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PubMed2005

Fluorescence ratiometric pH sensor prepared from covalently immobilized porphyrin and benzothioxanthene.

A fluorescence ratiometric sensor for pH determination is described in this paper. The sensor incorporated the pH-sensitive dye meso-5,10,15,20-tetra-(4-allyloxyphenyl)porphyrin (TAPP) as an indicator and a pH-insensitive dye N-(2-methacryloxyethyl)benzo[k,l]thioxanthene-3,4-dicarboximide (MBTD), a benzothioxanthene derivative, as a reference for fluorescence ratiometric measurement. To prevent leakage of the dyes, both were photocopolymerized with acrylamide, hydroxyethyl methacrylate, and triethylene glycol dimethacrylate on the silanized glass surface. The reproducibility and response time of the prepared sensor were sufficient. Most common coexisting inorganic ions and organic compounds did not interfere with pH sensing. In the acidic pH range from 1.5 to 5.0 the fluorescence intensity ratio of the two dyes varied linearly as a function of pH. The sensing membrane was found to have a lifetime of at least one month. The sensor was applied to the analysis of waste water and artificial samples.

Acrylamide↗

PubMed2004

pH-independent release of a basic drug from pellets coated with the extended release polymer dispersion Kollicoat SR 30 D and the enteric polymer dispersion Kollicoat MAE 30 DP.

The objective of this study was to obtain pH-independent release profiles from coated pellets containing drugs with pH-dependent solubility. pH-independent release of the basic model drug verapamil HCl was achieved by coating with a combination of the neutral polymer dispersions Kollicoat SR 30 D (aqueous dispersion of polyvinyl acetate) and the enteric polymer dispersion Kollicoat MAE 30 DP (aqueous dispersion of methacrylic acid and ethyl acrylate copolymer; methacrylic acid copolymer type C). The two polymers where applied either as separate layers (enteric polymer + extended release polymer or vice versa) or as a polymer blend. A careful balance of the ratios of the polymers allowed the achievement of a pH-independent release. Higher amounts of the enteric polymer in the polymer blend resulted in a reversal of the pH-dependency, e.g. a faster release at pH 6.8 than in 0.1 N HCl.

Delayed-Action Preparations↗

PubMed2005

Drug release from complexes with a series of poly(carboxyalkyl methacrylates), a new class of weak polyelectrolytes.

Carboxyalkyl methacrylates, a new class of non-cross-linked, hydrophobic weak polyelectrolytes, were synthesized, and then bound to cationic drugs (propranolol.HCl, diltiazem.HCl and verapamil.HCl) to form water-insoluble complexes that release the bound drug only in ionic media (pH 7.4). Compressed tablets were prepared from these cation exchange polyelectrolytes. Release profiles followed zero order kinetics (n>0.90; n is the release exponent). As the hydrophobicity of the polyelectrolytes increased, the rate of release decreased and deviated from linearity (n=0.7). Both the ionic strength of the medium as well as the solubility of the drug affected the rate of release. In acidic media (pH 1.2) a burst of drug was released but the release was halted by a layer of non-ionized polymer precipitated on the surface of the tablets. The results indicate that it is possible to "tailor-make" the release kinetics by using a polyelectrolyte from the series with the suitable hydrophobicity.

Cations↗

PubMed1995

Poly(methacrylic acid)-induced liposome aggregation for measuring drug entrapment.

This report characterizes a procedure for rapidly and accurately determining the entrapment of vincristine or other water-soluble drugs in polyethylene glycol-derivatized liposomes. Rapid liposome aggregation with poly(methacrylic acid) and pelleting by mild centrifugation separates liposome-associated vincristine from unentrapped drug. After collecting the supernatant fraction, the pellet is resuspended and solubilized in isopropyl alcohol. Quantitative uv spectrophotometry determines vincristine mass in both fractions. The mean accuracy (recovery) is 100.6% over an entrapped drug range from 70 to 99%. Within and between day precision of the method has a relative standard deviation of 0.76% for a single measurement.

Centrifugation↗

PubMed2000

Effect of formulation and processing variables on the characteristics of microspheres for water-soluble drugs prepared by w/o/o double emulsion solvent diffusion method.

80% except for acetaminophen, due to its lower solubility in water and higher solubility in corn oil. The release profile of the drug was pH dependent. In acidic medium, the release rate was much slower, however, the drug was released quickly at pH 7.4. Tacrine showed unexpected release profiles, probably due to ionic interaction with polymer matrix and the shell structure and the highest release rate was obtained at pH 2.0. The prepared microspheres had a sponge-like inner structure with or without central hollow core and the surface was dense with no apparent pores.

Acetaminophen↗

PubMed1987

Monkey pulp reactions to cavities treated with Gluma Dentin Bond and restored with a microfilled composite.

Deep buccal cavities were cut in 72 incisors and canines in six young monkeys. The cavities were restored as follows: Group One: acid etching of the enamel followed by an intermediate layer of unfilled resin and a light-cured microfilled composite. Group Two: acid etching of the enamel followed by treatment of the dentin with Gluma Cleanser and Gluma Bond. The cavities were restored as in Group One. Group Three: same procedure as in Group Two except for application of a calcium hydroxide cement on the pulpal wall prior to acid etching. Pulp reactions, presence and location of bacteria were studied after 8 and 90 days. A significant association between presence of bacteria and moderate to severe inflammatory reactions were observed. Bacteria were only found in a very few cavities pretreated with Gluma Dentin Bond. In general, slight inflammatory changes prevailed in Groups Two and Three. When the pulpal wall was extremely thin a toxic effect of Gluma Dentin Bond was observed.

Adhesives↗

PubMed1992

New medical-purpose absorbent materials based on polyacrylic acid and alpha-cyanoacrylates, their structure and properties.

Hydrophylic porous polymers (HPP) obtained by polymerization of the alpha-cyanoacrylates under contact with solution of the polymeric carboxylic acids has the degree of water absorption up to 50.000 percent. Disclosed are the data on the HPP porosity investigation, water absorptions HPP are not toxic, do not exhibit allergenic and irritative actions, admit introduction of the medicine into HPP. The HPP films and sheets were used in the course of the experiment for treatment of purulent wounds. Their high effectiveness expressed in reduction of the adhesion time by 1.5 to 2 times was established.

Absorption↗

PubMedDate not supplied

An engineered microenvironment for multidimensional microscopy of live cells.

Multidimensional imaging (MD) of live cells is gaining importance in biomedical research as the commercial availability of confocal, nonlinear optical microscopes, environmental chambers, and specific fluorescence probes grows. One crucial aspect of the MD live cell imaging involves the proper immobilization of cells, which refers to the rapid and sufficient immobilization of cells on the microscope stage, neither disrupting the cellular structure and functions nor affecting the optical properties of the cells and the environments. Conventional cell immobilization methods glue the anchoring cells to coated surfaces, but such methods require centrifugation or extended incubation and are not suitable for cells in suspension. Most of the current three-dimensional (3-D) gels either exhibit unsatisfactory optical properties or have adverse effects on cell functions in culture. Recently, an engineered 3-D microcapsule has been developed that involves the complex coacervation of a positively charged collagen and a negatively charged polymer of 2-hydroxyethyl methacrylate--methacrylic acid--methyl methacrylate (HEMA-MMA-MAA). Hence, confocal imaging of live cells in this engineered 3-D microenvironment was investigated for its optical properties and cellular function compatibility. We report here that this microenvironment facilitates efficient cell immobilization, exhibits good optical properties, and can preserve cellular structures and functions, which will be useful in MD imaging of live cells for various applications.

Animals↗

PubMedDate not supplied

Affinity precipitation of proteins.

Affinity precipitation is being studied as a technique to be introduced at an early stage of downstream processing for the selective isolation of proteins. The technique utilizes a heterobifunctional ligand, which, in addition to having affinity for the target protein(s), possesses another function for controlling precipitation. The latter component is comprised of a polymer which can be made reversibly soluble and insoluble by altering a specific parameter such as pH or temperature. Different polymers of natural and synthetic origin have been used for this purpose. The soluble form of the ligand is used for the affinity binding step and precipitation is induced for obtaining separation of the affinity complex. Some of the polymers used in this laboratory include chitosan, alginate, Eudragit S-100 (copolymer of methacrylic acid and methyl methacrylate) and polyethyleneimine. Chitosan and alginate served as natural ligands for wheat germ agglutinin and pectinase, respectively. The aromatic dye Cibacron Blue 3GA coupled to Eudragit S 100 and polyethyleneimine way used for the affinity precipitation of some model enzymes such as lactate dehydrogenase and alcohol dehydrogenase. As prior removal of cell debris, etc., is essential for affinity precipitation, the possibility of integration of the technique with extraction in aqueous two-phase systems was also demonstrated.

Chemical Precipitation↗

PubMed1998

Effect of drug-polymer interaction on the release characteristics of methacrylic acid copolymer microcapsules containing theophylline.

Theophylline anhydrate microcapsules with different amounts of MA/MMA copolymer (Eudragit L) were prepared by the solvent evaporation method. Qualitative as well as quantitative investigation of the drug-polymer interaction by Fourier transform infrared (FTIR) spectroscopy with a curve fitting program was undertaken. The release mechanisms of theophylline in pH 1.2 and pH 6.8 media were also studied to elucidate the effect of drug-polymer interaction on the release characteristics of microcapsules. Direct evidence for a hydrogen bonding interaction between theophylline and Eudragit L in microcapsules was obtained. Moreover, the fraction of hydrogen bonded theophylline increased with the increase of Eudragit L. The dissolution of theophylline from microcapsules exhibited an enteric-coated release property. The drug release mechanism was found to fit the Higuchi matrix model in the simulated gastric acid condition, but drug release was much more rapid in the pH 6.8 buffer solution. The drug release rate decreased as the composition of theophylline increased, and it was proportional to the fraction of hydrogen bonded theophylline. These results suggest that the increased fraction of hydrogen bonded theophylline in microencapsulation might improve the mixing and dispersibility of theophylline in the Eudragit L matrix, thus resulting in the increase of the release rate of theophylline from microcapsules.

Chemical Phenomena↗

PubMedDate not supplied

The interaction of urea with the generic class of poly(2-hydroxyethyl methacrylate) hydrogels.

Work reported here shows that, contrary to reports in the literature, hydrogels made from pure poly(2-hydroxyethyl methacrylate), pHEMA, at crosslinker content greater than 0.15 mol % do not swell above the usual equilibrium values of 39-42% water content in aqueous urea solution. However, hydrogels containing small (impurity) amounts of methacrylic acid (MAA) do swell dramatically (approximately 90%) in dilute urea solution, but not directly due to the urea. The urea decomposes to produce ammonium ions, thus raising the pH of the solution. Ionization of MAA occurs above pH 6, causing electrostatic interactions within the gel. The grossly swollen state of these gels represents an internal equilibrium among forces due to rubber elasticity, polymer-polymer/solvent affinity, and electrostatic interactions.

Aluminum Hydroxide↗

PubMed2004

The effect of surface treatment of hydroxyapatite on the properties of a bioactive bone cement.

Bioactive bone cements based on a paste-paste system for orthopaedic applications have been developed. They consist of hydroxyapatite (HA) filler particles in a methacrylate matrix comprising urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA). To improve the interface between inorganic filler and organic matrix the HA particles were subjected to two different surface treatment methods, using polyacrylic acid (PAA) and gamma-methacryloxypropyltrimethoxy silane (gammaMPS). The aim of the present study was to determine the influence of surface treatment on the mechanical properties, namely compressive strength (CS), diametral tensile strength (DTS) and three-point flexural strength (FS) of the cements and the effect of ageing in simulated body fluid (SBF). Comparing the mechanical properties of the two cements after fabrication, the gammaMPS-HA cement showed higher strength values for all tests conducted (CS = 185+/-19.6 MPa, DTS = 27+/-2.5 MPa, FS=50.2+/-4.9 MPa), whereas PAA-HA containing cement had strength values around 20% lower. However, poly(acrylic acid) surface treatment was found to be more effective in improving the interface, and PAA-HA cements maintained their mechanical properties after immersion in SBF whereas gammaMPS-HA cement showed a reduction in strength values post ageing. From the results of this study, it is concluded that PAA treatment of the HA filler is a viable alternative to silanation with gammaMPS which may provide increased durability in aqueous environments.

Acrylic Resins↗

PubMedDate not supplied

Formulation and in vitro characterization of ciprofloxacin floating and bioadhesive extended-release tablets.

Ciprofloxacin is mainly absorbed in the proximal areas of the gastrointestinal tract. The purpose of our study was production of floating-bioadhesive tablets to lengthen the stay of drug in its absorption area. Effervescent tablets were made using sodium carboxymethyl cellulose (CMC), hydroxypropyl methylcellulose (HPMC), polyacrylic acid (AA), polymetacrylic acid (MAA), citric acid, and sodium bicarbonate. Tablets with 5% effervescent base had longer lag time than 10%. The type of polymer had no significant effect on the floating lag time. All tablets floated atop the medium for 23-24 hr. Increasing CMC caused higher mucoadhesion than AA (p < 0.05). All formulations showed a Higuchi, non-Fickian release mechanism. Tablets with 10% effervescent base, 80% CMC/20% HPMC, or 80% AA /20% MAA seemed desirable.

Acrylic Resins↗

PubMed1981

Localized chemotherapy of Gardner's lymphosarcoma of C3H mice using combinations of carrier-sorbed antifolics and detoxicating tetrahydrofolates.

The effect of aminohexyl-2-hydroxyethylmethacrylate polymer (HEMA-Hex) with sorbed methotrexate (MTX) or 3',5'-dibromoaminopterin (BrAP) on the survival of C3H mice with Gardner lymphosarcoma was studied. The measured bits of HEMA-Hex-MTX or HEMA-Hex-BrAP were implanted into the solid tumor growing 4 to 8 8 days. The doses of sorbed antimetabolites amounting in MTX 4.3 to 13.5 mg.kg-1 and in BrAP 5.1 and 12.6 mg.kg-1 were calculated from the area of the carrier and mean weight of animals. Following implantation i. p. injections of leucovorin or anhydroleucovorin were applied. The treatment of early tumors showed better results than that of advanced ones if evaluated either as prolonged survival or as a number of mice surviving the observation period. The 18-hr. interval between implantation of HEMA-Hex-MTX and anhydroleucovorin injection was optimum if considered both the protection of mice from lethal MTX toxicity and therapeutic effect measured as prolonged survival. Doses of leucovorin or anhydroleucovorin close to MTX doses in term mg.kg-1 resulted in best results. In case leucovorin was applied to tumor-bearing mice pretreated with HEMA-Hex with nonlethal dose of MTX, the survival of mice was shortened. Folic acid did not show this effect. Intra-tumorous implantation of HEMA-Hex-BrAP toxicity even if applied into an advanced tumor. The therapeutic effect of the sorbed BrAP seemed to decrease with tumor progression at a lower rate than of that the sorbed MTX. The application of anhydroleucovorin after implantation of HEMA-Hex-BrAP shortened the survival of tumor-bearing mice.

Aminopterin↗

PubMed1994

Effect of wettability of adhesive resins on bonding to dentin.

The purpose of this study was to investigate on human dentin the relationships between, on the one hand, the wettability of five adhesive compounds, characterized by different solubility parameters delta, and on the other, the thickness of the resin impregnated dentin layer (RIL) and the shear bond strength (SBS). Cut dentin surfaces were treated with conditioners of pH 1.25, 3.6 or 7.4. Shear bond strength was measured on 20 specimens each. RIL was determined by scanning electron microscope on specimens fractured perpendicularly to the bonding interface. When resins with delta 32, 30 or 39 (MJ1/2/m3/2) were used RILs were consistently 4 microns and 1 micron on dentin pretreated with the two acidic conditioners. No clearly measurable RIL was shown after application of the conditioner with pH 7.4, and when resins with delta-values of 20 and 25 were applied. For the same adhesive no difference in SBS was found, when applied on the differently conditioned dentin sites. Resins with delta > 30 produced significantly higher SBS than the two adhesives with smaller delta.

Analysis of Variance↗

PubMed2004

Oral insulin delivery using P(MAA-g-EG) hydrogels: effects of network morphology on insulin delivery characteristics.

Hydrogels of poly(methacrylic acid-g-ethylene glycol) were prepared using different reaction water contents in order to vary the network mesh size, swelling behavior and insulin loading/release kinetics. Gels prepared with greater reaction solvent contents swelled to a greater degree and had a larger network mesh size. All of the hydrogels were able to incorporate insulin and protected it from release in acidic media. At higher pH (7.4), the release rates increased with reaction solvent content. Using a closed loop animal model, all of the insulin loaded formulations produced significant insulin absorption in the upper small intestine combined with hypoglycemic effects. In these studies, bioavailabilities ranged from 4.6% to 7.2% and were dependent on reaction solvent content.

Administration, Oral↗

PubMed1994

Some "sealants" seal--a scanning electron microscopy (SEM) investigation.

White spot lesions of enamel around orthodontic brackets as a result of demineralization have been well documented in the orthodontic literature. Various methods of treatment have been attempted to reduce or eliminate this danger. The purpose of this study was to evaluate, by means of scanning electron microscopy, the polymerization of the sealant layer around orthodontic brackets with direct and indirect methods of bonding. Twenty-four sound human lateral maxillary incisor teeth were collected, cleaned, divided equally into four groups A through D, and stored in 70% ethyl alcohol. Their buccal surfaces were pumiced, etched with 37% phosphoric acid for 1 minute, and washed under running water for 30 seconds. Metal brackets were bonded with the chemically cured BIS-GMA resin, Ortho Concise, as follows: group A, indirectly bonded with coping; group B, indirectly bonded without coping; and group C, directly bonded; light activated Transbond was used in group D, directly bonded brackets. After washing in alcohol for 20 seconds, all teeth were dried, and sectioned longitudinally, through the middle of the bracket. All were subjected to 5% hydrochloric acid for 30 seconds and then washed under running water for 30 seconds. After drying and sputter coating, the teeth were viewed under scanning electron microscopy. Groups A and D showed a sealant layer surrounding the brackets and covering the buccal enamel. Groups B and C showed total absence of a cured sealant layer around the brackets or surrounding enamel.(ABSTRACT TRUNCATED AT 250 WORDS)

Bisphenol A-Glycidyl Methacrylate↗

PubMed2003

Design of a new water-soluble pressure-sensitive adhesive for patch preparation.

This work was intended to improve the adhesion properties of an available medical water-soluble pressure-sensitive adhesive (PSA) through the addition of cellulose ethers or polyvinylpyrrolidone (PVP). The adhesion properties were evaluated by means of peel adhesion test and creep resistance test. Possible interactions between the polymethyl methacrylate (PMMA) and hydrocolloid were investigated by Fourier-transformed infrared spectroscopy. Moreover, a central composite design was used to estimate the effects of hydrocolloids and plasticizers and their interactions on the PSA performance. The addition of PVP made it possible to obtain a patch with a 40-fold improved creep compliance and a reduced peel adhesion. The significant increase of the matrix cohesion was due to attractive interactions between the amide group of PVP and the carboxylic acid group of PMMA. The water vapor permeability of the prepared systems was very high. Furthermore, no primary skin irritation was observed. The presence of plasticizers at high level increased both the peel values and creep compliance, showing an opposite behavior with respect to PVP. The new PSA system can be easily removed from the skin, is suitable for repeated applications on the same site, and has adhesive properties that can be modified by changing the component ratios.

Adhesives↗