Identification of a Model Organism for Giardia Lamblia by Raman Spectroscopy

Giardia Lamblia is a protozoan parasite which causes Giardiasis, the most common intestinal protozoan infection in the world. Several studies show the presence of blackish pigment granules in retinal layers due to Giardiasis, making of Giardia a pigment-related parasite. In the following work, Raman spectroscopy will be used for the identification of Euglena gracilis, model organism chosen because of its physical similarity, low cost and biosafety. In this study, Euglena samples were excited at 785 nm and signal optimization was performed using Surface-Enhanced Raman spectroscopy (SERS) utilizing gold (Au) nanoparticles as substrate. Our results indicate that SERS provides a four-fold signal enhancement for peaks at 1188 cm-1 and 1530 cm-1, corresponding to the β-carotene conjugated double-bond system present in Euglena, pigment concentrated in the light sensitive eyespot. Thus, we have shown the effectiveness of Raman and SERS Spectroscopy on the identifying of microbial pigments, constituting a robust method to detect and characterize pathogenic microbes such as Giardia, which will have significant downstream diagnostic implications.