Airborne analyte detection with an aircraft-adapted surface plasmon resonance sensor system

A portable surface plasmon resonance (SPR) biosensor system was designed for deployment in a surrogate unmanned aerial vehicle (UAV). The nose of the aircraft was fitted with two nozzles for release of analytes during flight. Ovalbumin and horseradish peroxidase were chosen as simulants for airborne toxic proteins. The two protein analytes were released sequentially from the nozzles as aerosols with low concentrations of analytes during the ground test and each of three flights. A two-stage collector accumulated the sample prior to de-aeration and monitoring by the SPR system. An automated liquid handling unit directed buffer, sample, amplification and regeneration solutions to the sensor and metered the flow rate. Following detection of analyte, secondary antibodies were pumped through the sensor to both amplify and verify analyte detection, thus avoiding false positive detection and at the same time achieving higher sensitivity with the system. Analyte concentrations varied from 1 to 10 nM and the altitude at which the detection was performed varied from 1800 to 10,000 feet. All analyte releases during the three flights were successfully detected and verified. Flight parameters, such as airspeed, altitude, position and meteorological conditions, data necessary for UAV applications, were automatically recorded. The aircraft flight path obtained by GPS was temporally aligned with the SPR detection signal, allowing mapping of the geographical distribution of analyte release. The results reported here illustrate the usefulness of the portable aircraft-mounted SPR system for detection of airborne analytes.