106 research outputs found
New procedure to synthesize silver nanoparticles and their interaction with local anesthetics
No full textAurora Mocanu,1 Roxana Diana Pasca,1 Gheorghe Tomoaia,2 Corina Garbo,1 Petre T Frangopol,1 Ossi Horovitz,1 Maria Tomoaia-Cotisel11Chemical Engineering Department, Babes-Bolyai University, 2Orthopedic Department, Iuliu Hatieganu University of Medicine and Pharmacy, Cluj-Napoca, RomaniaAbstract: Silver nanoparticles (AgNPs) were prepared in aqueous colloid dispersions by the reduction of Ag+ with glucose in alkaline medium. Tetraethyl orthosilicate and l-asparagine were added as stabilizers of NPs. The AgNPs were characterized, and their interaction with three local anesthetics (procaine, dibucaine, or tetracaine) was investigated. Optical spectra show the characteristic absorption band of AgNPs, due to surface plasmon resonance. Modifications in the position and shape of this band reflect the self-assembly of metal NPs mediated by anesthetic molecules and the progress in time of the aggregation process. Zeta-potential measuring was applied in order to characterize the electrostatic stability of the NPs. The size and shape of the AgNPs, as well as the features of the assemblies formed by their association in the presence of anesthetics, were evidenced by transmission electron microscopy images. Atomic force microscopy images showed the characteristics of the films of AgNPs deposited on glass support. The effect of the anesthetics could be described in terms of electrostatic forces between the negatively charged AgNPs and the anesthetic molecules, existing also in their cationic form at the working pH. But also hydrophobic and hydrogen bonding interactions between the coated nanoparticles and anesthetics molecular species should be considered.Keywords: self-assembled nanostructures, UV-vis spectra, TEM, AFM, zeta potentia
Ions release from hydroxyapatite and substituted hydroxyapatites in different immersion liquids. In vitro experiments and theoretical modelling study
No full textAdsorption dynamics with interfacial reaction
No full textAbstract: A quantitative theoretical model is developed for the surfactant adsorption from oil solution to the oil/water interface in a time scale from seconds to hours. The kinetic model takes into consideration the diffusion of surfactant molecules in the oil phase to the oil/water interface and the surface transformation between two adsorption conformations namely from conformation 1 to conformation 2 of surfactant molecules. Conformation 1 is supposed soluble in the oil phase. but conformation 2 is assumed to be insoluble in oil. Further, this model is based on the diffusion penetration theory associated with a reversible surface reaction of the first order that describes the surface transformation from conformation 1 to conformation 2. Both conformations are assumed to be insoluble in the aqueous phase. A general analytical expression is derived for the relaxation of interfacial tensions that is convenient for both. numerical calculations and for asymptotic analysis. At short and long diffusion relaxation times the extrapolated equations are deduced. To illustrate the applicability of-this model, the obtained equations are applied to the dynamic interfacial tensions generated by two carotenoids (i.e., ethyl ester of beta-apo-8'-carotenoic acid and beta-carotene, all trans isomers), that independently adsorb from the hexane phase to the hexane/water interface. The model calculations show the characteristic times for the carotenoid adsorption in terms of diffusion relaxation and kinetic relaxation times at the hexane/water interface. The surface reaction rate constants yield to mean values of 8.2 10(-4) s(-1) for ethyl ester of beta-apo8'-carotenoic acid and of 1.3 10(-3) s(-1) for beta-carotene. This model describes very well the experimental interfacial tension isotherms for the two biosurfactants studied. The calculated results are in good agreement with the molecular structure of the two carotenoids adsorbed at the hexane/water interface
IN MEMORIAM PROFESSOR EMIL CHIFU (1925-1997)
No full textThis year, we commemorate the 20th death anniversary of Professor Emil Chifu. 2017 also marks 40 years from the first scientific research project proposed by Professor Chifu and accepted for exploring in cosmos by NASA (National Aeronautics and Space Administration) of the United States of America. As a prominent Romanian scientist, Professor Emil Chifu was an outstanding physical chemist, recognized by the international scientific community. He was one of the founders of the modern science of colloids, surfaces and membrane phenomena, thermodynamics and hydrodynamics of thin layers formed by surface active substances self-assembled into supramolecular structures at liquid interfaces. Professor Emil Chifu has created a modern research school in thermodynamics and physical chemistry of colloids and surfaces, at the Faculty of Chemistry and Chemical Engineering within Babes-Bolyai University in Cluj-Napoca (UBB). Currently, this school is known as the Center of Research in Physical Chemistry and is accredited within UBB
IN MEMORIAM PROFESSOR EMIL CHIFU (1925-1997)
No full textThis year, we commemorate the 20th death anniversary of Professor Emil Chifu. 2017 also marks 40 years from the first scientific research project proposed by Professor Chifu and accepted for exploring in cosmos by NASA (National Aeronautics and Space Administration) of the United States of America. As a prominent Romanian scientist, Professor Emil Chifu was an outstanding physical chemist, recognized by the international scientific community. He was one of the founders of the modern science of colloids, surfaces and membrane phenomena, thermodynamics and hydrodynamics of thin layers formed by surface active substances self-assembled into supramolecular structures at liquid interfaces. Professor Emil Chifu has created a modern research school in thermodynamics and physical chemistry of colloids and surfaces, at the Faculty of Chemistry and Chemical Engineering within Babes-Bolyai University in Cluj-Napoca (UBB). Currently, this school is known as the Center of Research in Physical Chemistry and is accredited within UBB
Adsorption kinetics of some carotenoids at the oil/water interface
No full textAbstract: The kinetic analysis of the adsorption of two carotenoids (i.e., ethyl ester of beta-apo-8'-carotenoic acid and beta-carotene, all trans-isomers) from n-hexane solutions at the oil/water interface is presented for several carotenoid concentrations in the oil phase. A new kinetic approach is developed and it addresses the diffusion adsorption associated with a reversible interfacial reaction, which describes the reorientation of surfactant molecules between two conformations. This approach leads to a general analytical expression that contains four physical parameters and describes with high accuracy the experimental dynamic interfacial tensions for the two carotenoids, which independently adsorb from n-hexane phase to the n-hexane/water interface. The calculations give the characteristic times for the carotenoid adsorption at the oil/water interface in terms of diffusion relaxation and kinetic relaxation times. The results explain the long time effects on the adsorption of these carotenoids at the oil/water interface. The data are in substantial agreement with the molecular structure of these carotenoids and with the earlier data recorded for cholesterol adsorption at the n-heptane/water interface. Based on these findings, we propose a molecular mechanism for the interfacial transformation of carotenoid molecules at a hydrophobic/hydrophilic interface. (C) 2004 Elsevier B.V. All rights reserved
Relationship between dentifrices based on hydroxyapatites and human enamel remineralization
No full textEnamel demineralization is an intricate process that holds significant clinical consequences, being a central part of the emergence and progression of various dental problems, most notably dental caries. This demineralization of tooth enamel is linked to a variety of factors, including the composition of oral microbiota and that of saliva, the prevalence of sugar consumption or acidic soft drinks, and, of course, oral hygiene practices. The oral microbiome plays a role in generating organic acids that foster an environment conducive to enamel breakdown. Additionally, a decrease in saliva production can lower the oral environment’s ability to neutralize acids and support the remineralization process, thereby intensifying demineralization. Dentifrices enriched with biomimetic hydroxyapatites are important in preventing demineralization as they not only help with oral hygiene but also provide key ions that help strengthen enamel. Considering their similarity to the natural component in enamel, synthetichydroxyapatites have recently emerged as potent remineralizing agents. Hence, this work aims to illustrate in a simple and concise manner, some of the aspects involved in enamel demineralization and its subsequent remineralization, namely in the relationship between enriched toothpastes containing biomimetic hydroxyapatites and their remineralization eficacy
Development and characterization of new AR glass fiber‐reinforced cements with potential medical applications
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