Detection of Ampicillin Residues with a Miniature Integrated Surface Plasmon Resonance Sensor

Surface plasmon resonance (SPR) biosensors offer the ability to monitor binding rapidly, in real time, and without any labels, while the commercial instruments available have been large in size, high-cost, and not amenable to field applications. An SPR sensor system based on Spreeta devices was developed to detect the ampicillin residues in milk for field use. Analysis conditions, including ligand immobilization, flow-rate and regeneration have been defined. Two different mesurement formats were tested, direct detection and indirect competitive inhibition assay. Limits of detection (LOD) for ampicillin in milk were 50 ng mL^-1 and 2.5 ng mL^-1 with the direct detection and the indirect competitive inhibition assay, respectively. Results could be obtained rapidly and the test can be completed in about 20 min using a prepared sensor chip.