RESUMO
Dry olive leaf extract (DOLE) and its active component oleuropein (OLE) were applied as reducing and stabilizing agents to prepare colloidal 20-25 nm silver nanoparticles (Ag NPs). The Ag NPs were characterized using transmission electron microscopy, X-ray diffraction analysis, and absorption spectroscopy. The cytotoxic actions of coated Ag NPs, and their inorganic and organic components, were examined against trophoblast cells and human peripheral blood lymphocytes (PBLs), Gram-positive, Gram-negative bacteria, and yeast. The genotoxic potential was evaluated in PBLs in vitro with the comet assay. Ag/DOLE and Ag/OLE induced cytotoxic effects in both types of cells after 24 h exposure when silver concentrations were 0.025-0.2 mM. However, the most pronounced cytotoxicity exhibits Ag/OLE. Both colloids also caused reduced ROS production in both cell types at 0.1 mM and 0.2 mM, while bare Ag NPs did not alter ROS levels at any of the conditions. Functionalized Ag/DOLE and Ag/OLE did not show genotoxic effects in PBLs, while bare AgNPs increased DNA damage significantly only at 0.2 mM. Regarding the antimicrobial effects, the Ag/OLE had MIC values for all evaluated microorganisms from 0.0625 to less than 0.0312 mM. Also, the antimicrobial effect of Ag/DOLE was significantly higher on Gram-negative bacteria and yeast than on Gram-positive bacteria. Obtained results indicate that Ag/OLE induced the most pronounced biological effects, beneficial for its application as an antimicrobial agent, but with potential risks from exposure to high concentrations that could induce cytotoxicity in healthy human cells.
Assuntos
Anti-Infecciosos , Nanopartículas Metálicas , Humanos , Prata/toxicidade , Espécies Reativas de Oxigênio/metabolismo , Nanopartículas Metálicas/toxicidade , Nanopartículas Metálicas/química , Saccharomyces cerevisiae/metabolismo , Trofoblastos/metabolismo , Anti-Infecciosos/toxicidade , Anti-Infecciosos/química , Linfócitos/metabolismoRESUMO
The optical properties of surface-modified silver nanoparticles (Ag NPs) with aromatic amino acids tryptophan (Trp) and histidine (His) were examined using the cluster model for density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. Also, the redistribution of electronic charges upon chemisorption of ligand molecules onto silver's surfaces is determined. The obtained theoretical data, on one side, undoubtedly indicate the the formation of an interfacial charge transfer (ICT) complex between silver and this type of ligand, and, on the other side, partial oxidation of surface silver atoms accompanied by an increase of electron density in ligand molecules. The ICT complex formation, based on noble metal nanoparticles, has never been reported previously to the best of our knowledge. The experimental spectroscopic measurements support the theoretical data. A new absorption band in the visible spectral range appears upon surface modification of Ag NPs, and, when exposed to air, oxidation of surface-modified Ag NPs is significantly faster than the oxidation of the unmodified ones.
Assuntos
Nanopartículas Metálicas , Prata , Aminoácidos Aromáticos , Ligantes , Nanopartículas Metálicas/química , Prata/química , Análise EspectralRESUMO
Cerium dioxide (CeO2) finds applications in areas such as corrosion protection, solar cells, or catalysis, finding increasing applications in biomedicine. This work reports on surface-modified CeO2 particles in order to tune their applicability in the biomedical field. Stable aqueous CeO2 sol, consisting of 3-4 nm in size crystallites, was synthesized using forced hydrolysis. The coordination of catecholate-type of ligands (catechol, caffeic acid, tiron, and dopamine) to the surface-Ce atoms is followed with the appearance of absorption in the visible spectral range as a consequence of interfacial charge-transfer complex formation. The spectroscopic observations are complemented with the density functional theory calculations using a cluster model. The synthesized samples were characterized by X-ray diffraction analysis, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. The ζ-potential measurements indicated that the stability of CeO2 sol is preserved upon surface modification. The pristine CeO2 nanoparticles (NPs) are nontoxic against pre-osteoblast cells in the entire studied concentration range (up to 1.5 mM). Hybrid CeO2 NPs, capped with dopamine or caffeic acid, display toxic behavior for concentrations ≥0.17 and 1.5 mM, respectively. On the other hand, surface-modified CeO2 NPs with catechol and tiron promote the proliferation of pre-osteoblast cells.
RESUMO
The sorption ability of biogenic hydroxyapatite (BHAP) towards heavy metal ions (Pb, Cu, Ni, Cd, and Zn) is compared with functionalized BHAP powders with caffeic acid (CA) and 3,4-dihydroxybenzoic acid (3,4-DHBA). The functionalization of the BHAP with either CA or 3,4-DHBA is indicated by the appearance of the colored powders due to the formation of the interfacial charge transfer (ICT) complexes. The detailed characterization of as-prepared and functionalized BHAP samples was performed using transmission electron microscopy, reflection spectroscopy, thermogravimetric analysis and determination of zeta potential. All three sorbents clearly displayed preferential sorption of Pb ions when the total concentration of multi-component equimolar solutions of heavy metal ions is high. It should be emphasized that the sorption capacity of functionalized BHAP with either CA or 3,4-BHAP was found to be higher, up to 60%, compared to as-prepared BHAP without the decrease of selectivity towards Pb ions.
Assuntos
Ácidos Cafeicos/química , Cátions Bivalentes/química , Durapatita/química , Hidroxibenzoatos/química , Metais Pesados/química , Adsorção , SoluçõesRESUMO
Titania nanotubes were prepared by a simple hydrothermal route. Their electrochemical performance has been examined in detail and compared to TiO2(B) nanoparticles, TiO2 anatase and P25 titania nanoparticles. The cycling and rate performance of TiO2 nanotubes is superior to both types of nanoparticles, and it can be further improved by an in situ titanium precursor treatment, which results in the formation of TiO2 nanoparticles on/between the nanotubes. The obtained specific capacity after 200 cycles at 0.2 A g(-1) charge/discharge rate remained above 130 mAh g(-1). The enhanced lithium storage properties of these samples can be attributed to their unique morphology and crystal structure.
Assuntos
Lítio/química , Nanocompostos/química , Nanotubos/química , Titânio/química , Fontes de Energia Elétrica , EletrodosRESUMO
The surface modification of nanocrystalline TiO2 particles (45 Å) with catecholate-type ligands having different electron donating/electron withdrawing substituent groups, specifically 3-methylcatechol, 4-methylcatechol, 3-methoxycatechol, 3,4-dihydroxybenzaldehyde and 4-nitrocatechol, was found to alter the optical properties of nanoparticles in a similar way to catechol. The formation of the inner-sphere charge-transfer (CT) complexes results in a red shift of the semiconductor absorption compared to unmodified nanocrystallites and a reduction of the effective band gap, being slightly less pronounced in the case of electron withdrawing substituents. The investigated ligands have the optimal geometry for binding to surface Ti atoms, resulting in ring coordination complexes of the catecholate type (binuclear bidentate binding-bridging) thus restoring six-coordinated octahedral geometry of surface Ti atoms. From the absorption measurements (Benesi-Hildebrand plot), the stability constants in methanol/water = 90/10 solutions at pH 2 in the order of 10(3) M(-1) have been determined. The binding structures were investigated by using FTIR spectroscopy. Thermal stability of CT-complexes was investigated by using TG/DSC/MS analysis. Quantum chemical calculations on model systems using density functional theory (DFT) were performed to obtain the vibrational frequencies of charge transfer complexes, and the calculated values were compared with the experimental data.
Assuntos
Catecóis/química , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Modelos Químicos , Modelos Moleculares , Titânio/química , Adsorção , Simulação por Computador , Ligantes , Propriedades de SuperfícieRESUMO
Nanoparticles (NPs), a distinct class of particles ranging in size from 1 to 100 nm, are one of the most promising technologies of the 21st century, and titanium dioxide NPs (TiO2 NPs) are among the most widely produced and used NPs globally. The increased application of TiO2 NPs raises concerns regarding their global safety and risks of exposure. Many animal studies have reported the accumulation of TiO2 NPs in female reproductive organs; however, evidence of the resultant toxicity remains ambiguous. Since the surface area and chemical modifications of NPs can significantly change their cytotoxicity, we aimed to compare the toxic effects of pristine TiO2 powder with surface-modified TiO2 powders with salicylic acid (TiO2/SA) and 5-aminosalicylic acid (TiO2/5-ASA) on the ovaries, oviducts, and uterus on the 14th day following acute oral treatment. The results, based on alterations in food and water intake, body mass, organ-to-body mass ratio, hormonal status, histological features of tissues of interest, and antioxidant parameters, suggest that the modification with 5-ASA can mitigate some of the observed toxic effects of TiO2 powder and encourage future investigations to create NPs that can potentially reduce the harmful effects of TiO2 NPs while preserving their positive impacts.
RESUMO
The nano-sized copper tungstate (CuWO4) was prepared by precipitation method in the presence of non-ionic copolymer surfactant (polyoxyethylene-polyoxypropylene block copolymer) and consequent annealing at low temperature (400 °C). The scanning electron microscopy (SEM) indicated formation of spherical CuWO4 particles in the size range from 10 to 90 nm. The thermogravimetric analysis was used to study dehydration processes. The X-ray diffraction analysis undoubtedly confirmed formation of triclinic CuWO4 and the refinement of the diffraction data showed that CuWO4 powder belongs to the distorted tungstate type of structure with space group P1-. The structure of the CuWO4 can be described as infinite zigzag chains formed by edge-sharing alternating [W-O6] and [Cu-O6] octahedra. Indirect and direct band-gap energies of CuWO4 (2.3 and 3.5 eV, respectively) were determined using optical measurements.
RESUMO
Aqueous colloids, consisting of 15-30 nm-sized silver nanoparticles (Ag NPs), were prepared using the reducing and stabilizing abilities of glucose, sucrose, and dextran. The long-term stability of coated Ag NPs increases from glucose over sucrose to dextran, i.e., with the increase of the molecular weight of carbohydrate molecules. The density functional theory (DFT) calculations of the partial atomic (Mulliken) charges and adsorption energies are applied to explain the enhanced stability of coated Ag NPs. All coated Ag NPs have a significantly broader concentration range of nontoxic behavior toward pre-osteoblast cells than bare Ag NPs prepared using sodium borohydride. The carbohydrate-coated Ag NPs display the same level of toxic ability against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria as bare Ag NPs. The differences in toxicity mechanism of the coated and bare Ag NPs are a consequence of the absence and presence of co-occurring Ag+ ions in examined dispersion, respectively.
Assuntos
Nanopartículas Metálicas , Prata , Animais , Camundongos , Linhagem Celular , Dextranos/química , Glucose/química , Nanopartículas Metálicas/química , Nanopartículas Metálicas/toxicidade , Prata/química , Prata/toxicidade , Sacarose/químicaRESUMO
The search for alternative antimicrobial strategies capable of avoiding resistance mechanisms in bacteria are highly needed due to the alarming emergence of antimicrobial resistance. The application of physical stimuli as a mean of sensitizing bacteria for the action of antimicrobials on otherwise resistant bacteria or by allowing the action of low quantity of antimicrobials may be seen as a breakthrough for such purpose. This work proposes the development of antibacterial nanocomposites using the synergy between the electrically active microenvironments, created by a piezoelectric polymer (poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE)), with green-synthesized silver nanoparticles (AgNPs). The electrical microenvironment is generated via mechanical stimulation of piezoelectric PVDF-TrFE/AgNPs films using a lab-made mechanical bioreactor. The generated material's electrical response further translates to bacterial cells, namely Escherichia coli and Staphylococcus epidermidis which in combination with AgNPs and the specific morphological features of the material induce important antibacterial and antibiofilm activity. Both porous and non-porous PVDF composites have shown antibacterial characteristics when stimulated at a mechanical frequency of 4 Hz being the effect boosted when AgNPs were incorporated in the nanocomposite, reducing in more than 80% the S. epidermidis bacterial growth in planktonic and biofilm form. The electroactive environments sensitize the bacteria allowing the action of a low dose of AgNPs (1.69% (w/w)). Importantly, the material did not compromise the viability of mammalian cells, thus being considered biocompatible. The piezoelectric stimulation of PVDF-based polymeric films may represent a breakthrough in the development of antibacterial coatings for devices used at hospital setting, taking advantage on the use of mechanical stimuli (pressure/touch) to exert antibacterial and antibiofilm activity. STATEMENT OF SIGNIFICANCE: The application of physical methods in alternative to the common chemical ones is seen as a breakthrough for avoiding the emergence of antimicrobial resistance. Antimicrobial strategies that take advantage on the capability of bacteria to sense physical stimuli such as mechanical and electrical cues are scarce. Electroactive nanocomposites comprised of poly(vinylidene fluoride-co-trifluoroethylene (PVDF-TrFE) and green-synthesized silver nanoparticles (AgNPs) were developed to obtain material able to inhibit the colonization of microorganisms. By applying a mechanical stimuli to the nanocomposite, which ultimately mimics movements such as walking or touching, an antimicrobial effect is obtained, resulting from the synergy between the electroactive microenvironments created on the surface of the material and the AgNPs. Such environments sensitize the bacteria to low doses of antimicrobials.
Assuntos
Nanopartículas Metálicas , Nanocompostos , Animais , Antibacterianos/química , Antibacterianos/farmacologia , Nanopartículas Metálicas/química , Testes de Sensibilidade Microbiana , Nanocompostos/química , Polímeros/química , Polímeros/farmacologia , Prata/química , Prata/farmacologia , Staphylococcus epidermidisRESUMO
The antibacterial performance and cytotoxic examination of in situ prepared silver nanoparticles (Ag NPs), on inorganic-organic hybrid nanopowder consisting of zirconium dioxide nanoparticles (ZrO2 NPs) and dihydroquercetin (DHQ), was performed against Gram (-) bacteria Escherichia coli and Gram (+) bacteria Staphylococcus aureus, as well as against human cervical cancer cells HeLa and healthy MRC-5 human cells. The surface modification of ZrO2 NPs, synthesized by the sol-gel method, with DHQ leads to the interfacial charge transfer (ICT) complex formation indicated by the appearance of absorption in the visible spectral range. The prepared samples were thoroughly characterized (TEM, XRD, reflection spectroscopy), and, in addition, the spectroscopic observations are supported by the density functional theory (DFT) calculations using a cluster model. The concentration- and time-dependent antibacterial tests indicated a complete reduction of bacterial species, E. coli and S. aureus, for all investigated concentrations of silver (0.10, 0.25, and 0.50 mg/mL) after 24 h of contact. On the other side, the functionalized ZrO2 NPs with DHQ, before and after deposition of Ag NPs, do not display a significant decrease in the viability of HeLa MRC-5 cells in any of the used concentrations compared to the control.
RESUMO
The toxicity of hybrid nanoparticles, consisting of non-toxic components, zirconium dioxide nanoparticles (ZrO2 NPs), and caffeic acid (CA), was examined against four different cell lines (HTR-8 SV/Neo, JEG-3, JAR, and HeLa). Stable aqueous ZrO2 sol, synthesized by forced hydrolysis, consists of 3-4 nm in size primary particles organized in 30-60 nm in size snowflake-like particles, as determined by transmission electron microscopy and direct light scattering measurements. The surface modification of ZrO2 NPs with CA leads to the formation of an interfacial charge transfer (ICT) complex followed by the appearance of absorption in the visible spectral range. The spectroscopic observations are complemented with the density functional theory calculations using a cluster model. The ZrO2 NPs and CA are non-toxic against four different cell lines in investigated concentration range. Also, ZrO2 NPs promote the proliferation of HTR-8 SV/Neo, JAR, and HeLa cells. On the other hand, hybrid ZrO2/CA NPs induced a significant reduction of the viability of the JEG-3 cells (39 %) for the high concentration of components (1.6 mM ZrO2 and 0.4 mM CA).
Assuntos
Ácidos Cafeicos/toxicidade , Nanopartículas Metálicas/toxicidade , Placenta/efeitos dos fármacos , Zircônio/toxicidade , Ácidos Cafeicos/química , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Teoria da Densidade Funcional , Feminino , Humanos , Nanopartículas Metálicas/química , Modelos Químicos , Tamanho da Partícula , Placenta/patologia , Gravidez , Testes de Toxicidade , Zircônio/químicaRESUMO
The antibacterial ability of in situ prepared nanometer-sized silver particles, immobilized in agar-agar films, was studied as a function of the concentration of co-dopant, magnesium ions. Content of inorganic components in hybrid films was determined using inductively coupled plasma optic emission spectroscopy, and found to be low (<2â¯wt.-%). Morphology of prepared hybrid films, studied by transmission electron microscopy, revealed the presence of non-agglomerated and randomly distributed 10-20â¯nm silver nanoparticles (Ag NPs) within the agar-agar matrices. Fourier-transform infrared spectroscopy indicated the distinct chemical interaction between Ag NPs and polymer chains. Thermogravimetric analysis, as well as the determination of tensile strength, Young's modulus, and elongation at break showed improvement of thermal stability and mechanical properties of agar-agar matrices upon the incorporation of Ag NPs due to high compatibility between the hydrophilic organic component and inorganic components. The complete microbial reduction of Gram-positive bacteria Staphylococcus aureuswas observed for all agar-silver films, while satisfactory results were observed for Gram-negative bacteria Pseudomonas aeruginosa (≥99.6%). The release of Ag+ ions is suppressed by the increase of the concentration of Mg2+ ions and it was found to be significantly smaller (≤0.24â¯ppm) than the harmful ecological level (1â¯ppm).
Assuntos
Ágar/química , Antibacterianos/química , Antibacterianos/farmacologia , Magnésio/química , Nanopartículas Metálicas/química , Prata/química , Prata/farmacologia , Módulo de Elasticidade , Pseudomonas aeruginosa/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacos , Resistência à TraçãoRESUMO
The influence of shape and dielectric property of surrounding media on surface plasmon absorption band of silver nanoparticles was studied. Spherical silver nanoparticles (d = 5.6 nm) synthesized in water using NaBH4 as a reducing agent are transferred in non-polar solvent (chloroform) with phase-transfer reagent oleylamine. The absorption spectrum of oleylamine-capped silver nanoparticles dispersed in chloroform shows a strong surface plasmon resonance band that is 19 nm red-shifted compared to unmodified particles in water. The values for peak position and corresponding half widths are compared with theoretical calculations based on Mie theory. Prismatic and plate-like silver nanoparticles were synthesized in water using trisodium citrate as a reducing agent and cetyltrimethylammonium bromide as stabilizer. Due to structural anisotropy of prismatic and plate-like silver nanoparticles three surface plasmon resonance bands were observed in absorption spectrum. Nanocomposites consisting of non-spherical silver nanoparticles and polyvinyl alcohol exhibit different optical properties compared to water colloid. Instead of three surface plasmon bands, nanocomposite film has only one peak at 460 nm. Reason for appearance of single surface plasmon resonance band in nanocomposite film was discussed according to Maxwell-Garnet theory.
RESUMO
The acute toxicity of surface-modified TiO2 nanoparticles (NPs) with caffeic acid (CA) was compared with those of its separate constituents (free CA and bare TiO2 NPs) upon their oral administration in laboratory mice. Prior to in vivo experiments, the interfacial charge transfer (ICT) complex between surface Ti atoms and CA is thoroughly characterized. Composition and stability constants of ICT complex were determined using Job's method and Banesi-Hildebrand analysis, respectively. The experimental data were supported with quantum chemical calculations based on density functional theory (DFT). Acute toxicity signs, including biochemical alterations and extensive histopathological changes in the liver tissue of mice were detected 14 days after oral administration of bare TiO2 NPs. However, the clinical signs of toxicity, the fractional contribution of organs, biochemical parameters of liver and kidney function, and histopathological changes in liver upon treatment with surface-modified TiO2 NPs with CA were not observed. Also, the genotoxic potential of the ICT complex and its constituents were evaluated in leukocytes of whole blood cells in vivo by comet assay. Both, bare and surface-modified TiO2 NPs did not display DNA damaging effect in time frame of 24â¯h upon their oral administration in mice.
Assuntos
Ácidos Cafeicos/administração & dosagem , Nanopartículas Metálicas/toxicidade , Titânio/toxicidade , Administração Oral , Animais , Células Sanguíneas/efeitos dos fármacos , Ácidos Cafeicos/química , Dano ao DNA/efeitos dos fármacos , Portadores de Fármacos/química , Portadores de Fármacos/toxicidade , Feminino , Rim/efeitos dos fármacos , Rim/patologia , Fígado/efeitos dos fármacos , Fígado/patologia , Nanopartículas Metálicas/química , Camundongos , Titânio/químicaRESUMO
The TiO2 based hybrid supports with different functional groups (amino, glutaraldehyde or epoxy) were prepared and their influence on immobilization of dextransucrase (DS) was studied. Novel synthetic route for surface modification of TiO2 with amino and glutaraldehyde groups was developed taking advantage of charge transfer complex (CTC) formation between surface Ti atoms and salicylate-type of ligand (5aminosalicylic acid (5-ASA)). The proposed coordination of 5-ASA to the surface of TiO2 powder and optical properties of CTC was presented. The pristine TiO2 and amino functionalized TiO2 have higher sorption capacity for DS (12.6 and 12.0mgg-1, respectively) compared to glutaraldehyde and epoxy activated supports (9.6 and 9.8mgg-1, respectively). However, immobilized enzyme to either glutaraldehyde or epoxy functionalized TiO2 have almost two times higher expressed activities compared to pristine TiO2 support (258, 235 and 142IUg-1, respectively). Thermal stability of enzyme immobilized on glutaraldehyde and epoxy functionalized supports was studied at 40°C, as well as operational stability under long-run working conditions in repeated cycles. After five cycles, DS imobilized on glutaraldehyde activated support retained almost 70% of its initial expressed activity, while, after five cycles, performance of DS immobilized on epoxy activated support was significantly lower (15%).
Assuntos
Proteínas de Bactérias/química , Enzimas Imobilizadas/química , Glucosiltransferases/química , Leuconostoc mesenteroides/enzimologia , Titânio/químicaRESUMO
A simple, fast and non-costly method for selective cysteine (Cys) detection, based on optical changes of silver colloids, is developed. For that purpose, stable colloids consisting of silver nanoparticles (Ag NPs) coated with polysaccharide dextran (Dex), isolated from bacterium species Leuconostoc mesenteroides T3, were prepared. The synthesized samples were thoroughly characterized including absorption and FTIR spectroscopy, as well as transmission electron microscopy and X-ray diffraction analysis. The silver colloids display high sensitivity and selectivity towards Cys detection in aqueous solutions. The Ag NPs coated with Dex provide possibility to detect Cys among a dozen amino acids and its detection limit was found to be 12.0µM. The sensing mechanism - red shift of optical absorption - is discussed in terms of the agglomeration of Ag NPs due to formation of hydrogen bonds between Cys molecules attached to different Ag NPs.
Assuntos
Cisteína/análise , Glucosiltransferases/química , Nanopartículas Metálicas/química , Prata/química , Coloides , Glucosiltransferases/isolamento & purificação , Leuconostoc mesenteroides/química , Limite de Detecção , Nanopartículas Metálicas/ultraestrutura , Soluções , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
The antigenotoxic and antioxidative properties of surface-modified TiO2 nanoparticles (NPs) with ascorbic acid (AA) were compared with those of constituents (free AA and bare TiO2 NPs). Colloids consisting of the TiO2 NPs with anatase crystal structure were prepared by acidic hydrolysis of TiCl4. The synthesized TiO2 NPs were characterized using transmission electron microscopy and X-ray diffraction analysis. The charge transfer (CT) complex formation between surface Ti atoms and AA is indicated by immediate appearance of red color. Composition and stability constants of CT complex were determined using Job's method and Banesi-Hildebrand analysis, respectively. The surface structure of CT complex was determined from infra-red spectra of free and bound AA to the surface Ti atoms. The experimental data were supported with quantum chemical calculations based on density functional theory (DFT). The antigenotoxic potential of CT complex was evaluated in leukocytes of whole blood cells in vitro by comet assay method. For evaluation of antioxidant properties, total antioxidant status (TAS) and total oxidant status (TOS) were determined in human serum pool in vitro. The presented results indicate that bare TiO2 NPs have more pronounced antigenotoxic effects in comparison with either surface-modified TiO2 NPs with AA or free AA. No significant differences between the antigenotoxic and antioxidative properties of free and bound AA on the TiO2 NPs were noticed in the investigated concentration range. It seems that surface-modified TiO2 NPs with AA and/or similar compounds can be used to maintain its beneficial activities.
Assuntos
Ácido Ascórbico/farmacologia , Leucócitos Mononucleares/efeitos dos fármacos , Nanopartículas Metálicas/química , Titânio/farmacologia , Adulto , Antioxidantes/química , Antioxidantes/farmacologia , Ácido Ascórbico/química , Coloides , Ensaio Cometa , Dano ao DNA , Feminino , Humanos , Leucócitos Mononucleares/citologia , Leucócitos Mononucleares/metabolismo , Masculino , Nanopartículas Metálicas/ultraestrutura , Cultura Primária de Células , Teoria Quântica , Propriedades de Superfície , Titânio/químicaRESUMO
Nonaqueous reactions between titanium(IV) chloride and alcohols (benzyl alcohol or n-butanol) were used for the synthesis of anatase TiO2 particles, while rutile TiO2 particles were synthesized in aqueous media by acidic hydrolysis of titanium(IV) chloride. The X-ray diffraction measurements proved the exclusive presence of either the anatase or the rutile phase in prepared samples. The photoluminescence of both kinds of particles (anatase and rutile) with several well-resolved peaks extending in the visible spectral region was observed, and the quantum yield at room temperature was found to be 0.25%. Photon energy up-conversion from colloidal anatase and rutile TiO2 particles was observed at low excitation intensities. The energy of up-converted photoluminescence spans the range of emission of normal photoluminescence. The explanation of photon energy up-conversion involves mid-gap energy levels originating from oxygen vacancies.
Assuntos
Medições Luminescentes/métodos , Nanoestruturas/química , Titânio/química , 1-Butanol/química , Álcool Benzílico/química , Cloretos/química , Hidrólise , Tamanho da Partícula , Sensibilidade e Especificidade , Água/química , Difração de Raios XRESUMO
Ligand-stabilized nanocrystals (NCs) were strongly bound to the nanotube surfaces by simple van der Waals forces. Linear arrays of CdSe and InP quantum dots were formed by self-assembly using the grooves in bundles of carbon single-walled nanotubes (SWNTs) as a one-dimensional template. A simple geometrical model explains the ordering in terms of the anisotropic properties of the nanotube surface. CdSe quantum rods were also observed to self-organize onto SWNTs with their long axis parallel to the nanotube axis. This approach offers a route to the formation of ordered NC/SWNT architectures that avoids problems associated with surface derivatization.