Abstract
A novel device for cholesteric liquid crystal (CLC)-based microfluidic chips, accommodated in a polydimethylsiloxane material, was invented. In this device, the reorientation of the CLCs was consistently influenced by the surface of the four channel walls and adjacent CLCs. When the inside of the microchannel was coated with the alignment layer, the CLCs oriented homeotropically in a focal conic state under cross-polarizers. Once antigens had bound onto antibodies immobilized onto the orientation sheet-coated channel walls, the light intensity of the CLC molecules converted from a focal conic state to a bright planar state caused by disrupting the CLCs. By means of utilizing pressure-propelling flow, the attachment of antigen/antibody to the CLCs should be detectable within consecutive sequences. The multi-microfluidic CLC-based chips were verified by measuring bovine serum albumin (BSA) and immune complexes of pairs of BSA antigen/antibody. We showed that the multiple microfluidic immunoassaying can be used for measuring BSA and pairs of antigen/antibody BSA with a detection limit of about 1 ng/mL. The linear range is 0.1 μg/mL–1 mg/mL. A limit of immune detection of pairs of BSA antigens/antibodies was 10 ng/mL of BSA plus 1000 ng/mL of the anti-BSA antibodies was observed. According to this innovative creation of immunoassaying, an unsophisticated multi-detection device with CLC-based labeling-free microfluidic chips is presented.
Highlights
Due to fast detection, small sample volume and cheap price, microfluidic chips have been wildly applied [1,2]
Once the vertical anchoring force was diminished by bovine serum albumin (BSA), the focal conic (FC) state near the microfluidic channel changed to a planar (P) state
The cholesteric liquid crystal (CLC) microfluidic biosensor was blue when there was no of BSA, and it shifted to green with an increasing BSA concentration
Summary
Small sample volume and cheap price, microfluidic chips have been wildly applied [1,2]. The signal of microfluidic immunoassay is weak because of the microscale sample. In order to make the antigen and antibody binding become a detectable signal, the antigen or antibody is usually labeled by an fluorophores [3,4] enzyme [5,6], or nanoparticles [7,8]. When an antigen or antibody is conjugated with a label, the binding affinity might be affected when transducing the immune-binding response to measurable signs. Pairs of antibody/antigen are influenced by being conjugated with a label [9,10]. The most important is the detection of standard bovine serum albumin (BSA) for the observation and establishing of characteristics. The current research of BSA immunoassay detection involves labeling by fluorophores [3,4] for biochemical analysis
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