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Robust and specific ratiometric biosensing using a copper-free clicked quantum dot–DNA aptamer sensor† †Electronic supplementary information (ESI) available: Details on the synthesis, purification and characterisation of the DHLA–PEG600–N3, cyclooctyne–DNA, and QD–TBA20 conjugates as well as all supporting figures and tables. See DOI: 10.1039/c3nr02897fClick here for additional data file.

The Royal Society of Chemistry
Publication Date
DOI: 10.1039/c3nr02897f
  • Chemistry
  • Biology
  • Chemistry
  • Physics


We report herein the successful preparation of a compact and functional CdSe–ZnS core–shell quantum dot (QD)–DNA conjugate via highly efficient copper-free “click chemistry” (CFCC) between a dihydro-lipoic acid–polyethylene glycol–azide (DHLA–PEG–N3) capped QD and a cyclooctyne modified DNA. This represents an excellent balance between the requirements of high sensitivity, robustness and specificity for the QD-FRET (Förster resonance energy transfer) based sensor as confirmed by a detailed FRET analysis on the QD–DNA conjugate, yielding a relatively short donor–acceptor distance of ∼5.8 nm. We show that this CFCC clicked QD–DNA conjugate is not only able to retain the native fluorescence quantum yield (QY) of the parent DHLA–PEG–N3 capped QD, but also well-suited for robust and specific biosensing; it can directly quantitate, at the pM level, both labelled and unlabelled complementary DNA probes with a good SNP (single-nucleotide polymorphism) discrimination ability in complex media, e.g. 10% human serum via target-binding induced FRET changes between the QD donor and the dye acceptor. Furthermore, this sensor has also been successfully exploited for the detection, at the pM level, of a specific protein target (thrombin) via the encoded anti-thrombin aptamer sequence in the QD–DNA conjugate.

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