title: Antibody-free detection of human chorionic gonadotropin by use of liquid crystals.
abstract: Human chorionic gonadotropin (hCG) is an important biomarker for the diagnosis of pregnancy and cancers. In this study, we report an antibody-free and label-free mechanism for detecting hCG. To replace enzyme-labeled antibodies, we use a short oligopeptide as an hCG receptor to bind hCG. The short oligopeptide sequence, (N-)PPLRINRHILTR(-C), is identified after 5 rounds of screening by use of a phage library. After binding, liquid crystal (LC) is used to transduce the binding event into optical signals. The captured hCG can disrupt a thin layer (~6 μm) of LC covered on the surface. Depending on the initial concentration of hCG, LC gives distinct optical signals visible to the naked eye. The limit of detection (LOD) for this method is approximately 1 IU/mL (2 nM) in both phosphate-buffered saline and urine samples, and only 0.6 μL of hCG solution is required. This means that as little as 45.5 pg of hCG can be detected by this method. Compared to other detection methods for hCG, this detection method does not require the use of antibody and is label-free. It has the potential to become a portable diagnostic kit for hCG.
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore , 4 Engineering Drive 4, Singapore 117585.
authors.forename: Xiaokang
authors.initials: X
authors.lastname: Ding
authors.forename: Kun-Lin
authors.initials: KL
authors.lastname: Yang
mesh_terms: D001665:Binding Sites; D006063:Chorionic Gonadotropin / Q000032:analysis*; D005260:Female; D005456:Fluorescent Dyes; D006801:Humans; D057230:Limit of Detection; D050866:Liquid Crystals; D010446:Peptide Fragments / Q000032:analysis* / Q000378:metabolism; D019151:Peptide Library; D011247:Pregnancy; D020349:Surface Plasmon Resonance / Q000379:methods*
chemical_list: D006063:Chorionic Gonadotropin; D005456:Fluorescent Dyes; D010446:Peptide Fragments; D019151:Peptide Library