Enzyme Sensing Using 2-Mercaptopyridine-Carbonitrile Reporters and Surface-Enhanced Raman Scattering.

The high sensitivity and functional group selectivity of surface-enhanced Raman scattering (SERS) make it an attractive method for enzyme sensing, but there is currently a severe lack of enzyme substrates that release SERS reporter molecules with favorable detection properties. We find that 2-mercaptopyridine-3-carbonitrile ( ) and 2-mercaptopyridine-5-carbonitrile ( ) are highly effective as SERS reporter molecules that can be captured by silver or gold nanoparticles to give intense SERS spectra, each with a distinctive nitrile peak at 2230 cm. is a more sensitive reporter and can be detected at low nanomolar concentrations.

Supramolecular optimization of the visual contrast for colorimetric indicator assays that release resorufin dye.

A tetralactam macrocycle acts as a novel supramolecular adjuvant to capture a released resorufin dye and create a higher contrasting yellow/blue color change for enhanced naked eye interpretation of a colorimetric indicator assay.

Cell organelle targeting of near-infrared croconaine dye controls photothermal outcome.

Near-infrared croconaine-peptide conjugates that target the cell nucleus promote photothermal induced cell death. In contrast, a croconaine-morpholine conjugate that targets the cell lysosomes promotes lysosome permeabilization without measurable cell phototoxicity.

Paired Agent Fluorescence Imaging of Cancer in a Living Mouse Using Preassembled Squaraine Molecular Probes with Emission Wavelengths of 690 and 830 nm.

New methods are described for the construction of targeted fluorescence probes for imaging cancer and the assessment of tumor targeting performance in a living mouse model. A novel noncovalent assembly process was used to fabricate a set of structurally related targeted fluorescent probes with modular differences in three critical assembly components: the emission wavelength of the squaraine fluorochrome, the number of cRGDfK peptide units that target the cancer cells, and the length of the polyethylene glycol chains as pharmacokinetic controllers. Selective targeting of cancer cells was proven by a series of cell microscopy experiments followed by in vivo imaging of subcutaneous tumors in living mice.

High affinity threading of a new tetralactam macrocycle in water by fluorescent deep-red and near-infrared squaraine dyes.

A new tetralactam macrocycle was prepared and found to encapsulate deep-red and near-infrared squaraine and croconaine dyes in water with tunable threading kinetics. The new supramolecular paradigm of guest back-folding was used to increase macrocycle/squaraine affinity by 370-fold and achieve an association constant of 2.8 × 10 M.

Croconaine Rotaxane Dye with 984 nm Absorption: Wavelength-Selective Photothermal Heating.

Croconaines are an emerging class of near-infrared dyes that are useful for various sensing, photothermal, optoelectronic, and photoacoustic applications. Previous work encapsulated a dumbbell-shaped croconaine dye whose structure contains two thiophene flanking units inside a tetralactam macrocycle and produced a croconaine rotaxane with a narrow 824 nm absorption band. Herein, a new rotaxane is reported that encapsulates a croconaine dye with two thienothiophene flanking units.

Fluorescent Thienothiophene-Containing Squaraine Dyes and Threaded Supramolecular Complexes with Tunable Wavelengths between 600⁻800 nm.

A new family of fluorescent thiophene and thienothiophene-containing squaraine dyes is described with tunable wavelengths that cover the absorption/emission range of 600⁻800 nm. The deep-red and near-infrared fluorescent compounds were easily prepared by simple synthesis and purification methods. Spectral studies showed that each squaraine was rapidly encapsulated by a tetralactam macrocycle, with nanomolar affinity in water, to produce a threaded supramolecular complex with high chemical stability, increased fluorescence quantum yield, and decreased fluorescence quenching upon dye self-aggregation.

Structural switching in self-assembled metal-ligand helicate complexes ligand-centered reactions.

Ligand centered reactions are capable of conferring structural switching between a metastable, self-assembled Fe-iminopyridine aggregate and a stable ML helicate. The reactivity is directed and accelerated by the stability of the final product structure. Under aerobic conditions, both substitution and oxidation occurs at the ligand, exploiting atmospheric oxygen as the oxidant.