RESUMO
Cytotoxicity of CdSe and CdSe/ZnS nanoparticles has been investigated for different surface modifications such as coating with mercaptopropionic acid, silanization, and polymer coating. For all cases, quantitative values for the onset of cytotoxic effects in serum-free culture media are given. These values are correlated with microscope images in which the uptake of the particles by the cells has been investigated. Our data suggest that in addition to the release of toxic Cd(2+) ions from the particles also their surface chemistry, in particular their stability toward aggregation, plays an important role for cytotoxic effects. Additional patch clamp experiments investigate effects of the particles on currents through ion channels.
Assuntos
Neoplasias da Mama/metabolismo , Compostos de Cádmio/efeitos adversos , Compostos de Cádmio/farmacocinética , Fibroblastos/metabolismo , Nanotubos/efeitos adversos , Compostos de Selênio/efeitos adversos , Compostos de Selênio/farmacocinética , Sulfetos/efeitos adversos , Sulfetos/farmacocinética , Compostos de Zinco/efeitos adversos , Compostos de Zinco/farmacocinética , Animais , Materiais Biocompatíveis/efeitos adversos , Materiais Biocompatíveis/farmacocinética , Neoplasias da Mama/patologia , Células CHO , Adesão Celular/efeitos dos fármacos , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Coloides/efeitos adversos , Coloides/farmacocinética , Cricetinae , Cricetulus , Relação Dose-Resposta a Droga , Fibroblastos/efeitos dos fármacos , Fibroblastos/patologia , Teste de Materiais , Medição de Risco/métodos , Fatores de RiscoRESUMO
We report here an approach for simultaneous fluorescence imaging and electrical recording of single ion channels in planar bilayer membranes. As a test case, fluorescently labeled (Cy3 and Cy5) gramicidin derivatives were imaged at the single-molecule level using far-field illumination and cooled CCD camera detection. Gramicidin monomers were observed to diffuse in the plane of the membrane with a diffusion coefficient of 3.3 x 10(-8) cm(2)s(-1). Simultaneous electrical recording detected gramicidin homodimer (Cy3/Cy3, Cy5/Cy5) and heterodimer (Cy3/Cy5) channels. Heterodimer formation was observed optically by the appearance of a fluorescence resonance energy transfer (FRET) signal (irradiation of Cy3, detection of Cy5). The number of FRET signals was significantly smaller than the number of Cy3 signals (Cy3 monomers plus Cy3 homodimers) as expected. The number of FRET signals increased with increasing channel activity. In numerous cases the appearance of a FRET signal was observed to correlate with a channel opening event detected electrically. The heterodimers also diffused in the plane of the membrane with a diffusion coefficient of 3.0 x 10(-8) cm(2)s(-1). These experiments demonstrate the feasibility of simultaneous optical and electrical detection of structural changes in single ion channels as well as suggesting strategies for improving the reliability of such measurements.