Click chemistry reaction-triggered DNA walker amplification coupled with hyperbranched DNA nanostructure for versatile fluorescence detection and drug delivery to cancer cells

A new DNA hyperbranched hybridization chain reaction (HB-HCR)-amplified fluorescence platform combined with DNA walker was developed for versatile detection of Cu2+, adenosine triphosphate (ATP), and drug delivery to cancer cells. A novel click chemistry reaction-triggered DNA walking machine on magnetic beads (MBs) is introduced for the first time to convert target Cu2+ to lots of DNA S3 products. With the help of DNA S3 and H1 on the amino functionalized SiO2 microsphere, HB-HCR between super hairpin DNA (SH DNA), H3-DNA, and LT-DNA was initiated to assemble a novel dendritic DNA structure with numerous fluorescent Cy5, achieving enormously amplified signal for ultrasensitive detection of Cu2+. Furthermore, this contains large amounts of double-stranded DNA with plentiful GC bases, which can provide many loading sites for chemotherapeutic drug doxorubicin (Dox). The specific binding of ATP to aptamer in the dendritic DNA structure allows for release of Dox, leading to activation of Dox fluorescence for ATP assay. More importantly, this dendritic DNA nanostructure-loaded Dox enters into tumor cells by endocytosis, and then interacts with endogenous ATP, releasing Dox for efficient treatment of cancer cells. Taking advantages of these multiple amplification of HB-HCR on SiO2 microsphere, click chemistry reaction, DNA walking, and release of Dox, this method enables ultrasensitive detection of Cu2+ and ATP as low as 0.1 fM and 1.0 aM, respectively, which can be widely used for accurate detection of biomolecules in clinical diagnosis and biomedical applications. This dendritic DNA nanostructure provided an effective tool for designing smart nanodevices. Graphical abstract.