Ultrasensitive immunosensor for acrylamide based on chitosan/SnO2-SiC hollow sphere nanochains/gold nanomaterial as signal amplification.

An electrochemical immunosensor for ultrasensitive detection of acrylamide (AA) in water and food samples was developed. SnO2-SiC hollow sphere nanochains with high surface area and gold nanoparticles with good electroconductivity were fabricated onto the surface of a glassy carbon electrode pre-coated with chitosan. The coating antigen (AA-4-mercaptophenylacetic acid-ovalbumin conjugate, AA-4-MPA-OVA) was immobilized on the electrode. Polyclonal antibody specific for AA-4-MPA was conjugated to gold nanorod (AuNR) as primary antibody (AuNR-Ab1). Horseradish peroxidase labelled anti-rabbit antibody produced in goat was conjugated to AuNR as secondary antibody (HRP-AuNR-Ab2). For detection, the analyte (AA-4-MPA) in sample competed with coating antigen for binding with AuNR-Ab1. After washing, HRP-AuNR-Ab2 was added to capture the AuNR-Ab1, and the electrical signal was obtained by addition of hydroquinone and H2O2. After investigation of the binding ability on nanomaterials and optimization of competitive immunoassay conditions, the proposed immunosensor exhibited a sensitive response to AA with a detection limit of 45.9 ±â€¯2.7 ng kg-1, and working range of 187 ±â€¯12.3 ng kg-1 to 104 ±â€¯8.2 µg kg-1 for drinking water samples. Recoveries of AA from spiked samples were ranged from 86.0% to 115.0%. The specificity, repeatability and stability of the immunosensor were also proved to be acceptable, indicating its potential application in AA monitoring.

Development of an enhanced chemiluminescence ELISA for the rapid detection of acrylamide in food products.

In this work, a polyclonal antibody for acrylamide (AA) was obtained by immunization of rabbits with N-acryloxysuccinimide (NAS) and keyhole limpet hemocyanin (KLH) conjugate. A direct enzyme-linked immunosorbent assay (ELISA) based on this antibody was developed with enhanced chemiluminescent (ECL) detection of AA in food samples. Assay conditions, such as concentrations of antibody and enzyme conjugate and competition time, were optimized. The effects of ionic strength and pH value were investigated. The optimized ECL-ELISA system allowed AA determination in a linear working range of 26.3-221.1 ng mL(-1) with an IC(50) value of 60.6 ng mL(-1) and a limit of detection of 18.6 ng mL(-1). Good recoveries with spiked food samples were obtained with a recovery range from 74.4 to 98.1%, and these results correlated well with those obtained using an HPLC method. This indicates that ECL-ELISA is applicable to the specific detection and routine monitoring of AA in food samples.

Monoclonal antibody development for acrylamide-adducted human haemoglobin; a biomarker of dietary acrylamide exposure.

The spontaneous formation of the neurotoxic carcinogen acrylamide in a wide range of cooked foods has recently been discovered, leading to dietary exposure estimates of 30.8 microg of acrylamide day(-1) for an average 77 kg human male. This is considerably higher than the European legal limit of acrylamide in drinking water, which is approximately 0.2 microg of acrylamide person(-1) day(-1). A recent study of 62,573 women over 11.3 years has observed an increased risk of postmenopausal endometrial and ovarian cancer (but not breast cancer) with increasing dietary acrylamide intake, demonstrating significant risk to human health. As individual acrylamide exposure is affected by dietary habits, cooking methods, and cigarette consumption; accurate extrapolation from estimated dietary exposure is extremely difficult. Quantifying biomarkers of acrylamide exposure therefore remains the most effective means of rapidly determining individual exposure to acrylamide, and correlating exposure with lifestyle choices. Current methodologies for the analysis of blood biomarkers of acrylamide are focused on expensive, slower chromatographic techniques such as GC and LC coupled to mass spectrometry. This paper describes the first successful development of two monoclonal antibodies specific to acrylamide-adducted haemoglobin (IC(50) of 94 ng ml(-1) and 198 ng ml(-1)), that are suitable for use in a high-throughput biomarker immunoassay to determine individual acrylamide exposure. Further development of acrylamide-haemoglobin standards with defined levels of acrylamide adduction will enable a fully quantitative assay, and allow sensitivity comparisons with alternative chromatographic methods of analysis.

Antigen synthetic strategy and immunoassay development for detection of acrylamide in foods.

Acrylamide, a toxic and carcinogenic compound, has been found to be present in a range of processed starchy foods. To prepare an effective immunogen compound for acrylamide, N-acryloxysuccinimide (NAS) was conjugated to bovine serum albumin (BSA) at a high molar ratio of 21.2:1. Antisera were obtained by immunization of rabbits with additional booster injections of the NAS-BSA conjugate after the regular process. The IgGs purified by an ammonium sulfate precipitation method were further fractionated with a BSA-immobilized immunoaffinity column. The affinity constant between the collected antibody and coated antigen (NAS-ovalbumin) is found to be 6.7 x 10(7) L mol(-1). Asparagine, the key precursor of acrylamide formation in foods, showed negligible cross-reactivity to the antibody. A biotin-avidin enzyme-linked immunosorbent assay (BA-ELISA) was developed and the optimum assay medium was found to be 0.1 mol L(-1) NaHCO(3) (pH 8.3, containing 0.5 mol L(-1) NaCl). The BA-ELISA afforded a practical sensitivity with a working range of 10-100,000 ng mL(-1) and a detection limit of 6 ng mL(-1). The assay was applied to detect acrylamide in potato fries and biscuits and the quantitative results were in good agreement with those obtained by the high-performance liquid chromatography method. This immunoassay will be very useful for monitoring acrylamide in food samples.