TOMAZ PUGA LEIVAS

Índice h a partir de 2011
5
Projetos de Pesquisa
Unidades Organizacionais
Instituto do Coração, Hospital das Clínicas, Faculdade de Medicina
Instituto de Ortopedia e Traumatologia, Hospital das Clínicas, Faculdade de Medicina
LIM/41 - Laboratório de Investigação Médica do Sistema Músculoesquelético, Hospital das Clínicas, Faculdade de Medicina

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  • article 6 Citação(ões) na Scopus
    Evaluation of Laser Marked ASTM F 139 Stainless Steel in Phosphate Buffer Solution with Albumin
    (2014) PIERETTI, Eurico F.; PALATNIC, Ricardo P.; LEIVAS, Tomaz P.; COSTA, Isolda; NEVES, Mauricio D. M. das
    Albumin is the most abundant protein found in human serum and sinovial fluids. Investigations on its effects on the corrosion resistance of metallic biomaterials have led to controversial conclusions. The BSA (bovine serum albumin) concentration used in most of the studies is below the usual concentration found in the human physiological fluids. This is possibly the reason for the lack of agreement on the conclusions reported in literature. The aim of this study is to evaluate the effect of albumin in concentration on the susceptibility to corrosion of the ASTM F139 austenitic stainless steel (SS) used in fabrication of orthopedic implants, specifically on the areas marked by a Nd: YAG laser. The electrolyte used was a phosphate buffer solution (PBS) and the effect of albumin was investigated by adding 10 g/L into the electrolyte and comparing the corrosion resistance in the two environments, with and without albumin, by electrochemical methods. The Mott-Schottky approach was used to evaluate the electronic properties of ASTM F139 SS oxide layer marked by laser beam. The results showed a strong effect of the albumin on the electronic properties of the passive film and on the resistance to localized corrosion. The albumin changes the flat band potential position, increasing the oxide layer doping densities. The laser marked surface showed lower corrosion resistance in the electrolyte with albumin, when compared to the tests performed with pure PBS.
  • article 7 Citação(ões) na Scopus
    Measurement of the concentration and size of aerosol particles and identification of the sources in orthopedic surgeries
    (2012) PEREIRA, Marcelo Luiz; VILAIN, Rogerio; LEIVAS, Tomaz Puga; TRIBESS, Arlindo
    In this study, the measurement of the concentration and size of particles and the identification of their sources were carried out at five orthopedic surgeries. The aerosol concentration and particle size distribution, ranging from 0.3 mu m 10 mu m, were measured and related to the type of indoor activity. The handling of surgical linen and gowns, handling of the patient, use of electrosurgical apparatus, use of a bone saw, handling of equipment, and cleaning of the room were identified as the most important sources of particles, with each of these activities posing different risks to the health of the patients and workers. The results showed that most of the particles were above 0.5 mu m and that there was a strong correlation among all particles of sizes above 1 mu m. Particles with diameters in the range of 0.3 mu m-0.5 mu m had a good correlation only with particles in the ranges of 0.5 mu m-1.0 mu m and 1.0 mu m-3.0 mu m in three of the surgeries analyzed. Findings led to the conclusion that most of the events responsible for generating aerosol particles in an orthopedic surgery room are brief, intermittent, and highly variable, thus requiring the use of specific instrumentation for their continuous identification and characterization.
  • article 8 Citação(ões) na Scopus
    Electrochemical Study of a Laser Marked Biomaterial in Albumin Solution
    (2014) PIERETTI, Eurico F.; COSTA, Isolda; MARQUES, Rogerio A.; LEIVAS, Tomaz P.; NEVES, Mauricio D. M. das
    Proteins are widely used in solutions in order to simulate the physiological fluids and study corrosion mechanisms. The present work appraised the ASTM F 139 austenitic stainless steel (SS), employed in prostheses manufacture, and engraved by a nanosecond laser beam, using a phosphate buffered solution with 10 g/L of bovine serum albumin (PBS + BSA). Due to the complexity of the interaction between protein and the biomaterial, it was necessary to use higher BSA concentrations, however, similar to those found in human serum. The electrochemical tests consisted in monitoring the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and cyclic polarisation measurements. The results showed that the laser marked areas are more susceptible to corrosion; suggesting that the laser marking technique has a more preponderant effect on the passive film protective character than the albumin addition to the electrolyte.