DNA-based nanostructure is emerging as a promising tool for cell identification and regulation. Here we engineer an allosteric DNA triangular prism that responds to target cells with a folding behavior. It not only outputs signal via structural change that can avoid DNA nanostructure degradation-caused false positives, but also shows a fast migration inside cells via its folded structure that obtains a rapid regulation. The DNA prism simultaneously recognizes membrane receptors of human epidermal growth factor receptor 2 (HER2) and mucin 1 oncoprotein (MUC1), through the blocked aptamer unlocking and inner-structure strand displacement. Then the ipsilateral sides in the two triangle faces become single-stranded and form hairpin, forcing the DNA prism to be folded. The donor and acceptor fluorophores get close to each other and fluorescence resonance energy transfer is greatly enhanced. The folded DNA prism is further taken up by cells via HER2-mediated endocytosis, showing a faster arrival in lysosomes and leading to more rapid degradation of HER2 when compared with the unfolded prism structure. The folded DNA prism results in the reduction of cell motility and induction of cell apoptosis. Such an allosteric DNA nanostructure may offer new strategies for cancer cell diagnosis and treatment.

The detection of telomerase activity inside cells is valuable for early cancer diagnosis and telomerase function study. However, besides cancerous cells, telomerase is also found to be expressed in few non-cancerous cells, which influences the assay reliability. By virtue of the extracellular pH, we design a DNA tetrahedron docking assembly (DTDA) for only responding telomerase activity in cancerous cells. The DTDA maintains structural integrity with extracellular acid pH of cancerous cells, but releases a telomerase substrate-containing strand after its cell internalization due to intracellular alkaline pH. The strand gets elongated by intracellular telomerase, docks to the vertex of tetrahedron, and returns to the DTDA after its separation, accompanied by fluorescence enhancement. For non-cancerous cells, the telomerase substrate-containing strand is already dissociated with extracellular alkaline pH and cannot enter into cells to achieve subsequent docking event. DTDA well distinguishes cancerous cells from non-cancerous cells in which telomerase are both expressed. The strategy can provide a more reliable way for telomerase-based cancer diagnosis and telomerase oncogenic study.

Telomerase is a ribonucleoprotein that can catalyze the addition of telomerase repeats onto the end of telomere, compensating for the telomere shortening during cell division and maintaining the continuous cell proliferation. Telomerase activity is overexpressed in cancerous cells but inhibited in normal somatic cells, and thus it is regarded as an important biomarker for cancer diagnosis and prognosis evaluation. In this work, a test strip is constructed for visual detection of telomerase activity and determination of cancerous cells. The test strip is constituted of sample pad, conjugate pad that is sprayed with DNA-functionalized gold nanoparticles, nitrocellulose membrane that contains test zone and control zone, and absorbent pad, which are all assembled onto the backing plate. Under the action of telomerase, the substrate sequence gets extended, which are then dropped onto the sample pad. The solution migrates by capillary action and rehydrates the DNA-functionalized AuNPs on the conjugate pad. Subsequently, the telomeric products hybridize with the capture DNA in the test zone and the modified DNA on AuNPs in a sandwich manner, causing the accumulation of AuNPs on the test zone and the color development of T-line. Meanwhile, the DNA-functionalized AuNPs continue flowing and then hybridize with the capture DNA on the control zone, causing the color development of C-line and confirming the validity of the test strip. Through responding to the telomerase from cell extracts, the method can achieve the visual differentiation of cancerous cells from normal cells in a convenient and rapid way by observation of color development of T-line.

Herein, we report the in situ analysis of human telomerase by a multicolor DNA tetrahedron nanoprobe. The elongated telomeric repeats can hybridize with settled molecular beacons in order, accompanied by sequentially lighted up fluorescence. Imaging telomerase activity, real-time monitoring telomerase action and determining product length distribution in living cells are realized. It detects multiple information of intracellular telomerase and provides deeper insights into the function of telomerase.