Electrochemical and Raman studies of the biointeraction between Escherichia coli and mannose in polydiacetylene derivative supported on the self-assembled monolayers of octadecanethiol on a gold electrode

Detection of bacteria using glyco-dendronized polylysine prepared by continuous flow photofunctionalization

Biocompatible glyco-dendronized poly-l-lysine (PLL) polymers carry either three or nine mannose- or galactose-bearing dendrons that selectively bind, and thus can be used to detect, bacteria. Central to the synthesis of glyco-dendronized polymers was the development of a continuous flow [2 + 2] photocycloaddition reaction to connect the dendrons and PLL. Glycodendronized polymers cluster bacteria by binding to cell-surface carbohydrate receptors and thereby result in an easy read-out using microscopic analyses.

On the Structure and Desorption Dynamics of DNA Bases Adsorbed on Gold: A Temperature-Programmed Study

The structure and desorption dynamics of mono- and multilayer samples of adenine, cytosine, guanine, and thymine on polycrystalline gold thin films are studied using temperature-programmed desorption-infrared reflection absorption spectroscopy (TPD-IRAS) and temperature-programmed desorption-mass spectroscopy (TPD-MS). It is shown that the pyrimidines, adenine and guanine, adsorb to gold in a complex manner and that both adhesive (adenine) and cohesive (guanine) interactions contribute the apparent binding energies to the substrate surface. Adenine displays at least two adsorption sites, including a high-energy site (210 degrees C, approximately 136 kJ/mol), wherein the molecule coordinates to the gold substrate via the NH2 group in an sp3-like, strongly perturbed, nonplanar configuration. The purines, cytosine and thymine, display a less complicated adsorption/desorption behavior. The desorption energy for cytosine (160 degrees C, approximately 122 kJ/mol) is similar to those obtained for adenine and guanine, but desorption occurs from a single site of dispersed, nonaggregated cytosine. Thymine desorbs also from a single site but at a significantly lower energy (100 degrees C, approximately 104 kJ/mol). Infrared data reveal that the monolayer architectures discussed herein are structurally very different from those observed for the bases in the bulk crystalline state. It is also evident that both pyrimidines and purines adsorb on gold with the plane of the molecule in a nonparallel orientation with respect to the substrate surface. The results of this work are discussed in the context of improving the understanding of the design of capturing oligonucleotides or DNA strands for bioanalytical applications, in particular, for gold nanoparticle-based assays.

Biosensor signal amplification of vesicles functionalized with glycolipid for colorimetric detection of Escherichia coli

A supramolecular assembly of phospholipid-polymerized diacetylene vesicles functionalized with glycolipid can provide a molecular recognition function. The Escherichia coli-glycolipid binding event leads to a visible color change from blue to red, readily seen with the naked eye and quantified by absorption spectroscopy. The biosensor signal is amplified through a suitable increase of phospholipid content in the mixed lipid vesicles and pH of aqueous solutions.

Functionalized polydiacetylene-glycolipid vesicles interacted with Escherichia coli under the TiO2 colloid

The interaction of the conjugated system between functionalized polydiacetylene-glycolipid vesicles and Escherichia coli was investigated under the bactericidal effect of TiO(2) colloid. With various pre-incubation and irradiation time, controllable bacteria quantity in the presence of TiO(2) colloid was obtained in real time. UV-visible and Raman spectra were utilized to monitor and evaluate the structural transition of bacteria-polydiacetylene-glycolipid vesicles conjugated system under the different conditions, which supplied the detailed information of the transform of the polydiacetylene backbone in real time. Thus controllable conjugated bio-interaction between two bio-interfaces was obtained through the introduction of the third factor and monitored in real time. This would be great aid in fundamental understanding more complex interfaces in the biological environment and would be applicable to the biomedical and biophysical fields.

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.

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.

Enhanced affinochromism of polydiacetylene monolayer in response to bacteria by incorporating CdS nano-crystallites

By incorporating bio-specific receptors, such as p-10,12-pentacosadiyne-1-N-(3,6,9-trioxaundecylamide)-alpha-D-mannopyranoside (MPDA), into 10,12-pentacosadiyonic acid (PDA) monolayer, the MPDA/PDA monolayer underwent affinochromatic transition in response to the bacteria binding to the receptor. Here, we described a new method to study the membrane/macromolececular interaction between Escherichia coli (E. coli) and mannose and its relative affinochromism by modifying MPDA/PDA with CdS nano-crystallites (MPDA/PDA-CdS). CdS not only triggered the strong tropism of the bacteria but also reduced the rigidity of the MPDA/PDA backbone, resulting in the enhanced affinochromism. This discovery might be of significance in basic biophysical studies of membrane/macromolececular and designing novel biosensor.