Activatable QD-Based Near-Infrared Fluorescence Probe for Sensitive Detection and Imaging of DNA

Accurate detection of DNA is essential for the precise diagnosis of diseases. Here we report an activatable near-infrared (NIR) fluorescence nanoprobe (QD-Al-GFLX) composed of NIR quantum dots (QDs) and Al(III)-gatifloxacin (Al-GFLX) complexes for the sensitive detection of double-stranded DNA (dsDNA) both in aqueous solution and in living cells. We demonstrated that the initial strong NIR fluorescence of QDs in QD-Al-GFLX was quenched by the Al-GFLX complex via a photoinduced electron transfer (PET) mechanism. Upon interaction with dsDNA, the high binding affinity between dsDNA and Al-GFLX complex could trigger QD-Al-GFLX dissociation, which could eliminate the PET process, resulting in significant enhancement of NIR fluorescence. QD-Al-GFLX was sensitive and specific to detect dsDNA in aqueous solution, with a detection limit of 6.83 ng/mL. The subsequent fluorescence imaging revealed that QD-Al-GFLX holds a high ability to enter into live cells, generating strong NIR fluorescence capable of reporting on dsDNA levels. This study highlighted the potential of using QD-Al-GFLX nanoprobe for the real-time detection and imaging of dsDNA in living cells.