Surface-Enhanced Resonance Raman Spectroscopy for the Rapid Detection of Cryptosporidium parvum and Giardia lamblia

A rapid surface-enhanced resonance Raman spectroscopy (SEERS) method has been developed for the detection of two waterborne pathogens, Cryptosporidium parvum and Giardia lambia. Raman labels were prepared by conjugating gold nanoparticles with commercial antibodies and dye molecules. After incubation with the immunogold labels, C. parvum oocysts and G. lamblia could easily be measured and differentiated by Raman spectroscopy. The immunogold signal intensities were optimized by testing several sizes of gold nanoparticles, four different commercially available dye molecules, and two Raman excitation wavelengths. Raman maps were collected across fixed and labeled Cryptosporidium oocysts and Giardia cysts, and the maps were used to determine which C. parvum and G. lamblia antibodies exhibited the best specificities and organism coverages. Ultimately, 40 nm gold nanoparticles were conjugated with rhodamine B isothiocyanate and malachite green isothiocyanate for the C. parvum and G. lamblia immunogold syntheses, respectively. C. parvum monoclonal IgM antibodies and G. lamblia monoclonal lgG1 antibodies resulted in the best immunogold coverage. The research presented here demonstrates the feasibility of utilizing SEERS labeling for sensitive multipathogen monitoring strategies.