Quaternized Poly 4-vinylpyridine Research Articles

A Graftable Quaternary Ammonium Biocidal Polymer Reduces Biofilm Formation and Ensures Biocompatibility of Medical Devices

AbstractA quaternized polyvinylpyridine (Q‐PVP) polymer methanolic solution synthesized in a single step is used to covalently graft titanium surfaces. Q‐PVP is quaternized with varying N+/N ratios. 1 cm2 pure titanium plates are polished and activated. Treated samples are grafted by spin coating or dip‐coating (grafting‐to method). Surfaces are characterized by X‐ray photoelectron spectroscopy, polarization modulation reflection absorption IR spectroscopy, atomic force microscopy, scanning electron microscopy, and surface charge density calculation. Polymer leaching is assessed at 7 days. Biocompatibility is assessed on MC3T3 and L929 cells (MTT‐assay) and SEM. In vitro antibacterial activity is assessed on methicillin‐resistant Staphylococcus aureus (MRSA) at 1 and 24 h (37 °C in brain heart infusion) and at 7 days in a biofilm model. Polymers exceeding 31.3 ± 0.7% quaternization led to bactericidal surfaces. Bactericidal activity increased with surface cationic density. Surface cationic density and biocompatibility are inversely correlated. Polymers with 44.6 ± 1.2% quaternization are antibacterial and biocompatible. High‐density Q‐PVP inhibited MRSA biofilm formation. Q‐PVP is a promising candidate for antibacterial surface modification. Further in vivo studies are required.

Shape transition in ABC triblock copolymer micelles complexed with SDS through quaternized polyvinyl pyridine central block

Polystyrene-b-poly-2-vinylpridine-b-polyethyleneoxide (PS13-PVPy62-PEG47) block copolymer forms spherical core-shell-corona micelles (~50 nm) in water. At acidic pH~3, the central PVPy block gets quaternized (hydrophilic) and gets complexed with sodium dodecyl sulfate (SDS), which strongly interacts with PVPy+ electrostatically as reflected from marked increase in turbidity. The charge neutralization of the central block and accordingly favored hydrophobicity induces interesting structural transitions. Cryo-TEM images for micellar solution of block copolymer in the presence of 10 mM SDS at pH~3 show presence of micelles of ribbon type and threadlike morphology. SANS measurements support the micelle growth and shape transition for the block copolymer aggregates as fitted by core-shell model.

Interactions and Translational Dynamics of Phosphatidylinositol Bisphosphate (PIP2) Lipids in Asymmetric Lipid Bilayers.

Phosphatidylinositol phosphate (PIP) lipids are critical to many cell signaling pathways, in part by acting as molecular beacons that recruit peripheral membrane proteins to specific locations within the plasma membrane. Understanding the biophysics of PIP-protein interactions is critical to developing a chemically detailed model of cell communication. Resolving such interactions is challenging, even in model membrane systems, because of the difficulty in preparing PIP-containing membranes with high fluidity and integrity. Here we report on a simple, vesicle-based protocol for preparing asymmetric supported lipid bilayers in which fluorescent PIP lipid analogues are found only on the top leaflet of the supported membrane facing the bulk solution. With this asymmetric distribution of lipids between the leaflets, the fluorescent signal from the PIP lipid analogue reports directly on interactions between the peripheral molecules and the top leaflet of the membrane. Asymmetric PIP-containing bilayers are an ideal platform to investigate the interaction of PIP with peripheral membrane proteins using fluorescence-based imaging approaches. We demonstrate their usefulness here with a combined fluorescence correlation spectroscopy and single particle tracking study of the interaction between PIP2 lipids and a polycationic polymer, quaternized polyvinylpyridine (QPVP). With this approach we are able to quantify the microscopic features of the mobility coupling between PIP2 lipids and polybasic QPVP. With single particle tracking we observe individual PIP2 lipids switch from Brownian to intermittent motion as they become transiently trapped by QPVP.

Single Molecule Diffusion of Phosphatidylinositol Bisphosphate (PIP2) Lipids on Asymmetric Lipid Bilayers under the Influence of Polycationic Macromolecules

Proteins binding with PIP2 lipids in the plasma membrane initiate and regulate many cell signaling events. Previous research suggests that proteins interact with PIP2 lipids through electrostatic interactions between polycationic protein motifs and anionic lipid head groups, leading to potential sequestration of multiple PIP2 lipids. The sequestration of PIP2 lipids will cause a change in the lipid mobility and the spatial distribution of PIP2 in the plasma membrane. We set out to understand the molecular structure and dynamics of the protein-PIP2 interface at single molecule level. In this study, a polycationic polymer, quaternized polyvinylpyridine (QPVP), and Myristoylated alanine-rich C-kinase substrate (MARCKS) peptide were chosen to mimic the membrane binding proteins. The behavior of PIP2 lipids in response to QPVP and MARCKS binding was evaluated by a time-resolved fluorescence technique, pulsed interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS), along with single particle tracking (SPT) of individual PIP2 molecules. The trajectories of individual PIP2 lipids indicate intermittent-type diffusion in which confined small steps are separated by steps typical of free Brownian motion. The confined movement is a result of stalling during binding events with QPVP molecules and reveals the microscopic details of the PIP2 lipid mobility decrease observed previously by FCCS measurements. FCCS measurements also indicate a collective diffusion of a cationic peptide, MARCKS, and PIP2, suggesting the existence of a large peptide-lipid assembly formed through electrostatic sequestration of PIP2 lipids by MARCKS. SPT analysis shows the diffusive behavior the peptide-lipid assemblies. The results suggest that PIP2 diffusion is significantly altered upon binding to polycationic molecules and is the first direct experimental evidence of stable lipid-peptide complexes formed through electrostatic interactions between MARCKS peptide and PIP2 lipid.

Tuning the Mobility Coupling of Quaternized Polyvinylpyridine and Anionic Phospholipids in Supported Lipid Bilayers

Binding of biomacromolecules to anionic lipids in the plasma membrane is a common motif in many cell signaling pathways. Previous work has shown that macromolecules with cationic sequences can form nanodomains with sequestered anionic lipids, which alters the lateral distribution and mobility of the membrane lipids. Such sequestration is believed to result from the formation of a lipid-macromolecule complex. To date, however, the molecular structure and dynamics of the lipid-polymer interface are poorly understood. We have investigated the behavior of polycationic quaternized polyvinylpyridine (QPVP) on supported lipid bilayers doped with phosphatidylserine (PS) or phosphatidylinositol phosphate (PIP) lipids using time-resolved fluorescence microscopy, including pulsed interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). PIE-FCCS is a dual-color fluorescence spectroscopy that translates fluctuations in fluorescence signal into a measurement of diffusion and colocalization. By labeling the polymer and lipids, we investigated the adsorption-induced translational mobility of lipids and systematically studied the influence of lipid charge density and solution ionic strength. Our results show that alteration of anionic lipid lateral mobility is dependent on the net charge of the lipid headgroup and is modulated by the ionic strength of the solution, indicating that electrostatic interactions drive the decrease in lateral mobility of anionic lipids by adsorbed QPVP. At physiological salt concentration we observe that the lipid lateral mobility is weakly influenced by QPVP and that there is no evidence of stable lipid-polymer complexes.

PIE-FCCS Study of the Effects of Polycationic Macromolecules on Phosphatidylserine and Phosphatidylinositol Phosphate Lipid Mobility

The interaction between proteins and anionic lipids in the plasma membrane is a common motif in cell communication at the plasma membrane. Such interactions can gate membrane protein function and have also been proposed to sequester membrane lipids during quiescent phases of signaling. To date, however, the molecular structure and dynamics of the lipid-protein interface is poorly understood. To isolate these interactions in a biophysical assay, we have investigated the behavior of a polycationic polymer, quaternized polyvinylpyridine (QPVP), on supported lipid bilayers doped with tail-labeled phosphatidylserine (PS) or phosphatidylinositol phosphate (PIP) lipids. To measure the mobility and association of the lipid and adsorbed polymer, we use a time-resolved fluorescence technique, pulsed interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). PIE-FCCS is a dual-color fluorescence spectroscopy that translates fluctuations in fluorescence signal into a measurement of diffusion and co-localization. With PIE-FCCS we have investigated the polymer adsorption-dependent translational mobility of the lipids and systematically studied the influence of lipid head-group charge and solvent ionic strength. Our results indicate that alteration of anionic lipid lateral mobility is dependent on the net charge of the lipid head group and is significantly screened by the ionic strength of the solution. At physiological salt concentration we observe that the lipid lateral mobility is nearly unaffected by mobile, adsorbed polymers and that there is no evidence of stable lipid-polymer complexes.

Uptake of Organic Pollutants by Silica−Polycation-Immobilized Micelles for Groundwater Remediation

Interest has grown in designing new materials for groundwater treatment via "permeable reactive barriers". In the present case, a model siliceous surface, controlled pore glass (CPG), was treated with a polycation (quaternized polyvinyl pyridine, QPVP) which immobilizes anionic/nonionic mixed micelles, in order to solubilize a variety of hydrophobic pollutants. Polymer adsorption on CPG showed atypically slow kinetics and linear adsorption isotherms, which may be a consequence of the substrate porosity. The highest toluene solubilization efficiency was achieved for the silica-polycation-immobilized micelles (SPIM) with the highest polymer loading and lowest micelle binding, a result discussed in terms of the configuration of the bound polymer and the corresponding state of the bound micelles. The ability of SPIM to treat simultaneously a wide range of pollutants and reduce their concentration in solution by 20-90% was demonstrated. Optimization of SPIM systems for remediation calls for a better understanding of both the local environment of the bound micelles and their intrinsic affinities for different hydrophobic pollutants.

Nanorheology of Aqueous Polyethylene Glycol (PEG)

Static and dynamic surface interactions in deionized water were studied between poly(ethylene glycol) (PEG) and an opposed layer of either the same PEG or a highly charged cationic polymer, quaternized polyvinylpyridine (QPVP). The PEG, molecular weight 5000 g mol-1, was end-attached to hydrophobized mica by hydrophobic-driven adsorption of the lipid portion (distearoyl-phosphatidylethanolamine) of PEG-lipid diblock copolymers. The QPVP homopolymer, 98% quaternized and molecular weight 39,000 g mol-1, was allowed to adsorb statistically onto mica. Within the scatter of the data the force−distance curves could be fit equally well by the Alexander-de Gennes expression for brush-brush interactions or by exponential decay (decay length 4 nm). However, at every film thickness, the shear modulus of the PEG-PEG interface was less than that of PEG-QPVP by an order of magnitude. When the layers were compressed strongly, they remained demonstrably fluid, even in the most strongly compressed state, in the sense that...

Local Environment of Surface-Polyelectrolyte-Bound DNA Oligomers

AbstractTwo-photon time-resolved fluorescence anisotropy methods were used to study the dynamical environment when fluorescent-labelled DNA oligomers (labelled with FAM, 6-fluorescein-6-carboxamido hexanoate) formed surface complexes with quaternized polyvinylpyridine (QPVP) cationic layers on a glass surface. We compared the anisotropy decay of DNA in bulk aqueous solution, DNA adsorbed onto QPVP, and QPVP-DNA-QPVP sandwich structures. When DNA was adsorbed onto QPVP, its anisotropy decay was dramatically retarded compared to the bulk, which means it had very slow rotational motion on the surface. Motions slowed down with increasing salt concentration up to a level of 0.1 M NaCl, but mobility began to increase at still higher salt concentration owing to detachment from the surface-immobilizing QPVP layers.

Adsorption of human serum albumin: Dependence on molecular architecture of the oppositely charged surface

We contrast the adsorption of human serum albumin (HSA) onto two solid substrates previously primed with the same polyelectrolyte of net opposite charge to form one of two alternative structures: randomly adsorbed polymer and the “brush” configuration. These structures were formed either by the adsorption of quaternized poly-4-vinylpyridine (QPVP) or by end-grafting QPVP chains of the same chemical makeup and the same molecular weight to surfaces onto which QPVP segments did not adsorb. The adsorption of HSA was quantified by using Fourier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR). The two substrates showed striking differences with regard to HSA adsorption. First, the brush substrate induced lesser perturbations in the secondary structure of the adsorbed HSA, reflecting easier conformational adjustment for longer free segments of polyelectrolyte upon binding with the protein. Second, the penetration of HSA into the brush substrate was kinetically retarded relative to the randomly adsorbed polymer, probably due to both pore size restriction and electrostatic sticking between charged groups of HSA and QPVP molecules. Third, release of HSA from the adsorbed layer, as the ionic strength was increased from a low level up to the high level of 1 M NaCl, was largely inhibited for the brush substrate, but occurred easily and rapidly for the substrate with statistically adsorbed QPVP chains. Finally, even after addition of a strong polymeric adsorption competitor (sodium polystyrene sulfonate), HSA remained trapped within a brush substrate though it desorbed slowly from the preadsorbed QPVP layer. This method to produce irreversible trapping of the protein within a brush substrate without major conformational change may find application in biosensor design.

ADSORPTION OF COLLOIDAL MATERIALS ON POLYMER SURFACES

ABSTRACT Polypropylene surfaces were rendered cationic by hydrophobic implantation and by grafting a quaternized polyvinyl pyridine onto a plasma treated surface. The polypropylene surface with the grafted polymer showed a strong adsorption of an anionic surfactant, corresponding to about ten monomolecular layers. High concentration of electrolyte caused a reduction of the adsorption at low concentrations of surfactant.