electrocatalytic activity toward H 2 O 2 reduction, with an overpotential shift of 0.69 V. Overall, the stability, magnetic properties and film-forming ability indicate that the Fe 3 O 4 -PDAC NPs may be used for nanoelectronics and bioelectrochemical devices requiring reversible and magnetic redox materials.

International Journal of Molecular Sciences, 2013

Journal of Applied Polymer Science, 2012

Biophysical Journal, 2012

Colloids and Surfaces B: Biointerfaces, 2010

Materials Science and Engineering: C, 2008

Analytical and Bioanalytical Chemistry, 2011

Thin Solid Films, 2007

Physical Review E, 2006

Journal of Colloid and Interface Science, 2008

The journal of physical chemistry. B, Jan 21, 2005

Applied Spectroscopy, 2005

Advanced Functional Materials, 2007

Biomacromolecules, 2007

Nanotoxicology, 2013

Journal of Nanoparticle Research, 2012

Langmuir, 2006

This paper reports the surface activity of phytase at the air-water interface, its interaction wi... more This paper reports the surface activity of phytase at the air-water interface, its interaction with lipid monolayers, and the construction of a new phytic acid biosensor on the basis of the Langmuir-Blodgett (LB) technique. Phytase was inserted in the subphase solution of dipalmitoylphosphatidylglycerol (DPPG) Langmuir monolayers, and its incorporation to the air-water interface was monitored with surface pressure measurements. Phytase was able to incorporate into DPPG monolayers even at high surface pressures, ca. 30 mN/m, under controlled ionic strength, pH, and temperature. Mixed Langmuir monolayers of phytase and DPPG were characterized by surface pressure-area and surface potential-area isotherms, and the presence of the enzyme provided an expansion in the monolayers (when compared to the pure lipid at the interface). The enzyme incorporation also led to significant changes in the equilibrium surface compressibility (in-plane elasticity), especially in liquid-expanded and liquid-condensed regions. The dynamic surface elasticity for phytase-containing interfaces was investigated using harmonic oscillation and axisymmetric drop shape analysis. The insertion of the enzyme at DPPG monolayers caused an increase in the dynamic surface elasticity at 30 mN m(-)(1), indicating a strong interaction between the enzyme and lipid molecules at a high-surface packing. Langmuir-Blodgett (LB) films containing 35 layers of mixed phytase-DPPG were characterized by ultraviolet-visible and fluorescence spectroscopy and crystal quartz microbalance nanogravimetry. The ability in detecting phytic acid was studied with voltammetric measurements.