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The overall interest in nanotoxicity, triggered by the increasing use of nanomaterials in the material and life sciences, and the synthesis of an ever increasing number of new functional nanoparticles calls for standardized test procedures and for efficient approaches to screen the potential genotoxicity of these materials. Aiming at the development of fast and easy to use, automated microscopic methods for the determination of the genotoxicity of different types of nanoparticles, we assess the potential of the fluorometric γH2AX assay for this purpose. This assay, which can be run on an automated microscopic detection system, relies on the detection of DNA double strand breaks (DSB) as a sign for genotoxicity. Here, we provide first results obtained with broadly used nanomaterials like CdSe/CdS and InP/ZnS quantum dots as well as iron oxide, gold, and polymer particles of different surface chemistry with previously tested colloidal stability and different cell lines like Hep-2 and 8E11 cells, which reveal a dependence of the genotoxicity on the chemical composition as well as the surface chemistry of these nanomaterials. These studies will be also used to establish nanomaterials as positive and negative genotoxicity controls or standards for assay performance validation for users of this fluorometric genotoxicity assay. In the future, after proper validation, this microscopic platform technology will be expanded to other typical toxicity assays.
Luminescence techniques are amongst the most commonly used analytical methods in the life and the material sciences due to their sensitivity and nondestructive character. All photoluminescence signals are, however, affected by wavelength-, polarization- and time-dependent instrument-related effects. Furthermore, substantial challenges to measure absolute luminescence intensities complicate the comparison of data recorded with different instruments and on the same instrument at different times. These problems can be easily resolved with fluorescence standards used for instrument performance validation (IPV) and determination of instrument-to-instrument variations, which allow to measure, quantify, and monitor the wavelength-dependent spectral responsivity for typically used instrument settings. For example, a set of liquid fluorescence standards, the BAM Kit F001-F005, and a ready-to-use glass-based fluorescence standard BAM F-012 developed and certified by BAM enable the characterization of many fluorescence parameters in the UV/vis wavelength range. For the increasingly used near infrared (NIR) region, standards and calibration tools are still very rare. Reliable spectral fluorescence standards and intensity or quantum yield standards are currently not available for the NIR, even though in biology, molecular imaging, and clinical diagnostics fluorescence labels absorbing and emitting in the long wavelength region beyond 650 nm are being increasingly used.
This limitation hampers the reliability and comparability of fluorescence measurements in the NIR and calls for simple fluorescence standards for instrument characterization and for the quantification of fluorescence intensities and efficiencies to improve the comparability of the emission measurements in the NIR. This encouraged us to assess the potential of several NIR-emitting materials as spectral fluorescence standards, thereby extending the BAM Kit from the UV/vis into the NIR up to 950 nm. Moreover, we currently certify quantum yield standards for the UV/vis/NIR to improve the reliability of relative measurements of this spectroscopic key quantity particularly > 650 nm. These tools enable an instrument characterization, signal referencing, quality assurance, traceability, and method validation now also for wavelengths > 650 nm, thereby improving the reliability of fluorescence data in pharmaceutical research, medical and clinical diagnostics, material analysis, and environmental monitoring.