Rational Design and in-Situ FTIR Analyses of Colorimetrically Reversibe Polydiacetylene Supramolecules

Polydiacetylene-based colorimetric self-assembled vesicular receptors for biological phosphate ion recognition

Self-assembled vesicular polydiacetylene (PDA) particles with embedded metal complex receptor sites have been prepared. The particles respond to the presence of ATP and PPi (pyrophosphate) in buffered aqueous solution by visible changes of their color and emission properties. Blue PDA vesicles of uniform size of about 200 nm were obtained upon UV irradiation from mono- and dinuclear zinc(II)-cyclen and iminodiacetato copper [Cu(II)-IDA] modified diacetylenes, embedded in amphiphilic diacetylene monomers. Addition of ATP and PPi to the PDA vesicle solution induces a color change from blue to red observable by the naked eye. The binding of ATP and PPi changes the emission intensity. Other anions such as ADP, AMP, H2PO4-, CH3COO-, F-, Cl-, Br- and I-, failed to induce any spectral changes. The zinc(II)-cyclen nanoparticles are useful for the facile detection of PPi and ATP in millimolar concentrations in neutral aqueous solutions, while Cu(II)-IDA modified vesicular PDA receptors are able to selectively discriminate between ATP and PPi.

Unusual photopolymerization behavior of amino Acid-derived polydiacetylene supramolecules

UV-irradiation of aqueous suspensions of amino acid-derived amphiphilic diacetylene supramolecules promotes a process that involves initial formation of species that absorb at 640 nm followed by the generation of polymers that have longer wavelength (686 nm) absorbance. The initially formed intermediate polydiacetylenes display substantial colorimetric reversibility while the long wavelength absorbing polymers show irreversible thermochromism during heating and cooling cycles. The long wavelength absorbing polydiacetylenes, formed from amino acid-derived amphiphilic diacetylene supramolecules, are suggested to have more planer backbone structures that allow more efficient overlap of the conjugated p-orbitals.

Structural transitions in polydiacetylene Langmuir films

Polydiacetylene (PDA) Langmuir films (LFs) were investigated directly at the air/water interface using in situ synchrotron grazing incidence X-ray diffraction, and ex situ transmissison electron microscopy and diffraction. The films were compressed and polymerized on pure water. A crystallographic model describes the structures and phase transitions of the unpolymerized (monomer) film, via the metastable (blue phase), to the fully stable PDA red phase as a function of irradiation dose. The monomer-to-blue-to-red chromatic phase transitions are accompanied by changes in the in-plane crystal structure and pendant chains packing arrangement from arced alkyl chains (in the monomer and blue phases) to near-vertical closely packed chains in the red phase. Notably, the characteristic linear strand morphology of PDA films can be explained as a direct result of the marked decrease in spacing between adjacent polymer chains upon transition from the blue to the red phase.

Fluorogenic polydiacetylene supramolecules: immobilization, micropatterning, and application to label-free chemosensors

This Account describes a new strategy for the preparation of label-free sensor systems based on the fluorogenic properties of the conjugated polymer, polydiacetylene (PDA). PDA has been extensively investigated as a sensor matrix, owing to a brilliant blue-to-red color transition that takes place in response to environmental perturbations. It has been known for some time that "blue-phase" PDAs are nonfluorescent while their "red-phase" counterparts fluoresce. For the most part, however, the significance of the different fluorogenic properties of PDAs has been ignored in the context of sensor applications. In the course of developing PDA-based sensors, we discovered that PDA vesicles can be readily immobilized on solid substrates. This is an attractive property of PDAs since it leads to the combined advantages of the vesicle sensors (which have three-dimensional interactions between sensor and target molecules) and film sensors (which are applicable to a two-dimensional array or chip format). Stable blue-phase immobilized PDAs can be prepared by employing one of three strategies involving the formation of covalent adducts, biotin-avidin complexes, or complexes formed through nonspecific physical adsorption. A procedure for generating well-patterned fluorescence images is necessary for the immobilized PDAs to function in chip-based sensor systems. Patterned fluorescence images are readily constructed by employing (1) the photolithographic technique, (2) the micromolding in capillaries (MIMIC) method, or (3) an array spotting system. Heat treatment of the patterned "blue-phase" PDA vesicles transforms the nonfluorescent images into their fluorescent red forms. The observation that finely resolved fluorescence patterns can be generated by heat treatment of microarrayed PDAs is highly significant in that it indicates that fluorescence signals might be produced by specific molecular recognition events. Indeed, red fluorescence emission is observed when immobilized PDAs are subjected to specific molecular recognition events, such as ligand--cyclodextrin or protein-protein interactions. The facile immobilization of PDA vesicles on solid substrates and the affinity-induced fluorescence emission combine to make this system applicable to the fabrication of label-free PDA sensors. Since in theory any molecular recognition event that promotes the blue-to-red color transition of PDAs should result in the generation of fluorescence, it should be possible to reformat a variety of previously described colorimetric PDA sensors into fluorescence-based sensor systems. The fluorescence properties of PDAs, when combined with modern methods for the fabrication of microarrays, should stimulate the development of a number of new label-free chemosensor systems.

Photopolymerization of and patterned fluorescence imaging with a bispyrenyl group-containing diacetylene

Photopolymerization of a diacetylene monomer having terminal pyrene groups afforded formation of polydiacetylene nanoparticles in aqueous solvent along with fluorescence quenching of pyrene moieties.

Vancomycin-induced morphological transformation of self-assembled amphiphilic diacetylene supramolecules

Reversible ribbon-sphere microstructural transformation of dipeptide-containing diacetylene supramolecules was observed by specific ligand-receptor interactions.