Energy transfer followed by electron transfer (ETET) endows a TPE-NBD dyad with enhanced environmental sensitivity

J-Aggregates Formed by NaCl Treatment of Aza-Coating Heptamethine Cyanines and Their Application to Monitoring Salt Stress of Plants and Promoting Photothermal Therapy of Tumors

The cationic nature of heptamethine cyanines gives them the capacity to form aggregates with salts by electrostatic interactions. In this work, NaCl promoted J-aggregate formation of aza-coating heptamethine cyanines is explored. NaCl can induce the N-benzyloxycarbonyl Cy-CO₂ Bz to assemble into a J-aggregate having an absorption at 890 nm. Its excellent fluorescence response to NaCl implies that it has great potential for use as a probe for tracing salt stress in plants. Moreover, NaCl also promotes formation of J-aggregates from the N-ethyloxycarbonyl Cy-CO₂ Et. The aggregate shows an intense absorption at 910 nm compared to the monomer which absorbs at 766 nm. Its J-aggregated form can serve as a photothermal agent. And the photothermal conversion efficiency is increased from 29.37 % to 57.59 %. This effort leads to the development of two applications of new cyanine J-aggregates including one for tracing salt stress of plants and the other for promoting photothermal therapy of tumors.

Molecular Design and Photothermal Application of Thienoisoindigo Dyes with Aggregation-Induced Emission

Organic fluorescent dyes with aggregation-induced emission (AIE) property have an extensive application range, especially in the fields of imaging, labeling, and adjusting microprocesses in aggregated environments. In particular, the thienoisoindigo skeleton, which exhibits an outstanding electron-withdrawing capacity in optoelectronic materials, has been defined as a promising AIE candidate. For instance, by installing AIE blocks or other rotatable groups at two terminal sites, such as various arylamine groups, thienoisoindigo derivatives can be efficiently turned to be functional AIE structures. In this work, a thienoisoindigo derivative with AIE characteristics, namely, TII-TPE, was developed. This AIE system was expanded by linking typical AIE fragments, namely, tetraphenylethene, with the proposed thienoisoindigo derivative, which exhibited typical AIE fluorescence in the 600-850 nm range and maintained high photostability. Then, employing the reported derivative TII-TPA coating thienoisoindigo and triphenylamine as a contrast, aggregated TII-TPE and TII-TPA nanoparticles were prepared and demonstrated photothermal conversion efficiencies of 36.2 and 35.6%, respectively. Moreover, both nanoparticles were evaluated as photothermal therapeutic (PTT) agents in a tumor mouse model, which showed to significantly inhibit tumor growth after four treatment cycles in vivo. This work not only presents an enriched thienoisoindigo system but also provides a pattern for subsequent construction of functional AIE molecules.

Overcoming Spectral Dependence: A General Strategy for Developing Far-Red and Near-Infrared Ultra-Fluorogenic Tetrazine Bioorthogonal Probes

Bioorthogonal fluorogenic dyes are indispensable tools in wash-free bioimaging of specific biological targets. However, the fluorogenicity of existing tetrazine-based bioorthogonal probes deteriorates as the emission wavelength shifts towards the NIR window, greatly limiting their applications in live cells and tissues. Herein, we report a generalizable molecular design strategy to construct ultra-fluorogenic dyes via a simple substitution at the meso-positions of various far-red and NIR fluorophores. Our probes demonstrate significant fluorescence turn-on ratios (10² -10³ -fold) in the range 586-806 nm. These results will greatly expand the applications of bioorthogonal chemistry in NIR bioimaging and biosensing.

Recent progress in fluorescent probes for bacteria

Food fermentation, antibiotics, and pollutant degradation are closely related to bacteria. Bacteria play an irreplaceable role in life. However, some bacteria seriously threaten human health and cause large-scale infectious diseases. Therefore, there is a pressing need to develop strategies to accurately monitor bacteria. Technology based on molecular probes and fluorescence imaging is noninvasive, results in little damage, and has high specificity and sensitivity, so it has been widely applied in the detection of bacteria. In this review, we summarize the recent progress in bacterial detection using fluorescence. In particular, we generalize the mechanisms commonly used to design organic fluorescent probes for detecting and imaging bacteria. Moreover, a perspective regarding fluorescent probes for bacterial detection is discussed.