Development of SERS-active forensic evidence swabs for rapid, non-destructive confirmatory serological screening and STR typing of human bodily fluids

As submitted by the proposer: In a crime laboratory, evidentiary swabs that may potentially contain human bodily fluids are screened using both presumptive and confirmatory tests. These tests, such as the acid phosphatase (AP) test and the so-called Christmas tree stain for semen and the Kastle-Meyer and Takayama tests for blood, are quite time consuming, expensive, only test for one bodily fluid and are prone to both false positives and false negatives. Recent literature reports however, have indicated that Raman spectroscopy may have a far lower limit of detection than traditional methods and may allow investigators to perform one type of measurement for all body fluids, potentially leading to higher efficiency, more definitive results, and higher accuracy. Another recent report utilized surfaced enhanced Raman spectroscopy (SERS) as a means to decrease the limit of detection of certain forensic samples. SERS, in which an analyte is placed on or near a nanostructured metal surface, has the potential to increase the Raman cross-section of the analyte by many orders of magnitude. Herein, we propose to develop SERS-active forensic evidence swabs by attaching silver nanoparticles grown via the hydrogen reduction method to the fibers of commercially available swabs. We will determine the synthetic protocol and measurement that maximizes the intensity of Raman signal of human biological fluids such as semen and vaginal fluid while simultaneously minimizing any possible negative effects the silver swabs may have on typical DNA extraction and quantification protocols. STR typing of semen and vaginal fluid samples collected on SERS- active swabs as well as those collected on pristine swabs will also be performed to determine the effect silver may have on the quality of data that is produced using protocols typical to forensic crime laboratories. We will also explore the Raman limit of detection of human bodily fluids collected on swabs and determine the relationship between intensity of Raman signal and amount of recovered DNA. Using forensically relevant sampling scenarios, we will also develop sampling protocols that maximize the amount of evidentiary material being transferred to the SERS-active swab. Finally, we will explore the ability of Raman measurements conducted using the SERS- active swabs to differentiate and possibly quantify the ratios of the mixtures of semen and vaginal fluid. This project contains a research and/or development component, as defined in applicable law. ca/ncf