LSPR/TIRE bio-sensing platform for detection of low molecular weight toxins

This work is a part of ongoing NATO SPS research project dedicated to optical detection of bio-toxins, particularly mycotoxins. One of the detection technologies chosen is a combination of localized surface plasmon resonance (LSPR) transducer with direct immunoassay with specific bio-receptors immobilized on the surface. The LSPR platform is based on gold nano-islands produced by thermal annealing of thin gold films deposited on glass. The gold nano-structures produced were analysed with SEM, AFM, optical absorption spectroscopy, and spectroscopic ellipsometry. The method of total internal reflection ellipsometry (TIRE) was chosen for LSPR bio-sensing because of its superior sensitivity as compared to conventional UV-vis absorption spectroscopy. The sensitivity of LSPR measurements is however limited by a finite evanescent decay length in gold nano-islands which is typically in the range of tens of nanometres. In order to achieve the best results, the bioreceptors must be small and placed as close to the gold surface as possible. In our case the problem was solved using either halved antibodies or aptamers immobilized covalently on the surface of gold. A series of bio-sensing experiments on detection of mycotoxins, i. e. aflatoxin B1, zearalenone, and ochratoxin A, went successfully and resulted in detection of the above mycotoxins in concentrations down to 10 ppt.