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PubMed2004

Binding of sodium dodecyl sulfate to linear and star homopolymers of the nonionic poly(methoxyhexa(ethylene glycol) methacrylate) and the polycation poly(2-(dimethylamino)ethyl methacrylate): electromotive force, isothermal titration calorimetry, surface tension, and small-angle neutron scattering measurements.

We investigated the binding of sodium dodecyl sulfate (SDS) to various linear and star polymers of the nonionic methoxyhexa(ethylene glycol) methacrylate (PMHEGMA) and the ionic 2-(dimethylamino)ethyl methacrylate (PDMAEMA), the latter being a polycation at low pH. The dodecyl sulfate ion selective electrode (EMF), isothermal titration calorimetry (ITC), and surface tension (ST) were applied to gain detailed information about interactions. In all cases there is evidence of significant binding of SDS over an extensive SDS concentration range spanning from ca. 10(-6) to 0.1 mol dm(-3). At pH 3, the polymer PDMAEMA is a strong polycation and here the binding is dominated by electrostatic 1:1 charge neutralization with the anionic surfactant. At their natural pH of 8.6, PMHEGMA and PDMAEMA polymers are essentially nonionic and bind SDS in the form of polymer-bound aggregates in the concentration range of ca. 1 x 10(-3) to 3 x 10(-2) mol dm(-3). All the polymers also bind SDS to a lesser extent at concentrations below 1 x 10(-3) mol dm(-3) reaching as low as 10(-7) mol dm(-3). This low concentration binding process involves the polymer and nonassociated SDS monomers. As far as we are aware, this is the first example that such a low concentration noncooperative binding process could be observed in SDS/neutral polymer systems by EMF and ST. We also showed that the nonionic surfactant hexa(ethylene glycol) mono-n-dodecyl ether (C12EO6) and the cationic cetyltrimethylammonium bromide (C16TAB) interact with star PDMAEMA. We believe that the interaction of C12EO6 and CTAB is of similar noncooperative type as the first SDS binding process in the range from ca. 10(-5) to 0.3 x 10(-3) mol dm(-3). At the high concentration binding limit Csat of SDS, the above polymers become fully saturated with bound SDS micelles. We applied small angle neutron scattering (SANS) to determine the structure and aggregation numbers of the star polymer/bound SDS micelles and calculated the stoichiometry of such supramolecular complexes. The SANS data on PDMAEMA star polymers in the presence of C12EO6 showed only a limited monomer binding in contrast to linear PDMAEMA, which showed monomer C12EO6 binding at low concentrations but micellar aggregates at 6 x 10(-3) mol dm(-3).

Journal Article↗
PubMed2005

Transformations of poly(methoxy hexa(ethylene glycol) methacrylate)-b-(2-(diethylamino)ethyl methacrylate) block copolymer micelles upon metalation.

Micelle transformations upon metalation (i.e., incorporation of metal compounds and metal nanoparticle formation) in poly(methoxy hexa(ethylene glycol) methacrylate)-block-poly((2-(diethylamino)ethyl methacrylate)), PHEGMA-b-PDEAEMA, solutions have been studied using transmission electron microscopy (TEM) and photon correlation spectroscopy (PCS). Three different methods for the formation of metalated micelles are compared: (A) dissolution of the block copolymers in pure water followed by incorporation of platinic acid (H(2)PtCl(6).6H(2)O), (B) micellization in acidic molecular solutions of block copolymers induced by interaction of the protonated amino groups with the PtCl(6)(2)(-) ions, and (C) incorporation of metal species in pH-induced micelles. The latter method leads to well-defined metalated micelles of 22-25 nm diameter containing nanoparticles with diameters of 1.3-1.5 nm. No nanoparticle aggregation is observed. Good agreement is obtained for the sizes of the platinic acid-containing micelles assessed by TEM and PCS.

Light↗
PubMed2001

Preparation of poly(D,L-lactide) nanoparticles assisted by amphiphilic poly(methyl methacrylate-co-methacrylic acid) copolymers.

When co-precipitated with amphiphilic copolymers from DMSO, poly(D,L-lactide) (PLA) can be readily converted into stable sub-200 nm nanoparticles by addition of an aqueous phase, free of any polymeric stabilizers such as poly(vinyl alcohol) or Poloxamer. In this work, the ability of random poly(methyl methacrylate-co-methacrylic acid) copolymers (PMMA-co-MA) to stabilize PLA nanoparticles was demonstrated, and the properties of PLA/PMMA-co-MA nanoparticles were investigated. When co-precipitated with PMMA-co-MA, PLA was totally converted into nanoparticles using a polymer concentration in DMSO (Cp) below 17.6 mg ml(-1), and a PMMA-co-MA proportion above a critical value depending on the content of MA repeating units (X). For instance, the lowest PMMA-co-MA proportion required was 0.9 mg mg(-1) PLA for X = 12%, and 0.5 mg mg(-1) PLA for X = 25% (for C(PLA) = 16 mg ml(-1) DMSO). The nanoparticle diameter was essentially independent of X, the proportion of PMMA-co-MA, and the PLA molecular weight, except for oligomers for which the nanoparticle diameter was smaller. It decreased when the organic phase was diluted (126 +/- 13 nm for Cp = 17.6 mg ml(-1), and 81 +/- 5 nm for C(P) = 5.6 mg ml(-1)). The time-dependence of the stability and the degradation of PLA/PMMA-co-MA nanoparticles was discussed. One of the main advantages of this technique is the ability to control surface properties and to bring functional groups to otherwise non-functionalized PLA nanoparticles. To illustrate this, a conjugate of PMMA-co-MA25 and biotin was synthesized, and used to prepare biotinylated nanoparticles that could be detected by fluorescence and transmission electron microscopy after infiltration into ligatured rat small intestine.

Animals↗
PubMed2005

Fabrication of long-period gratings in poly(methyl methacrylate-co-methyl vinyl ketone-co-benzyl methacrylate)-core polymer optical fiber by use of a mercury lamp.

Polymer optical fiber (POF) with a highly photosensitive poly(methyl methacrylate-co-methyl vinyl ketone-co-benzyl methacrylate) core is fabricated. Gratings can be fabricated in the core of a POF with a low-cost mercury lamp. The part of the emission spectrum of the mercury lamp in which the cladding material exhibits photosensitivity is effectively filtered by a 1.5-mm-thick Pyrex glass to ensure that a long-period grating is formed only in the core of a POF. A long-period grating with a 3-dR resonant peak at 1568 nm is fabricated with 0.3 mW/cm2 of UV irradiation over a period of 200 s.

Journal Article↗
PubMed1976

Tissue reaction to methyl methacrylate monomer. A comparative study in the rabbit's ear on the toxicity of methyl methacrylate monomer of varying composition.

The aim of the present investigation was to evaluate if a bone cement monomer with a high concentration of accelerator (N,N-dimethyl-p-toluidine) is more toxic than a methyl methacrylate monomer, free from accelerator. 1) No difference in the acute local toxicity between CMW, Simplex-P and pure methyl methacrylate monomer was seen. 2) By gas chromatography. N,N-dimethyl-p-toluidine was shown to be water soluble to a small extent. Any bone cement monomer in current use can be fully dissolved in saline to a concentration of about 1 per cent.

Animals↗
PubMed1975

[Studies on the dental methacrylic resins (part 4). Flow properties and curing times of the pour methacrylic resins (author's transl)].

Flow properties and curing times of the pour resins consisted of polymethyl methacrylate and methyl methacrylate were investigated by the viscosity and the temperature measurements. The polymers with various article sizes and molecular weights and the monomer with 0.005 per cent hydroquinone were used the pour resins respectively. The initiator system of benzoyl peroxide--N, N-dimethyl-p-toluidine was used for the polymerization. The results were as follows: 1) The viscosities of the pour resins were increased with the time elapsed. That was for reasons of physical phenomenon, that is, dissolution of polymer into monomer. The logarithmic viscosities increased linearly in proportion to the time elapsed. 2) The viscosities of the pour resins were increased by the reduction of the particle size of the polymer and by the increase of the molecular weight of the polymer. 3) The curing times of the pour resins were reduced by the increase of the concentrations of benzoyl peroxide and N, N-dimethyl-p-toluidine, and by the reduction of the particle size and the molecular weight of the polymer respectively.

Acrylic Resins↗
PubMed1979

[Studies of dental methacrylic resin. (Part. 6) Adhesive strength of self-curing methacrylic resin to polymethylmetacrylates with various cross-linking density. (author's transl)].

The adhesive property of dental acrylic resin to resin teeth and denture base resins is an important property, in the case of preperating, repairing and rebasing denture. Then, as models of denture base resin and resin tooth, heat-curing methacrylic resins which were cross-linked with three kinds of polyethylene glycol dimethacrylate, i.e., EDMA, tri-EDMA, nona-EDMA, were prepared, and the tensile adhesive strengths of self-curing methacrylic resin to them were examined. The results were as follows. 1) The tensile adhesive strength under the dry condition was dependent on cross-linking density of adherent resin, and decreased according to the increase of concentration of cross-linking agent added in adherent resin. 2) The greater the number of chain members of cross-linking agent used to adherent resin was, the higher the adhesive strength was. In particular, the adhesive strength to adherent resin added with nona-EDMA in concentration from 16.7 to 30 mole%, agreed with the tensile strength of adherent resin itself indicating a favourable adhesion. 3) The adhesive strengths under the wet condition, that is, when specimens were immersed in water at 37 degrees C for 21 days, decreased from 30 to 50%, compared with that under the dry condition.

Acrylic Resins↗
PubMed1979

[Studies of dental methacrylic resin. (Part 7) Adhesive strength of fluid methacrylic resin to polymethylmethacrylates with various cross-linked density (author's transl)].

Heat-curing methacrylic resins cross-linked with three kinds of dimethacrylates, i.e. EDMA, tri-EDMA and nona-EDMA, were prepared, and the tensile adhesive strength of fluid methacrylic resin to them was examined. The results obtained were as follows. (1) To adherent resin cross-linked with EDMA, the adhesive strength of fluid resin showed the maximum at the concentration near 2 mole% and decreased with increasing the concentration. (2) To adherent resin cross-linked with tri-EDMA or nona-EDMA, the effect of the concentration of cross-linking agent on the adhesive strength was little, except that the adhesive strength to the latter adherent resin showed a steep increase in the range of lower concentration. (3) The adhesive strength did not appreciably change in the range of L/P ratio of fluid resin from 0.57 to 0.71 ml/g. (4) The adhesive strength under the wet condition decreased about 40 to 50% compared under the dry condition. (5) To cross-linked adherent resin, the adhesive strength of fluid resin was somewhat higher than that of self-curing resin under the dry condition. But, under the wet condition this difference was little. (6) Contrarily, to non-cross-linked adherent resin, the adhesive strength of fluid resin was somewhat lower than of self-curing resin. This may be because the cracks, which are occured on the surface of non-cross-linked adherent resin by contact with abundant MMA of fluid resin, work as defects to decrease the adhesive strength.

Acrylic Resins↗
PubMed1997

The differential effects of poly(2-hydroxyethyl methacrylate) and poly(2-hydroxyethyl methacrylate)/poly(caprolactone) polymers on cell proliferation and collagen synthesis by human lung fibroblasts.

Because of its chemical versatility and demonstrated biocompatibility, poly(2-hydroxyethyl methacrylate) (pHEMA) has been widely used as a polymer for biomedical applications. Since this hydrophilic material shows a poor interface with cells, blendings with other polymers were done to improve cytocompatibility. In our polymer, the presence of hydrophobic dominions on the material surface, due to the interpenetrating polymerization of pHEMA with poly(caprolactone) (PCL), seems to ameliorate the cytocompatibility in terms of cell adhesion and metabolism. For our experiments, we used IMR-90 human fibroblasts, as these cells strongly regulate DNA, RNA, and protein synthesis as anchorage-dependent variables. Cell attachment on a pHEMA/PCL interpenetrating polymer network was optimal, suggesting a strong adhesion between the cells and the polymer surface. Cell adhesion was weaker on pHEMA, as a significant fraction of the fibroblasts revealed a lack of spreading, with most cells remaining spherical. Moreover, only fibroblasts seeded on pHEMA significantly decreased mRNA synthesis; collagen production and cell shapes ranged from fully flat and proliferating, to minimally spread and nonproliferating. Finally, DNA synthesis, as a measure of cell proliferation, was markedly inhibited in cells cultured on pHEMA but not on pHEMA/PCL. In conclusion, our results suggest that control of cell growth and metabolism by biomedical polymers is based on physicochemical mechanism(s) in which the hydrophilicity/hydrophobicity ratio of the material surfaces may play an important role.

Base Sequence↗
PubMed1994

Effect of esterase on methacrylates and methacrylate polymers in an enzyme simulator for biodurability and biocompatibility testing.

Current in vitro biocompatibility methods do not evaluate the degradation of biomaterials after contact with enzymes that might be present in the oral or systemic environment. In this study, two methods of in vitro enzyme degradation and a method for the separation of the degradative products by high performance thin-layer chromatography (HPTLC) are reported. In the first method two dental adhesives, Scotchbond and Scotchbond II, and two dental composites, Heliomolar and P-50, were evaluated. These materials were incubated with four different enzymatic preparations for periods of up to 72 h. The enzymes were lipase, esterase, and liver enzyme extracts from both mouse and rat. Chloroform soluble products extracted from the aqueous phase were examined by HPTLC for decomposition products resulting from enzyme activity. The second method was similar, but analyzed the aqueous fraction directly without chloroform extraction. In this method five dental restorative materials, P-50, P-30, Scotchbond II, Silux, and Silux Plus, were incubated with a nonspecific porcine liver esterase. In addition to the polymerized biomaterials, monomers containing methacrylic acid units were also hydrolyzed with esterase and analyzed by ion chromatography to establish the sensitivity of the enzyme simulator. Each biomaterial presented thin-layer zones not present before enzymatic action. These experiments provide support that aqueous enzymatic action may facilitate the hydrolytic weakening of polymeric biomaterials.

Animals↗
PubMed1976

Affinity chromatography on hydroxyalkyl methacrylate gels. III. Adsorption of chymotrypsin to poly(hydroxyalkyl methacrylates) with covalently bound benzyloxycarbonyl-glycyl-D-phenylalanine and -D-leucine as function of pH and ionic strength.

Chymotrypsin is specifically adsorbed at low ionic strength and alkaline pH to hydroxyalkyl methacrylate gels with N-benzyloxycarbonylglycl-D-phenylalanine or N-benzyloxycarbonylglycyl-D-leucine attached through 1,6-hexanediamine. Chymotrypsin is not adsorbed either to the unmodified gel (Spheron) or to the gel with attached, 1,6-hexanediamine (NH2-Spheron). The adsorption of chymotrypsin to Z-Gly-D-Phe-NH2-Spheron was investigated as a function of pH and ionic strength. Trypsin is not adsorbed to this gel. Chymotrypsin isolated from a crude pancreatic extract by affinity chromatography on Z-Gly-D-Phe-NH2-Spheron had the same activity as the enzyme isolated on a column of Spheron, to which the naturally-occurring trypsin inhibitor had been coupled.

Binding Sites↗
PubMed2002

New approach to characterise physicochemical properties of solid substrates by inverse gas chromatography at infinite dilution. II. Study of the transition temperatures of poly(methyl methacrylate) at various tacticities and of poly(methyl methacrylate) adsorbed on alumina and silica.

The determination of the temperature transitions in polymers and more particularly when polymers are adsorbed on oxides is very important in many industrial processes. In this second part, we used inverse gas chromatography (IGC) at infinite dilution to determine the second order transition temperatures of poly(methyl methacrylate) (PMMA) adsorbed (or not) on alumina or on silica. Three types of PMMA were used: atactic (a), syndiotactic (syndio) and isotactic (iso). The IGC technique allowed to obtain the net retention volume Vn and the dispersive component of the surface energy gamma(s)d for various theoretical models of molecules, using the results of Part I. By plotting RT ln Vn as a function of (1/T) or gamma(s)d as a function of the temperature T, we proved the presence of three particular temperatures that correspond respectively to the transition temperature relative to beta-relaxation (Tbeta), the glass transition temperature (Tg), and the liquid-liquid transition temperature or order-disorder transition (T1.1). Results obtained in this part allowed us to show the effect of the tacticity of PMMA and the recovery fraction of polymer adsorbed on alumina or silica on the transition temperatures.

Adsorption↗
PubMed2002

Influence of poly(methyl methacrylate) impregnation ratio on the surface properties of fumed silica and on the glassy temperature of poly(methyl methacrylate) using inverse gas chromatographic analysis.

The surface properties of poly(methyl methacrylate) (PMMA) impregnated fumed silicas, in a large range of impregnation ratios, were examined using inverse gas chromatography at infinite dilution. It was observed that the dispersive component gamma(s)d does not decrease monotonously with the impregnation ratio. Two critical coverage ratios were evidenced corresponding at first to the shielding of the most energetic sites and then to the achievement of total coverage of the silica surface. The influence of the coverage ratio on the glassy temperature (tg) of the adsorbed PMMA was also studied, which was evidenced down to a very low coverage ratio (1 monomer unit/nm2).

Adsorption↗
PubMed2002

Snowflake degeneration of polymethyl methacrylate posterior chamber intraocular lens optic material: a newly described clinical condition caused by unexpected late opacification of polymethyl methacrylate.

OBJECTIVE: To report 25 cases of gradual, but sometimes progressive, late-postoperative degeneration of polymethyl methacrylate (PMMA) optics of posterior chamber (PC) intraocular lens (IOL) implants, often resulting in a clinically significant visual decrease long after the implantation, sometimes to a severity that required IOL explantation/exchange. DESIGN: Analysis of explanted PC IOLs, clinical histories, and photographs. PARTICIPANTS: We analyzed 25 case histories/photographs and/or explants from 18 patients implanted in the 1980s to mid-1990s with three-piece PC IOLs with PMMA optics and with polypropylene or PMMA haptics. The IOL optic from each case had characteristic snowflake or crystalline opacifications. This condition occurred with more than one manufacturer and in some cases was restricted to certain lot numbers. METHODS: The explanted IOLs (n = 10) were studied by gross inspection and by light and scanning electron microscopy, as well as confocal and energy dispersive spectroscopy. MAIN OUTCOME MEASURES: The snowflake lesions were noted within the IOL optics. The nature of these lesions was investigated. RESULTS: Assimilation of clinical information with pathologic and morphologic profiles of all cases suggested that the snowflake opacification was a small spherical lesion surrounded by an outer pseudocapsule composed of compressed, degenerated PMMA, with a central core containing convoluted fragments of PMMA. The lesions were classified into four clinical and pathologic grades according to their density and severity. CONCLUSIONS: This is the first clinicopathologic correlative report on this complication. We postulate that manufacturing variations in some IOL models fabricated in the 1980s and early 1990s are responsible. The snowflake lesions seem to represent a destruction of the PMMA material. The cluster of lesions in implanted lenses manufactured by Surgidev was less progressive than some other models, including lenses made by IOPTEX Research Corporation. This identification of a condition previously unreported is important to alert clinicians regarding these perplexing lesions that may otherwise be considered idiopathic, with no obvious clinical hint as to their origin. The prevalence noted thus far is still too low to in any way suggest that this condition would occur in 100% of PMMA IOLs from these manufacturers. However, these late-occurring lesions, present in lens models that were implanted in hundreds of thousands of patients in the last decade or so, could have constituted a true epidemic, except that many of the patients are now deceased.

Device Removal↗
PubMed2002

Preparation of poly(methacrylic acid-g-poly(ethylene glycol)) nanospheres from methacrylic monomers for pharmaceutical applications.

Nanospheres of poly(methacrylic acid-grafted-poly(ethylene glycol)) were prepared by solution/precipitation polymerization. As colloidal drug delivery carriers, they present unique properties that render them promising candidates for oral protein delivery. The polymerization was carried out in water and the resulting suspension was freeze-dried. As with many colloidal systems, the freeze-dried suspension showed strong agglomeration after drying. The effects of preparation conditions on the particle size and redispersion were investigated using photon correlation spectroscopy. Furthermore, the ability of different types and concentrations of stabilizers (cryoprotectants and steric stabilizers) in preventing this phenomenon was addressed. Pluronics, block copolymers widely used as nonionic surfactants, were the most effective in stabilizing the particles during the freeze-drying process. Pluronic P123, however, increased significantly the particle size of the nanospheres. On the other hand, lyophilizates obtained in the presence of Pluronic F68 had good redispersion properties and no change in particle size was observed.

Drug Compounding↗
PubMed2003

Methacrylate-tethered analogs of the laser dye PM567--synthesis, copolymerization with methyl methacrylate and photostability of the copolymers.

The synthesis and characterization of new analogs of the laser dye PM567 (4,4-difluoro-1,3,5,7,8-pentamethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene) with the 8-position substituted by a linear chain with n methylenes (n = 1, 3, 5, 10 or 15) tethered with an acetoxy or methacryloyloxy group (PnAc and PnMA, respectively) is described. The monomeric dyes PnMA have been successfully copolymerized with methyl methacrylate (MMA), yielding linear copolymers of high optical quality where the covalently bonded chromophore is separated from the polymeric main chain by a spacer of variable length. The photostability of the solid polymeric materials under UV (310 nm) irradiation (method ASTM G 53-77) has been compared with those of the model dyes PnAc and PM567 as solid solutions in poly-MMA (PnAc-PMMA and PM567-PMMA, respectively). In all the cases, the chromophore bound to the polymer is more photostable than that simply dissolved in the same polymer, with photodegradation quantum yields in the range 2.3 x 10(-5) to 4.8 x 10(-5), which was interpreted as due to additional modes for the dissipation of the absorbed energy along the polymeric chain. In both polymer solutions and copolymers, the length of the polymethylene chain has low or null influence on the photostability. In ethanol solution, PnAc model dyes with polymethylene chains with three or more methylene groups show about the same photostability; this is of an order of magnitude higher than that of the parent dyes P1Ac and PM567 in the same solvent.

Journal Article↗