Design and Synthesis of Near-Infrared Mechanically Interlocked Molecules for Specific Targeting of Mitochondria

Cucurbit[8]uril Confinement-Based Secondary Coassembly for High-Efficiency Phosphorescence Energy Transfer Behavior

Aqueous supramolecular long-lived near-infrared (NIR) material is highly attractive but still remains great challenge. Herein, we report cucurbit[8]uril confinement-based secondary coassembly for achieving NIR phosphorescence energy transfer in water, which is fabricated from dicationic dodecyl-chain-bridged 4-(4-bromophenyl)-pyridine derivative (G), cucurbit[8]uril (CB[8]), and polyelectrolyte poly(4-styrene-sulfonic sodium) (PSS) via the hierarchical confinement strategy. As compared to the dumbbell-shaped G, the formation of unprecedented linear polypseudorotaxane G⊂CB[8] with nanofiber morphology engenders an emerging phosphorescent emission at 510 nm due to the macrocyclic confinement effect. Moreover, benefiting from the following secondary assembly confinement, such tight polypseudorotaxane G⊂CB[8] can further assemble with anionic polyelectrolyte PSS to yield uniform spherical nanoparticle, thereby significantly strengthening phosphorescence performance with an extended lifetime (i.e., 2.39 ms, c.f., 45.0 μs). Subsequently, the organic dye Rhodamine 800 serving as energy acceptor can be slightly doped into the polyelectrolyte assembly, which enables the occurrence of efficient phosphorescence energy transfer process with efficiency up to 80.1% at a high donor/acceptor ratio, and concurrently endows the final system with red-shifted and long-lived NIR emission (710 nm). Ultimately, the as-prepared assembly is successfully exploited as versatile imaging agent for NIR window labeling and detecting in living cells.

Oxocarbon Acids and their Derivatives in Biological and Medicinal Chemistry

The biological and medicinal chemistry of the oxocarbon acids 2,3- dihydroxycycloprop-2-en-1-one (deltic acid), 3,4-dihydroxycyclobut-3-ene-1,2-dione (squaric acid), 4,5-dihydroxy-4-cyclopentene-1,2,3-trione (croconic acid), 5,6-dihydroxycyclohex- 5-ene-1,2,3,4-tetrone (rhodizonic acid) and their derivatives is reviewed and their key chemical properties and reactions are discussed. Applications of these compounds as potential bioisosteres in biological and medicinal chemistry are examined. Reviewed areas include cell imaging, bioconjugation reactions, antiviral, antibacterial, anticancer, enzyme inhibition, and receptor pharmacology.

Design of Water-Soluble Rotaxane-Capped Superparamagnetic, Ultrasmall Fe3O4 Nanoparticles for Targeted NIR Fluorescence Imaging in Combination with Magnetic Resonance Imaging

Integrating an NIR fluorescent probe with a magnetic resonance imaging (MRI) agent to harvest complementary imaging information is challenging. Here, we have designed water-soluble, biocompatible, noncytotoxic, bright-NIR-emitting, sugar-functionalized, mechanically interlocked molecules (MIMs)-capped superparamagnetic ultrasmall Fe3O4 NPs for targeted multimodal imaging. Dual-functional stoppers containing an unsymmetrical NIR squaraine dye interlocked within a macrocycle to construct multifunctional MIMs are developed with enhanced NIR fluorescence efficiency and durability. One of the stoppers of the axle is composed of a lipophilic cationic TPP+ functionality to target mitochondria, and the other stopper comprises a dopamine-containing catechol group to anchor at the surface of the synthesized Fe3O4 NPs. Fe3O4 NPs surface-coated with targeted NIR rotaxanes help to deliver ultrasmall magnetic NPs specifically inside the mitochondria. Two carbohydrate moieties are conjugated with the macrocycle of the rotaxane via click chemistry to improve the water solubility of MitoSQRot-(Carb-OH)2-DOPA-Fe3O4 NPs. Water-soluble, rotaxane-capped Fe3O4 NPs are used for live-cell mitochondria-targeted NIR fluorescence confocal imaging, 3D and multicolor imaging in combination with T2-weighted MRI on a 9.4 T MR scanner with a high relaxation rate (r2) of 180.7 mM-1 s-1. Biocompatible, noncytotoxic, ultrabright NIR rotaxane-capped superparamagnetic ultrasmall monodisperse Fe3O4 NPs could be a promising agent for targeted multimodal imaging applications.

Viscosity probes towards different organelles with red emission based on an identical hemicyanine structure

A series of viscosity probes targeting different organelles were obtained using a single hemicyanine dye as the matrix structure. Specifically, probes 1a-d were obtained by introducing four amines (6-amino-2H-chromen-2-one, N-(2-aminoethyl)-4-methylbenzenesulfonamide, dodecan-1-amine and N,N diphenylbenzene-1,4-diamine) into the indole hemicyanine dye of the carboxylic acid with a D-π-A structure. Their maximum absorption wavelengths were in the range 570-586 nm and they had relatively large molar absorption coefficients, while their maximum emission wavelengths in the red light region were in the range 596-611 nm. Moreover, their fluorescence intensity in glycerol was 35-184 times higher than that in phosphate buffer solution (PBS). The lg(Fl) and lg η of probes 1a-d showed good linearity with high correlation coefficients according to the Förster-Hoffman equation. In addition, cell staining experiments demonstrated that 1a-c could target lysosomes, endoplasmic reticulum and mitochondria, respectively. They could also undergo viscosity-detectable changes in the corresponding organelles under the action of the corresponding ion carriers.

Vanillin Benzothiazole Derivative Reduces Cellular Reactive Oxygen Species and Detects Amyloid Fibrillar Aggregates in Alzheimer's Disease Brain

The misfolding of amyloid beta (Aβ) peptides into Aβ fibrillary aggregates is a major hallmark of Alzheimer's disease (AD), which responsible for the excess production of hydrogen peroxide (H₂O₂), a prominent reactive oxygen species (ROS) from the molecular oxygen (O₂) by the reduction of the Aβ-Cu(I) complex. The excessive production of H₂O₂ causes oxidative stress and inflammation in the AD brain. Here, we have designed and developed a dual functionalized molecule VBD by using π-conjugation (C═C) in the backbone structure. In the presence of H₂O₂, the VBD can turn into fluorescent probe VBD-1 by cleaving of the selective boronate ester group. The fluorescent probe VBD-1 can undergo intramolecular charge transfer transition (ICT) by a π-conjugative system, and as a result, its emission increases from the yellow (532 nm) to red (590 nm) region. The fluorescence intensity of VBD-1 increases by 3.5-fold upon binding with Aβ fibrillary aggregates with a high affinity (K_d = 143 ± 12 nM). Finally, the VBD reduces the cellular toxic H₂O₂ as proven by the CCA assay and DCFDA assay and the binding affinity of VBD-1 was confirmed by using in vitro histological staining in 8- and 18-month-old triple transgenic AD (3xTg-AD) mice brain slices.

Construction of Red Fluorescent Dual Targeting Mechanically Interlocked Molecules for Live Cancer Cell Specific Lysosomal Staining and Multicolor Cellular Imaging

We have designed and synthesized red fluorescent mechanically interlocked molecules with dual targeting functionality for live cancer cell specific active targeting followed by selective internalization and imaging of malignant lysosomes along with real-time tracking, 3D, and multicolor cellular imaging applications.

Multifunction in One Molecule: Mitochondrial Imaging and Photothermal & Photodynamic Cytotoxicity of Fast-Response Near-Infrared Fluorescent Probes with Aggregation-Induced Emission Characteristics

HJS and DHJS, two near-infrared emissive and mitochondria-targeted therapy probes, have been designed. They exhibited photothermal & photodynamic cytotoxicity and aggregation-induced emission (AIE) characteristics. Interestingly, we could receive fluorescence immediately after adding the probes without washing in 1 min. They could quickly enter cancer cells and selectively localized to the mitochondria firstly. When the concentration of probes was low (<5 μM), they could respond sensitively to the mitochondrial membrane potential and would selectively enter the mitochondria with red fluorescence. However, when the concentration was high (≥5 μM), they would preferentially enter the mitochondria and have the property of dual-channel fluorescence imaging (red and near-infrared) even after 24 h. What's more, they increased the intracellular reactive oxygen species (ROS) levels, decreased the mitochondrial membrane potentials, and then induced apoptosis, which were proved by confocal imaging and flow cytometry experiments. In addition, the results of photothermal experiment and cytotoxicity test showed that the probes had good photothermal and photodynamic toxicity to cancer cells. In vitro and in vivo experiments also proved the excellent near-infrared (NIR) imaging ability, good biocompatibility and certain inhibition of tumor growth ability of DHJS.