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Biomedical subjects

Marek W Urban

Publications and source records attributed to Marek W Urban.

At least 19 recordsLinked to original sources
PubMed2007

Effect of sequential layer-by-layer surface modifications on the surface energy of plasma-modified poly(dimethylsiloxane).

Surface-initiated grafting of N,N-dimethylacrylamide, styrenesulfonate (SS), and (ar-vinylbenzyl)trimethylammonium chloride (VBTAC) from microwave plasma carboxylated, initiator-functionalized poly(dimethylsiloxane) (PDMS) surfaces was accomplished utilizing reversible addition-fragmentation chain transfer (RAFT) polymerization. Surface spectroscopic attenuated total reflectance (ATR) FT-IR analysis and atomic force microscopy (AFM) measurements were utilized to determine surface grafting and morphological surface features. The VBTAC-grafted PDMS provided a smooth, hydrophilic cationic surface for creating layer-by-layer (LBL) surfaces via alternating deposition of well-defined poly(SS) and poly(VBTAC), also prepared via aqueous RAFT. Comparisons of the ATR FT-IR spectra of the LBL assemblies and those of respective anionic poly(SS) and cationic poly(VBTAC) components confirmed strong electrostatic complexation of a fraction of the sulfonate and quarternary ammonium species in the layers as well as the existence of noncomplexed species. AFM images of surface topology indicated the presence of domains, likely phase-separated segments of the respective homopolymers, as well as interlayer mixing. The employed LBL methodology results in formation of stable, highly hydrophilic surfaces on a PDMS substrate. To our knowledge, this is the first study that illustrates surface functionalization of PDMS using microwave plasma and RAFT polymerization, followed by LBL deposition of polyelectrolytes.

Journal Article↗
PubMed2006

Creating patterned poly(dimethylsiloxane) surfaces with amoxicillin and poly(ethylene glycol).

This paper reports a simple microwave plasma patterning of poly(dimethylsiloxane) (PDMS) surfaces, which is accomplished by allowing selective surface areas to microwave plasma exposure in the presence of gaseous monomer. When maleic anhydride is used for microwave plasma reaction in the presence of physical barrier on the PDMS substrate, the resulting patterned surfaces with chemically bonded maleic anhydride and carboxylic acid groups are generated. In this particular study we attached amoxicillin via ammonolysis under weak base conditions in the presence of a catalyst as well as poly(ethyleneglycol) (PEG). A combination of internal reflection IR imaging (IRIRI) and atomic force microscopy (AFM) revealed that amoxicillin and PEG can be readily reacted on the microwave plasma patterned PDMS surfaces. Surface areas directly exposed to microwave plasmons exhibit the highest reactivity due to higher content of functional groups. These studies also show that molecular weight of PEG has also significant effect on kinetics of surface reactions.

Journal Article↗
PubMed2006

Phospholipid-assisted synthesis of stable F-containing colloidal particles and their film formation.

This letter illustrates for the first time the preparation of p-methyl methacrylate/n-butyl acrylate/heptadecafluorodecyl methacrylate (p-MMA/nBA/FMA) colloidal dispersions containing up to 15% w/w FMA, which is accomplished by the utilization of biologically active phospholipids (PLs) and ionic surfactants. The use of monomer-starved conditions during emulsion polymerization and the utilization of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), sodium dodecyl sulfate (SDS), and phosphoric acid bis(tridecafluoro-octyl) ester ammonium salt (FSP) as surfactants, which function as transfer and dispersing agents, facilitate a suitable environment for the polymerization of p-MMA/nBA/FMA colloidal dispersions that exhibit nonspherical particle morphologies. Such nonspherical particles upon coalescence form phase-separated films with unique surface properties.

Biocompatible Materials↗
PubMed2006

Lectin-recognizable colloidal dispersions stabilized by n-dodecyl beta-D-maltoside: particle-particle and particle-surface interactions.

Recently, we reported that it is possible to utilize sugars as stabilizing agents for colloidal particles. This study shows that when n-dodecyl beta-D-maltoside (DDM) is utilized as a dispersing and stabilizing agent in the synthesis and stabilization of poly[methyl methacrylate-co-(n-butyl acrylate)] (p-MMA/nBA) colloidal particles, stable colloidal dispersions can be formed. Since understanding of sugar-protein interactions have numerous practical and scientific implications, these studies examine DDM-stabilized p-MMA/nBA colloidal particles and their specific binding properties with concanavalin A (Con A). By use of spectroscopic analysis, unique binding characteristics that are a function of DDM concentration, time, and the concentration of Con A are detected. When DDM-stabilized p-MMA/nBA particles are allowed to coalesce, DDM is released from the particle surfaces and, under suitable conditions, selectively stratifies in the areas of the excess of interfacial energy near the film-air (F-A) interface, thus providing sites for attracting Con A via alpha-glucose-OH hydrogen bonding. Consequently, adsorption of Con A at the F-A interfaces occur and the degree of adsorption is controlled by the amount of DDM at the F-A interface.

Adsorption↗
PubMed2005

Cocklebur-shaped colloidal dispersions.

Unique cocklebur-shaped colloidal dispersions were prepared using a combination of a nanoextruder applied to the aqueous solution containing methyl methacrylate (MMA) and n-butyl acrylate (n-BA) with azo-bis-isobutyronitrile (AIBN) or potassium persulfate (KPS) initiators and stabilized by a mixture of sodium dioctyl sulfosuccinate (SDOSS) and 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DCPC) phospholipid. Upon extrusion and heating to 75 degrees C, methyl methacrylate/n-butyl acrylate (MMA/nBA) colloidal particles containing tubules pointing outward were obtained as a result of DCPC phospholipids present at the particle surfaces. The same cocklebur-shaped particles were obtained when classical polymerization was used without a nanoextruder under similar compositional and thermal conditions, giving a particle size of 159 nm. However, when Ca(2+) ions are present during polymerization, cocklebur morphologies are disrupted. Because DCPC tubules undergo a transition at 38 degrees C, such cocklebur morphologies may offer numerous opportunities for devices with stimuli-responsive characteristics.

Letter↗
PubMed2005

Stimuli-responsive surface localized ionic cluster (SLICs) formation from nonspherical colloidal particles.

Structural features of phospholipids provide a unique opportunity for utilizing these amphiphilic species to stabilize the synthesis of colloidal dispersion particles by controlling concentration levels relative to dispersion synthesis components. 1,2-Bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DCPC) phospholipid was utilized as cosurfactant in the synthesis of sodium dioctyl sulfosuccinate (SDOSS) stabilized methyl methacrylate/n-butyl acrylate (MMA/nBA) colloidal dispersions. Aqueous dispersions containing various concentration levels of DCPC result in the formation of cocklebur particle morphologies, and when prepared in the presence of Ca2+ and annealed at various temperatures, stimuli-responsive behaviors of coalesced films were elucidated. The formation of surface localized ionic clusters (SLICs) at the film-air (F-A) and film-substrate (F-S) interfaces is shown to be responsive to concentration levels of DCPC, Ca2+/DCPC ratios, and temperature. These studies show that it is possible to control stratification and mobility to the F-A and F-S interfaces during and after coalescence. Using attenuated total reflectance Fourier transform infrared (ATR-FTIR) and internal reflection infrared imaging (IRIRI) spectroscopies, molecular entities responsible for SLIC formation were determined. These studies also show that stimuli-responsive behaviors during film formation can be controlled by colloidal solution morphologies and synergistic interactions of individual components.

Journal Article↗
PubMed2005

Hollow colloidal particles obtained by nano-extrusion in the presence of phospholipids.

Using nano- and microsize extrusion, a simple synthetic procedure of preparing hollow monodispersed colloidal particles dispersed in an aqueous phase was developed. Hydrophobic styrene monomer containing 2-hydroxy-2-methyl propiophenone photoinitiator was forced into desired diameter membrane channels and stabilized by the hydrophobic regions of a liposome obtained from 1,2-dilauroyl-phosphocholine phospholipid in an aqueous phase. Such moieties exposed to 254-nm UV radiation polymerize monomers in the hydrophobic zone of the liposome, thus resulting in reinforced hollow vesicles. The size of such particles is controlled by the size of the membrane channels in the extruder and may vary from a few nanometers to micrometers, thus allowing the synthesis of monodisperse hollow colloidal spheres.

Letter↗
PubMed2005

Film formation from aqueous polyurethane dispersions of reactive hydrophobic and hydrophilic components; spectroscopic studies and Monte Carlo simulations.

Film formation of waterborne two-component polyurethanes is exceedingly complex due to the heterogeneous nature along with simultaneous progression of several parallel physicochemical processes which include water evaporation, cross-linking reactions, phase separation, and droplet coalescence, to name a few. While internal reflection infrared imaging (IRIRI) spectroscopy clearly facilitates analysis of chemical changes resulting from film formation, the complexity of processes leading to formation of specific surface/interfacial entities is a major experimental challenge. For this reason, we combined a spectrum of surface/interfacial analytical approaches including IRIRI, atomic force microscopy, and attenuated total reflectance Fourier transform infrared spectroscopy with Monte Carlo computer simulations to advance the limited knowledge of how temperature, stoichiometry, concentration levels, and reactivities of individual components affect the development of surface morphologies and compositional gradients across the film thickness. These studies show that in heterogeneous systems having both hydrophobic and hydrophilic components stratification of individual components to the film-air (F-A) interface is ultimately responsible for formation of rough surface topographies. These studies show that simultaneous stratification of hydrophobic components along with water evaporation to the F-A interface results in metastable interfacial layers, leading to surface dewetting. Subsequently, surface roughness is enhanced by higher concentrations of water in the cross-linking film.

Journal Article↗
PubMed2005

Release and formation of surface-localized ionic clusters (SLICs) into phospholipid rafts from colloidal solutions during coalescence.

Stimuli-responsive behavior of phospholipids in the presence of ionic surfactants utilized in synthesis of MMA/nBA colloidal particles was investigated. Utilizing 1-myristoyl-2-hydroxy-sn-glycero-phosphocholine (MHPC) phospholipid, and sodium dioctyl sulfosuccinate (SDOSS) surfactant as dispersing media in H(2)O, narrow unimodal particle size distributions of methyl methacrylate (MMA)/n-butyl acrylate (nBA) copolymers were synthesized. The particle diameters were 154 nm when a SDOSS/MHPC mixture was used and 161 nm using MHPC as the only surface-stabilizing species. When such colloidal dispersions are exposed to 1.7, 3.3, and 6.7 mM aqueous CaCl(2) and KCl electrolyte solutions, surface-localized ionic clusters are generated at the film-air interface that may serve as lipid rafts composed of crystalline phases of MHPC deposited on poly(MMA)/nBA films. These studies illustrate that it is possible to control release and morphology developments of surface phospholipid rafts on artificial surfaces.

Colloids↗
PubMed2004

Photoacoustic FT-IR depth imaging of polymeric surfaces: overcoming IR diffraction limits.

It is well established that the photoacoustic effect based on absorption of electromagnetic radiation into thermal waves allows surface depth profiling. However, limited knowledge exists concerning its spatial resolution. The spiral-stepwise (SSW) approach combined with phase rotational analysis is utilized to determine surface depth profiling of homogeneous and nonhomogeneous multilayered polymeric surfaces in a step-scan photoacoustic FT-IR experiment. In this approach, the thermal wave propagating to the surface is represented as the integral of all heat wave vectors propagating across the sampling depth xn, and the spiral function K'beta(lambda)e(-beta)(lambda)xne(-x)n/mu(th)e(i)(omegat-(xn/mu(th))) represents the amplitude and phase of the heat wave vector propagating to the surface. The SSW approach can be applied to heterogeneous surfaces by representing thermal waves propagating to the surface as the sum of the thermal waves propagating through homogeneous layers that are integrals of all heat vectors from a given sampling depth. The proposed model is tested on multilayered polymeric surfaces and shows that the SSW approach allows semiquantitative surface imaging with the spatial resolution ranging from micrometer to 500 nm levels, and the spatial resolution is a function of the penetration depth.

Acoustics↗
PubMed2004

Reactions of antimicrobial species to imidazole-microwave plasma reacted poly(dimethylsiloxane) surfaces.

Microwave plasma reactions of imidazole, 2-methylimidazole, and 2-ethylimidazole on poly(dimethylsiloxane) (PDMS) surfaces resulted in the formation of species containing conjugated surface domains which can be utilized for further reactions. When imidazole and its derivatives were used, polymerization of imidazole and the formation of C=C and CN conjugated species occurred. However, the extent of reactions for each monomer depends on not only the reaction time but also the molecular structure. For methyl- and ethyl-substituted imidazole, more stable radical species are generated and sustain their excited state in the high-energy plasma environments. Specifically, dehydrogenated 2-methyl, 2-ethylimidazole radicals and (*)N=CR-NH(*) (R = -CH(3), -CH(2)CH(3)) species exhibit higher stability than dehydrogenated imidazole radicals and (*)N=CH-NH(*) species under plasma reaction conditions. Such prepared surfaces are capable of attaching antimicrobial drugs via the Pinner synthesis. These studies show that it is possible to react antimicrobial species such as chloramphenicol, and this promising approach offers numerous applications of microwave plasma reactions in biotechnology. Quantitative analysis of the depth of surface reactions was accomplished by using variable angle ATR FT-IR spectroscopy.

Dimethylpolysiloxanes↗
PubMed2004

Stimuli-responsive surface crystallization of phospholipids from bimodal colloidal particles.

These studies focus on the effect of phospholipids in the presence of ionic surfactants on the behavior of poly(methylmethactrylate/n-butyl acrylate) (p-MMA/nBA) colloidal particles during film formation. With the presence of two surfactants, it is possible to obtain particles that exhibit two distinct particle sizes. The presence of hydrogenated soybean phosphatidylcholine (HSPC) and sodium dioctyl sulfosuccinate (SDOSS), which stabilize these bimodal colloidal dispersions, has a significant effect on the mobility of individual components during coalescence. Specifically, the presence of HSPC inhibits migration of SDOSS to the film-air (F-A) interface. Furthermore, the presence of electrolyte species such as aqueous CaCl2 has a very pronounced effect on film formation. When the Ca2+/HSPC ratio is 0.1/1.0, SDOSS is released to the F-A interface during coalescence. At 2.0/1.0 Ca2+/HSPC, HSPC diffuses to the F-A interface and crystalline domains consisting of HSPC are formed. This stimuli-responsive behavior is confirmed using IRIR imaging that ultimately exhibits different surface morphologies. These studies illustrate for the first time that it is possible to control the release of two different surface-active species during coalescence that form crystalline domains.

Acrylates↗
PubMed2004

Particle morphology as a control of permeation in polymer films obtained from MMA/nBA colloidal dispersions.

The combination of precision-controlled weight loss measurements and spectroscopic surface FT-IR analysis allowed us to identify unique behaviors of poly(methyl methacrylate) (p-MMA). When MMA and n-butyl acrylate (nBA) are polymerized into p-MMA and p-nBA homopolymer blends, MMA/nBA random copolymers, and p-MMA/p-nBA core-shell morphologies, a controlled mobility and stratification of low molecular weight components occurs in films formed from coalesced colloidal dispersions. Due to different affinities toward water, p-MMA and p-nBA are capable of releasing water at different rates, depending upon particle morphological features of initial dispersions. As coalescence progresses, water molecules are released from the high free volume p-nBA particles, whereas p-MMA retains water molecules for the longest time due to its hydrophilic nature. As a result, water losses at extended coalescence times are relatively small for p-MMA. MMA/nBA copolymer and p-MMA/p-nBA blends follow the same trends, although the magnitudes of changes are not as pronounced. The p-MMA/p-nBA core-shell behavior resembles that of p-nBA homopolymer, which is attributed to significantly lower content of the p-MMA component in particles. Annealing of coalesced colloidal films at elevated temperatures causes migration of SDOSS to the F-A interface, but for films containing primarily p-nBA, reverse diffusion back into the bulk is observed. These studies illustrate that the combination of different particle morphologies and temperatures leads to controllable permeation processes through polymeric films.

Journal Article↗
PubMedDate not supplied

Release of phospholipids from colloidal particles to polymeric surfaces.

This study presents a small-scale polymerization of high molecular weight methyl methacrylate/n-butyl acrylate (MMA/n-BA) colloidal particles that are synthesized in an aqueous environment in the presence of phospholipid hydrogenated soybean phosphatidylcholine (HSPC) molecules that also serve as the particle stabilizing agents. When such particles coalesce to form polymeric films, they release phospholipids, which, in turn, form organized structures near the film-air (F-A) interface. Diffusion and mobility of phospholipid molecules are affected not only by their compatibility with colloidal particles but also by electrolyte environments of colloidal dispersions. When Na(+), K(+), and Ca(2+) counterions are added to MMA/n-BA aqueous colloidal dispersions stabilized with HSPC, and such films are coalesced, different degrees of diffusion of HSPC to the F-A interface exist, depending on the counterion, and conformational changes of HSPC result. For example, in the presence of Ca(2+), HSPC molecules collapse entropically to form random surface layers, as opposed to smaller Na(+) and K(+), which force amphiphilic HSPC ends to align preferentially parallel to the film surface. These studies show that it is possible to design stimuli-response colloidal systems triggered by chemical environments of active molecules on colloidal polymer particles.

Colloids↗
PubMedDate not supplied

Stimuli-responsive surfactant/phospholipid stabilized colloidal dispersions and their film formation.

Methyl methacrylate (MMA) and n-butyl acrylate (nBA) were copolymerized into stable colloidal particles in the presence of micelle forming sodium dioctyl sulfosuccinate (SDOSS) and liposome forming 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) in aqueous media that serve as thermodynamically stable loci for lipophilic monomers and nanostructured templates. These studies show for the first time that hollow colloidal particles may coalesce to form polymeric films and the combination of SDOSS and DLPC dispersing agents provides a stimuli-responsive environment during film formation through which individual surface stabilizing components can be driven to the film-air (F-A) or film-substrate (F-S) interface. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) of p-MMA/nBA colloidal dispersions revealed preferential and enhanced mobility of SDOSS and DLPC lipid rafts to the F-A and F-S interfaces in response to thermal, ionic, and enzymatic stimuli.

Colloids↗
PubMedDate not supplied

Phospholipid-stabilized Au-nanoparticles.

This communication outlines a simple two-step approach of modification of 1 nm diameter Au nanoparticles using an aqueous solution of (1,2-dipalmitoyl-sn-glycero-3-phosphothio-ethanol) phospholipid (PL). Transmission electron microscopy as well as particle size analysis show that, as a result of PL reactions with Au particles, the initial Au nanoparticle size increases to 5 nm. Considering the size of the PL and their ability to form liposomes, 5 nm diameter spheres indicate that the PL bilayer was attached to the surface of Au particles and the PL-Au interactions are facilitated by the presence of thiol functionality. The change of surface electronic properties of PL-stabilized Au particles is manifested by the disappearance of the 217 and 290 nm absorbances due to 5d-6sp transitions in Au, which is likely attributed to the presence of S-H functionalities which increase the free electron density of the particle. As a consequence, two surface plasmons resulting from a collective oscillation of electrons in response to UV excitation disappear.

Drug Stability↗
PubMedDate not supplied

Film formation from colloidal dispersions stabilized by sugar derivatives and their controllable release for selective protein adsorption.

Although the use of sugar and sugar derivatives has been documented in polymer research for many years, there are no reports that would utilize these species as polymerization sites of colloidal polymeric particles that, later on, may be released during particle coalescence to form films with surfaces that differentiate protein adsorption. These studies show that, when n-dodecyl-beta-D-maltoside (DDM) is utilized for the synthesis and stabilization of poly[methyl methacrylate-co-(n-butyl acrylate)] (p-MMA/nBA) colloidal particles, upon particle coalescence DDM stratifies near the film-air (F-A) interface. By using attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy and internal reflection infrared imaging (IRIRI), comparative adsorption studies on p-MMA/nBA surfaces exposed to globulin (Glo), fibrinogen (Fib), and bovine serum albumin (BSA) reveal that the presence of DDM selectively inhibits Glo and Fib adsorption, but does not affect BSA. The presence of DDM also enhances the rate of mobility of sodium dioctylsulfosuccinate (SDOSS) resulting from interactions between DDM and SDOSS moieties, and the surface morphologies change as a result of concentration variations of DDM in the colloidal dispersions.

Acrylates↗