Multiple cycle regulation of the supramolecular chirality of a cyanine dye has been successfully achieved by using DNA G-quadruplexes as templates, which is easily controllable by repeated addition of Ag+ and cysteine (Cys). This work provides an easy and controllable strategy for the chiral regulation of supramolecules.

•A new insight for developing Na+ detection technology is provided.•The mechanism relies on G-quadruplex conformation-related DNAzyme activity.•The Na+ sensor can effectively avoid the interference of K+.•Detection of the Na+ level in serum is proved.There has been a big challenge in developing the Na+ sensor that can be practically used in the physiological system with the interference of large amounts of K+. In this research, a novel Na+ sensor has been designed based on the G-quadruplex-conformation related DNAzyme activity. The sensor exhibits high selectivity and sensitivity with the detection limit of 0.6 μM, which enables the sensor to be practically used in determination of the Na+ level in serum. The research not only provides a simple Na+ sensor but also opens a new way for developing the detection technology of Na+.

A colorimetric and fluorometric dual-modal DNA logic gate has been constructed, which is based on the response of a cyanine dye supramolecule to K+–Pb2+-switched G-quadruplexes. Only when the input is K+, the output is 1, which made the system an INHIBIT logic gate. The gate operation constructed here is label-free, and is of simple design and low-cost, showing great promise for practical onsite applications.

The G-quadruplexes located in the P1 promoter of B-cell lymphoma-2 (Bcl-2) gene are implicated to regulate Bcl-2 expression. Here, we designed a new pyridostatin analog named PDF, which exhibited high specificity and stabilizing effect toward G-quadruplexes. The luciferase assay demonstrated that PDF could significantly suppress Bcl-2 transcriptional activation in human laryngeal squamous carcinoma cells (Hep-2) cells. Besides, PDF also induced cell apoptosis in vitro assays. These results provide an excellent G-quadruplex specific ligand as an efficient Bcl-2 inhibitor. These results also implicate that PDF may be a potential anticancer drug to head neck cancer.

•Ag+ shows a high specificity for inducing i-motif formation.•A cyanine dye was designed to recognize i-motif formation.•A novel Ag+ sensor is designed.•The sensor shows excellent performance in specificity, sensitivity, and real time response.•Detection of the Ag+ level in freshwater system is proved.A novel Ag+ sensor has been designed based on the mechanism that i-motif formation induced by Ag+ was sensitively recognized by a cyanine dye. The sensor exhibited an over 130–16,000 fold selectivity toward Ag+ than that toward other metal ions. This research not only provides a step forward toward the development of Ag+ detection but also represents a new application for i-motif DNA.The scheme for sensing Ag+ based on DMSB recognizing motif formation and the molecular structure of DMSB.

A supramolecular probe for visual detection of mercury (Hg) has been designed by using a cyanine dye and AS1411 G-quadruplexes, which exhibits an obvious color change from red to blue in response to an increased level of Hg2+. The supramolecular probe exhibits high selectivity and sensitivity towards Hg2+ and is promising for the detection of environmental samples with the naked eye.

A colorimetric probe of Pb2+ has been designed based on the mechanism that a supramolecular probe selectively recognized the Pb2+-induced conformational transition of G-quadruplexes. The probe exhibited high sensitivity and selectivity towards Pb2+, which enabled it to be practically used in detection of the Pb2+ level in a freshwater system.

•A probe is designed for colorimetric detection of Pb2+.•A clip-like cyanine dye is synthesized.•The dye can recognize Pb2+-induced G-quadruplex transition.•The probe shows a high specificity and sensitivity.•Detection of the Pb2+ in freshwater system is applied.A probe for colorimetric detecting lead ion (Pb2+) has been designed by using a newly synthesized clip-like cyanine dye and G-quadruplex. The unique structure of the clip-like cyanine dye endowed the probe with a high selectivity towards Pb2+. Significant changes in absorption spectra of the cyanine dye recognizing the Pb2+-induced conformational transition of G-quadruplexes made the probe show a high sensitivity towards Pb2+ with a detection limit of 1 nM. The excellent performance enabled the probe to be practically applied in measuring the Pb2+ pollution in freshwater system.

A simple technology to construct diverse DNA logic gates (OR and INHIBIT) has been designed utilizing a H+ and/or Ag+ induced i-motif structure. The logic gates are easily controlled and also show a real time response towards inputs. The research provides a new insight for designing DNA logic gates using an i-motif DNA structure.

A colorimetric and fluorometric dual-modal supramolecular chemosensor has been fabricated by using the H- and J-aggregates of a cyanine dye, which has been successfully applied to detect human serum albumin (HSA) in urine with high specificity.

A simple technology to construct diverse DNA logic gates (OR and INHIBIT) has been designed utilizing a H+ and/or Ag+ induced i-motif structure. The logic gates are easily controlled and also show a real time response towards inputs. The research provides a new insight for designing DNA logic gates using an i-motif DNA structure.

Multiple cycle regulation of the supramolecular chirality of a cyanine dye has been successfully achieved by using DNA G-quadruplexes as templates, which is easily controllable by repeated addition of Ag+ and cysteine (Cys). This work provides an easy and controllable strategy for the chiral regulation of supramolecules.