l-Histidine-DNA interaction: a strategy for the improvement of the fluorescence signal of poly(adenine) DNA-templated gold nanoclusters

An interesting phenomenon is described that the fluorescence signal of poly(adenine) (A) DNA-templated gold nanoclusters (AuNCs) is greatly improved in the presence of l -histidine by means of l -histidine-DNA interaction. The modified nanoclusters display strong fluorescence emission with excitation/emission maxima at 290/475 nm. The fluorescence quantum yield (QY) is improved from 1.9 to 6.5%. Fluorescence enhancement is mainly ascribed to the l -histidine-DNA interaction leading to conformational changes of the poly(A) DNA template, which offer a better microenvironment to protect AuNCs. The assay enables l -histidine to be determined with good sensitivity and a linear response that covers the 1 to 50 nM  l -histidine concentration range with a 0.3 nM limit of detection. The proposed method has been applied to the determination of imidazole-containing drugs in pharmaceutical samples. Graphical abstract A turn-on fluorescent method has been designed for the sensitive detection of l -histidine as well as imidazole-containing drugs on the basis of the l -histidine-DNA interaction.