Finding DNA: Using fluorescent in situ detection

Abstract

It is known that DNA can be deposited onto a surface by touch yet few means have been developed for its in situ detection. Collecting touch-DNA samples can be difficult as likely locations rather than the DNA is targeted leading to many samples that are submitted to a forensic laboratory containing little or no DNA. A range of dyes are available that bind to DNA at high specificity for application within the laboratory and here we report on the use of these dyes to detect latent DNA on various substrates and within biological samples. Six common nucleic acid-binding dyes were selected due to their increase in fluorescence when in the presence of double stranded-DNA; four of the six dyes are permeable to cell membranes. The fluorescence from dye/DNA complex was detected using a high intensity light source, the Polilight 1 (PL500), an excitation wavelength of 490 nm and emission observed/recorded through interference filters centred at 530 nm or 550 nm depending on the dye emission. The samples were visualised under a fluorescent microscope (Nikon Optiphot) using a B2A filter cube. The detection limit of DNA was determined for the selected dyes along with the optimal conditions, such as buffer composition and dye concentration for a range of surfaces. The ability for the dyes to detect DNA within biological samples such as saliva, hair, skin, fingermarks, and hair follicles was also determined. 2015 Elsevier Ireland Ltd. All rights reserved.

Touch DNA localization and direct PCR: An improved workflow for STR typing from improvise explosive devices

“…Hence, we selected Diamond Dye as a touch DNA visualization reagent. Background fluorescence mentioned in a previous study [2] due to bacterial DNA was also seen in this study.…”

“…Touch DNA from bomb assemblers usually yields low success rate due to the inability to locate the areas where DNA has been left [1]. Previous studies showed that touch DNA and other biological fluids could be stained with a fluorescent dye but STR typing was unsuccessful because the dyes interrupt DNA extraction and other processes [2,3]. In this study, we therefore investigated the efficiency of three fluorescent dyes to locate touch DNA on the IED substrates.…”

A review of trace “Touch DNA” deposits: Variability factors and an exploration of cellular composition

“…This may be supported by published observations of more DNA deposited by individuals with drier hands [42] and with active skin diseases known to elevate keratinocyte turnover [128]. Nucleic acid staining of touched items and dead skin has shown clustered fluorescence distinct from a cellular structure which could be diffuse intracellular DNA [129]. Reported rabbit polyclonal anti-ssDNA antibody staining in the outermost skin tissue has revealed a few nuclei-like objects in the cornified layers of cells, suggesting either that these cells are not as entirely devoid of DNA as was previously thought or that compromised cells have left residual nuclei.…”

Visualising latent DNA on swabs

“…Diamond ™ Nucleic Acid Dye (DD) (Promega, Madison, WI, USA) has recently been reported to stain DNA in samples such as hair roots and shafts [1,2], saliva [3,4], fingermarks [5] and other forensically relevant items [6]. The DD molecule is an external groove-binder that is able to bind to the backbone of DNA effectively, but it does not bind effectively to RNA and prokaryote supercoiled DNA [1,7].…”