Development of surface‐enhanced Raman spectroscopy evidence swabs using a silver nanoparticle biosynthesis for the detection of animal blood

Identifying the type of body fluid recovered from crime scenes before DNA typing may be critical to qualify its relevancy to the case. Presumptive tests are often used first to detect blood traces; however, they require confirmation, are destructive, and are susceptible to false positives. This study aims to develop a method of collection and identification for nonhuman blood using biosynthesized SERS swabs as a more accurate, specific, and nondestructive detection technique. Silver nanoparticles were synthesized directly on nylon swabs using a biosynthesis reaction and curcumin as the reducing agent to form the nanoparticles. The detection of bovine blood was investigated by analyzing decreasing volumes of blood swabbed with the surface‐enhanced Raman spectroscopy (SERS) swabs. Although swabbing 30 and 20 μl of blood resulted in the most resolved spectra, swabbing 10 μl of blood still produced identifiable peaks. Wetted swabs were used to analyze dried bovine bloodstains on cotton fabrics and glass slides: The spectra collected when swabbing the bloodstain on the glass sides had a higher signal‐to‐noise ratio than on fabrics. The SERS swabs were subsequently used to collect and analyze horse and sheep blood. Although Raman bands characteristic of blood were identifiable for each specie, showing that the SERS swabs allowed the successful detection of the three animal blood species, the spectra from the three species could not be differentiated. This study demonstrates the efficiency of the biosynthesis to grow nanoparticles on the swabs and shows their viability to be used as SERS substrates to collect and identify animal blood.