engleski

INFLUENCE OF UVC RADIATION ON BLOOD, SALIVA AND SEMEN SAMPLES

The major threat in forensic laboratories is a sample mix-up and contamination of forensic evidence with foreign DNA, which could lead to identification of mixed DNA profiles, inhibition of PCR reactions or wrong DNA genotyping. The aim was to study in real conditions the true possibility of working surfaces contamination in the laboratory and the anti-contamination effects of commercial cleaning agents and ultraviolet C (UVC) radiation on naked DNA, diluted and non-diluted blood, semen, saliva samples and controls. The doses of UVC radiation, which would cause a complete loss of DNA profile in biological samples were also investigated. Buccal swab sample, blood, saliva and semen were obtained from a single male donor. Genomic DNA was extracted using Chelex. DNA was amplified using the AmpFlSTR® NGM™ PCR Amplification Kit. Statistical data analysis was performed using Excel. DNA concentration, UVC dose, sample volume, radiation time, number of correctly detected alleles on genetic loci and number of correctly detected alleles in four loci groups were tested. To our knowledge, the rate of UVC induced DNA damage of semen stains was not analyzed so far. The results of this study pointed out the inefficiency of commercial cleaning agents for working surfaces decontamination, when dealing with non-diluted blood and semen. High UVC doses are necessary for complete decontamination of working surfaces with inflicted non-diluted blood and semen controls. It is recommended to carefully and thoroughly clean working surfaces with commercial agents followed by minimal 16 hour UVC exposure (dose approximately 4380 mJ/cm2) for complete and successful decontamination.

ultraviolet C (UVC) radiation; blood; saliva; semen; DNA; contamination of forensic evidence

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