Direct colorimetric study on the interaction of Escherichia coli with mannose in polydiacetylene Langmuir–Blodgett films

The membranes of polydiacetylene backbone decorated with mannose assembled by Langmuir–Blodgett technology can interact with Escherichia coli. The interactions lead to the color transition of the membranes which was readily visible to the naked eyes and could be quantified by visible absorption spectroscopy. To understand the mechanism of the chromatic transition, the affinochromism properties of polydiacetylene were examined by resonance Raman spectroscopy. The results demonstrated that the side chains of polymer backbone performed rearrangement, and the electronic structure in the polymer backbone changed from acetylene to butatriene form when the chromatic transformation from blue to red. The direct colorimetric detection by polydiacetylene membranes not only opens a new path for the use of these membranes in the area of biosensor development but also offers new possibilities for diagnostic applications and screening for binding ligand.     

聚联乙炔囊泡负载的Bola型两亲分子识别三聚氰胺过程中Chaotrope促进型显色机制及热力学

用聚联乙炔囊泡为载体,将bola型两亲分子1,12-二乳清酸十二胺盐(DDO)对三聚氰胺的分子识别作用用肉眼可见的颜色变化显示出来.通过比较不同碳链长度的聚联乙炔囊泡对分子识别过程的反映,发现二十三烷基-2.4-二炔酸(TCDA)囊泡的显色灵敏度较高.研究表明,TCDA肉眼可见的颜色变化来自于DDO与三聚氰胺多重氢键的形成以及溶液环境中水结构的变化.为了更好地理解显色机理,用差示扫描量热(DSC)仪详细研究了分子识别过程中聚联乙炔囊泡的相变行为及热力学参数.结果表明:TCDA囊泡和带有识别分子的DDO/TCDA囊泡在三聚氰胺存在下,相变温度Tm均向高温方向移动,并且,随三聚氰胺浓度的增加,Tm值逐渐增大直至囊泡瓦解;但是Tm值的变化没有与囊泡变色必然关联,仅仅DDO/TCDA囊泡具有变色现象,而且,只有当三聚氰胺的浓度超过分子识别氢键形成所需理论量时,肉眼才能可见明显的由蓝到红的颜色变化.为了理解溶液中过量的三聚氰胺对囊泡变色的作用,选用蔗糖和尿素作为典型的水结构促进剂和水结构破坏剂(chaotrope),详细研究了它们对聚联乙炔囊泡反映分子识别过程中相变温度的影响及显色规律.结果表明,过量的三聚氰胺在溶液中起到类似尿素水结构破坏剂的作用.这种作用和分子识别过程中多重氢键的形成对聚联乙炔囊泡的变色缺一不可.本研究首次揭示了由水结构破坏剂参与的聚联乙炔囊泡变色机理,有助于理解共轭聚合物热相变过程中的Hofmeister效应.     

Colorimetric detection and fingerprinting of bacteria by glass-supported lipid/polydiacetylene films

Glass-supported films of lipids and polydiacetylene were applied for visual detection and colorimetric fingerprinting of bacteria. The sensor films comprise polydiacetylene domains serving as the chromatic reporter interspersed within lipid monolayers that function as a biomimetic membrane platform. The detection schemes are based on either visible blue-red transitions or fluorescence transformations of polydiacetylene, induced by amphiphilic molecules secreted by proliferating bacteria. An important feature of the new film platform is the feasibility of either naked-eye detection of bacteria or color analysis using conventional scanners. Furthermore, we find that the degrees of bacterially induced color transformations depend both on the bacterial strains examined and the lipid compositions of the films. Accordingly, bacterial fingerprinting can be achieved through pattern recognition obtained by recording the chromatic transformations in an array of lipid/PDA films having different lipid components.     

Chromatic immunoassay based on polydiacetylene vesicles

A new approach of chromatic immunoassay based on polydiacetylene vesicles is described. Antibodies were covalently coupled with mixed vesicles of 10,12-tricosadiynoic acid (TCDA) and dimyristoylphosphatidycholine (DMPC). The vesicle-antibody conjugates were irradiated with UV light to yield a blue-colored polydiacetylene. After antigen injection, specific immunoreactions took place at the vesicle surface alter polydiacetylene conformation and lead to a color change from blue to red. The chromatic immunoassay described here is simple, rapid, sensitive; the color change was readily discernible by naked eye when the concentration of antigen is 1 ng/mL. Incorporation of DMPC in the mixed vesicles increases the sensitivity of the chromatic immunoassay.     

One-dimensional order/disorder in a polydiacetylene

A polydiacetylene film, found to be amorphous by x-ray diffraction, possesses some kind of order as suggested by differential scanning calorimetry (DSC). The order/disorder phenomenon which occurs upon heatingcooling is also accompanied by a green/yellow color transition. On the basis of analogies between crystallization and the order in this material, we have extended the application of the Avrami equation to determine the dimensionality of the order in the polymer. Kinetic analysis of the exothermic transition (disorder → order) by DSC suggests that the material has one-dimensional order. The disruption and formation of this order, which accompany the color changes in this polydiacetylene, give rise to endothermic and exothermic transitions, respectively. Supporting evidence for the proposed one-dimensional order/disorder concept is cited.     

Phase transition of a single sheet of sashlike polydiacetylene atomic sash on a solid surface

The phase transition of sashlike polydiacetylene (PD) atomic sash in an extrathin (0.4 nm) vapor-deposited monolayer on a graphite (0001) surface has been observed by in-situ scanning tunneling microscopy (STM). The conformation of the atomic sash composed of a row of lying alkyl chains stitched up with a PD chain is different around the crossing points of the alkyl and PD chains in the two phases, and hence the contrast of the STM image is different in the middle of the sashes. The difference is associated with the color transition of bulk PDs.     

Thermochromism in polydiacetylene solutions

A novel planar ? nonplanar visual thermochromic conformational transition of polydiacetylene molecules in poor solvents is reported. The conformational transition is associated with both a color change (blue or red ? yellow) and a change in the state; the yellow solution (liquid) transforms to a blue or red gel (solid). The color transition occurs within a narrow range of temperature and has a large associated hysteresis. The enthalpy of the conformational transition is 29 kJ/mole of repeat unit. Fourier-transform infrared studies show that molecules acquire a planar conformation in red or blue gels by formation of intramolecular H bonds between the adjacent substituent groups. Virtually all H bonds break (a nonplanar conformation) when the gels turn into yellow solutions.     

Induced Color Change of Conjugated Polymeric Vesicles by Interfacial Catalysis of Phospholipase A2

A blue to red color change is induced on addition of phospholipase A₂ to modified PDA vesicles 1 (PDA=polydiacetylene). This bathochromic transition results from chemical modification of the vesicles by hydrolysis of the enzyme substrate embedded in the PDA matrix. Addition of a known phospholipase inhibitor or removal of Ca²⁺ ions suppresses the color change, which suggests the potential for applications in high‐throughput screening assays.     

Microbead-assisted PDA sensor for the detection of genetically modified organisms

A simple and sensitive approach for the detection of marker protein, phosphinothricin acetyltransferase, from genetically modified crops was developed based on the colorimetric transition of polydiacetylene (PDA) vesicles in combination with silica microbeads. PDAs have attracted a great deal of interests as a transducing material due to their special features that allow colorimetric response to sensory signals, as well as their inherent simplicity. However, most PDA-based biosensors require additional analytical equipment such as a fluorescence microscope or UV–Vis spectrometer. In this study, we report a new approach to increase the degree of color transition by coupling antibody-conjugated PDA vesicles with silica microbeads in an effort to monitor the results with the unaided eye or simple RGB analysis. By immobilizing PDA vesicles on silica microbeads, we were able to overcome the disadvantages of colloidal PDA-based sensors and increase the degree of colorimetric changes in response to target molecules to a concentration as low as 20 nM. The additional stresses were given to PDA vesicles by antigen–antibody bridging of PDA vesicles coupled with microbeads, resulting in enhanced blue–red color transition. All the results showed that PDA vesicles in conjunction with silica microbeads will be a promising transducing material for the detection of target proteins in diagnostic and biosensing applications.     

Effect of amphiphilic molecules upon chromatic transitions of polydiacetylene vesicles in aqueous solutions

Effect of amphiphilic molecules upon the chromatic transitions of polymerized 10,12-pentacosadiynoic acid (PCDA) vesicles in aqueous solutions was reported. The colorimetric response of polymerized PCDA vesicles for 1-pentanol is higher than that for ethanol due to more hydrophobic property of 1-pentanol. The colorimetric response of polymerized PCDA vesicles for sodium dodecyl sulfate (SDS) and Triton X-100 is lower than that for cetyltrimethylammonium bromide (CTAB). The strong ability of CTAB to induce chromatic transition of the vesicles is related to the positively charged headgroups of CTAB, which favors approach of CTAB to the negatively charged carboxylate groups at the vesicle surface. The insertion of alkyl chain of CTAB into the hydrophobic domain perturbs the conformation of the conjugated polymer backbone and induces color change of polydiacetylene vesicles. For a series of alkylamine hydrochloric salts, the longer the alkyl chain, the stronger the ability of alkylamine to induce chromatic transition of polydiacetylene vesicles.     

A colorimetric and fluorescent chemosensor for detection of Hg2+ using counterion exchange of cationic polydiacetylene

In this study, a colorimetric and fluorescent chemosensor for mercury ions (Hg²⁺) was developed. Cationic polydiacetylene (PDA) vesicles with a quaternary ammonium cation and iodide as a counterion show a blue-to-red color transition; the color change is accompanied by a fluorescence enhancement in selective response to Hg²⁺ ions because of a perturbation of the ene–yne conjugated backbone induced by counterion exchange. It allows for selective detection of Hg²⁺ with the naked eye and the sensor is used to determine Hg²⁺ concentrations in tap water samples.     

Solid State Nuclear Magnetic Resonance Studies of the Thermochromic Phase Transition of the Polydiacetylene from the Bis-n-Propylurethane of 5,7-Dodecadiyne-1,12-diol

The polydiacetylene (PDA) from the bis-n-propylurethane of 5,7-dodecadiyne-1,12-diol (PUDO) undergoes a first order phase transition near 135°C that is associated with a color change from blue at temperatures below the transition to red at temperatures above the transition. We have studied PDA-PUDO by solid state ¹³C nuclear magnetic resonance (NMR) spectra using cross polarization and magic angle spinning (CP-MAS) techniques at temperatures between 25° and 140°C. As observed previously, the acetylene carbon shift moves up field as the temperature is raised above the transition temperature. In addition, near 130°C, the oxymethylene carbon shows 3 resonances, indicating multiple side chain conformations as the PDA undergoes the phase transition.     

Reversible thermal transition of polydiacetylene based on KTTKS collagen sequence

Here we explore the physico-chemical properties of a peptide amphiphile obtained by chemical conjugation of the collagen-stimulating peptide KTTKS with 10,12-pentacosadiynoic acid which photopolymerizes as a stable and extended polydiacetylene. We investigate the self-assembly of this new polymer and rationalize its peculiar behavior in terms of a thermal conformational transition. Surprisingly, this polymer shows a thermal transition associated with a non-cooperative increase in β-sheet content at high temperature.     

Rapid colorimetric detection of antibody-epitope recognition at a biomimetic membrane interface.

Biomolecular recognition of antigens and epitopes by antibodies is a fundamental event in the initiation of immune response and plays a central role in a variety of biochemical processes. Peptide binding requires, in many cases, presentation of the peptides at interfaces, such as protein surfaces, cellular membranes, and synthetic polymer surfaces. We describe a novel molecular system in which interactions between antibodies and peptide epitopes displayed at a biomimetic membrane interface can be detected through induction of visible, rapid color transitions. The colorimetric assembly consists of a phospholipid/polydiacetylene matrix anchoring a hydrophobic peptide displaying the epitope at its N-terminus. The colorimetric transitions observed in the assembly, corresponding to perturbation of the polydiacetylene framework, are induced only upon recognition of the displayed epitope by its specific antibody present in the aqueous solution. Significantly, the color changes occur after a single mixing step, without further chemical reactions or enzymatic processing. The new molecular system could be utilized for studying antigen-antibody interactions and peptide-protein recognition, epitope mapping, and rapid screening of biological and chemical libraries.     

A thermally reversible supramolecular system based on biphenyl polydiacetylene

A new type of diacetylene monomer which includes a biphenylcarboxylic acid group as its head group is synthesized.Polymerization was performed after monomer form spherical vesicle by self-assembly in the water.The polydiacetylene displayed completely thermochromic color change in the range of 20-95℃ owing to the presence of strong π-π interaction caused by biphenyl group and hydrogen bonding between head group.     

Interfacial catalysis by phospholipases at conjugated lipid vesicles: colorimetric detection and NMR spectroscopy

Background: Self-assembled conjugated polymers are rapidly finding biological and biotechnological applications. This work describes a synthetic membrane system based on self-assembled polydiacetylenes, which are responsive to the enzymatic activity of phospholipases - a ubiquitous class of enzymes that catalyze the hydrolysis of phospholipid molecules embedded in cell membranes.Results: We show that phospholipases are active at bilayer vesicles composed of the natural enzyme substrate, dimyristoylphosphatidylcholine (DMPC), and a synthetic π-conjugated polymerized lipid based on polydiacetylene (PDA). In addition, the enzymatic reaction induces an optical transition in the surrounding PDA matrix, visible to the naked eye. Nuclear magnetic resonance spectroscopy confirms the occurrence of enzymatic catalysis and reveals the fate of the cleavage products.Conclusions: The results indicate that the structural and color changes of the PDA matrix are directly related to interfacial catalysis by phospholipase. This novel biocatalytic method of inducing optical transitions in conjugated polymers might lead to new approaches towards rapidly screening new enzyme inhibitor compounds.     

Excitonic quadrupole absorption in a polydiacetylene

Excitonic states in a polydiacetylene (polyTCDU) single crystal have been investigated using temperature-dependent optical absorption, Raman and polarization-dependent optical spectroscopy. The expected significance of a linear quadrupolar component in the excitonic transition has been experimentally demonstrated. Formation and detectability of such quadrupoles is a unique attribute of the symmetry, order, valence geometry and one-dimensionality of the polydiacetylene backbone.     

Dipole transitions from excited S states of two-electron systems in time-dependent Hartree-Fock theory

Surface enhanced Raman scattering has been observed for O₂ molecules adsorbed on polydiacetylene single crystals. The spectral dependence of the Raman cross section suggests that the enhancement is due to a well-defined electronic transition of energy 2.39 eV which involves a significant degree of charge transfer from the conjugated polydiacetylene backbone to the O₂ molecule.     

Single-crystal reflection and Raman spectra of the polydiacetylene THD

The 298 K. Raman and reflection spectra of the polydiacetylene THD, a close structural variant of DCHD, are presented. The polymer double- and triple-bond stretch frequencies are 1485 and 2111 cm⁻¹, respectively, and the lowest electronic transition peaks at 17600 cm⁻¹. The reflection spectrum is more reminiscent of the polydiacetylene TCDU than DCHD.     

ESR study of the diacetylene polymer 4BCMU

Electron Spin Resonance (ESR) measurements of the polydiacetylene 4BCMU in the solid-state indicate the presence of a thermally activated paramagnetic center with g ≈ 2.002 and first-derivative peak-to-peak linewidth of ≈ 17G. An abrupt and irreversible decrease in ESR signal intensity is observed at ca. 400 K, and appears to be associated with the solid-state planar-nonplanar conformational transformation manifested by an irreversible color change from metallic brown to red.