Bioimaging

C-TPA is a fluorescent probe used for hypochlorite detection and bioimaging of lipid droplet polarity in cancer cells. For hypochlorite detection, when its derivative C-TPA-S is exposed to hypochlorite, an oxidative desulfurization reaction converts the thiocarbonyl group of C-TPA-S to the carbonyl group of C-TPA, thus restoring bright fluorescence from the almost non-fluorescent C-TPA-S. For bioimaging of lipid droplet polarity, the intramolecular charge transfer process between its Triphenylamine (HY-W011998) donor group and Coumarin (HY-N0709) acceptor group endows C-TPA with solvatochromism-it exhibits stronger fluorescence in less polar environments (such as lipid droplets in cancer cells) and weaker fluorescence in more polar environments (such as lipid droplets in normal cells), enabling the differentiation of cancer cells and cancer tissues from normal cells and normal tissues. The excitation wavelength of C-TPA is 405 nm, and the emission wavelengths used for cell and tissue imaging cover 425-475 nm and 500-550 nm; in solvents, its emission peak shifts from 494 nm in non-polar toluene to 528 nm in polar water .

TPEP-6-NH-MA is a Fluorescent probe that selectively detects cysteine (Cys) and homocysteine (Hcy) without interference from glutathione (GSH) and other amino acids, and can also be used for bioimaging of biothiols in living cells. Its detection mechanism relies on terminating the photoinduced electron transfer (PET) effect via a Michael addition reaction between the maleimide recognition moiety and the thiol group of Cys or Hcy. The excitation wavelength of TPEP-6-NH-MA is Ex = 361 nm .

Nile Red phenoxyacetic acid (Compound 4) is a pharmaceutical intermediate that can be used for the synthesis of GPR84 fluorescent probes .

Silver nanoclusters (AgNCs) are ultrasmall nanoparticles composed of several to tens of silver atoms. Their size is close to the Fermi wavelength of electrons, thus exhibiting unique molecular-like properties, such as strong fluorescence. Silver nanoclusters possess small size, low toxicity, excellent photostability, large Stokes shift, and good biocompatibility. Lipoic acid (also known as octylsulfonic acid) acts as a ligand in the synthesis of silver nanoclusters, primarily playing a role in stabilizing and protecting the silver nanoclusters. The ligand binds to silver atoms through its specific chemical structure, forming a stable nanocluster structure and influencing the physicochemical properties of the clusters, such as fluorescence performance, catalytic activity, and biocompatibility. This demonstrates potential application value in various fields such as chemical analysis, biosensing, catalysis, medicine, and bioimaging.

MBCB is a two-photon Fluorescent probe for dual-detection of mitochondrial SO₂ derivatives and viscosity. For SO₂ derivatives detection, the probe utilizes a Michael addition mechanism: nucleophilic addition of SO₂ derivatives to the C=C bond between the carbazole skeleton and 3-methylbenzothiazolium moiety destroys the strong intramolecular charge transfer (ICT) system between these groups, while enhancing the weak ICT system between the benzothiazole group and carbazole framework; this causes the red emission at 600 nm to decrease and the blue emission at 434 nm to increase, creating a ratiometric response based on the I₄₃₄ₙₘ/I₆₀₀ₙₘ intensity ratio. For viscosity detection, in low-viscosity environments, steric hindrance creates a twisted ICT (TICT) system with weak fluorescence, while in high-viscosity environments, intramolecular rotation is blocked, the TICT state is disrupted, and the strong ICT system is recovered, leading to a strong red emission at 567 nm with negligible change to the short-wavelength emission at 415 nm, creating a ratiometric response based on the I₅₆₇ₙₘ/I₄₁₅ₙₘ intensity ratio that has a logarithmic linear relationship with viscosity. The probe has excitation/emission wavelengths of Ex/Em = 351/434, 600 nm for SO₂ derivatives detection and Ex/Em = 351/567 nm for viscosity detection, with two-photon excitation at 740 nm for bioimaging; it also exhibits good mitochondrial targeting ability with a Pearson's colocalization coefficient of 0.93 when paired with Mito-Tracker Green. The probe shows high sensitivity and selectivity for SO₂ derivatives, has low cell cytotoxicity, and can be applied to detect exogenous/endogenous HSO₃⁻ in living cells and in vivo, as well as visualize mitochondrial viscosity changes induced by nystatin[1].