In this study, a novel liquid crystal (LC) biosensor was developed for the highly sensitive and selective detection of Cd2+ based on Cd2+ inducing the bending of PS-oligo. This strategy makes use of the DNA conformational change to enhance the disruption of orientation of LC leading to an amplified optical signal. DNA containing-SH was bound on the glass slide of the LC cell modified with the DMOAP/APTES. The DMOAP can effectively induce the homeotropic alignment of LC. In the presence of Cd2+, Cd2+ can induce DNA to bend and become a 2 nm spherical structure, which can greatly disrupt the orientational arrangement of LC, resulting in the correspond changes of the optical image of LC cell birefringent under the polarizing microscope. When the Cd2+ concentration is low to 0.1 nM, the optical signal of LC biosensor has an obvious change. But in the absence of Cd2+, there is no orientational response of LC and the optical image under the polarizing microscope is still a uniform dark background. Thus, this LC sensing method has a sensitive and clear distinction between positive and negative results and offers a highly sensitive detection of Cd2+ with a low detection limit down to 0.1 nM.
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