A Tetrazine-Caged Carbon-Dipyrromethene as a Bioorthogonally Activatable Fluorescent Probe

Unveiling the photophysical mechanistic mysteries of tetrazine-functionalized fluorogenic labels

Tetrazine-based fluorogenic labels are widely utilized in medical and biological studies, exhibiting substantial fluorescence enhancement (FE) following tetrazine degradation through bio-orthogonal reactions. However, the underlying mechanisms driving this fluorogenic response remain only partially resolved, particularly regarding the diminished FE efficiency in the deep-red and near-infrared (NIR) regions. This knowledge gap has impeded efforts to optimize these labels for extended emission wavelengths and improved FE ratios. This review offers a photophysical perspective, discussing the fluorescence quenching pathways (i.e., energy flows and charge separation) that regulate the fluorogenic properties exhibited in various types of tetrazine labels. Moreover, this work examines the emerging role of intramolecular rotations in certain tetrazine-based structures and the integration of additional quencher units. The proposed alternative quenching channel offers the potential to surpass traditional wavelength constraints while achieving improved FE. By examining these photophysical mechanisms, this review aims to advance the understanding of tetrazine-functionalized fluorogenic labels and provide guiding principles for their future design and practical applications.

Multifunctional Fluorescent Material Based Red-emitting Carbon Dots for Cell Imaging and Photodynamic Sterilization

In this paper, a new carbon dot (R1-CDs) was prepared by one-pot hydrothermal method by using 1,8-diaminonaphthalene and o-phthalic acid (o-PA) as precursors. Due to the high purity of R1-CDs, NMR analysis was performed to identify the types of H and C atoms in their graphene sheets. From our research findings, three important information was disclosed such as (1) five types H atoms are presented in R1-CDs; (2) 18 kinds of C atoms in the graphene sheets are observed, and 8 kinds of them are quaternary atoms, and 10 kinds of carbon atoms as tertiary one; (3) functional groups of -COOH and -NH2 from precursors cannot be inherited into the edges or defect sites of graphene sheet. Obviously, our research findings for the first time revealed the more details of chemical structures of CDs. We believe that our works can supply a general concept to fabricate CDs by selecting specific precursors, also can encourage CDs' development in a more "chemistry" way by employing NMR as a powerful method.

Benzo-pyrrolidinyl substituted silicon phthalocyanines: A novel two-photon lysosomal nanoprobe for in vitro photodynamic therapy

Lysosomes are pivotal in diverse physiological phenomena, encompassing autophagy, apoptosis, and cellular senescence. The demand for precise tumors treatment has led to the development of specific lysosome-targeting probes capable of elucidating lysosomal dynamics and facilitating targeted cell death. In this research, we report the synthesis and characterization of a novel benzopyrrolidinyl-substituted silicon phthalocyanine (Py-SiPc), designed for selective lysosome labeling and Fluorescence imaging-guided in vitro photodynamic therapy. Furthermore, we encapsulated Py-SiPc within a biocompatible nanocarrier, dipalmitoylphosphatidylethanolamine-polyethylene glycol 2000 (DSPE), to create water-soluble nanoparticles (DSPE@Py-SiPc). These nanoparticles exhibit exceptional lysosome labeling capabilities, as evidenced by bioimaging techniques. Upon exposure to laser irradiation, DSPE@Py-SiPc efficiently induces the production of reactive oxygen species, impairing lysosomal function and triggering lysosomal-mediated cell death. The DSPE@Py-SiPc system emerges as a promising photosensitizer.

Bioorthogonally activated probes for precise fluorescence imaging

Over the past two decades, bioorthogonal chemistry has undergone a remarkable development, challenging traditional assumptions in biology and medicine. Recent advancements in the design of probes tailored for bioorthogonal applications have met the increasing demand for precise imaging, facilitating the exploration of complex biological systems. These state-of-the-art probes enable highly sensitive, low background, in situ imaging of biological species and events within live organisms, achieving resolutions comparable to the size of the biomolecule under investigation. This review provides a comprehensive examination of various categories of bioorthogonally activated in situ fluorescent labels. It highlights the intricate design and benefits of bioorthogonal chemistry for precise in situ imaging, while also discussing future prospects in this rapidly evolving field.

Strategic Construction of meso-Aryl-Substituted N,N-Carbonyl-Bridged Dipyrrinones as Small, Bright, and Tunable Fluorophores

A series of novel N,N-carbonyl-bridged dipyrrinone fluorophores have been directly constructed from α-halogenated dipyrrinones, which are conveniently obtained from the acid-catalyzed hydrolysis of readily available α,α'-dihalodipyrrins. This novel methodology affords efficient modulation of the functional groups at both the meso- and α-positions of this fluorophore. These resultant dyes show tunable absorption and emission wavelengths, good molar absorption coefficients, relatively large Stokes shifts, and excellent fluorescence quantum yields up to 0.99, and have been successfully applied in both one- and two-photon fluorescence microscopy imaging in living cells.