Highly sensitive and label-free detection of catalase by a H2O2-responsive liquid crystal sensing platform

Abnormal levels of catalase are implicated in multiple clinical diseases, so it is of great importance to monitor the levels of catalase in real samples. In this report, a H2O2-responsive liquid crystal (LC) sensing platform was developed and applied to the detection of catalase in human serum for the first time. The platform was constructed by doping LCs with a synthesized surfactant, namely N,N-dimethyl-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)tetradecan-1-aminium bromide (PBEC14A), which can be decomposed by H2O2. Self-assembled monolayers formed at the aqueous/LC interface when immersing the surfactant-doped LCs into an aqueous solution. Accordingly, the LCs displayed a dark image that indicates a perpendicular state of the LCs at the interface. However, when H2O2 was present in the aqueous solution, the optical image of the LCs became bright that represents a planar state of the LCs at the interface. It is caused by disruption of the surfactant monolayers due to decomposition of PBEC14A by H2O2. Interestingly, it was found that the LCs still displayed the dark image when the pre-incubated mixture of catalase and H2O2 was transferred onto the LC sensing platform due to enzymatic hydrolysis of H2O2 by catalase. The detection limit of catalase reached as low as 5.5 mU/mL. In addition, it also shows excellent performance for the detection of catalase in human serum. As a simple and convenient method, it shows high promise in the highly sensitive and label-free detection of catalase in practical applications.