Adaptations of Cell Autofluorescence for Cell Identification

Abstract

Often in the examination of sexual assault evidence, buccal cells are indistinguishable from vaginal cells. Both are epithelial cells and therefore they have a similar appearance. Many approaches have been taken to develop a method for distinguishing between these two types of cells. ESR is in the process of developing a ribonucleic acid fluorescent in situ hybridisation method which will allow the distinction between these two cell types. Cellular autofluorescence makes this process difficult. This project investigated the autofluorescence of body cells commonly found at crime scenes (semen, vaginal cells, buccal cells, skin cells, and blood) and the application of chemical treatments to these cells for the reduction of autofluorescence. Buccal cells which had been ribonucleic acid fluorescent in situ hybridisation treated were also chemically treated to determine the efficacy of the chemical treatments as these cells show an increase in autofluorescence after they have been labelled using fluorescent in situ hybridisation. Sodium dithionite, carbonyl cyanide m-chlorophenylhydrazone, copper sulphate, and sodium azide treatments were tested and showed promising results. The most effective treatment for the reduction of autofluorescence proved to be copper sulphate at a concentration of 2.5mM incubated for a total of ten minutes at room temperature. This treatment successfully reduced autofluorescence in cell samples and enhanced ribonucleic acid fluorescent in situ hybridisation signals. Studies on the effects of beverages including Diet Coke®, Coca-Cola®, and Pepsi® on buccal cell autofluorescence were also conducted. Buccal cells showed an increased pink/orange autofluorescence due to the caramel colouring in these drinks. As caramel colourings are present in some kinds of alcohol these results suggest it is possible that in oral sexual assaults involving alcohol the perpetrator’s buccal cells could be identified through the examination of cellular autofluorescence.