  Plasmonic metamaterials can be used to enhance mid-infrared sensors and
detectors for immunosensing applications. The major challenge is to integrate
these technologies in low-cost, compact, and promising platforms. In this
study, as an emerging approach, we utilized toroidal resonant plasmonic
metasurfaces to develop an ultrasensitive label-free analytical platform for
the detection of specific antibiotics in the mid-IR regime. Taking advantage of
unique sensitivity of robustly squeezed electromagnetic fields in toroidal
meta-atoms, we validated that our proposed technique based on toroidal
metastructures can provide sensing of biological targets with the weight of
~0.6 KDa at attomolar concentrations. We believe that this understanding
extends the capabilities of plasmonic metamaterials analyze the presence of
specific biological targets with high precision.
