A surface plasmon resonance (SPR) immunobiosensor assay was developed and validated to detect microcystin toxins in Spirulina and Aphanizomenon flos-aquae blue-green algae (BGA) food supplements. A competitive inhibition SPR-biosensor was developed using a monoclonal antibody to detect microcystin (MC) toxins. Powdered BGA samples were extracted with an aqueous methanolic solution, centrifuged and diluted in HBS-EP buffer prior to analysis. The assay was validated in accordance with the performance criteria outlined in EU legislation 2002/657/EC. The limit of detection (LOD) of the assay was calculated from the analysis of 20 known negative BGA samples to be 0.561 mg kg−1. The detection capability (CCβ) of the assay was determined to be ≤0.85 mg kg−1 for MC-LR. The biosensor assay was successfully applied to detect MC-LR toxins in BGA samples purchased on the Irish retail market. MC-LR was detected in samples at levels ranging from <0.5 to 2.21 mg kg−1. The biosensor results were in good agreement with an established LC–MS/MS assay. The assay is advantageous because it employs a simple clean-up procedure compared to chemical assays and allows automated unattended analysis of samples unlike ELISA.

Coumarin molecules are ubiquitous in nature. Several have come to prominence as potential clinical therapeutic candidates. The principal example is warfarin, which is a very widely prescribed anticoagulant. Other coumarin derivatives, such as aflatoxin B-1, are insidious contaminants in crop-derived foodstuffs. Extreme potency is a common feature of all biochemically active coumarins and, thus reliable methods for their rapid and sensitive detection are of paramount importance. Accordingly, this review examines the current methods used in the analysis of these molecules and compares them with immunoassay-based strategies. As a case study, we report on our experiences with using coumarin-specific polyclonal, monoclonal, and recombinant antibodies in conjunction with a surface plasmon resonance-based biosensor for analysis of coumarins. We chart the assay development process and demonstrate high sensitivity and reproducibility that compares favorably with established methodologies.

Abstract Aflatoxin B1 (AFB1) is a highly toxic secondary metabolite of the fungal species Aspergillus flavus and Aspergillus parasiticus produced under certain environmental conditions. The gene encoding an AFB1‐specific single‐chain fragment variable (scFv) was isolated from a pre‐immunized phage display library and used to express a monomeric and dimeric scFv, specific for AFB1, in Escherichia coli. The monomeric and dimeric scFv were then applied to the development of surface plasmon resonance‐based inhibition immunoassays for the detection of AFB1. Regeneration of the sensor surface, which consisted of a CM5 chip immobilized with an AFB1 derivative, was investigated and enabled at least 75 binding regeneration cycles. The inhibition assays developed had ranges of detection between 390 and 12,000 pg mL−1 (ppb) for the monomeric scFv and between 190 and 24,000 pg mL−1 (ppb) for the dimeric scFv, with coefficients of variation for the inter‐day variability studies ranging from 1.9–4.18% and 3–11.53%, respectively. This paper was by special invitation as a contribution to a special issue of the journal entitled “Application of Spectroscopic Methods to Environmental Problems”. The special issue was organized by Professor Peter A. Tanner, Professor in the Department of Biology and Chemistry at City University of Hong Kong.

A binding protein displaying broad-spectrum cross-reactivity within the sulfonamide group was used in conjunction with a sulfonamide specific sensor chip and a surface plasmon resonance biosensor to develop a rapid broad spectrum screening assay for sulfonamides in porcine muscle. Results for 40 samples were available in just over 5h after the completion of a simple sample preparation protocol. Twenty sulfonamide compounds were detected. Acetylated metabolites were not recognised by the binding protein. Limit of detection (mean–three times standard deviation value when n=20) was calculated to be 16.9ngg−1 in tissue samples. Intra-assay precision (n=10) was calculated at 4.3 %CV for a sample spiked at 50ngg−1 with sulfamethazine, 3.6 %CV for a sample spiked at 100ngg−1 with sulfamethazine, 7.2 %CV for a sample spiked at 50ngg−1 with sulfadiazine and 3.1 %CV for a sample spiked at 100ngg−1 with sulfadiazine. Inter-assay precision (n=3) was calculated at 9.7 %CV for a sample spiked at 50ngg−1 with sulfamethazine, 3.8 %CV for a sample spiked at 100ngg−1 with sulfamethazine, 3.5 %CV for a sample spiked at 50ngg−1 with sulfadiazine and 2.8 %CV for a sample spiked at 100ngg−1 with sulfadiazine.

Immunochemical screening assays using surface plasmon resonance have been developed for chloramphenicol and chloramphenicol glucuronide residues in poultry muscle, honey, prawn and cows’ milk using a sensor chip coated with a chloramphenicol derivative and an antibody. The antibody cross-reacted with chloramphenicol glucuronide 73.8% (poultry), 69.2% (honey), 75.7% (prawn) and 84.8% (milk). There was no cross-reaction with similar drugs or other commonly used antibiotics. The assay allowed the direct analysis of bovine milk (fat content ∼3.5%). Poultry, honey and prawn samples were extracted with ethyl acetate followed by analysis on the biosensor. The decision limits (CCα) for each assay were determined as: poultry (0.005μgkg−1), honey (0.02μgkg−1), prawn (0.04μgkg−1) and milk (0.04μgkg−1) and the detection capabilities (CCβ) were 0.02, 0.02, 0.07 and 0.05μgkg−1, respectively. Poultry muscle, honey and milk were spiked at 0.1μgkg−1 and prawn at 0.15μgkg−1 and the intra-assay precision (n=10) calculated as 10.5, 5.0, 4.6 and 8.8%, respectively. Between run precision (n=3) performed at the same levels yielded the following results: 3.0% (poultry), 4.7% (honey), 7.6% (milk) and 5.5% (prawn).

The performance of a prototype multi-channel optical biosensor in both the laboratory and on site at an abattoir was evaluated. The high-throughput surface plasmon resonance (SPR) instrument allows either simultaneous analysis of eight samples for a single analyte or multi-analyte analysis. In conjunction with an automated sample pipetting station, direct analysis of up to 650 bile samples for sulfamethazine (SMZ) and sulfadiazine (SDZ) per day was possible. Instrument performance was assessed in a laboratory based trial by comparing results of the prototype assay method with the routine Biacore 1000 procedure used in the laboratory. During the assay of 1751 samples, false positive rates were calculated as 0.86% for SMZ and 1.48% for SDZ using the prototype biosensor as compared to 0.63% (SMZ) and 0.69% (SDZ) when using the Biacore 1000 instrument. During a 2-month on-site study at an abattoir, a total of 6069 bile samples were analysed. No false negative results were recorded while extremely low false positive rates (0.13% for SMZ and 0.74% for SDZ) were found. The present study clearly demonstrates the potential of high-speed SPR biosensor technology for high-throughput veterinary drug detection.