Nucleic acids, as important substances for biological inheritance, have attracted extensive attention in the biomedical field. More and more cyanine dyes are emerging as one of the probe tools for nucleic acid detection due to their excellent photophysical properties. Here, we discovered that the insertion of the AGRO100 sequence can specifically disrupt the twisted intramolecular charge transfer (TICT) mechanism of the trimethine cyanine dye (TCy3), resulting in a clear "turn-on" response. Moreover, the fluorescence enhancement of TCy3 combined with the T-rich AGRO100 derivative is more obvious. One explanation for the interaction between dT (deoxythymidine) and positively charged TCy3 may be that its outer layer carries the most negative charge. This study provides a theoretical basis for the use of TCy3 as a DNA probe, which has promising applications in the DNA detection of biological samples. It also provides the basis for the following construction of probes with specific ability for recognition.

SO 2 , a gas signaling molecule, can be produced endogenously in mitochondria. Its hydrolysate, HSO 3 − , plays a key role in food preservation, cardiovascular relaxation, and other fields, suggesting that it is important to achieve its detection. Here, based on the Michael addition mechanism, four hemicyanine dye fluorescent probes (ETN, ETB, STB, and EIB) were designed and synthesized for responding to HSO 3 − . We evaluated the reaction ability of different probes with HSO 3 − and tried to explain the reasons for the significantly different response effects between probes and HSO 3 − according to the structure−activity relationship. The influence of different substituents of probes on the properties of mitochondria-targeting was also discussed. Finally, we screened out ETN as the optimal HSO 3 − probe due to its high sensitivity, rapid reactivity, and good mitochondria-targeting, and it could sensitively respond to HSO 3 − in living cells. The LODs of ETN for HSO 3 − were calculated by both absorption and fluorescence methods, respectively, which were 2.727 and 0.823 μM. Our work provided valuable references for designing strategies and potential tools for response to SO 2 derivatives in biosystems.

In recent years, the assembly of cyanine dye supramolecular aggregates has been a very important task because its photophysical and photochemical properties are widely used in many scientific fields, such as, materials, biomedical and industrial. In this work, H-and J-aggregates of cyanine dyes were constructed under controllable conditions, and a simple method was developed to achieve cycle induction around these aggregates which induced by rare earth ions, and the process can be repeated for many cycles. Assembly and circulation induce these aggregates to be easy to manipulate and identify, which can be directly observed with the naked eye. This simple supramolecular assembly provides another direction in the field of sensors, while bringing a new idea to the control of supramolecular aggregates.

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