A dual-modal red-emitting fluorescence probe for proteins based on modulation of AIE or TICT state

Utilization of Nonradiative Excited-State Dissipation for Promoted Phototheranostics Based on an AIE-Active Type I ROS Generator

As for effective multimodal phototheranostic AIEgens, it is important to find strategies for manipulating photophysical dissipation to achieve optimized performance. Herein, a "all-in-one" phototheranostic AIEgen, (E)-3-(2-(2-(5-(4-(diphenylamino)phenyl)thiophen-2-yl)vinyl)naphtho[1,2-d]thiazol-1-ium-1-yl)propane-1-sulfonate (NS-STPA) was constructed by a rigid coplanar grafting flexible rotor. NS-STPA nanoparticles (NPs) exhibited NIR fluorescent luminescence (FL) with φ_FL 2.78%. Upon 660 nm irradiation, the high photothermal conversion efficiency (39.01%) and effective reactive oxygen species (ROS) generation (5.28 times to Ce6) indicated the nonradiative decays are valuable in phototherapy. High ^•OH outputs showed NS-STPA NPs were outstanding type I ROS generators. The twisted D-A structure induced a large spin-orbit coupling (SOC), and insertion of thiophene decreased the S₁-T₁ energy gap (ΔE_ST). The nanoaggregate prolonged the triplet-state lifetime (τ_T). These all facilitate the intersystem crossing (ISC) for NS-STPA NPs. The photoinduced electron transfer resulted in ^•O₂^- and then ^•OH generation. In vivo evaluation indicated the promising application of NS-STPA NPs in FL and photothermal dual imaging-guided synergistic photodynamic and photothermal therapies.

Fluorescent chameleon labels for bioconjugation and imaging of proteins, nucleic acids, biogenic amines and surface amino groups. a review

Chameleon labels (ChLs) possess the unique property of changing (visible) color and fluorescence on binding to amino groups of biomolecules. MostChLs react with primary aliphatic amino groups such as those in lysine or with amino groups artificially introduced into polynucleic acids or saccharides, but someothers also react with secondary amino groups. Under controlled circumstances, the reactions are fairly specific. The review is subdivided into the following sections: (1) An introduction and classification of fluorescent labels; (2) pyrylium labels that undergo shortwave color changes upon labelling, typically from blue to red; (3) polymethine type of labels (that also undergo shortwave color changes, typically from green to blue; (4) various other (less common) chromogenic and fluorogenic systems; (5) hemicyanine labels that undergolongwavecolor changes, typically from yellow to purple; (6) the application of ChLs to labeling of proteins and oligonucleotides; (7) applications to fluorometric assays and sensing; (8) applications to fluorescence imaging of biomolecules; (9) applications in studies on affinity interactions (receptor-ligand binding); (10) applications in surface and interface chemistry; and (11) applications in chromatography, electrophoresis and isotachophoresis of biomolecules.

Specific and Quantitative Detection of Albumin in Biological Fluids by Tetrazolate-Functionalized Water-Soluble AIEgens

The analysis of albumin has clinical significance in diagnostic tests and obvious value to research studies on the albumin-mediated drug delivery and therapeutics. The present immunoassay, instrumental techniques, and colorimetric methods for albumin detection are either expensive, troublesome, or insensitive. Herein, a class of water-soluble tetrazolate-functionalized derivatives with aggregation-induced emission (AIE) characteristics is introduced as novel fluorescent probes for albumin detection. They can be selectively lighted up by site-specific binding with albumin. The resulting albumin fluorescent assay exhibits a low detection limit (0.21 nM), high robustness in aqueous buffer (pH = 6-9), and a broad tunable linear dynamic range (0.02-3000 mg/L) for quantification. The tetrazolate functionality endows the probes with a superior water solubility (>0.01 M) and a high binding affinity to albumin (K_D = 0.25 μM). To explore the detection mechanism, three unique polar binding sites on albumin are computationally identified, where the multivalent tetrazolate-lysine interactions contribute to the tight binding and restriction of the molecular motion of the AIE probes. The key role of lysine residues is verified by the detection of poly-l-lysine. Moreover, we applied the fluorogenic method to quantify urinary albumin in clinical samples and found it a feasible and practical strategy for albumin analysis in complex biological fluids.

TDDFT study on aluminum and fluoride dual-sensing mechanism of a Schiff-Base sensor

The aluminum and fluoride dual-sensing mechanism of a previously reported sensor with a Schiff-base moiety (Spectrochim. Acta A, 2017, 183, 267-274) has been investigated by density functional theory (DFT) and time-dependent DFT (TDDFT) methods. The present calculations reproduce the photoproperties of the sensor as well as its aluminum and fluoride complexes, which illustrates that DFT and TDDFT constitute a reliable tool for uncovering detailed fluorescence-based sensing mechanisms in diverse electronic states. Theoretical results indicate that there are two OH⋯N hydrogen bonds in the sensor and two OH⋯F hydrogen bonds in its F¯ complex. Different degrees of coplanarity caused by these hydrogen bonds are responsible for their distinct absorption wavelengths. However, excited-state geometry optimization and a scan of the potential-energy surface show that there is twisted intramolecular charge transfer about the CN bond in the sensor molecule and an excited-state proton-transfer process from the fluoride anion to the neighboring N atom in the fluoride-sensor complex, whereby the fluorescence is quenched. A chelation-enhanced fluorescence effect associated with the aluminum-sensor complex shows a different excited-state process. The local excitation and emission occur exclusively within the planar fluorophore, and negligible structural change upon excitation of the aluminum-sensor complex leads to its strong fluorescence. Therefore, it is theoretically explained why the sensor may be successfully used to analyze the fluoride anion by absorption spectroscopy and the aluminum cation by emission spectroscopy.

A viscochromic, mechanochromic, and unsymmetrical azine for selective detection of Al3+ and Cu2+ ions and its mitotracking studies

A mechanoresponsive, viscochromic, and unsymmetrical azine NDEA probes Al³⁺ and Cu²⁺ ions and also co-localizes in the mitochondria of C6 glioma cell lines.