Spore and micro-particle capture on an immunosensor surface in an ultrasound standing wave system.
The capture of Bacillus subtilis var. niger spores on an antibody-coated surface can be enhanced when that coated surface acts as an acoustic reflector in a quarter wavelength ultrasonic (3 MHz) standing wave resonator. Immunocapture in such a resonator has been characterised here for both spores and 1 microm diameter biotinylated fluorescent microparticles. A mean spatial acoustic pressure amplitude of 460 kPa and a frequency of 2.82 MHz gave high capture efficiencies. It was shown that capture was critically dependent on reflector thickness. The time dependence of particle deposition on a reflector in a batch system was broadly consistent with a calculated time of 35 s to bring 95% of particles to the coated surface. A suspension flow rate of 0.1 ml/min and a reflector thickness of 1.01 mm gave optimal capture in a 2 min assay. The enhancement of particle detection compared with the control (no ultrasound) situation was x 70. The system detects a total of five particles in 15 fields of view in a 2 min assay when the suspending phase concentration was 10(4) particles/ml. A general expression for the dependence of minimum concentration detectable on; number of fields examined, sample volume flowing through the chamber and assay time shows that, for a practical combination of these variables, the threshold detection concentration can be two orders of magnitude lower.
Martin
Stacey P
SP
School of Biosciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3TL, UK.
Townsend
Rosemary J
RJ
Kuznetsova
Larisa A
LA
Borthwick
Kathryn A J
KA
Hill
Martyn
M
McDonnell
Martin B
MB
Coakley
W Terence
WT
D001412:Bacillus subtilis / Q000166:cytology / Q000302:isolation & purification*; D002469:Cell Separation / Q000295:instrumentation* / Q000379:methods; D015169:Colony Count, Microbial / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007118:Immunoassay / Q000295:instrumentation* / Q000379:methods; D008856:Microscopy, Fluorescence / Q000295:instrumentation* / Q000379:methods; D008863:Microspheres; D013171:Spores, Bacterial / Q000276:immunology / Q000302:isolation & purification*; D013499:Surface Properties; D014465:Ultrasonics