(76h) Portable Surface Plasmon Resonance Biosensor for Detecting Marine Toxin Domoic Acid

Domoic acid (DA) is a neurotoxin produced by marine diatoms of the genus Pseudo-nitzschia that can accumulate in edible shellfish.  Amnesic shellfish poisoning (ASP) is a serious illness that is caused by eating shellfish contaminated with DA and in some cases it can be fatal. The increasing intensity and frequency of toxic blooms has drawn more attention to develop fast and effective techniques to detect DA. High-performance liquid chromatography with ultraviolet detection (HPLC-UVD) is the current official method for detecting DA. Unfortunately, due to the complexity and relatively large size of the equipment, HPLC-UVD detection needs to be performed by trained personnel in the laboratory. Surface plasmon resonance (SPR) biosensors have been demonstrated to provide a fast and sensitive DA detection.  However, the size of conventional SPR biosensors makes them unsuitable for working in the field. Newer developed surface plasmon resonance coupler and disperser (SPRCD) biosensor are significantly smaller and lighter than conventional SPR biosensors and could potentially become the perfect tool for detecting DA on-site.

In this paper we present the detection of DA using a SPRCD biosensor and compare the detection sensitivity with a conventional spectroscopic SPR biosensor. The inhibition assay was used for both SPRCD and SPR biosensors with polyclonal anti-DA antibody. A salt calibration was performed in order to be able to directly compare the response of the SPRCD biosensor to that of the conventional SPR biosensor. DA was immobilized onto the gold coated surface of the sensor chip previously functionalized with a mixed self assembled monolayer (SAM) of HS(CH₂)₁₁(C₂H₅O)₄OH  and  HS(CH₂)₁₁(C₂H₅O)₆NH₂ thiols. The OH-terminated thiol serves as a protein non-fouling background while the NH2-terminated thiol provides a functional group to which DA molecules could bind via the NHS/EDC chemistry. The ratio of OH to NH₂ terminated thiols was optimized for both types of sensors in order to reduce the non-specific binding but in the meantime to provide sufficient functional groups for immobilization of DA. Polyclonal anti-DA and DA were mixed to the final concentrations of 1 - 5 μg/mL for polyclonal anti-DA and 0.1 – 1500 ng/mL for DA prior to flowing through the sensors. The detection curves were obtained for both sensors and, finally, the limit of detection and the working range were determined.  The influence of surface fictionalization on the sensitivity and specificity of detection as well as SPRCD sensing mechanisms will be discussed.