Antibody-free Detection of Human Chorionic Gonadotropin
by Use of Liquid Crystals
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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