Adhesion of Escherichia coli on to a series of poly(methacrylates) differing in charge and hydrophobicity.

The adhesion of three Escherichia coli strains on to six poly(methacrylates) differing in hydrophobicity and surface charge was measured as a function of time under laminar flow conditions. Polymers used were poly(methy) methacrylate) (PMMA), poly(hydroxyethy) methacrylate) (PHEMA) and copolymers of MMA or HEMA with either 15% methacrylic acid (MAA) or 15% trimethylaminoethyl methacrylate-HCl salt (TMAEMA-CI). Bacterial and polymer surfaces were characterized by means of water contact angles and zeta potentials. Both the sessile drop contact angles and the zeta potentials of the bacterial surfaces were significantly different. No significant differences in the sessile drop contact angles of the polymer surfaces were observed. Using the Wilhelmy plate technique large contact angle hysteresis was observed for the different polymer surfaces. Surfaces of copolymers with MAA had more negative zeta potentials than those of the corresponding homopolymers. Surfaces of copolymers with TMAEMA-CI had positive zeta potentials. The highest numbers of adherent bacteria were found on materials with positive zeta potentials, irrespective of the bacterial strain used. Bacterial adhesion on to copolymers with MAA was less than on to the corresponding homopolymers. Bacterial equilibrium adhesion values correlate with the zeta potentials of the polymer surfaces (r > 0.85). On substrates with less negative zeta potentials high numbers of adhered bacteria were observed. Additionally, the equilibrium bacterial adhesion values could be related with receding contact angles of polymer surfaces with negative zeta potentials (r > 0.86). High equilibrium adhesion values were obtained for polymers with high contact angles. No correlation between the zeta potentials and contact angles of the bacteria with the adhesion values was found.     

Studies on blood compatibility of terpolymers composed of methyl methacrylate,methoxypolyethyleneglycol methacrylate,and dimethylsiloxane methacrylate

Terpolymers composed of methyl methacrylate (MMA), polydimethylsiloxane methacrylate (PDMSMA), and methoxypolyethyleneglycol methacrylate (MPEGMA), having different compositions were synthesized. Platelets were not adsorbed onto terpolymer surfaces composed of 50 wt% MMA, 25 wt% PDMSMA and 25 wt% MPEGMA, while on terpolymers with the other compositions, platelet adsorption and fibrin clot were observed. It was shown that PDMS segment was predominant on these terpolymer surfaces via XPS. Receding contact angles of terpolymers, on which no platelet was observed, showed intermediate values between PDMS- and MPEG-rich surfaces. It was suggested that these terpolymers had blood compatibility.     

Growth of uropathogenic Escherichia coli strains at solid surfaces

The adhesion and growth of two catheter-associated (O2K2 and O83K?) and two non catheter-associated (O111K58 and 0157K-) uropathogenic Escherichia coli strains on glass, poly(methyl methacrylate) (PMMA), a negatively charged copolymer of MMA and methacrylic acid (MAA) and a positively charged copolymer of MMA and trimethylaminoethyl methacrylate chloride (TMAEMA-Cl) were studied. The solid surfaces were placed in a parallel plate perfusion system. After preadhesion of the bacteria onto the surfaces, growth was initiated by perfusing the system with MacConkey broth. Growth was measured by counting adherent bacteria as a function of time. Bacterial strains were characterized by means of water contact angle, microbial adhesion to hydrocarbon (MATH), anion exchange resin retention (ARR) and zeta potential measurements. Solid surfaces were characterized by means of water contact angle and zeta potential measurements. The catheter-associated strains had significantly higher water contact angles, zeta potentials and ARR values than the non catheter-associated strains. Non catheter-associated strains did not grow at the surfaces used. Catheter-associated strains did not grow at the positively charged surface but exhibited growth at the other surfaces. Strains grew more rapidly at surfaces with a relatively high negative zeta potential and a low water contact angle than at surfaces with a relatively low negative zeta potential and a high water contact angle. The growth of strain O2K2 on glass was significantly reduced when urine instead of MacConkey broth was used as perfusion medium.     

Growth of uropathogenic Escherichia coli strains at solid surfaces.

The adhesion and growth of two catheter-associated (O2K2 and O83K?) and two non catheter-associated (O111K58 and O157K-) uropathogenic Escherichia coli strains on glass, poly(methyl methacrylate) (PMMA), a negatively charged copolymer of MMA and methacrylic acid (MAA) and a positively charged copolymer of MMA and trimethylaminoethyl methacrylate chloride (TMAEMA-Cl) were studied. The solid surfaces were placed in a parallel plate perfusion system. After preadhesion of the bacteria onto the surfaces, growth was initiated by perfusing the system with MacConkey broth. Growth was measured by counting adherent bacteria as a function of time. Bacterial strains were characterized by means of water contact angle, microbial adhesion to hydrocarbon (MATH), anion exchange resin retention (ARR) and zeta potential measurements. Solid surfaces were characterized by means of water contact angle and zeta potential measurements. The catheter-associated strains had significantly higher water contact angles, zeta potentials and ARR values than the non catheter-associated strains. Non catheter-associated strains did not grow at the surfaces used. Catheter-associated strains did not grow at the positively charged surface but exhibited growth at the other surfaces. Strains grew more rapidly at surfaces with a relatively high negative zeta potential and a low water contact angle than at surfaces with a relatively low negative zeta potential and a high water contact angle. The growth of strain O2K2 on glass was significantly reduced when urine instead of MacConkey broth was used as perfusion medium.     

Adhesion of Escherichia coli on to a series of poly(methacrylates) differing in charge and hydrophobicity

The adhesion of three Escherichia coli strains on to six poly(methacrylates) differing in hydrophobicity and surface charge was measured as a function of time under laminar flow conditions. Polymers used were poly(methy) methacrylate) (PMMA), poly(hydroxyethy) methacrylate) (PHEMA) and copolymers of MMA or HEMA with either 15% methacrylic acid (MAA) or 15% trimethylaminoethyl methacrylate-HCl salt (TMAEMA-CI). Bacterial and polymer surfaces were characterized by means of water contact angles and zeta potentials. Both the sessile drop contact angles and the zeta potentials of the bacterial surfaces were significantly different. No significant differences in the sessile drop contact angles of the polymer surfaces were observed. Using the Wilhelmy plate technique large contact angle hysteresis was observed for the different polymer surfaces. Surfaces of copolymers with MAA had more negative zeta potentials than those of the corresponding homopolymers. Surfaces of copolymers with TMAEMA-CI had positive zeta potentials. The highest numbers of adherent bacteria were found on materials with positive zeta potentials, irrespective of the bacterial strain used. Bacterial adhesion on to copolymers with MAA was less than on to the corresponding homopolymers. Bacterial equilibrium adhesion values correlate with the zeta potentials of the polymer surfaces (r > 0.85). On substrates with less negative zeta potentials high numbers of adhered bacteria were observed. Additionally, the equilibrium bacterial adhesion values could be related with receding contact angles of polymer surfaces with negative zeta potentials (r > 0.86). High equilibrium adhesion values were obtained for polymers with high contact angles. No correlation between the zeta potentials and contact angles of the bacteria with the adhesion values was found.     

Water absorption and surface properties of novel poly(ethylmethacrylate) polymer systems for use in bone and cartilage repair

The surface and bulk properties of novel methacrylate polymers prepared by gelling poly(ethyl methacrylate) (PEMA) powder with different ratios of tetrahydrofurfuryl methacrylate (THFMA) and hydroxyethyl methacrylate (HEMA) monomers were investigated. The water adsorption and desorption characteristics of these polymers were measured in water and phosphate buffered saline (PBS). The desorption diffusion coefficients were higher than the adsorption coefficients in both water and PBS. Linear relationships between the equilibrium mass of water taken up and the mass of water desorbed with the concentration of HEMA in the polymer were established. Polymer surfaces were analysed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Surface features varied with polymer composition; during hydration only selective areas of the surface hydrated indicating a heterogeneous surface. Contact angle data showed no trend between the different polymers indicating that contact angles are not an acceptable method of assessing hydrophobicity/wettability of a material which does not have a homogeneous surface. The effect of these bulk and surface characteristics on biological interactions were examined using bovine chondrocytes and human osteoblast (HOB) cell cultures. Cell attachment decreased when HEMA was present in the copolymer.     

Polyethylene/hydrophilic polymer blends for biomedical applications

Polyethylene blends with poly(2-hydroxyethyl methacrylate) [poly(HEMA)] or poly(2,3-dihydroxypropyl methacrylate) [poly(DHPMA)] were prepared by swelling polyethylene with HEMA or 2,3-epoxypropyl methacrylate (EPMA) and by polymerization of the respective monomers. Poly(EPMA) in blends was hydrolysed to poly(DHPMA) with acetic acid. The blends had similar surface and bulk compositions. Swelling with water and surface wettability were proportional to the content of the hydrophilic component; at the same content the polyethylene/poly(DHPMA) blends appeared more hydrophilic than those of polyethylene/poly(HEMA). Thrombus formation in contact with blood examined ex vivo and in vivo was considerably slower on the blends than on unmodified polyethylene. The tests indicated optima in composition; the best biological response was achieved with the blends containing about 14% poly(HEMA) or 16% poly(DHPMA).     

Crosslinkable coatings from phosphorylcholine-based polymers

2-Methacryloyloxyethyl phosphorylcholine (MPC) was synthesised and then used in the preparation of crosslinked polymer membranes with lauryl methacrylate, hydroxypropyl methacrylate and trimethoxysilylpropyl methacrylate (crosslinker) comonomers. Some physical aspects of the membrane properties were evaluated in order to establish the basis for the synthesis of a series of post-crosslinkable polymers. These materials were made by copolymerisation of the constituent monomers via a free radical method, and characterised using NMR, FT-IR, viscometry and elemental analysis. The optimum crosslink density and conditions required for curing coatings of these polymers were investigated using atomic force microscopy (AFM) and showed the inclusion of 5 mol% silyl crosslinking agent to be ideal. A nanoindentation technique was employed to determine if the coating developed elasticity upon crosslinking. The biological properties of the coatings were evaluated using a variety of protein adsorption assays and blood contacting experiments, and an enzyme immunoassay was developed to detect E. coli in order to assess the level of bacterial adhesion to these biomaterials. Polymers of this type were shown to be very useful as coating materials for improving the biocompatibility of, or reducing the levels of adherent bacteria to medical devices.     

Studies on contact lens materials

The development of plastics with the optical properties of glass led promptly to their use as contact lenses and intra-ocular lenses to rectify certain visual defects. Research to improve these polymeric materials is continuous but there is not much in the literature since most of the findings are patented. In this work, polymethyl methacrylate, the most commonly used lens material was chosen as the base material and its co and terpolymers were prepared using 2-hydroxyethyl methacrylate, N-vinyl-2-pyrrolidinone, hexamethyl disiloxane, and polypropylene glycol. The transparency, refractive index, contact angle, density, equilibrium water content, and percent hydration properties were examined. Theoretical values were calculated for linear expansion and oxygen permeation from the density and hydration values.     

Friction studies of hydrogel contact lenses using AFM: non-crosslinked polymers of low friction at the surface

The surface of soft contact lenses made of crosslinked poly(2-hydroxyethyl methacrylate), pHEMA, has been investigated with atomic force microscopy in contact mode. The friction force and adhesive force measurements were able to differentiate the non-crosslinked pHEMA chains from the surface of the crosslinked pHEMA networks. These non-crosslinked pHEMA chains at the surface were anchored to the crosslinked pHEMA network, most likely by entanglement and their surfaces were about 2–4 nm higher than the surrounding surface in a dehydrated state. In saline solution, the surface friction and adhesive force of the contact lens were significantly reduced compared to those measured for the surface-dehydrated contact lens.     

Role of endothelial cell-substrate contact area and fibronectin-receptor affinity in cell adhesion to HEMA/EMA copolymers.

The objective of this study was to examine the effect of substrate hydrophobicity on cell-substrate contact area and the affinity between adsorbed fibronectin (Fn) and its receptor. Homo- and copolymer films of hydrophobic ethyl methacrylate (EMA) and hydrophilic hydroxyethyl methacrylate (HEMA) were spun-cast onto glass slides. Bovine aortic endothelial cells (BAEC) were plated for 2 h in serum-free medium onto polymers preadsorbed with Fn. Cells were fixed, labeled, and examined by total internal reflection fluorescence microscopy (TIRFM) to determine the topography of the basal surface as a function of distance from the substrate. Phase contrast microscopy was used to examine the total projected area of adherent cells. The cumulative contact area was greatest on cells attached to surfaces prepared from 0% HEMA and lowest on surfaces with the highest HEMA content. An equilibrium adhesion model used these data together with the critical force for detachment and the Fn density (Burmeister et al., J Biomed Mater Res 1996;30:13-22) to determine the affinity between Fn and its receptor and the bond strength. The affinity and force per bond decreased with increasing HEMA content. These results indicate that differences in the strength of endothelial cell adhesion to polymers are influenced by the conformation of the adsorbed adhesion proteins.     

Modification of polyetherurethane for biomedical application by radiation induced grafting. II. Water sorption, surface properties, and protein adsorption of grafted films

A series of polyetherurethane films grafted by means of gamma radiation with hydrophilic or reactive monomers (2-hydroxyethyl methacrylate, 2,3-epoxypropyl methacrylate, 2,3-dihydroxypropyl methacrylate, and acrylamide) and partially chemically modified were subjected to various physico-chemical investigation methods involving water sorption, contact angle, and protein adsorption measurements. From contact angle data the interfacial free energy gamma sw between grafted films and water was calculated. It was found that the water uptake of grafted films increases with grafting yield or, in the case of grafted and afterwards chemically modified films, with reaction yield; the diffusion coefficient of water in the modified films also increases with grafting yield. Contact angle studies revealed all grafted films to have surfaces more hydrophilic than the ungrafted trunk polymer. The degree of hydrophilicity--especially of HEMA-grafted films--strongly depends on grafting conditions. For some grafted samples with high surface hydrophilicity very low interfacial free energies approaching zero were measured. The study of the competitive adsorption of bovine serum albumin, gamma-globulin, and fibrinogen from a synthetic protein solution onto modified films showed that the adsorption of albumin increases markedly with increasing grafting yields, whereas the fibrinogen and gamma-globulin adsorption only slightly increases. A correlation between interfacial free energy and protein adsorption in the sense of the "minimum interfacial free energy hypothesis" was found only for samples with grafting yields below 5%. At higher grafting yields the increased surface area complicates the analysis.     

Poly(vinyl alcohol) hydrogels as soft contact lens material

A new type of soft contact lens was developed from the poly(vinyl alchol) (PVA) hydrogel prepared by a low temperature crystallization technique using a water-dimethyl sulfoxide mixed solvent. The PVA contact lens materials had a water content of 78% and a tensile strength of 50 kg/cm², five times as strong as that of commercial poly(2-hydroxyethyl methacrylate) soft contact lens. The amount of proteins adsorbed to the PVA soft hydrogel material was half to one thirtieth of that of conventional soft contact lenses. Histological and scanning electron microscopic observation of rabbit eyes which had worn the PVA soft contact lens for 12 weeks showed no difference in corneal epithelium and cell arrangement in the corneal epithelium from the non-wearing eyes.     

Surface characterizations of copolymer films with pendant monosaccharides

We copolymerized a monomer with a pendant glucose unit (GEMA) with methyl methacrylate (MMA) and prepared copolymer films with pendant monosaccharides by casting the copolymer solution on glass plates. The surfaces of the copolymer films were characterized by contact angle measurements, X-ray photoelectron spectroscopy (XPS) and protein adsorption measurements, and compared with the surface of 2-hydroxyethyl methacrylate (HEMA)-MMA copolymer films. The surface free energy of the GEMA-MMA and HEMA-MMA copolymer was calculated from the contact angle of methylene diiodide and glycerol on the copolymer films. The surface free energy of the films increased gradually with increasing GEMA or HEMA content. The surface free energy of GEMA-MMA copolymers was larger than that of HEMA-MMA copolymers in the whole range of composition. The results of XPS measurements suggest that the fraction of GEMA at the copolymer surface increases as the content of GEMA in the copolymer increases. This indicates that introduction of GEMA makes the copolymer surface more hydrophilic. Further more, the higher the GEMA content is, the smaller amounts of fibrinogen and γ-globulin are adsorbed at the copolymer surface. The copolymer with a GEMA content of 20 mol-% hardly adsorbs fibrinogen and γ-globulin at all.     

Rat peritoneal macrophage adhesion to hydroxyethyl methacrylate-ethyl methacrylate copolymers and hydroxystyrene-styrene copolymers

Macrophage adhesion to a wide variety of substrates has been measured, but no systematic study of the influence of specific substrate chemical properties on adhesion is available. These studies were conducted using two series of materials, copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) and copolymers of hydroxystyrene and styrene, to determine the effect of a single chemical property, polar character, on adhesion. Rat peritoneal macrophages were allowed to contact polymer substrates for periods ranging from 1 to 240 min before being subjected to a shear stress of 60-120 dynes/cm2 in a thin-channel flow cell. Percentage adhesion was calculated from the number of cells that remained adherent to the substrate after 30 s of applied shear stress. Macrophages remained adherent to 100% EMA and all hydroxystyrene-styrene copolymer surfaces after only 1 min of contact. In copolymers of the HEMA-EMA series, the time required to attain peak adhesion levels increased with increasing substrate hydrophilicity (increasing HEMA content). Cells did not attach to the 20% EMA/80% HEMA copolymer and the 100% HEMA polymer. The results demonstrate that there is a time delay between contact and adhesion of the cells to surfaces of increasing hydrophilicity within the HEMA-EMA series and no time delay with the hydroxystyrene-styrene series. The time delay is thought to be a function of the excluded volume provided by polymers that are able to undergo significant chain rotation and or swelling in the solvent, water. Small excluded volumes present in copolymers of high EMA content and all hydroxystyrene-styrene copolymers offer little or no resistance to formation of adhesive bonds by macrophages, whereas copolymers with large excluded volumes (high HEMA content) prevent contact and/or adhesion. A mechanism based on the net excluded volumes of both the cell and substrate surface macromolecule is proposed to explain this phenomenon.     

Characterization of the physicochemical, antimicrobial, and drug release properties of thermoresponsive hydrogel copolymers designed for medical device applications

In this study, a series of hydrogels was synthesized by free radical polymerization, namely poly(2-(hydroxyethyl)methacrylate) (pHEMA), poly(4-(hydroxybutyl)methacrylate) (pHBMA), poly(6-(hydroxyhexyl)methacrylate) (pHHMA), and copolymers composed of N-isopropylacrylamide (NIPAA), methacrylic acid (MA), NIPAA, and the above monomers. The surface, mechanical, and swelling properties (at 20 and 37 degrees C, pH 6) of the polymers were determined using dynamic contact angle analysis, tensile analysis, and thermogravimetry, respectively. The T(g) and lower critical solution temperatures (LCST) were determined using modulated DSC and oscillatory rheometry, respectively. Drug loading of the hydrogels with chlorhexidine diacetate was performed by immersion in a drug solution at 20 degrees C (相似文献   

Functional Surfaces Constructed with Hyperbranched Copolymers as Optical Imaging and Electrochemical Cell Sensing Platforms

In the present study, hyperbranched copolymers (HBCs), namely poly(methyl methacrylate) (PMMA)‐co‐poly(2‐hydroxyethylmethacrylate) and PMMA‐co‐poly(2‐dimethylamino ethyl methacrylate), are photochemically synthesized by self‐condensing vinyl polymerization of methyl methacrylate with the corresponding inimer using Type II photoinitiators. HBCs with different functional group and branching densities are used as surface coating materials in cellular adhesion and the respective electrochemical‐based studies. After the main surface characterization of the synthesized three HBCs with contact angle measurements and atomic force microscopy, HaCaT keratinocytes and human neuroglioblastoma (U‐87MG) cell lines to the surfaces are conducted. The adherence of cells is proven by both fluorescence cell imaging and electrochemical methods such as cyclic voltammetry and differential pulse voltammetry. The described strategy involving hyperbranched polymers offers great potential for fabricating various new surfaces in particular “on‐chip‐sensing” applications.     

Protein adsorption on a copolymer having pendant monosaccharide groups. Relationship between surface free energy and protein adsorption

Protein adsorption on copolymer films having pendant monosaccharide groups was investigated from the viewpoint of surface chemistry. The copolymers were synthesized by the copolymerization of a monomer having a pendant monosaccharide (GEMA) and methyl methacrylate (MMA). The contact angles of methylene iodide and air bubble on the GEMA-MMA copolymer films were measured in water, and the surface free energy of the copolymer films in water was calculated from the contact angles. With increasing GEMA content, the amount of protein adsorbed on the GEMA-MMA copolymer films decreased gradually. The relationship between protein adsorption and the surface free energy of the copolymer films in water is discussed. The differences between surface free energy before and after protein adsorption on the copolymer surface is closely related to the amount of adsorbed protein.     

Tailor-made functional surfaces: potential elastomeric biomaterials I

In the present investigation, different functional monomers, like hydroxyethyl methacrylate, acrylic acid, N-vinyl pyrrolidone and glycidyl methacrylate, have been grafted onto the surface of EPDM film (approx. 200 microm) using simultaneous photo-grafting (lambda > or = 290 nm) and cold plasma-grafting techniques, to alter the surface properties, such as hydrophilicity and, therefore, biocompatibility. Here, we have carried out simultaneous plasma-grafting, unlike the conventional post plasma-grafting. The effect of different surface grafting techniques on the degree of surface modification and resultant biocompatibility has been investigated. The chemical changes on the polymer backbone are followed from the results of attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS), which shows the peaks corresponding to the functional groups of the monomers grafted onto the film surface. The morphology of the modified surfaces was investigated using scanning electron microscopy (SEM) technique. The induced hydrophilicity and resultant cell compatibility were followed from the water contact angle measurements and in vitro human carcinoma cell adhesion/proliferation tests, respectively. All the grafted samples exhibited variable cell compatibilities depending upon the type of monomer and their degree of grafting; however, always better than the neat samples. Hydroxyethyl methacrylate and acrylic acid showed exceptionally high cell compatibility in terms of cell adhesion and proliferation.     

Simple Photochemical Route to Block Copolymers via Two‐Step Sequential Type II Photoinitiation

A simple method for the preparation of block copolymers by a two‐step sequential Type II photoinitiation is described. In the first step, amine functionalized poly(methyl methacrylate) (PMMA‐N(Et)₂) is prepared by photopolymerization of methyl methacrylate at λ = 350 nm using benzophenone and triethyl amine as photosensitizer and hydrogen donor, respectively. Subsequent benzophenone‐sensitized photopolymerization of tert‐butyl acrylate using PMMA‐N(Et)₂ as hydrogen donor yielded poly(methyl methacrylate)‐block‐poly(tert‐butyl acrylate). The obtained hydrophobic block copolymer is readily converted to amphiphilic polymer by hydrolysis of the tert‐butyl ester moieties of the block copolymer as demonstrated by contact angle measurements. All polymers are characterized by NMR, Fourier transform infrared and UV–vis spectroscopies, and differential scanning calorimetry (DSC) thermal analyses.