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At least 1,099 records · Page 61Linked to original sources
PubMed1991

Numerical simulation of heating from an acrylic implant in bone.

Heat transfer in an acrylic cement-bone system during hyperthermia has been has been simulated by using a spectral element method, using a 2-D linear model which combines the geometric flexibility of low-order finite element methods and high accuracy of spectral methods. The work is directed at obtaining a fundamental understanding of factors affecting hyperthermia therapy applied to giant cell tumors of bone in a two-dimensional model at a cross-section of the distal femur. Results suggest the heating may be significant within approximately 4 mm to 7 mm of the interface of the acrylic and the cancellous bone. Computational results are compared with published experimental results.

Bone Cements↗
PubMed1987

The use of acrylic copolymers as antibody carriers for immunoaffinity chromatography.

Among several various acrylic copolymer used as carriers for anti-bovine serum albumin the best are copolymers obtained from acrylonitrile and ethyl or butyl acrylate crosslinked with divinylbenzene which after aminolysis with di- or triamines were activated with glutardialdehyde. The immunoadsorbents thus obtained were successfully used for purification of bovine serum albumin from bovine serum or from crude fraction of the albumin by immunoaffinity chromatography. Electrophoretically pure bovine albumin was eluted from immunoadsorbent column with deionised water and with glycine/HCl buffer, pH 2.5. The albumin was contamined with less than 0.1% of bovine immunoglobulins and with 0.05% of rabbit immunoglobulins. No contamination with rabbit immunoglobulin was observed when immunoadsorbents were pre-treated with sodium borohydride.

Acrylonitrile↗
PubMed1987

[Experimental study on osteosarcoma of local chemotherapy diffusing from surgical acrylic cement and plaster].

An experimental study has been made to explore the possibility of using plaster or surgical cement as a vehicle for the diffusion of local chemotherapeutic agents in osteosarcoma. In vitro, leeching out of methotrexate from plaster or acrylic cement occurred with a peak during the first few hours followed by a decreasing curve lasting for an average of two weeks. In dogs suffering from a spontaneous osteosarcoma, the loss of substance produced by excision was filled with cement to which methotrexate had been added extemporaneously. This method of administration produced a general diffusion of methotrexate whose blood levels were measured for three to five days. In laboratory rats into which osteosarcomata had been grafted, tablets of plaster containing antimitotic drug were implanted into the tumour, which was left in situ. This made it possible to show that the local chemotherapy was having a true effect, particularly when the antimitotic used was cisplatinum. In patients who had acrylic cement containing methotrexate inserted during operation, local diffusion resulted in very high concentrations, evidenced by the concentration found in fluid obtained from suction drains during the early days after operation.

Animals↗
PubMed1985

[Use of poly(meth)acrylates for the control and release of pholedrine sulfate from microdragees].

Pellets with pholedrine sulphate are coated by means of a fluid-bed process with six different poly(meth)acrylate coating materials. The coatings showed drug release widely different. A wide pH-independent release showed film-coated pellets with Eudragit RS, RL and E 30D as coating material. By application of Scopacryl D 336, D 339 and D 340 the acceleration of liberation by the pH-value of 7,4 is related to the increasing amount of acrylic acid in polymer. The rate of release can be controlled by mixing coatings with different permeability in wide range. Diagram of logarithm permeability coefficient against the mixing proportion can be used for selection a coating composition with wished permeability.

Capsules↗
PubMed1983

Composite acrylic cement with added hydroxyapatite: a study of the polymerization temperature.

Varying percentages (0 to 50%) of crystalline hydroxyapatite (HA) in powder form were added to ordinary acrylic cement (PMMA). The exothermic peak of the polymerization reaction and the setting time of this compound cement were investigated. Its mechanical properties are far superior to those of ordinary cement. The addition of small percentages of HA to acrylic cement produces a sharp fall in the exothermic polymerization peak; it also increases the setting time, although this remains within time limits that are only slightly greater than those for ordinary cement.

Bone Cements↗
PubMed1984

Antibiotic-loaded acrylic cement: current concepts.

Antibiotic-loaded acrylic cement has been used routinely since 1972 at the authors' hospitals, where a series of some 22,000 joint arthroplasty operations was performed from 1964-1983. The current status of the material is presented with up-to-date follow-up statistics on prophylactic therapy and on established deep infections. The results of 869 exchange arthroplasties are compared with results published in 1981. In the future, results will be presented in the form of survival curves. The method by which survival tables and curves are constructed is critical. Investigators should use survival curves for ease of comparison and because of the wide range of possibilities in an analysis of covariable factors. A retrospective actuarial analysis was made of 825 one-stage reimplantations in which antibiotic-loaded acrylic cement was used for infected total hip arthroplasties. Staphylococcus aureus was the most commonly encountered organism. Failure rates of prostheses infected by S. aureus, S. species, and anaerobic corynebacteria did not differ statistically. A factor that significantly contributed to failure of this method of treatment was Pseudomonas infection. By actuarial analysis five years after operation, a success (survival) rate of 77% was calculated.

Anti-Bacterial Agents↗
PubMed1995

Giant-cell tumours with fracture at diagnosis. Curettage and acrylic cementing in ten cases.

Between 1971 and 1991 we treated 98 patients with giant-cell tumours, 15 of whom presented with a pathological fracture. They were most common around the knee (12). Nine fractures were intra-articular. The tumours were treated by curettage and acrylic cementing (10), excision and endoprosthesis (1), excision and allograft (1), curettage and autologous graft (2) or by resection of the fibular head (1). Four patients had local recurrence, three of whom were cured by repeat curettage and cementing. Pathological fracture through a giant-cell tumour is not a contraindication to treatment by curettage and acrylic cementing.

Adolescent↗
PubMed1976

Curettage and acrylic cementation in surgery of giant cell tumors of bone.

True giant cell tumors of bone (osteoblastomas) are comparatively rare but often large at time of discovery, making the surgical treatment controversial. Simple curettage or resection with bone filling is used when the lesion is small. Resection with arthroplasty or arthrodesis and possibly amputation is used in advanced cases. Thorough curettage with acrylic cementation is presented in a series of 6 cases from Rotterdam and Lund with a follow-up time between 2 and 7 years. The advantages of this method are full and early mobility and stability as well as a simplified postoperative X-ray control, especially when barium sulphate contrast has been added to the acrylic cement. Finally, if this technique is used in cases where more extensive surgery becomes necessary later, there is much to gain and little to lose. The operation may turn out to be the method of choice for this special type of tumor when a simple curettage or resection is no longer possible without loss of function. No recurrences or spread have been observed among these 6 cases. It is suggested that the heat generation could be an advantage of the method.

Adult↗
PubMed2003

Monocyte/macrophage interactions with base and linear- and star-like PEG-modified PEG-poly(acrylic acid) co-polymers.

Poly(ethylene glycol):poly(acrylate) PEG-g-PA co-polymers were made that inhibited nonspecific protein and cellular adhesion. PEG-g-PA co-polymers were then covalently modified with either cell adhesion peptides or fragments of antibodies to monocyte/macrophage integrin receptors (anti-VLA4, anti-beta(1), anti-beta(2), and anti-CD64) known to enhance macrophage adhesion and, perhaps, modulate their activation. Peptides were either directly conjugated to the base material or linked by way of PEO-star tethers. Fragments of the antibody region containing the antigen-binding site (Fab' fragments) were coupled to other PEG-g-PA samples using the sulhydryl end groups on Fab' fragments to amine-bearing PEO stars. Macrophage adhesion rates, phagocytic response (oxidative burst), and cytokine expression were determined for each PEG-g-PA material. Luminol-enhanced chemiluminescence was used as a semiquantitative indication of monocyte-macrophage phagocytic activation (oxidative burst). Macrophage cytokine expression in response to control, base, and modified materials was determined by ELISAs for TNF-alpha, IL-1 beta, IL-6, and IL-8. Tissue culture poly(styrene) (TCPS)-mediated the greatest number of adherent monocyte/macrophage cells relative to PEG-g-PA materials. Both YRGDS and YEILDV peptides, whether directly or indirectly (via StarPEO) conjugated to PEG-g-PA, increased adhesion versus controls. Fab' fragments of all four antibodies also promoted enhanced adhesion versus controls. Fab'StarPEO materials presented two orders of magnitude fewer ligands per surface unit area than peptide star materials (10(8) vs. 10(10)), but were able to adhere similar numbers of cells. For surfaces presenting Fab'(VLA-4) or YEILDV, both of which may both bind to a cell's VLA-4 receptor, the Star:VLA4 surface showed a greater number of adherent monocyte/macrophages. This result suggests that the Fab' had a higher affinity to the cell receptor than a corresponding minimal peptide binding sequence. All materials exhibited low oxidative burst (luminescence counts per minute, LCPM) per cell DNA without the addition of exogenous stimuli (LCPM/DNA < 100). Directly conjugated peptide materials, poly(propylene) (PP), and TCPS showed the lowest levels of LCPM/DNA without the addition of exogenous stimulus (LCPM/DNA < 20). There was no correlation between LCPM/DNA ratios, with and without added LPS stimulus, versus the individual substrates. Monocyte/macrophages adherent to TCPS substrata showed the overall highest stimulatory potential in cytokine expression response to exogenous LPS, followed by PP > PEG-g-PA > StarPEO. Cells adherent to peptide-modified materials and Fab'-modified materials were overall less stimulated. The method of presenting the peptides (i.e., directly or via Star PEO) influenced the level of cytokine secreted by the adherent macrophage.

Acrylates↗
PubMed2006

Preparation and characterization of poly(N-isopropylacrylamide)-modified poly(2-hydroxyethyl acrylate) hydrogels by interpenetrating polymer networks for sustained drug release.

In order to investigate the influence of hydrophobic moieties formed by poly(N-isopropylacrylamide) (PNIPAm) in a hydrogel matrix on the release behavior of the hydrogel, a series of poly(N-isopropylacrylamide) (PNIPAm)-modified poly(2-hydroxyethyl acrylate-co-2-hydroxyethyl 2-hydroxyethyl methacrylate) (P(HEA-co-HEMA)) via interpenetrating polymer networks (IPNs) were prepared by a sequential UV solution polymerization. Interestingly, it was found that P(HEA-co-HEMA)/PNIPAm IPN indicated a single glass transition temperature (T(g)) and the T(g)s of the IPNs increased with an increase in the PNIPAm component. This phenomenon may be attributed to hydrogen bonding between the two polymer networks, but the hydrogen bonding exerts less influence on the swelling behavior of the IPNs, due to the fact that IPNs can respond to changes in temperature like PNIPAm. Using 2-[(diphenylmethyl)sulphiny]acetamide (modafinil, MOD) and p-hydroxybenzoic acid (HBA) as model drug compounds, the release behavior of the IPNs was studied at body temperature, and it was found that the presence of PNIPAm could retard drug release regardless of the solubility of the drugs. Release profiles of HBA from the IPNs and their component samples as a function of time at 37 degrees C.

Acrylates↗
PubMed2004

Interaction between pentaethylene glycol n-octyl ether and low-molecular-weight poly(acrylic acid).

The interaction between pentaethylene glycol n-octyl ether (C8E5) and low-molecular-weight poly(acrylic acid) (PAA, M(w)=2000) in aqueous solution has been investigated by various experimental techniques at constant polymer concentration (0.1% w/w) with varying surfactant molality. Spectrofluorimetry, using pyrene as molecular probe, shows (i) the formation of surfactant-polymer aggregates at a surfactant molality (T(1)) lower than the critical micelle concentration (cmc) of C8E5 in water and (ii) the formation of free micelles at a surfactant molality (T(2)) slightly higher than the cmc. Fluorescence quenching measurements indicate that the presence of PAA induces a lowering of the C8E5 aggregation number. Calorimetry confirms spectrofluorimetric evidence; in addition, it shows the presence of weak interactions below T(1) between monomeric surfactant molecules and the polymer chains. Tensiometry shows that, above T(1), only a low fraction of surfactant molecules interact with the polymer and that free micelle formation occurs before polymer saturation. The peculiarities of the interaction between surfactants and low-molecular-weight polymers have been discussed.

Acrylates↗
PubMed2004

Poly(N-isopropylacrylamide)-based semi-interpenetrating polymer networks for tissue engineering applications. Effects of linear poly(acrylic acid) chains on rheology.

Semi-interpenetrating polymer networks (semi-IPNs), comprised of poly(N-isopropylacrylamide-co-acrylic acid) (p(NIPAAm-co-AAc)) hydrogels and linear p(AAc) chains, were synthesized, and the effects of the p(AAc) chains on semi-IPN rheology were examined. Oscillatory shear rheometry studies were performed and the rheological data were analyzed as a function of temperature, frequency, and p(AAc) chain amount (weight average molecular weight (Mw) 4.5 x 10(5) g/mol). At 22 degrees C, the semi-IPNs, as well as control p(NIPAAm-co-AAc) hydrogels, demonstrated rheological data that were representative of soft, loosely cross-linked solids. Furthermore, only the highest p(AAc) chain amount tested affected the rigidity of the p(NIPAAm-co-AAc)-based semi-IPNs, as compared to the p(NIPAAm-co-AAc) hydrogels. At 37 degrees C, the complex shear moduli (G*) demonstrated by the p(NIPAAm-co-AAc)-based semi-IPNs were significantly greater than G* exhibited by the p(NIPAAm-co-AAc) hydrogels, and the semi-IPN G* values significantly increased with increasing p(AAc) chain amount. These results can be used to develop p(NIPAAm)-based semi-IPNs with tailored mechanical properties that may function as scaffolds in tissue engineering initiatives.

Acrylates↗
PubMed2004

The effect of pH on the LCST of poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide-co-acrylic acid).

Poly(N-isopropylacrylamide) (PNIPAAm) and poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAAm-co-AAc)) hydrogels are synthesized by irradiating the aqueous solutions of NIPAAm and NIPAAm/AAc with 60Co gamma-ray. The effects of pH on the swelling ratio and on the lower critical solution temperature (LCST) are studied by determining the dependence of swelling ratio on temperature in different pH butter solutions. Differential scanning calorimetry (DSC) is applied in determination of the LCST of the hydrogels. Fourier transform infrared (FT-IR) spectrometry is used in the comparison of hydrogels swelled in various pH conditions. As a result, PNIPAAm was found to be a pH-sensitive hydrogel and the LCST of the PNIPAAm and P(NIPAAm-co-AAc) hydrogels are influenced by pH.

Acrylamides↗
PubMedDate not supplied

Spontaneous formation of drug-containing acrylic nanoparticles.

Nanoparticles containing ibuprofen, indomethacin or propranolol were formed spontaneously after the addition of solutions of the drugs and acrylic polymers (Eudragit RS or RL 100) in the water-miscible solvents, acetone or ethanol, to water without sonication or microfluidization. The colloidal dispersions were stabilized by quaternary ammonium groups and did not require the addition of surfactants or polymeric stabilizers. The nanoparticles were compared to nanoparticles prepared either by a microfluidization-solvent evaporation method with a water-immiscible organic solvent, methylene chloride, or by a melt method with respect to particle size and redispersibility of freeze- or spray-dried samples. Nanoparticles prepared by microfluidization or the melt method were easily redispersed while Eudragit RS nanoparticles prepared by spontaneous emulsification were not redispersible. Flexible films were formed from the nanosuspensions after the addition of 15 per cent triethyl citrate, a water-soluble plasticizer. The release of propranolol from the films increased with increasing proportion of RL, but was independent of the order of mixing of the two polymers or nanosuspensions during film preparation. The drug release from indomethacin films was increased by adding water-soluble polymers to the nanosuspension.

Acrylates↗
PubMed1996

Mechanical properties of single pellets containing acrylic polymers.

Three aqueous-based acrylic latex dispersions, Eudragit L 30 D, NE 30 D, and RS 30 D, were incorporated as granulating binders into a powder blend of microcrystalline cellulose and anhydrous lactose by wet massing. Spheronized pellets were prepared by extrusion-spheronization and the mechanical properties of single pellets, including the tensile strength at break and the Young's modulus were determined from the stress-strain profiles using a Chatillon TCD-200 tension/compression digital test gauge. The influence of particle size and plasticizer on the mechanical properties of pellets containing Eudragit RS 30 D was investigated. All bead formulations deformed by brittle fracture under a diametral compression force. The mechanical strength was found to be influenced by the adhesive strength between the polymers and the powder particles instead of the cohesive strength of each polymer. The Young's modulus and the tensile strength were also significantly influenced by the type and concentration of polymer, the presence of plasticizer, and the particle size of the beads. The results were related to the properties of the polymers and the fracture mechanisms of the beads. Furthermore, the polymer type and the incorporation of plasticizer influenced the susceptibility of the moistened extruded granules to the shearing forces during the spheronization process, which influenced the surface morphological properties of the pellets.

Acrylates↗
PubMed1996

Calorimetric characterization of the formation of acrylic type bone cements.

The formation of acrylic bone cements upon heating was investigated by differential scanning calorimetry (DSC). The effects of the contents of initiators, accelerator, biocompatibilizer, and crosslinking agents on the rate and the heat of polymerization during DSC heating were studied. The rate and the heat of polymerization (delta H) were characterized by the peak temperature and the area of the DSC exotherm, respectively. It was found that both the rate and heat of polymerization decreased with increasing heating rate. The delta H was increased considerably with increasing benzoyl peroxide (BPO) initiator concentration from 1 to 10% (w/v), whereas the rate of polymerization was reduced significantly. An increase in azobisisobutyronitrile (AIBN) initiator concentration also induced an increase in delta H, but the rate of reaction was not affected considerably. The addition of accelerator promoted the rate of reaction but resulted in a drop in delta H. The rate of polymerization for the system containing BPO initiator was increased quite significantly with the addition of hydroxyethyl methacrylate (HEMA) biocompatibilizer, while the delta H was slightly increased. For the system using AIBN as the initiator, the rate of polymerization was decreased slightly and the delta H dropped significantly with the addition of HEMA. The effect of ethylene glycol dimethacrylate (EGDMA) crosslinking agent was also examined. Polymerization became more rapid with the addition of EGDMA in the bone cement using BPO initiator, while it remained approximately constant for the system using AIBN as the initiator. No systematic change in delta H was observed with the addition of EGDMA in both systems. This study demonstrated that DSC is a potential tool to measure the amount of heat released and also the rate of polymerization for bone cements.

Acrylates↗
PubMed1997

Application of tertiary amines with reduced toxicity to the curing process of acrylic bone cements.

4-Dimethylaminobenzyl alcohol (DMOH) and 4-dimethylaminobenzyl methacrylate (DMMO) were used as the activators in the benzoyl peroxide initiated redox polymerization for the preparation of acrylic bone cement based on poly(methylmethacrylate) beads of different particle size. The residual monomer content of the cured cements was about 2 wt %, independent of the redox system used in the polymerization, indicating that the activating effect of the tertiary aromatic amines DMOH or DMMO was sufficient to reach a polymerization conversion similar to that obtained with the benzoyl peroxide (BPO) N,N-dimethyl-4-toluidine (DMT) system. The BPO/DMOH and BPO/DMMO redox systems provided exotherms of decreasing peak temperature and increasing setting time, and the cured materials presented higher average molecular weight and similar glass transition temperatures in comparison with those obtained when DMT was used as the activator. In addition, these activators are three times less toxic than the classical DMT.

Acrylates↗
PubMed1997

Reduced plaque accumulation on hydrocarbon thin film deposited on restorative acrylic polymers.

The deposition of a thin polymeric film from ethylene plasma was used to modify the surface properties of acrylic teeth, commonly used in the dental practice for crown and bridge restorations. The effects of the surface modification process on the surface composition, morphology, and energetics were evaluated by electron spectroscopy for chemical analysis, atomic force microscopy, and contact angle measurement respectively. Plaque accumulation on the plasma-coated and untreated material was evaluated in in vivo experiments, in which the same patient received conventional and plasma-coated restorations. The hydrocarbon-like surface of the plasma-coated restoration remained remarkably free from plaque, even in the absence of brushing. On the other hand, plaque accumulation was observed on the unmodified restoration. Results are discussed according to recent theories on bioadhesive phenomena.

Acrylates↗