Raman tweezers and their application to the study of singly trapped eukaryotic cells.

In this review the recent emergence of Raman tweezers as an analytical technique for single eukaryotic cell analysis is described. The Raman tweezer technique combines Raman spectroscopy as a diagnostic tool with optical tweezers by which means single cells can be trapped and manipulated in a laser beam using a high numerical aperture imaging microscope. Necessary instrumental requirements to facilitate Raman tweezer experiments are discussed together with practical considerations such as the potential for photodamage of cells subjected to trapping and Raman excitation. Specific applications of Raman tweezers to the analysis of cancer cells, erythrocytes and lymphocytes, micro-organisms and sub-cellular components e.g.chromosomes and mitochondria are then discussed followed by a summary of the future potential of the technique for single cell analysis.

The effect of temperature and NaCl concentration on the kinetic method of toxicity determination using Vibrio fischeri.

In this paper the effect of temperature and NaCl concentration on the kinetic method of toxicity determination using Vibrio fischeri was studied for 50 ppm Zn(2+). This work shows that both NaCl concentration and temperature affect the kinetics of toxicity as well as the luminescence of the bacteria, and hence these are important factors that need to be considered in the development of a miniaturised portable instrument. Furthermore, this work shows that the conditions for which the kinetic test was most sensitive, i.e. exhibited the greatest response, were 23 degrees C and 2% NaCl. However, at these conditions small variations in temperature and NaCl concentration could lead to great errors in the results. Thus 12.5 degrees C and 2% NaCl are preferred as at these conditions the obtained results are more robust. Although at the latter conditions the toxicity rate constant was found to be 5.5 times less than that for 23 degrees C, the value is comparable to that obtained for 15 degrees C. From the data available it was also found that the temperature dependence of the toxicity rate fits the Arrhenius equation, in a behaviour similar to that of simpler chemical reactions.