Cytotoxicity

1. What is Cytotoxicity?

Cytotoxicity is the quality of being toxic to cells. Cells exposed to a cytotoxic compound can respond in a number of ways. The cells may undergo necrosis, in which they lose membrane integrity and die rapidly as a result of cell lysis; they can stop growing and dividing; or they can activate a genetic program of controlled cell death, termed apoptosis.

2. How is Cytotoxicity being measured?

There are many ways to measure cytotoxicity, but most involve assessment of cell membrane integrity. Membrane integrity can be evaluated by using vital dyes (such as trypan blue or propidium iodide), by protease biomarkers, with MTT or MTS redox potential assays, or by measuring ATP content. Many of these assays involve colorimetric, fluorescence, or luminescencedetection.

With one of the widest ranges of detection technologies on the market today, Molecular Devices can provide the bioanalytical and analytical products that you need to conduct cytotoxicity measurements, from cytometry and high-content screening systems to multi-mode microplate analysis systems to high-throughput cellular screening systems.

Cell Cytotoxicity

Atomic Absorption Spectroscopy (AAS)

1. What is AAS?

Atomic absorption spectroscopy (AAS) is a spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state.

In analytical chemistry the technique is used for determining the concentration of a particular element (the analyte) in a sample to be analyzed. AAS can be used to determine over 70 different elements in solution or directly in solid samples used in pharmacology, biophysics and toxicology research.

Atomic absorption spectroscopy was first used as an analytical technique, and the underlying principles were established in the second half of the 19th century by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, both professors at the University of Heidelberg, Germany.

The modern form of AAS was largely developed during the 1950's by a team of Australian chemists. They were led by Sir Alan Walsh at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Chemical Physics, in Melbourne, Australia.

An Example of AAS Machine

2. What is the use of AAS?

Atomic absorption spectrometry has many uses in different areas of chemistry such as:

• Clinical analysis: Analyzing metals in biological fluids and tissues such as whole blood, plasma, urine, saliva, brain tissue, liver, muscle tissue, semen

• Pharmaceuticals: In some pharmaceutical manufacturing processes, minute quantities of a catalyst that remain in the final drug product

• Water analysis: Analyzing water for its metal content.

3. How does the AAS Machine works?

In order to analyze a sample for its atomic constituents, it has to be atomized. The atomizers most commonly used nowadays are flames and electrothermal (graphite tube) atomizers. The atoms should then be irradiated by optical radiation, and the radiation source could be an element-specific line radiation source or a continuum radiation source. The radiation then passes through amonochromator in order to separate the element-specific radiation from any other radiation emitted by the radiation source, which is finally measured by a detector.

Atomic absorption spectrometer block diagram