19 - DNA Equilibrium in Chromophoric Silver Nanocluster-based Sensors
DNA-templated silver nanoclusters are hybrid systems with favorable sensing properties. Silver clusters form on the 5’ end of a single-stranded DNA template (CCCCAACTCCTT) with variable 3’ recognition sites complementary to target oligonucleotides. The composite strand houses an ~11 atom silver adduct with 400 nm absorption and weak emission. Hybridization to a specific DNA sequence transforms the cluster conjugate, resulting in an absorption shift from 400 to 490 nm and an intensified emission at 550 nm. The cluster composition remains intact and spectra revert upon removal of the complement. This transformation is an equilibrium between dissociated complement and hybridized DNA-cluster species. Hybridized cluster species are less stable than their native DNA counterparts, an effect increased when nucleobases proximal to the 5’ template are exposed. Coordination between unpaired nucleobases and the cluster balances internal folding with exogenous hybridization interactions. These equilibria demonstrate how chromophoric silver clusters sense analytes. A thorough understanding of these interactions is necessary for developing in vivo biosensors that can withstand complex biological environments such as blood and serum.