Terahertz chiral enantiomers recognition via chiral selective bio-molecular film on anapole metasurface sensor in water environment

•The anapole resonance is experimentally used to detect bio-sample.•High sensitivity detection for liquid samples in THz range is realized.•Realized the distinction of chiral enantiomers for amino acids. Terahertz (THz) label-free and real-time metasurface-based biosensors have attracted significant attention in the biological field, but it is still challenging to achieve the efficient distinction of isomers, especially for absorptive liquid samples. Here, we demonstrated a chiral selective bio-molecular film constructed on an anapole metasurface sensor and realized the chiral recognition of the amino acid enantiomers. The proposed sensor can provide an ultrahigh localized field with a strong THz reflected signal even in a water environment. We utilized it to detect different concentrations of l-Met and l-Phe, the highest detection sensitivity is 0.516 GHz∙ml/μmol, and the detection limit can reach nanomole-level. More importantly, the sensor surface is modified by bovine serum albumin (BSA) through amine coupling, whichhas different binding abilities to D- and l-amino acids. The binding process has been monitored in real time, and the binding rate of l-amino acids to the metasurface is always higher than that of d-amino acids. The maximum sensitivity for l-amino acids is 2.23 times the d-type enantiomer. Our results illustrate a new avenue for chiral recognition of chiral samples, and it is expected that the biomolecule-metasurface hybrid structure is promising for developing THz sensors for biomolecular detection.