Comparison of glycosphingolipids and antibodies as receptor molecules for ricin detection

Glycosphingolipids (GSLs) have been shown to undergo strong interactions with a number of protein toxins, including potential bioterrorism agents such as ricin and botulinum neurotoxin. Characterization of this interaction in recent years has led to a number of studies where GSLs were used as the recognition molecules for biosensing applications. Here, we offer a comparison of quartz crystal microbalance (QCM) sensors for the detection of ricin using antibodies and the GSLs GM1 and asialoGM1, which have been shown to undergo strong interactions with ricin. The presence, orientation, and activity of the GSL and antibody films were confirmed using ellipsometry, Fourier transform infrared spectroscopy (FT-IR), and QCM. It was found that the GSLs offered more sensitive detection limits when directly compared with antibodies. Both GSLs had lower detection limits at 5 μg/mL, approximately 5 times lower than were found for antibodies (25 μg/mL), and their linear detection range extended to the highest concentrations tested (100 μg/mL), almost an order of magnitude beyond the saturation point for the antibody sensors. Potential sites for nonspecific adsorption were blocked using serum albumin without sacrificing toxin specificity.