Miniaturized portable surface plasmon resonance immunosensor applicable for on-site detection of low-molecular-weight analytes

This paper presents the sensing characteristics of a new, versatile and portable surface plasmon resonance (SPR) immunosensor for detecting 2-hydroxybiphenyl (HBP) employing an indirect competitive immunoreaction principle. The HBP–bovine serum albumin (HBP–BSA) conjugate prepared by covalent binding of HBP with BSA using an aliphatic chain spacer is immobilized onto the SPR sensor surface by simple physical adsorption. A monoclonal antibody against HBP (anti-HBP antibody) is allowed to flow over the conjugate surface, and the binding interaction was monitored by SPR. HBP is quantified based on the changes in the resonance angle for binding interaction between the HBP–BSA immobilized sensor chip and anti-HBP antibody in the presence of free HBP in solution. It is observed that the competition between the HBP–BSA conjugate and HBP for binding with anti-HBP antibody results in the resonance angle shift that is inversely proportional to the concentration of HBP. The lowest detection limit of 0.1 ng ml−1 (ppb) HBP is established with a response time of 15 min. A simple regeneration procedure using a pepsin solution allowed more than 30 measurement cycles without appreciable change in the original immunoresponse (<6%). The antibody showed negligible cross-reactivity to examined polyaromatic hydrocarbons such as benzo[a]pyrene (BaP) and anthracene. The proposed portable immunosystem possesses highly desirable analytical characteristics and is promising for online analysis of even small molecules of clinical and environmental interest.