A DNA-Mediated
Homogeneous Binding Assay for Proteins and Small Molecules
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Abstract
Optical
detection of molecular targets typically requires immobilization,
separation, or chemical or enzymatic processing. An important exception
is aptamers that allow optical detection in solution based on conformational
changes. This method, however, requires the laborious selection of
aptamers with high target specificity and affinity, and the ability
to undergo the required conformational changes. Here we report on
an alternative generic scheme for detecting small molecules and proteins
in solution based on a shift in the equilibrium of DNA-based strand
displacement competition reaction. The shift occurs upon binding of
a protein, for example, an antibody to its target. We demonstrate
nanomolar detection of small molecules such as biotin, digoxigenin,
vitamin D, and folate, in buffer and in plasma. The method is flexible,
and we also show nanomolar detection of the respective antibodies
or protein targets of these molecules. The detection scheme provides
a generic alternative to aptamers for detection of analytes