High-Q photonic aptasensor based on avoided crossing bound states in the continuum and trace detection of ochratoxin A

High quality factor (𝑄) optical biosensors find many applications, from environmental monitoring to food safety and clinical diagnostics. In particular, bound states in the continuum (BICs) can be implemented in planar large-area nanostructures for facile microfluidic integration and straightforward interrogation. In this paper the interference leading to the Friedrich–Wintgen type BIC is engineered to make high-𝑄 flat dispersion bands over a large set of interrogation angles. A thorough numerical study is first carried out to adapt the process to an aptasensor scheme. Then, experiments are carried out tracking the high-𝑄 bands evolution forming around the avoided crossing point as a function of the interaction of ochratoxyn A with the bioprobe. An excellent LOD of 2.3 pg/mL is achieved, and a large FOM > 160 RIU−1 is estimated despite the sub-monolayer adsorbate film of thickness ∼ 10 nm. The proposed sensing architecture can be extended to other mycotoxins and small molecules, finding application in many fields for monitoring physical and biochemical processes.