title: Surface modification of alignment layer by ultraviolet irradiation to dramatically improve the detection limit of liquid-crystal-based immunoassay for the cancer biomarker CA125.
abstract: Liquid crystal (LC)-based biosensing has attracted much attention in recent years. We focus on improving the detection limit of LC-based immunoassay techniques by surface modification of the surfactant alignment layer consisting of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP). The cancer biomarker CA125 was detected with an array of anti-CA125 antibodies immobilized on the ultraviolet (UV)-modified DMOAP monolayer. Compared with a pristine counterpart, UV irradiation enhanced the binding affinity of the CA125 antibody and reproducibility of immunodetection in which a detection limit of 0.01 ng∕ml for the cancer biomarker CA125 was achieved. Additionally, the optical texture observed under a crossed polarized microscope was correlated with the analyte concentration. In a proof-of-concept experiment using CA125-spiked human serum as the analyte, specific binding between the CA125 antigen and the anti-CA125 antibody resulted in a distinct and concentration-dependent optical response despite the high background caused by nonspecific binding of other biomolecules in the human serum. Results from this study indicate that UVmodification of the alignment layer, as well as detection with LCs of large birefringence, contributes to the enhanced performance of the label-free LC-based immunodetection, which may be considered a promising alternative to conventional label-based methods.
authors.affiliation: National Chiao Tung University, Institute of Imaging and Biomedical Photonics, College of Photonics, Guiren District, Tainan 71150, Taiwan.
authors.forename: Hui-Wen
authors.initials: HW
authors.lastname: Su
authors.affiliation: Chang Jung Christian University, Department of Bioscience Technology, Guiren District, Tainan 71101, Taiwan.
authors.forename: Mon-Juan
authors.initials: MJ
authors.lastname: Lee
authors.affiliation: National Chiao Tung University, Institute of Imaging and Biomedical Photonics, College of Photonics, Guiren District, Tainan 71150, Taiwan.
authors.forename: Wei
authors.initials: W
authors.lastname: Lee
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood* / Q000276:immunology; D018394:CA-125 Antigen / Q000097:blood* / Q000276:immunology; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation*; D050866:Liquid Crystals / Q000737:chemistry* / Q000528:radiation effects; D008565:Membrane Proteins / Q000097:blood* / Q000276:immunology; D012031:Refractometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013499:Surface Properties; D014466:Ultraviolet Rays
chemical_list: D014408:Biomarkers, Tumor; D018394:CA-125 Antigen; C451759:MUC16 protein, human; D008565:Membrane Proteins