A Magnetically Responsive Polydiacetylene Precursor for Latent Fingerprint Analysis

A magnetically responsive diacetylene (DA) powder was developed for the visualization of latent fingerprints. A mixture of the DA and magnetite nanoparticles, applied to a surface containing latent fingermarks, becomes immobilized along the ridge patterns of the fingerprints when a magnetic field is applied. Alignment along the ridge structures is a consequence of favorable hydrophobic interactions occurring between the long alkyl chains in the DAs and the lipid-rich, sebaceous latent fingermarks. UV irradiation of the DA–magnetite composite immobilized on the latent fingerprint results in the generation of blue-colored PDAs. Heat treatment of the blue-colored image promotes a blue-to-red transition as well as fluorescence turn-on. A combination of the aligned pale brown-colored monomeric state, UV irradiation generated blue-colored PDA state, as well as the heat treatment generated red-colored and fluorescent PDA state enables efficient visual imaging of a latent fingerprint, which is deposited on various colored solid surfaces

Controlling and Assessing the Surface Display of Cell-Binding Domains on Magnetite Conjugated Fluorescent Liposomes

Biological systems provide us with a diverse source of peptide-based ligands for cellular adhesion. Controlling and assessing the ligand surface density as well as tailoring the surface chemistry to have specific cellular adhesion properties are important in biomaterials design. In the following work, we provide a means for displaying peptide-based ligands on magnetic liposomes in which the surface density and chemistry may be controlled. Simultaneously, the conjugated vesicles provide a fluorescent signal for examining steric hindrance among surface ligands. In addition, the inherent magnetic and fluorescence features of this system revealed potential for magnet-based cell isolation and fluorescent labeling of adhered cells, respectively. Adhered cells were found to remain viable and proliferative, thereby allowing them to be used for subsequent evaluation. In a specific demonstration, we control the density of fibronectin-mimetic ligands on the polydiacetylene liposome surfaces. We find that steric limitation occurring at over 20% surface density result in decreased cell adhesion, in accord with related techniques. The magnetic-liposome system offers the means for not only separating cells adhered to the biomaterial, but also providing the ability to control and assess the biomaterial surface. This may prove particularly useful for examining combinations of peptide-based ligands or for evaluating the molecular-level ligand accessibility and its effect on cell attachment to a biomaterial surface

Stimulus-Responsive Azobenzene Supramolecules: Fibers, Gels, and Hollow Spheres

Novel, stimulus-responsive supramolecular structures in the form of fibers, gels, and spheres, derived from an azobenzene-containing benzenetricarboxamide derivative, are described. Self-assembly of tris­(4-((<i>E</i>)-phenyldiazenyl)­phenyl)­benzene-1,3,5-tricarboxamide (<b>Azo-1</b>) in aqueous organic solvent systems results in solvent dependent generation of microfibers (aq DMSO), gels (aq DMF), and hollow spheres (aq THF). The results of a single crystal X-ray diffraction analysis of <b>Azo-1</b> (crystallized from a mixture of DMSO and H₂O) reveal that it possesses supramolecular columnar packing along the <i>b</i> axis. Data obtained from FTIR analysis and density functional theory (DFT) calculation suggest that multiple hydrogen bonding modes exist in the <b>Azo-1</b> fibers. UV irradiation of the microfibers, formed in aq DMSO, causes complete melting while regeneration of new fibers occurs upon visible light irradiation. In addition to this photoinduced and reversible phase transition, the <b>Azo-1</b> supramolecules display a reversible, fiber-to-sphere morphological transition upon exposure to pure DMSO or aq THF. The role played by amide hydrogen bonds in the morphological changes occurring in <b>Azo-1</b> is demonstrated by the behavior of the analogous, ester-containing tris­(4-((<i>E</i>)-phenyldiazenyl)­phenyl)­benzene-1,3,5-tricarboxylate (<b>Azo-2</b>) and by the hydrogen abstraction in the presence of fluoride anions

Stimulus-Responsive Azobenzene Supramolecules: Fibers, Gels, and Hollow Spheres

Novel, stimulus-responsive supramolecular structures in the form of fibers, gels, and spheres, derived from an azobenzene-containing benzenetricarboxamide derivative, are described. Self-assembly of tris­(4-((<i>E</i>)-phenyldiazenyl)­phenyl)­benzene-1,3,5-tricarboxamide (<b>Azo-1</b>) in aqueous organic solvent systems results in solvent dependent generation of microfibers (aq DMSO), gels (aq DMF), and hollow spheres (aq THF). The results of a single crystal X-ray diffraction analysis of <b>Azo-1</b> (crystallized from a mixture of DMSO and H₂O) reveal that it possesses supramolecular columnar packing along the <i>b</i> axis. Data obtained from FTIR analysis and density functional theory (DFT) calculation suggest that multiple hydrogen bonding modes exist in the <b>Azo-1</b> fibers. UV irradiation of the microfibers, formed in aq DMSO, causes complete melting while regeneration of new fibers occurs upon visible light irradiation. In addition to this photoinduced and reversible phase transition, the <b>Azo-1</b> supramolecules display a reversible, fiber-to-sphere morphological transition upon exposure to pure DMSO or aq THF. The role played by amide hydrogen bonds in the morphological changes occurring in <b>Azo-1</b> is demonstrated by the behavior of the analogous, ester-containing tris­(4-((<i>E</i>)-phenyldiazenyl)­phenyl)­benzene-1,3,5-tricarboxylate (<b>Azo-2</b>) and by the hydrogen abstraction in the presence of fluoride anions