Functional π-Gelators and Their Applications

In this review we intend to provide a relatively comprehensive summary of the work of supramolecular hydrogelators after 2004 and to put emphasis particularly on the applications of supramolecular hydrogels/hydrogelators as molecular biomaterials. After a brief introduction of methods for generating supramolecular hydrogels, we discuss supramolecular hydrogelators on the basis of their categories, such as small organic molecules, coordination complexes, peptides, nucleobases, and saccharides. Following molecular design, we focus on various potential applications of supramolecular hydrogels as molecular biomaterials, classified by their applications in cell cultures, tissue engineering, cell behavior, imaging, and unique applications of hydrogelators. Particularly, we discuss the applications of supramolecular hydrogelators after they form supramolecular assemblies but prior to reaching the critical gelation concentration because this subject is less explored but may hold equally great promise for helping ...

Supramolecular Hydrogelators and Hydrogels: From Soft Matter to Molecular Biomaterials

Supramolecular Chirality in Self-Assembled Systems

Mitochondria are recognized as one of the most important targets for new drug design in cancer, cardiovascular, and neurological diseases. Currently, the most effective way to deliver drugs specifically to mitochondria is by covalent linking a lipophilic cation such as an alkyltriphenylphosphonium moiety to a pharmacophore of interest. Other delocalized lipophilic cations, such as rhodamine, natural and synthetic mitochondria-targeting peptides, and nanoparticle vehicles, have also been used for mitochondrial delivery of small molecules. Depending on the approach used, and the cell and mitochondrial membrane potentials, more than 1000-fold higher mitochondrial concentration can be achieved. Mitochondrial targeting has been developed to study mitochondrial physiology and dysfunction and the interaction between mitochondria and other subcellular organelles and for treatment of a variety of diseases such as neurodegeneration and cancer. In this Review, we discuss efforts to target small-molecule compounds to mitochondria for probing mitochondria function, as diagnostic tools and potential therapeutics. We describe the physicochemical basis for mitochondrial accumulation of lipophilic cations, synthetic chemistry strategies to target compounds to mitochondria, mitochondrial probes, and sensors, and examples of mitochondrial targeting of bioactive compounds. Finally, we review published attempts to apply mitochondria-targeted agents for the treatment of cancer and neurodegenerative diseases.

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Mitochondria-Targeted Triphenylphosphonium-Based Compounds: Syntheses, Mechanisms of Action, and Therapeutic and Diagnostic Applications

1. Host−Guest Supramolecular Chemistry A 1.

Biomedical Applications of Supramolecular Systems Based on Host-Guest Interactions.

As a marker for oxidative stress and a second messenger in signal transduction, hydrogen peroxide (H2O2) plays an important role in living systems. It is thus critical to monitor the changes in H2O2 in cells and tissues. Here, we developed a highly sensitive and versatile ratiometric H2O2 fluorescent probe (NP1) based on 1,8-naphthalimide and boric acid ester. In response to H2O2, the ratio of its fluorescent intensities at 555 and 403 nm changed 1020-fold within 200 min. The detecting limit of NP1 toward H2O2 is estimated as 0.17 μM. It was capable of imaging endogenous H2O2 generated in live RAW 264.7 macrophages as a cellular inflammation response, and especially, it was able to detect H2O2 produced as a signaling molecule in A431 human epidermoid carcinoma cells through stimulation by epidermal growth factor. This probe contains an azide group and thus has the potential to be linked to various molecules via the click reaction. After binding to a Nuclear Localization Signal peptide, the peptide-based c...

A Highly Sensitive Ratiometric Fluorescent Probe for the Detection of Cytoplasmic and Nuclear Hydrogen Peroxide

It is important to detect hydrogen peroxide (H2O2) near mitochondrial DNA (mtDNA) because mtDNA is more prone to oxidative attack than nuclear DNA (nDNA). In this study, a mitochondria-targeted fluorescence probe, pep3-NP1, has been designed and synthesized. The probe contains a DNA-binding peptide, a H2O2 fluorescence reporter, and a positively charged red emissive styryl dye to facilitate accumulation in mitochondria. Due to groove binding of the peptide with DNA, the styryl dye of pep3-NP1 intercalated into the bases of DNA, leading to an increase in red fluorescence intensity (centered at 646 nm) and quantum yield. In this case, pep3-NP1 was a turn-on probe for labeling DNA. Subcellular locations of pep3-NP1 and MitoTracker suggested that pep3-NP1 mostly accumulated in the mitochondria of live cells. Namely, as an intracellular DNA marker, pep3-NP1 bound to mtDNA. In the presence of H2O2, pep3-NP1 emitted green fluorescence (centered at 555 nm). Thus, the ratio of green with red fluorescence of pep3-N...

Mitochondria-Directed Fluorescent Probe for the Detection of Hydrogen Peroxide near Mitochondrial DNA.

Phenol substituted 1,8-naphthalimide derivatives acting as a donor and an iridium(III) complex which emits orange light acting as an acceptor were synthesized to fabricate a novel white-light-emitting two-component gel. The intermolecular energy transfer between the two components plays a crucial role in providing the tuneable emission in the mixed gels. The emission of white light can be obtained by carefully tuning the ratio of the two components. These gels are ideal constituents for the design of supramolecular light-harvesting materials, which afford a novel approach to displaying information in soft materials with tuneable optical properties. Furthermore, the two-component gel can respond to cysteine with an obvious change in luminescence that is visible to the naked eye.

Iridium complex triggered white-light-emitting gel and its response to cysteine

DNA gated photochromism and fluorescent switch in a thiazole orange modified diarylethene

Two organometallic terpyridyl platinum gelators containing hydrophobic cholesterol with or without large steric hindrance were synthesized and characterized. The complex with three bulky tert-butyl groups (1a) can form a stable gel in several kinds of solvent, such as alcohol, ethyl acetate and toluene with ultrasound irradiation. These sonicated gels display different colour and emission properties compared with their related solutions and precipitates. The intensity of the photoluminescence in gel or solid state of 1a is obviously enhanced by aggregation. The morphology, as well as the surface wettability of 1a can also be reversibly adjusted by sonication and heating. However, the complex without three bulky tert-butyl groups (1b) has poorer solubility and gelation capability, and lower luminescence quantum yield due to strong intermolecular π–π stacking and metal–metal interaction. The spectral and structural variation was characterized by UV-visible and fluorescence spectra, SEM and TEM images, and XRD analysis. The mechanism of the molecularly self-assembled pattern indicates that the large steric hindrance is the reason for the different gelation capabilities and emission properties of the two complexes. Sonication may change the molecular conformation of 1a and promote the ionic dipolar interaction and hydrophobic interactions for gelation, and thus switch the optical properties of the complex in the aggregated state.

Keyin Liu

Papers

A Highly Sensitive Ratiometric Fluorescent Probe for the Detection of Cytoplasmic and Nuclear Hydrogen Peroxide

Mitochondria-Directed Fluorescent Probe for the Detection of Hydrogen Peroxide near Mitochondrial DNA.

Iridium complex triggered white-light-emitting gel and its response to cysteine

DNA gated photochromism and fluorescent switch in a thiazole orange modified diarylethene

Colour change and luminescence enhancement in a cholesterol-based terpyridyl platinum metallogel via sonication