Characteristics of porous implant steel 316L for orthopedic applications

The porous materials are recently considered to be the prospective biomaterials for restorative medicine. The Young’s modulus of porous metallic biomaterials is much lower than those of non-porous and comparable to modulus of hard tissues, which can improve the conditions of bone remodeling and heading. The porous structure is also interesting from tribological point of view. The usage of porous material for friction elements of joint endoprostheses changes the wear mechanisms and causes decrease of resistance to motion and material wear loss. The aim of present research was to analyze the structure of porous 316L implant steel and its influence on main functional properties of sinters. Samples with porosity of 26, 33, and 41% were made of the 316 stainless steel by the powder metallurgy method. Microstructure was described using conventional image analysis techniques. The mechanical properties were determined in static compressing tests. Fatigue tests were conducted under the fully reversed strain controlled mode. A good correlation has been found between structural parameters and tribological as well as mechanical properties. The low-cyclic fatigue investigations confirm the steady properties of porous materials in the certain range of strai

Usage of the powder metallurgy method for fabrication of titanium implant alloy

In the paper research of the new implant titanium alloy obtained by powder metallurgy method were presented. The Ti15Mo2,8Nb alloy was fabricated from pure alloying component powders. The structure was observed by scanning electron microscope and analyzed by X-ray diffraction. The effect of grinding time of mixtures as well as the size of titanium powder grain on compatibility, compression strength and yield point of sintered alloys was analysed. It was found that grain size has a significant effect on strength properties of the alloy. However, the prolonging of grinding time caused deterioration of compatibility as well as mechanical properties of sinter

Usage of the powder metallurgy method for fabrication of titanium implant alloy

In the paper research of the new implant titanium alloy obtained by powder metallurgy method were presented. The Ti15Mo2,8Nb alloy was fabricated from pure alloying component powders. The structure was observed by scanning electron microscope and analyzed by X-ray diffraction. The effect of grinding time of mixtures as well as the size of titanium powder grain on compatibility, compression strength and yield point of sintered alloys was analysed. It was found that grain size has a significant effect on strength properties of the alloy. However, the prolonging of grinding time caused deterioration of compatibility as well as mechanical properties of sinter

Procjena cito-/genotoksičnosti irinotekana u V79-stanicama primjenom komet-testa, mikronukleus-testa i testa kromosomskih aberacija

Irinotecan is a topoisomerase I interactive agent, widely used in the treatment of metastatic colorectal cancer. The genotoxic effects of the maximum single dose (18 μg mL-1), recommended monotherapy dose (9 μg mL-1), and recommended combined therapy dose (4.5 μg mL-1) of irinotecan were studied on V79 cells using the comet assay, chromosome aberration assay, and micronucleus test. The cells were treated with irinotecan for 2 h or 24 h. The statistical signifi cance of the results was determined using the one-way ANOVA test and a nonparametric Mann Whitney U test. The comet assay did not show dose-dependent or time-dependent effects. The chromosome aberration analysis showed large DNA rearrangements, i.e., chromosome exchanges. Although the exposed cultures showed a signifi cant increase in micronucleated cells in respect to control, no dose-dependent relation was established among the treated cultures. Timedependent effect was also not observed.Irinotekan je citotoksični lijek koji inhibira enzim DNA-topoizomerazu I. U širokoj je primjeni u terapiji metastatskog karcinoma kolona i rektuma. U uvjetima in vitro primjenom komet-testa, analize kromosomskih aberacija i mikronukleus-testa na V79-stanicama istražili smo genotoksični učinak maksimalne pojedinačne doze (18 μg mL-1), preporučene monoterapijske doze (9 μg mL-1) i preporučene doze irinotekana za kombiniranu terapiju (4,5 μg mL-1). Kulture stanica bile su tretirane irinotekanom 2 h i 24 h. Statistička značajnost određivana je jednosmjernim ANOVA-testom i neparametrijskim Mann Whitneyevim U-testom. Komet-testom nije utvrđen učinak koncentracije i/ili vremena izloženosti. Analiza kromosomskih aberacija pokazala je prisutnost izmjena kromatida, tj. porast broja triradijusa i tetraradijusa. Iako je u kulturama stanica izloženi irinotekanu opažen značajan porast broja mikronukleusa u odnosu na kontrolu, nije uočena ovisnost o dozi lijeka ni o vremenu izloženosti u opisanim eksperimentalnim uvjetima. Dobiveni rezultati upućuju na genotoksičnost irinotekana za V79-stanice. Nijednom od primijenjenih metoda nije utvrđena ovisnost učinka irinotekana o vremenu ili dozi

A new class of glycomimetic drugs to prevent free fatty acid-induced endothelial dysfunction

Background: Carbohydrates play a major role in cell signaling in many biological processes. We have developed a set of glycomimetic drugs that mimic the structure of carbohydrates and represent a novel source of therapeutics for endothelial dysfunction, a key initiating factor in cardiovascular complications. Purpose: Our objective was to determine the protective effects of small molecule glycomimetics against free fatty acid­induced endothelial dysfunction, focusing on nitric oxide (NO) and oxidative stress pathways. Methods: Four glycomimetics were synthesized by the stepwise transformation of 2,5­dihydroxybenzoic acid to a range of 2,5­substituted benzoic acid derivatives, incorporating the key sulfate groups to mimic the interactions of heparan sulfate. Endothelial function was assessed using acetylcholine­induced, endotheliumdependent relaxation in mouse thoracic aortic rings using wire myography. Human umbilical vein endothelial cell (HUVEC) behavior was evaluated in the presence or absence of the free fatty acid, palmitate, with or without glycomimetics (1µM). DAF­2 and H2DCF­DA assays were used to determine nitric oxide (NO) and reactive oxygen species (ROS) production, respectively. Lipid peroxidation colorimetric and antioxidant enzyme activity assays were also carried out. RT­PCR and western blotting were utilized to measure Akt, eNOS, Nrf­2, NQO­1 and HO­1 expression. Results: Ex vivo endothelium­dependent relaxation was significantly improved by the glycomimetics under palmitate­induced oxidative stress. In vitro studies showed that the glycomimetics protected HUVECs against the palmitate­induced oxidative stress and enhanced NO production. We demonstrate that the protective effects of pre­incubation with glycomimetics occurred via upregulation of Akt/eNOS signaling, activation of the Nrf2/ARE pathway, and suppression of ROS­induced lipid peroxidation. Conclusion: We have developed a novel set of small molecule glycomimetics that protect against free fatty acidinduced endothelial dysfunction and thus, represent a new category of therapeutic drugs to target endothelial damage, the first line of defense against cardiovascular disease