Raman Spectroscopy for Forensic Identification of Body Fluid Traces: Method Validation for Potential False Negatives Caused by Blood-Affecting Diseases

Two critical issues in forensic science are identifying body fluid traces found at crime scenes and preserving them for DNA analysis. However, the majority of current biochemical tests for body fluid identification, which are applicable at the crime scene, are presumptive and destructive to the sample. Raman Spectroscopy provides a suitable alternative to current methods as a nondestructive, confirmatory, and potentially in field method. Our laboratory has developed a chemometric model for the identification of five main body fluids using Raman spectroscopy. This model was developed using samples obtained from healthy donors. Thus, it is of most importance for the forensic application of the method to validate its performance for donors with diseases that might affect the biochemical composition of body fluids. In this study, the developed method was validated using peripheral blood samples acquired from donors with Celiac Disease, Sickle Cell Anemia, and Type 2 Diabetes. It was shown that the method correctly identified all samples as peripheral blood indicating that no false positives could occur because the blood traces were originated from donors suffering from the diseases.

Quantification and discovery of PCR inhibitors found in food matrices commonly associated with foodborne viruses

Human norovirus is the leading cause of foodborne illness globally.Detection and quantification of norovirus commonly involves the use of reverse transcriptase quantitative polymerase chain reaction(RT-qPCR);however,the presence of inhibitory compounds in foods limit detection and accurate quantification.Although some studies have been done on PCR inhibitors from foods,many of them are over a decade old and do not investigate inhibition in contemporary one-step RT-qPCR-based detection chemistries.The purpose of this work was to quantify the degree of inhibition that occurs from inhibitory compounds found in produce(pectin)and mollusks(hemocyanin,glycogen)—foods commonly associated with norovirus outbreaks.RT-qPCR reactions containing different amounts of genomic bacteriophage MS2 RNA,a norovirus surrogate,were spiked with different concentrations of pectin(0.0625%–0.25%w/V),glycogen(1.25%–10%),and hemocyanin(0.0625%–0.25%).Past research has implicated glycogen as an inhibitory compound in oysters;however,even high levels of glycogen(10%)had no significant effect(P>0.05)on amplification.Conversely,both pectin and hemocyanin caused complete inhibition at 0.25%,with no significant inhibition observed at 0.0625%(P<0.05).Hemocyanin is abundant in the hemolymph of mollusks and previously untested as a PCR inhibitor.This work demonstrates that pectin and hemocyanin should be considered when testing produce and mollusk samples with PCR-based methods.