Assembly of polydiacetylene vesicles on solid substrates

A method to create assembly of polydiacetylene vesicles on solid substrates in a novel fashion is described. The formation of the assembly is based on electrostatic layer-by-layer deposition using negatively charged 10,12-pentacosadiynoic acid (PCDA) vesicles and polyelectrolyte polyethylenimine, or positively charged PCDA-2(')-aminoethylamide (PCDANH2) vesicles. This is an efficient method for preparing the chromatic sensor films of polydiacetylene vesicles after ultraviolet light irradiation. The strategy would be useful in the development of polydiacetylene-based chemosensors and biosensors.     

Size effect of polydiacetylene vesicles functionalized with glycolipids on their colorimetric detection ability

In this paper, the size effect of the polydiacetylene vesicles functionalized with glycolipids on their colorimetric detection ability has been studied. Polydiacetylene vesicles in which were incorporated glycolipids acted as a model system for the affinochromatic property. Visible color changes from blue to red could be observed to the naked eye owing to Con A binding to the sugar moiety and be detected quantitatively by the visible absorption spectrum. In the experiment, small and uniform vesicles were obtained after extrusion through membranes with different pore sizes. The morphology and mean size distribution of the extruded vesicles were studied by transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. Our work shows that the smaller the vesicles are, the stronger is the effect, making the detection of Con A easier. The results may apply to the sensitivity enhancement of polydiacetylene biosensors for the recognition of other biomolecules.     

Electronic absorption spectroscopy probed side-chain movement in chromic transitions of polydiacetylene vesicles

Thermochromism, solvatochromism, and alkalinochromism of a poly-10,12-pentacosadiynoic acid (poly(PCDA)) vesicle solution are studied by electronic absorption spectroscopy. The spectroscopic profiles reveal different sequences of side-chain movement during the chromic transitions. The gradual hypsochromic shift and reversibility of the purple solution at low temperature in the thermochromic transition indicates that the transition starts with reversible conformational alteration of methylene side chains leading to metastable purple vesicles. Further heating to 80 degrees C or higher eventually causes the hydrogen bonds at the carboxylic head groups to break and turns the vesicle solution to red. The irreversibility of the red vesicles indicates that it is the most thermodynamically stable form. In the ethanolochromism and alkalinochromism, the processes are however induced at the vesicle-media interface, directly bringing about the hydrogen bond breaking. The purple solutions observed in the ethanolochromism and alkalinochromism cannot reverse back to the blue one. The absorption spectra clearly demonstrate that they are mixtures of the blue and red vesicles.     

Color fingerprinting of proteins by calixarenes embedded in lipid/polydiacetylene vesicles

"Naked eye" color detection of proteins was achieved by embedding calixarene receptors within vesicles comprising phospholipids and the chromatic polymer polydiacetylene. Dramatic visible absorbance changes were induced through electrostatic interactions between the protein surface and the vesicle-incorporated hosts. The colorimetric responses could be induced by micromolar protein concentrations, and furthermore, specific protein fingerprints could be obtained by incorporating different receptors within the vesicles. Fluorescence and circular dichroism experiments confirmed the relationship between the colorimetric phenomena and protein docking on the surface of the chromatic vesicles. The colorimetric assay constitutes a generic platform for high-sensitivity detection of soluble proteins and for evaluation of protein surface charge distribution.     

Selective detection of catecholamines by synthetic receptors embedded in chromatic polydiacetylene vesicles

A new detection scheme for catecholamines was constructed through embedding synthetic receptors within vesicles comprising phospholipids and polydiacetylene. Fluorescence emission of the polydiacetylene was induced through specific interactions between the soluble ligands and the vesicle-incorporated hosts. The system demonstrated remarkable selectivity among structurally similar ligands and achieved much lower detection thresholds compared to that of other reported catecholamine sensors. The chromatic assembly provides a generic route for high sensitivity detection of ligand-receptor interactions.     

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.     

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.     

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.     

Triggering blue-red transition response in polydiacetylene vesicles: an electrochemical surface plasmon resonance method

Electrochemical surface plasmon resonance (E-SPR) was used to investigate whether the chromic properties of a polydiacetylene (PDA) vesicle films, adsorbed onto an ultra-thin gold electrode, could be triggered by applied potential. This approach constitutes a preliminary model for a novel approach to the use of a triggered chromic transition, as an indicator of biorecognition headgroup binding in these materials. A PDA chromic blue-red transition was identified in E-SPR against the background Deltaepsilon(e) and Deltaepsilon(m). The latter resulted in a ca. 100 mDeg V(-1) shift in the SPR minimum, in the presence of PDA, with the PDA shielding changes in epsilon(e). Electrochemical charge transfer processes in the pre-oxide/oxide anodic region with adsorbed oxygen and hydroxide, involving a change in Au redox state (Au(0)/Au(+)) were visible in the SPR, due to a change in the gold layer thickness and gold oxide layer. However, the cathodic processes, not involving a change in the Au redox state or a increase/decrease in the surface layer dielectric, did not cause a change in the SPR. Based on this, dramatic changes in the optical properties of the adsorbed PDA film could be triggered at an applied cathodic potential, and were identified using SPR. These correlated with a pH-induced chromic transition. Both protonation and ion binding, linked with headgroup environment, were implicated in causing structural transitions in the adsorbed vesicle layer that may also be linked with their bulk optical properties.     

New DNA-sensor based on thiacalix[4]arene-modified polydiacetylene particles

Russian Chemical Bulletin - New p-tert-butyl thiacalix[4]arene derivative in the 1,3-alternate stereoisomeric form containing two diethylenetriamine groups and pentacosa-10,12-diynoic moieties on...     

Roles of head group architecture and side chain length on colorimetric response of polydiacetylene vesicles to temperature, ethanol and pH

In this contribution, we report the relationship between molecular structures of polydiacetylene (PDA) vesicles, fabricated by using three monomers, 10,12-tricosadiynoic acid (TCDA), 10,12-pentacosadiynoic acid (PCDA) and N-(2-aminoethyl)pentacosa-10,12-diynamide (AEPCDA), and their color-transition behaviors. The modification of side chain length and head group of the PDA vesicles strongly affects the colorimetric response to temperature, ethanol and pH. A shorter side chain of poly(TCDA) yields weaker inter- and intra-chain dispersion interactions in the bilayers compared to the system of poly(PCDA), which in turn results in a faster color transition upon exposure to all stimuli. A change of head group in poly(AEPCDA) slightly reduces the transition temperature. Interestingly, the colorimetric response of poly(AEPCDA) vesicles to the addition of ethanol is found to occur in a two-step fashion while the response of poly(PCDA) vesicles takes place in a one-step process. The amount of ethanol required for inducing complete color-transition of poly(AEPCDA) vesicles is also much higher, about 87% v/v. The increase of pH to ~9 and ~10 causes a color-transition of poly(TCDA) and poly(PCDA) vesicles, respectively. The poly(AEPCDA) vesicles, on the other hand, change color upon decreasing pH to ~0. The colorimetric response also occurs in a multi-step fashion. These discrepancies are attributed to the architecture of surface layers of poly(AEPCDA), constituting amine and amide groups separated by ethyl linkers.     

Effect of alkyl chain length on chemical sensing of polydiacetylene and polydiacetylene/ZnO nanocomposites

Polydiacetylenes (PDAs) and PDA/ZnO nanocomposites based on the monomers 10,12-pentacosadiynoic acid (PCDA), 10,12-tricosadiynoic acid (TCDA), and 10,12-docosadiynedioic acid (DCDA) monomers have been investigated for chromatic chemical sensing of a number of organic liquids. Chromatic sensitivity is associated with the interaction of the organic liquid with the PDA side chain to give rise to the strain-induced blue to red colorimetric transition. Attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy demonstrated that in the PDA/ZnO nanocomposites, the PDA side chains form chelates with ZnO. The chromatic properties of PDAs and PDA/ZnO composites in organic liquids, to certain extent, depend on the side-chain length and the number of carboxylic head groups. Pure PDAs and PDA/ZnO nanocomposites in different organic liquids studied by Raman spectroscopy show that the chromatic selectivity of PDAs for certain organic liquids with respect to the blue to red phase transition is closely related to the side-chain structure of the PDAs. Moreover, the interactions are stronger with those PDAs where the blue to red transition is irreversible. Density functional theory (DFT) simulations show that the chromatic sensitivity of the PDAs toward a particular organic correlates with the C–C bond torsion angle of the PDA backbone.     

Aqueous sols of oligo(ethylene glycol) surface decorated polydiacetylene vesicles for colorimetric detection of Pb 2+

A series of ethylene glycol (EG), triethylene glycol (3EG) and pentaethylene glycol (5EG) esters of 10,12-pentacosadiynoic acid (PCDA) are synthesized. The glycol ester lipids can be hydrated and well dispersed in water but they cannot form polydiacetylenes upon UV irradiation. They however can be mixed with PCDA up to 30 mol% and polymerized to form blue sols. The mixed polydiacetylene sols show blue to red thermochromic transition with two-stepped transition temperatures. The first transition temperature decreases with the increase of the glycol ester content as well as the length of their chains indicating greater fluidity of the self-assembled structure due to less collaborative hydrogen bonding among the lipid head groups. These mixed polydiacetylene sol prepared from 30 mol% of the penta(ethylene glycol) ester show linear colorimetric response selectively to Pb²⁺ in the range of 5-30 μM.     

High-modulus polydiacetylene single-crystal fibers

The relationship between structure and mechanical properties of polydiactetylene single-crystal fibers has been studied in detail. It is shown by transmission electron microscopy that the fibers have a high degree of internal perfection, with the polymer molecules aligned parallel to the fiber axes. The fibers of the dicarbazolyl derivative investigated were found to have a Young's modulus of 45 GPa and fracture strengths of up to 1.5 GPa, the strengths being controlled by defects such as surface steps. It is shown that the stiffness of the polymer backbone is similar to that of polyethylene, and the theoretical strength of the polydiacetylene singlecrystal fibers is determined to be about 3 GPa, corresponding to a fracture strain of between 6 and 8% and a force required to break molecules to the order of 3 nN. The derivative studied is also found to have good thermal stability, not degrading below 300°C, and excellent creep resistance up to at least 100°C. The possibility of using the single-crystal fibers in composites is also discussed.     

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.     

pH-responsive vesicles based on a hydrolytically self-cross-linkable copolymer

A new type of shape-persistent, pH-responsive vesicle was prepared by the self-assembly of a novel poly(ethylene oxide)-block-poly[2-(diethylamino)ethyl methacrylate-stat-3-(trimethoxysilyl)propyl methacrylate], PEO-b-P(DEA-stat-TMSPMA), copolymer. Vesicles were formed spontaneously in aqueous THF solution, with the hydrophilic PEO chains forming the corona and the pH-sensitive P(DEA-stat-TMSPMA) blocks being located in the membrane walls. Hydrolytic cross-linking within the hydrophobic membrane walls fixed the vesicle morphology. The resulting colloidally stable vesicles were characterized by 1H NMR, transmission electron microscopy (TEM), dynamic laser light scattering (DLS), and stopped-flow fluorescence experiments. The latter technique indicated that the permeability of the vesicle walls was sensitive to the pH of the aqueous solution, as expected. Gold-decorated vesicles were obtained by in situ reduction of AuCl4- anions to produce gold nanoparticles within the vesicle walls. (Yellow, hydrophilic PEO; green, pH-responsive DEA residues; blue, hydrolytically self-cross-linkable TMSPMA residues.)     

Glucose-oxidase based self-destructing polymeric vesicles

We have designed oxidation-responsive vesicles from synthetic amphiphilic block copolymers ("polymersomes") of ethylene glycol and propylene sulfide. Thioethers in the hydrophobic poly(propylene sulfide) block are converted into the more hydrophilic sulfoxides and sulfones upon exposure to an oxidative environment, changing the hydrophilic-lipophilic balance of the macroamphiphile and thus inducing its solubilization. Here we sought to explore generation of the oxidative environment and induction of polymersome destabilization through production of hydrogen peroxide by the glucose-oxidase (GOx)/glucose/oxygen system. We studied the encapsulation of GOx within polymersomes, its stability and activity, and glucose-triggered polymersome destabilization. Stimulus-responsive polymersomes may find applications as nanocontainers in sensing devices and as drug delivery systems.     

Fluorescence polarization immunoassay for salinomycin based on monoclonal antibodies

A fluorescence polarization immunoassay(FPIA) for the determination of salinomycin(SAL) was developed by using anti-SAL monoclonal antibodies(mAb).Fluorescein labeled SAL(tracer) was synthesized by the N-hydroxysuccinimide active ester method and purified using thin layer chromatography(TLC).The developed FPIA for SAL had a dynamic range from 0.60 to 2193 ng/mL with an IC50 value of 33.2 ng/mL and a detection limit(LOD) of 0.08 ng/mL.No significant cross-reactivities were observed with other drugs but 67.6%...     

Automated chemiluminescent dual-analyte immunoassay based on resolved immunosensing channels

A novel system of series-wound immunosensing channels (SWIC) was proposed for automated chemiluminescent (CL) dual-analyte immunoassay by immobilizing respectively different capture antibodies on the inner walls of series-wound glass channels. This system could use a single enzyme as label to perform multiplex immunoassay in one fluid way. Using α-fetoprotein (AFP) and carcinoembryonic antigen (CEA) as model analytes, the mixture including AFP, horseradish peroxidase (HRP)-labeled anti-AFP antibody, CEA and HRP-labeled anti-CEA antibody was introduced into the SWIC for carrying out the on-line incubation. Upon injection of CL substrate the CL signals from the two immunosensing channels were conveniently resolved and near-simultaneously collected with the aid of optical shutter. AFP and CEA could be rapidly assayed in the ranges of 1.0-100 and 1.0-80 ng/ml with detection limits of 0.41 and 0.39 ng/ml, respectively. The assay results of clinical serum samples were in an acceptable agreement with the reference values. This designed flow-through immunosensing system based on SWIC provided an automated, reusable, simple, sensitive and low-cost approach for multianalyte immunoassay.     

A highly sensitive fluorescent immunoassay based on avidin-labeled nanocrystals

Nanocrystals of the fluorogenic precursor fluorescein diacetate (FDA) were applied as labels in order to improve on the assay sensitivity achieved in our previous studies. Each FDA nanocrystal can be converted into ∼2.6×10⁶ fluorescein molecules, which is useful for improving immunoassay sensitivity and limits of detection. NeutrAvidin was simply adsorbed onto the surface of the FDA nanocrystals, which were coated with distearoylglycerophosphoethanolamine (DSPE) modified with amino(poly(ethylene glycol))(PEG(2000)-Amine) as an interface for coupling biomolecules. This can be applied to detect different kinds of analytes that are captured by corresponding biotinylated biomolecules in different bioanalytical applications. The applicability of the NeutrAvidin-labeled nanocrystals was demonstrated in an immunoassay using the labeled avidin–biotin technique. Biotinylated antibody and FDA-labeled avidin were applied to the assay sequentially. The performance was compared with the traditional sandwich-type assay for mouse immunoglobulin G detection. Following the immunoreaction, the nanocrystals were released by hydrolysis and dissolution instigated by adding a large volume of organic solvent/sodium hydroxide mixture. The limit of detection was lower (by a factor of 2.5–21) and the sensitivity was (3.5–30-fold) higher than immunoassays using commercial labeling systems (FITC and peroxidase). This study shows that using fluorescent nanocrystals in combination with the avidin–biotin technique can enhance assay sensitivity and provide a lower limit of detection without requiring long incubation times as in enzyme-based labels.