Effectiveness of adhesive tapes in forensic Laser Microdissection applications

Abstract

Recent studies have shown that the traditional elution method of recovering DNA material from swabs and tapes is inefficient with less than 30% recovery rate of intact cells. The low number of cells recovered lead to a low quantity of DNA available for testing which reduces the chance of a successful DNA analysis. Elution inefficiency is more problematic when a sample is a mixture, where the DNA of one individual is of low abundance, as profiling results from this contributor may not be able to be determined. The aim of this research was to test the effectiveness of adhesive tapes in a new proposed method of directly implementing taped samples of cells into Laser Microdissection (LMD) applications, including various visualisation techniques. Potentially, cells can be recovered using the adhesive tape and can be isolated and collected to produce a DNA profile using the LMD. Problems that occur with mixed samples can also be resolved by using differentiation staining methods such as X/Y Fluorescent in situ hybridisation (FISH) and Sperm Hy-liter™ in conjunction with the LMD. X/Y FISH enables the differentiation of sexes of the same cell type while the Sperm Hy-liter™ is an effective way to find human sperm cells. 12 potential tapes were tested for their compatibility with LMD applications but only one candidate, a screen protector, was found to be successful. The main characteristic that affects the compatibility of a tape with LMD was determined to be the adhesive material with silicone adhesive being the ideal option. Backing material and thickness of tapes have some but not as much impact as the adhesive type. For use in microscopy, the tapes had to be transparent. The screen protector was found to be compatible with Sperm Hy-liter™ staining and histological staining. DNA profiling was successfully obtained from samples collected using the LMD, although the results suggest the possibility of less sensitivity when compared to traditional LMD DNA methods. The X/Y FISH method at the time of this research was problematic and the results from testing this method in this study were inconclusive. This research has confirmed that a silicone adhesive tape can be used in this new proposed method combining sampling and direct LMD DNA applications and could benefit samples with small numbers of cells or mixed samples, circumventing the low cell recovery from samples using the traditional elution method.