Literature Review-Based Comparison of 4′, 6-diamidino-2-phenylindole and Hematoxylin for Hair Root DNA Staining

Two different staining methods for staining, visualizing, and counting nuclei in evidentiary hair roots, 4′, 6-diamidino-2-phenylindole (DAPI) and hematoxylin, were compared based on a review of relevant literature. Ease of use, safety, stability, and efficacy were evaluated. Overall, both staining methods were found to be successful, despite the individual challenges observed with each method. DAPI staining requires a fluorescence microscope for visualization. Hematoxylin staining is less effective on dark pigmented hair roots, can overstain light-colored hairs, requires a rinse step, and may cause polymerase chain reaction (PCR) inhibition in some cases. Based on these findings, DAPI staining is recommended when a fluorescence microscope is available. Studies show hematoxylin is an effective nuclear stain for hair roots under a simple compound microscope; however, a fluorescence microscope may still be required. Either stain can be added to a forensic hair examination workflow to increase the efficiency and efficacy of nuclear DNA analysis from hair roots.