Precise Synthesis and Thin Film Self-Assembly of PLLA--PS Bottlebrush Block Copolymers.

The ability of bottlebrush block copolymers (BBCPs) to self-assemble into ordered large periodic structures could greatly expand the scope of photonic and membrane technologies. In this paper, we describe a two-step synthesis of poly(l-lactide)--polystyrene (PLLA--PS) BBCPs and their rapid thin-film self-assembly. PLLA chains were grown from -5-norbornene-2-methanol via ring-opening polymerization (ROP) of l-lactide to produce norbornene-terminated PLLA.

Hierarchical honeycomb-structured films by directed self-assembly in "breath figure" templating of ionizable "clicked" PH3T-b-PMMA diblock copolymers: an ionic group/counter-ion effect on porous polymer film morphology.

The self-assembly of 1,2,3-triazole and ionic 1,2,3-triazolium "clicked" poly(3-hexylthiophene)-b-poly(methylmethacrylate) (P3HT-b-PMMA) rod-coil diblock copolymers was used to fabricate honeycomb-patterned porous films via "breath figure" templating. The surface and inner morphologies of the honeycomb films can be both controlled by either ionizing the 1,2,3-triazole linker or changing the counter-ion nature.

Photophysics and light-activated biocidal activity of visible-light-absorbing conjugated oligomers.

The photophysical properties of three cationic π-conjugated oligomers were correlated with their visible light activated biocidal activity vs S. aureus. The oligomers contain three arylene units (terthiophene, 4a; thiophene-benzotriazole-thiophene, 4b; thiophene-benzothiadiazole-thiophene, 4c) capped on each end by cationic -(CH2)3NMe3(+) groups.

Efficacy of end-only-functionalized oligo(arylene-ethynylene)s in killing bacterial biofilms.

Cationic end-only-functionalized oligo(arylene-ethynylene)s (EO-OPEs) have recently been found to be broad-spectrum and effective antimicrobial agents because of their unique structure and optical properties. In this study, we investigated their potential use for preventing and reducing Escherichia coli (E. coli) biofilms.

Light and dark-activated biocidal activity of conjugated polyelectrolytes.

This Spotlight on Applications provides an overview of a research program that has focused on the development and mechanistic study of cationic conjugated polyelectrolytes (CPEs) that function as light- and dark-active biocidal agents. Investigation has centered on poly-(phenylene ethynylene) (PPE) type conjugated polymers that are functionalized with cationic quaternary ammonium solubilizing groups. These polymers are found to interact strongly with Gram-positive and Gram-negative bacteria, and upon illumination with near-UV and visible light act to rapidly kill the bacteria.

Effect of polymer chain length on membrane perturbation activity of cationic phenylene ethynylene oligomers and polymers.

The interactions of poly(phenylene ethynylene)- (PPE-) based cationic conjugated polyelectrolytes (CPEs) and oligo(phenylene ethynylene)s (OPEs) with different model lipid membrane systems were investigated to gain insight into the relationship between molecular structure and membrane perturbation ability. The CPE and OPE compounds exhibit broad-spectrum antimicrobial activity, and cell walls and membranes are believed to be their main targets. To better understand how the size, in terms of the number of repeat units, of the CPEs and OPEs affects their membrane disruption activities, a series of PPE-based CPEs and OPEs were synthesized and studied.

Antibacterial activity of conjugated polyelectrolytes with variable chain lengths.

Cationic poly(phenylene ethynylene)- (PPE-) based conjugated polyelectrolytes (CPEs) with six different chain lengths ranging in degree of polymerization from ∼7 to ∼49 were synthesized from organic-soluble precursor polymers. The molecular weight of the precursor polymers was controlled by the amount of a monofunctional "end-capping" agent added to the polymerization reaction. Cationic CPEs were prepared by quaternization of amine groups to tetraalkylammonium groups.

Conjugated-polyelectrolyte-grafted cotton fibers act as "micro flypaper" for the removal and destruction of bacteria.

We demonstrate herein a method for chemically modifying cotton fibers and cotton-containing fabric with a light-activated, cationic phenylene-ethynylene (PPE-DABCO) conjugated polyelectrolyte biocide. When challenged with Pseudomonas aeruginosa and Bacillus atropheaus vegetative cells from liquid suspension, light-activated PPE-DABCO effects 1.2 and 8 log, respectively, losses in viability of the exposed bacteria.

pH-dependent optical properties of a poly(phenylene ethynylene) conjugated polyampholyte.

A poly(phenylene ethynylene) conjugated polymer (PPE-NMe(3)(+)-COO(-)) containing tetraalkylammonium groups and carboxylate groups has been synthesized by Sonogashira coupling. Due to the presence of the strong cationic and weak anionic pendant units, the polymer undergoes a pH-induced transition from cationic polyelectrolyte to polyampholyte due to deprotonation of the carboxylic acid units in basic solution. Studies of the pH dependence of the polymers' optical properties reveal changes in absorption oscillator strength and fluorescence quantum efficiency that are triggered by the transition from cationic polyelectrolyte to polyampholyte nature.

Intercalation-FRET biosensor with a helical conjugated polyelectrolyte.

A biotin-tetramethylrhodamine (biotin-TMR) quencher-ligand interacts with a (phenylene-ethynylene) based helical conjugated polyelectrolyte (poly-1) via intercalation of the TMR unit into the helix. The interaction is signaled by efficient fluorescence resonance energy transfer (FRET) from the polymer to the TMR chromophore. Avidin addition to the poly-1/biotin-TMR intercalation complex does not interrupt FRET, instead resulting in the formation of avidin-biotin "cross-links".

Membrane perturbation activity of cationic phenylene ethynylene oligomers and polymers: selectivity against model bacterial and mammalian membranes.

Poly(phenylene ethyneylene) (PPE)-based cationic conjugated polyelectrolytes (CPEs) and cationic phenylene ethynylene oligomers (OPEs) exhibit broad-spectrum antimicrobial activity, and their main target is believed to be the cell membrane. To understand better how these antimicrobial molecules interact with membranes, a series of PPE-based CPEs and OPEs with different side chains were studied. Large unilamellar vesicles with lipid compositions mimicking those of mammalian or bacterial membranes were used as model membranes.

Insight into the mechanism of antimicrobial poly(phenylene ethynylene) polyelectrolytes: interactions with phosphatidylglycerol lipid membranes.

The interactions of antimicrobial poly(phenylene ethynylene) (PPE)-based cationic conjugated polyelectrolytes (CPEs) with lipid membranes were investigated to gain insight into the mechanism of their biocidal activity. Three model membrane systems comprising negatively charged phosphatidylglycerol (PG) lipids were used to mimic the bacterial cell membrane, including unilamellar lipid vesicles in aqueous solution, lipid bilayer coated silica microspheres, and lipid monolayers at the air-water interface. Two PPE CPEs, one containing a thiophene moiety on the PPE repeat unit and the second containing a diazabicyclooctane (DABCO) moiety on the pendant side chain, were chosen, since the former exhibits distinct dark biocidal activity and the latter shows strong light-activated antimicrobial activity but little dark biocidal activity.

Light and dark biocidal activity of cationic poly(arylene ethynylene) conjugated polyelectrolytes.

In this paper we report a study of cationic poly(arylene ethynylene) conjugated polyelectrolytes. The objective of the study was to compare the behavior of a polymer where a thiophene has replaced a phenyl ring in poly(phenylene ethynylene) polycations (PPE) previously investigated. Properties of solution phase and physisorbed suspensions of the polymer on microspheres were investigated.

Conjugated polyelectrolyte supported bead based assays for phospholipase A2 activity.

A fluorescence based assay for human serum-derived phospholipase activity has been developed in which cationic conjugated polyelectrolytes are supported on silica microspheres. The polymer-coated beads are overcoated with an anionic phospholipid (1,2-dimyristoyl-sn-glycero-3-[phospho- rac-(1-glycerol)) (DMPG) to provide "lipobeads" that serve as a sensor for PLA2. The lipid serves a dual role as a substrate for PLA2 and an agent to attenuate quenching of the polymer fluorescence by the external electron transfer quencher 9,10-anthraquinone-2,6-disulfonic acid (AQS).

Light-induced biocidal action of conjugated polyelectrolytes supported on colloids.

A series of water soluble, cationic conjugated polyelectrolytes (CPEs) with backbones based on a poly(phenylene ethynylene) repeat unit structure and tetraakylammonium side groups exhibit a profound light-induced biocidal effect. The present study examines the biocidal activity of the CPEs, correlating this activity with the photophysical properties of the polymers. The photophysical properties of the CPEs are studied in solution, and the results demonstrate that direct excitation produces a triplet excited-state in moderate yield, and the triplet is shown to be effective at sensitizing the production of singlet oxygen.

Parental artistic drawings of the fetus before and after 3-/4-dimensional ultrasonography.

Objective: The purpose of this study was to assess the impact of 3-/4-dimensional ultrasonography (3D/4DUS) on parental impressions of their fetus using preexamination and postexamination parental drawings.

Methods: One hundred one parents (32 male and 69 female) were asked to draw pictures of their fetus immediately before and after undergoing 3D/4DUS. A drawing assessment instrument was used to evaluate the fetal anatomy by 4 reviewers.

Preexamination and postexamination assessment of parental-fetal bonding in patients undergoing 3-/4-dimensional obstetric ultrasonography.

Objective: The purpose of this study was to determine whether there is a change in parental bonding and couples' attitudes toward their fetus after undergoing 3-/4-dimensional ultrasonography (3D/4DUS).

Methods: Sixty-five fathers and 124 mothers were asked to fill out a maternal-fetal attachment questionnaire relating to how they felt about their fetus before and after 3D/4DUS and to mark on a line indicating their feelings about the ultrasonography experience. In addition, 135 parents filled out a positive feelings questionnaire consisting of 5 sections assessing their feelings about the fetus.

Isolated echogenic foci in the left upper quadrant of the fetal abdomen: are they significant?

Objectives: To evaluate fetuses with echogenic foci in the left upper quadrant of the abdomen by sonographic examination.

Methods: Between November 2000 and October 2001, we prospectively assessed fetuses with echogenic foci in the abdominal left upper quadrant on routine prenatal sonography. The location, number, and size of the foci were analyzed, and in utero and postpartum follow-up scans were performed.

Gender differences in the corpus callosum of neonates.

The gender difference of corpus callosum is a long standing controversy. Some investigators have reported that adult females have a more bulbous splenium and larger area relative to brain size, but others failed to replicate this. Few studies have reported on sexual dimorphism during development.