A liquid crystals-based sensing platform for detection of α-amylase coupled with destruction of host-guest...

A liquid crystals (LCs)-based sensing platform was constructed for simple, convenient, inexpensive and label-free detection of α-amylase, associated with disruption of host-guest interaction between sodium dodecyl sulphate (SDS) and β-cyclodextrin (β-CD). In the presence of SDS/β-CD solution, a bright optical image was observed corresponding to the tilted anchoring of LCs at the aqueous/LCs interface. While a black optical appearance was captured when the pre-incubated mixture containing SDS/β-CD complex and ≥0.0001 mg/mL α-amylase was transferred onto the fluid interface. The reason for this difference is that α-amylase could hydrolyze β-CD and subsequently destroy the host-guest interaction between SDS and β-CD. SDS molecules escaping from the cavity of β-CDs were adsorbed at the aqueous/LCs interface, which evoked the homeotropic state of LCs. In the case of α-amylase below 0.0001 mg/mL, a bright optical image was observed. Based on these, detection of α-amylase could be achieved and its detection limit was ∼0.0001 mg/mL (15 U/L). Moreover, this sensing platform was successfully utilized to monitor α-amylase in the body fluids, such as urine and saliva, indicating its potentiality in the relevant clinical diagnosis.