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A general method for the synthesis of (14)C-acrylic acid is described in detail. The material is used for the synthesis of a range of radiolabeled poly(acrylic acid)s in which the (14)C-label forms an integral part of the polymer backbone. The chemical structure of the synthesized polymers is examined in the light of spectroscopic data, molecular weight determinations, and rheological studies.
The poly(acrylic acid)-graft-poly(vinylidene fluoride) (PAAc-g-PVDF) and poly(4-vinylpyridine)-graft-poly(vinylidene fluoride) (P4VP-g-PVDF) copolymers were obtained by thermally induced molecular graft copolymerization of acrylic acid (AAc) and 4-vinylpyridine (4VP), respectively, with the ozone-pretreated poly(vinylidene fluoride) (PVDF) in N-methyl-2-pyrrolidone (NMP) solution. Microfiltration (MF) membranes were prepared from the respective copolymers by phase inversion in aqueous media. The effects of pH of the coagulation bath on the physicochemical and morphological characteristics of the membranes were investigated. The surface compositions of the membranes were determined by X-ray photoelectron spectroscopy (XPS). The surface graft concentration of the AAc polymer for the PAAc-g-PVDF MF membrane increased with decreasing pH value of the coagulation bath. Completely opposite pH-dependent behavior was observed for the surface graft concentration of the 4VP polymer in the P4VP-g-PVDF MF membranes. A substantial increase in mean pore size was observed for the PAAc-g-PVDF MF membranes cast in basic coagulation baths of increasing pH. In the case of the P4VP-g-PVDF MF membranes, a substantial increase in mean pore size was observed for membranes cast in low pH (acidic) baths. The permeation rate of aqueous solutions through the PAAc-g-PVDF and P4VP-g-PVDF MF membranes exhibited a reversible dependence on the pH of the solution, with the membranes cast near the neutral pH exhibiting the highest sensitivity to changes in permeate pH.
The purpose of this study was to evaluate the biocompatibility of different Amioca/poly(acrylic acid) and Amioca/Carbopol 974P co-spray dried mixtures with an alternative mucosal irritation test using slugs. The irritation potential of the mixtures was measured by the amount of mucus produced during a repeated 30-min contact period. Additionally, membrane damage was assessed by measuring the protein and enzyme release from the body wall of slugs after treatment. All the Amioca/poly(acrylic acid) co-spray dried mixtures (50:50 and 25:75 ratios) induced slight irritation of the mucosal tissue as was demonstrated by the significantly increased mucus production however no increased protein and enzyme release was detected. Co-spray dried Amioca/Carbopol 974P mixtures containing 40% and more Carbopol 974P demonstrated a significantly higher mucus production and release of cytosolic LDH, indicating membrane damage. The total mucus production of the slugs treated with the co-spray dried mixtures containing up to 20% Carbopol 974P was significantly higher compared to the blank slugs. However, these mixtures induced no membrane damage since no additional effect on the protein release and no enzyme release was detected. By co-spray drying up to 20% Carbopol 974P could be incorporated without showing a distinct sign of irritation. These mixtures can be considered as potentially safe bioadhesive carriers.
The mechanical properties of dry and wet polymeric films prepared from various aqueous polymeric dispersions were evaluated by a puncture test. They were studied with respect to type of polymer dispersion [cellulosic: Aquacoat and Surelease; acrylic: Eudragit NE, L, RS, and RL 30 D], plasticizer type (water-soluble or water-insoluble), drying or curing conditions, method of film preparation (pseudolatex-vs solvent casting) and ratio of Eudragit RS/RL 30 D in mixed Eudragit RS/RL films. Dry and wet mechanical strengths of the polymeric films depended primarily on the types of the colloidal polymer dispersion and the plasticizer. Films prepared from ethylcellulose dispersions resulted in very weak and brittle films when compared to the acrylic films. Pseudolatex-cast ethylcellulose films showed lower puncture strength and elongation values when compared to those of the solvent-cast films. Curing of the pseudolatex-cast ethylcellulose films had minimal effects on their mechanical properties. Eudragit L 30D, an enteric polymer dispersion, resulted in brittle films in the dry state, but in very flexible films in the wet state because of the plasticization effect of water. Wet Eudragit RS 30 D polymer films plasticized with water-insoluble plasticizers were significantly more flexible than the corresponding wet films plasticized with water-soluble plasticizers. The water-soluble plasticizers leached from the films during exposure to the aqueous medium, while the water-insoluble plasticizers were almost completely retained within the wet films. The low permeability of a water-soluble drug, chlorpheniramine maleate, and the weak mechanical properties of Aquacoat films could suggest osmotic driven/rupturing effects as the release mechanisms from Aquacoat-coated dosage forms.
A copolymer of N-isopropylacrylamide (98 mol% in feed) and acrylic acid, poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAAm-co-AAc)), was prepared by free radical polymerization for development of a thermally reversible polymer to entrap islets of Langerhans for a refillable biohybrid artificial pancreas. A 5 wt% solution of the polymer in Hanks' balanced salt solution forms a gel at 37 degrees C that exhibits no syneresis. Diffusion of fluorescein isothiocyanate (FITC) dextrans having molecular weights of 4400 and 70000 were used to evaluate mass transport in the gel at 37 degrees C. Insulin secretion from islets in the polymer gel was also investigated in both static and dynamic systems. The polymer gel exhibited excellent diffusion of FITC dextran 4400 and FITC dextran 70000 with diffusion ratios, D/D0 (ratio of diffusion in the gel to diffusion in water), of 0.20+/-0.04 and 0.35+/-0.17, respectively. Human islets entrapped in the polymer gel showed prolonged insulin secretion in response to basal (5.5 mM) glucose concentration compared to free human islets. Rat islets showed prolonged insulin secretion in response to high (16.5 mM) glucose concentrations compared to free rat islets. Rat islets in the polymer gel maintained insulin secretion in response to the higher glucose concentration for over 26 days. Rat islets entrapped by the polymer also released higher quantities of insulin more rapidly in response to changes in concentrations of glucose and other stimulants than rat islets entrapped in an alginate control. These results suggest that this material would provide adequate diffusion for rapid insulin release in an application as a synthetic extracellular matrix for a biohybrid artificial pancreas.
The cross-linking structure of the ultra violet (UV)-cured resin prepared from dipentaerithritol hexacrylate (DPHA) was characterized by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with supercritical methanolysis. The MALDI-mass spectrum of the decomposition products obtained by supercritical methanolysis contained a series of peaks of sodium-cationized methyl acrylate (MA) oligomers up to around m/z = 4000 formed through selective cleavage and methylation occurred at ester linkages in UV-cured DPHA. Furthermore, in order to observe widely distributed sequence lengths in the cross-linking junctions, the decomposed products of the cured resin were then fractionated using size exclusion chromatography followed by the MALDI-MS measurements of the individual fractions. The MALDI-mass spectra of the lower molar mass fractions mainly consisted of a series of peaks of MA oligomers around m/z values of several thousands, whereas those of higher molecular weight showed a broad peak up to m/z ca. 180000. The observed distributions of the supercritical methanolysis products suggested that the network junctions in the given UV-cured resin were composed of up to around 2000 acrylate units.
A light-cured acrylic adhesive for fixing resin retention devices to the wax pattern was prepared. The adhesive consisted of trimethylolpropane triacrylate, 2-ethylhexyl acrylate, benzoin methyl ether, p dimethylaminobenzaldehyde and p-methoxyphenol. The adhesive could be cured within 20 sec not only by an UV photo curing unit but by a visible-light source with a xenon lamp. The adhesive and retention beads burned out after about an hour in the electric furnace at 400 c. The metal specimens with retention devices were cast in Ag-Pd-Cu-Au alloy with the use of two types of retention beads adhesive. The light-cured adhesive was superior to the conventional one in handling and some other properties. This adhesive may be used to fabricate composite veneered prostheses with minimum errors in laboratory procedure.
The acrylic content of modern dental materials poses a risk of adverse reactions. Although the quantities of the substances released are normally too small to cause systemic reactions, local reactions may occur resulting in damage to the skin. A study, in which 81 dental workers referred to dermatologists for a variety of adverse reactions were patch tested, showed work-related dermatoses to represent a serious problem for dental staff, sometimes entailing occupational disability and re-schooling. Much of this could be avoided by observing special precautions to prevent direct contact with the sensitising substances in composite materials used in dental surgery. Since the use of dental amalgam has been reduced to about 10 per cent of all fillings in Sweden, the prevalence of adverse local reactions to the acrylic composite materials which are used instead may be expected to increase.
Ultrafine cellulose fiber (diameter 200-400 nm) surfaces were grafted with polyacrylic acid (PAA) via either ceric ion initiated polymerization or methacrylation of cellulose with methacrylate chloride (MACl) and subsequent free-radical polymerization of acrylic acid. PAA grafts by ceric ion initiated polymerization increased with increasing reaction time (2-24 h), monomer (0.3-2.4 M), and initiator (1-10 mM) concentrations, and spanned a broad range from 5.5-850%. PAA grafts on the methacrylated cellulose fibers also increased with increasing molar ratios of MACl to cellulosic hydroxyl groups (MACl/OH, 2-6.4) and monomer acrylic acid (AA) to initiator potassium persulfate (KPS) ratios ([AA]/[KPS], 1.5-6), and were in a much narrower range between 12.8% and 29.4%. The adsorption of lipase (at 1 mg/ml lipase and pH 7) and the activity of adsorbed lipase (pH 8.5, 30 degrees C), in both cases decreased with increasing PAA grafts. The highest adsorption and activity of the lipase on the ceric ion initiated grafted fibers were 1.28 g/g PAA and 4.3 U/mg lipase, respectively, at the lowest grafting level of 5.5% PAA, whereas they were 0.33 g/g PAA and 7.1 U/mg lipase, respectively, at 12.8% PAA grafts on the methacrylated and grafted fibers. The properties of the grafted fibers and the absorption behavior and activity of lipase suggest that the PAA grafts are gel-like by ceric-initiated reaction and brush-like by methacrylation and polymerization. The adsorbed lipase on the ceric ion-initiated grafted surface possessed greatly improved organic solvent stability over the crude lipase. The adsorbed lipases exhibited 0.5 and 0.3 of the initial activity in the second and third assay cycles, respectively.
Acrylic acids and alanines substituted with heteroaryl groups at the beta-position were synthesized and spectroscopically characterized (UV, HRMS, (1)H NMR, and (13)C NMR spectroscopy). The heteroaryl groups were furanyl, thiophenyl, benzofuranyl, and benzothiophenyl and contained the alanyl side chains either at the 2- or 3-positions. While the former are good substrates for phenylalanine ammonia-lyase (PAL), the latter compounds are inhibitors. Exceptions are thiophen-3-yl-alanine, a moderate substrate and furan-3-yl-alanine, which is inert. Possible reasons for these exceptions are discussed. Starting from racemic heteroaryl-2-alanines their D-enantiomers were prepared by using a stereodestructive procedure. From the heteroaryl-2-acrylates, the L-enantiomers of the heteroaryl-2-alanines were prepared at high ammonia concentration. These results can be best explained by a Friedel-Crafts-type electrophilic attack at the aromatic part of the substrates as the initial step of the PAL reaction.
Hydrophobically modified poly(acrylic acids) (HMPAs) are random copolymers of sodium acrylate and dodecyl acrylamide, containing 0-10% mol/mol of dodecyl grafts. The hydrophobic character of different HMPAs of average molecular weight 150,000 was studied by capillary electrophoresis (CE), using neutral surfactants as buffer additives. The differentiation of the electrophoretic mobilities of HMPAs with their hydrophobicity was achieved through the use of nonionic Brij 35 and zwitterionic DAPS surfactants. A nearly baseline separation of the precursor and three HMPAs derivatives was obtained in a poly(ethylene glycol)-coated capillary with a background electrolyte containing 10 mM N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DAPS) and 10 mM borax (pH 9.2). In addition to CE experiments, the polymer-surfactant interactions were also investigated by means of quasi-elastic light scattering (QELS) and viscosimetric measurements. According to the latter results, the separation mechanism was interpreted as an expansion of the polymer coil in the presence of micelles and subsequent change of its frictional properties. A true micellar electrokinetic capillary chromatography (MEKC) partitioning model was discarded on the basis of the relative sizes of the macromolecule and the micelles.
A range of zwitterionic acrylic acid derivatives, buffering in the neutral and basic pH ranges, have been synthesized by the Mannich reaction of malonic acid, formaldehyde and a secondary amine. These compounds include 2-(4-morpholinomethyl)propenoic acid pK2 7.59 +/- 0.03 (23 degrees C), 2-[bis(2-hydroxyethyl)aminomethyl]propenoic acid pK2 approximately 8.6 (20 degrees C), 2-[bis(2-hydroxypropyl) aminomethyl]propenoic acid PK2 approximately 8.7 (20 degrees C), 2-[N-(2-hydroxyethyl)-N-methylaminomethyl]propenoic acid pK2 9.22+/-0.08 (22 degrees C), 2-[N-ethyl-N-(2hydroxyethyl)aminomethyl]-propenoic acid pK2 approximately 9.6 (20 degrees C), and 2-[4-(2-carboxyprop-2-enyl)piperazinylmethyl]propenoic acid, which has a sigmoidal buffering profile over the pH range 3-10. These zwitterionic acrylic acid buffers were successfully copolymerized with acrylamide to prepare immobilized pH gradients (IPGs) in the neutral to alkaline portion of the pH range. Bovine erythrocyte carbonic anhydrase isozymes were resolved on a pH 5-8 IPG prepared using 2-[4-(2-carboxyprop-2-enyl)piperazinylmethyl]propenoic acid as the immobilized buffer, and horse heart myoglobin was focused on pH 7.1-8.1 and pH 7.5-7.7 IPGs, using 2-(4-morpholinomethyl)propenoic acid as the immobilized buffer. In both cases the pK 9.3 Immobiline compound was used as the strongly basic titrant. These new compounds, besides possessing more hydrophilic residues than the corresponding commercial basic acrylamido buffers (Immobilines), resist hydrolysis at alkaline pH values.
Two linear polymers of acrylic acid (average molecular weight = 2,000 and 4,500) and one linear copolymer of acrylic and maleic acids (average molecular weight = 12,000) were tested for mutagenicity with the Salmonella mammalian microsome assay, the L5178Y mouse lymphoma assay at the TK locus, an unscheduled DNA synthesis assay in primary cultures of rat hepatocytes, and either an in vitro cytogenetic assay with CHO cells or the bone marrow micronucleus assay in mice. The results of all the assays were uniformly negative for the three polymers.
Advanced micromedical devices may require computer-aided photofabrication, by which microarchitectural surface design and entire macroshaped body design are feasible. Liquid acrylate-endcapped poly(epsilon-caprolactone-co-trimethylene carbonate)s, poly(CL/TMC)s, prepared using trimethylene glycol (TMG) or poly(ethylene glycol) (PEG) as an initiator and an acrylate group for subsequent terminal capping, were used as photocurable copolymers. The stereolithographically microarchitectured photoconstructs were prepared using a custom-designed apparatus with a moving ultraviolet (UV) light pen driven by a computer-assisted design program. The prepared photoconstructs included microneedles, a microcylinder and microbanks on surfaces. In vitro hydrolytic degradation proceeded with surface erosion when hydrophobic TMG-based photocured copolymers were employed, whereas very fast degradation of hydrophilic PEG-based photocured copolymers probably via concerted actions of surface erosion and bulk degradation was observed. In vivo hydrolytic behavior upon subcutaneous implantation in rats indicated that surface erosion proceeded for TMG-based photoconstructs. Anti-inflammatory drug (indomethacin) loading into microneedle-structured surfaces minimized inflammatory reactions. The possible biomedical microarchitectural three dimensinal in biomedical application photoconstructs was discussed.
The use of acrylic bone cement has a number of shortcomings, viz., high curing temperatures that can cause thermal necrosis, release of toxic monomer, and a less than perfect cement-to-bone bond. However, by modifying the cement composition through the addition of a soluble, nontoxic filler such as sucrose or tricalcium phosphate which does not impair the workability of the material during surgery, a significant improvement in the performance of the cement can be achieved. Because the filler replaces part of the acrylic components, less heat is generated during curing while the filler itself acts as a heat sink. Also, less monomer, proportional to the amount replaced by the filler, diffuses from the implant site. Upon elution of the filler, a porous cement will be obtained provided that a critical minimum percentage loading is exceeded so that the filler crystals will make physical contact with each other. The value of this percentage depends on both crystal modification and size. In the 125-175 micron sucrose crystal size range, the critical minimum percentage lies in the range of 20-28 wt% loading. Above 30%, the interconnecting pore size increases sharply to a value which allows good tissue ingrowth into the pores. The introduction of filler and pores causes a drop in strength, but the diametral tensile strength of modified cement containing up to 40% pores and sucrose lies between .7 and 1.5 kg/mm2, respectively, which is still in the same range as that of bone.
An investigation was carried out into the release of chlorhexidine acetate, prednisolone sodium phosphate, and prednisolone alcohol from a cold cured acrylic denture base material. The drugs were added at 10% w/w with the powder phase of the material. Water, at the concentrations of 10%, 20%, and 30% of the monomer phase of the material was added to chlorhexidine-containing and chlorhexidine-free samples. Spectrophotometric and bioassay measurements of the release of chlorhexidine demonstrated protracted delivery to 140 days. The daily release rate was increased by the addition of water to the material and at 30% water incorporation the release was greater and increased up to 190 days. The release pattern of prednisolone sodium phosphate was similar to that of chlorhexidine without the addition of water. Prednisolone alcohol was released for a much shorter period and at lower levels. Scanning electron microscopic examination of the polished, etched, and fractured surfaces of the material demonstrated that chlorhexidine acetate and prednisolone sodium phosphate were incorporated into the interbead matrix areas of the material. The irregularities in the material increased with the addition of water. Prednisolone alcohol produced minimal changes in the specimens except after soaking in water for 140 days when numerous small defects could be seen in the matrix zones at high magnification. The use of materials such as water to increase porosity appears a simple method of improving the release pattern of drugs from acrylic. However, the strength of the resulting material would require support from an existing intraoral prosthesis or appliance.
Quantitative hemolysis assays of acrylate and methacrylate esters provided estimates of the intrinsic hemolytic activity (Hi, the slope of the concentration-response curve) and the concentrations effecting 5% (H5) and 50% (H50) hemolysis. The dependence of hemolytic activity and LD50 (mice) on physical properties (lipophilicity, molar refraction, and molecular volume) of the esters was determined by multiple regression analysis. The observed correlations were: Hi, R2 = 0.94; H5, R2 = 0.95; H50, R2 = 0.94; and LD50, R2 (all compounds) = 0.80, R2 (all compounds less the methyl esters) = 0.94. The difference of the methyl esters was associated with the smaller steric volume of the methyl ester substituent and the presence (methacrylates) or absence (acrylates) of the branched methyl group. Associative steric contributions of the branched methyl group and the ester substituents were probably responsible for greater variability in the methyacrylate series. The results were consistent with the conclusion that the mechanism of the action of the esters is membrane mediated and relatively nonspecific and that in vivo biotransformation was not a significant factor. Also, long-term toxic liability of the esters may be more closely related to intrinsic toxicity than acute toxicity.
Clinical and in vitro studies have implicated dietary components as major aetiological factors in staining of teeth and acrylic materials associated with chlorhexidine use, a local side effect not unique to this antiseptic. These experiments studied the precipitation and surface staining reactions of the cationic antiseptics alexidine, cetyl pyridinium chloride (CPC), chlorhexidine, and hexetidine, with the beverage tea. All of the antiseptics precipitated a standard tea solution and for alexidine and chlorhexidine acetate and gluconate, this was at concentrations greater than 100 mumol/L, for hexetidine greater than 200 mumol/L, and for CPC greater than 400 mumol/L. With the exception of CPC precipitation was reduced with decreasing pH and for chlorhexidine was inhibited below pH 3. The addition of polymethylmethacrylate (PMMA) to the antiseptic solutions increased the precipitation concentrations by an amount calculated to be adsorbed by polymer. Acrylic blocks treated with equimolar solutions of the antiseptics became progressively and significantly more stained by tea than control specimens over a 5-day period. Alexidine induced significantly greater staining and hexetidine significantly less than the other antiseptics. Staining was pH dependent and significantly reduced as the pH decreased. Both stain and precipitates were insoluble in strong acids and alkalis. It is concluded that staining observed clinically may represent a precipitation reaction with the complexing of antiseptics with dietary chromogenic material.