Comparative Analysis of Detection Lipopolysaccharides by Acoustic Biosensors Based on Concanavalin A and DNA Aptamers

Lipopolysaccharides (LPS) are indicators of inflammation or food contamination by Gram-negative bacteria. We performed comparative analysis of sensitivity and selectivity of detection of LPS from Salmonella typhimurium (S. typhi) and Escherichia coli O157:H7 (E. coli) by acoustics biosensors based on immobilized lectin Concanavalin A (Con A) or DNA aptamers (APT) specific to LPS from S. typhi. Both Con A and NH₂-modified APT were covalently attached to the surface of 11-mercaptoundecanoic acid (MUA) chemisorbed on a gold surface of AT-cut quartz. Using quartz crystal microbalance with dissipation monitoring (QCM-D) we studied the kinetics of binding of LPS isolated from bacterial lysate in a concentration range 0.3 ng/mL-30 μg/mL. Addition of LPS resulted in decrease of resonant frequency, Δf, which is evidence on the binding of LPS to Con A or APT. We estimated the limit of detection (LOD) for both sensors to be 139.6 ± 19.6 ng/mL (Con A) and APT (76.27 ± 26.45 ng/mL). The specificity of detection was higher for APT based sensors. The sensor has been tested in not diluted and in 10% diluted milk. However, certain matrix effects have been observed due to non-specific interactions of the sensing surface with some milk components such as caseins. Further effort is focused on application of antifouling surfaces to minimize non-specific interactions.

Acknowledgments. This work was funded under the Science Grant Agency VEGA, project No. 1/0445/23 (T.H.) and the Slovak Research and Development Agency under the contract No. APVV SK-HU-24-0011 (M.T.).