Rolling cycle amplification based single-color quantum dots–ruthenium complex assembling dyads for homogeneous and highly selective detection of DNA

•The single-color QDs–Ru assembling dyads were applied in homogeneous DNA assay.•This biosensor exhibited high selectivity against base mismatched sequences.•This biosensor could be severed as universal platform for the detection of ssDNA.•This sensor could be used to detect the target in human serum samples.•This DNA sensor had a good selectivity under the interference of other dsDNA.

In this work, a new, label-free, homogeneous, highly sensitive, and selective fluorescent biosensor for DNA detection is developed by using rolling-circle amplification (RCA) based single-color quantum dots–ruthenium complex (QDs–Ru) assembling dyads. This strategy includes three steps: (1) the target DNA initiates RCA reaction and generates linear RCA products; (2) the complementary DNA hybridizes with the RCA products to form long double-strand DNA (dsDNA); (3) [Ru(phen)2(dppx)]2+ (dppx = 7,8-dimethyldipyrido [3,2-a:2′,3′-c] phenanthroline) intercalates into the long dsDNA with strong fluorescence emission. Due to its strong binding propensity with the long dsDNA, [Ru(phen)2(dppx)]2+ is removed from the surface of the QDs, resulting in restoring the fluorescence of the QDs, which has been quenched by [Ru(phen)2(dppx)]2+ through a photoinduced electron transfer process and is overlaid with the fluorescence of dsDNA bonded Ru(II) polypyridyl complex (Ru-dsDNA). Thus, high fluorescence intensity is observed, and is related to the concentration of target. This sensor exhibits not only high sensitivity for hepatitis B virus (HBV) ssDNA with a low detection limit (0.5 pM), but also excellent selectivity in the complex matrix. Moreover, this strategy applies QDs–Ru assembling dyads to the detection of single-strand DNA (ssDNA) without any functionalization and separation techniques.

Graphical abstractA universal, label-free, homogeneous, highly sensitive, and selective fluorescent biosensor for DNA detection is developed by using rolling-circle amplification (RCA) based single-color quantum dots–ruthenium complex (QDs–Ru) assembling dyads.Figure optionsDownload full-size imageDownload as PowerPoint slide