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International Journal of Molecular... Jul 2023The hard template method for the preparation of monodisperse mesoporous silica microspheres (MPSMs) has been established in recent years. In this process, in...
The hard template method for the preparation of monodisperse mesoporous silica microspheres (MPSMs) has been established in recent years. In this process, in situ-generated silica nanoparticles (SNPs) enter the porous organic template and control the size and pore parameters of the final MPSMs. Here, the sizes of the deposited SNPs are determined by the hydrolysis and condensation rates of different alkoxysilanes in a base catalyzed sol-gel process. Thus, tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS) and tetrabutyl orthosilicate (TBOS) were sol-gel processed in the presence of amino-functionalized (glycidyl methacrylate--ethylene glycol dimethacrylate) ((GMA--EDMA)) templates. The size of the final MPSMs covers a broad range of 0.5-7.3 µm and a median pore size distribution from 4.0 to 24.9 nm. Moreover, the specific surface area can be adjusted between 271 and 637 m g. Also, the properties and morphology of the MPSMs differ according to the SNPs. Furthermore, the combination of different alkoxysilanes allows the individual design of the morphology and pore parameters of the silica particles. Selected MPSMs were packed into columns and successfully applied as stationary phases in high-performance liquid chromatography (HPLC) in the separation of various water-soluble vitamins.
Topics: Silicon Dioxide; Methylmethacrylates; Nanoparticles; Microspheres
PubMed: 37511487
DOI: 10.3390/ijms241411729 -
Molecules (Basel, Switzerland) Sep 2022Use of iron-based catalysts in atom transfer radical polymerization (ATRP) is very interesting because of the abundance of the metal and its biocompatibility. Although...
Use of iron-based catalysts in atom transfer radical polymerization (ATRP) is very interesting because of the abundance of the metal and its biocompatibility. Although the mechanism of action is not well understood yet, iron halide salts are usually used as catalysts, often in the presence of nitrogen or phosphorous ligands (L). In this study, electrochemically mediated ATRP (eATRP) of methyl methacrylate (MMA) catalyzed by FeCl3, both in the absence and presence of additional ligands, was investigated in dimethylformamide. The electrochemical behavior of FeCl3 and FeCl3/L was deeply investigated showing the speciation of Fe(III) and Fe(II) and the role played by added ligands. It is shown that amine ligands form stable iron complexes, whereas phosphines act as reducing agents. eATRP of MMA catalyzed by FeCl3 was investigated in different conditions. In particular, the effects of temperature, catalyst concentration, catalyst-to-initiator ratio, halide ion excess and added ligands were investigated. In general, polymerization was moderately fast but difficult to control. Surprisingly, the best results were obtained with FeCl3 without any other ligand. Electrogenerated Fe(II) effectively activates the dormant chains but deactivation of the propagating radicals by Fe(III) species is less efficient, resulting in dispersity > 1.5, unless a high concentration of FeCl3 is used.
Topics: Amines; Catalysis; Dimethylformamide; Ferrous Compounds; Iron; Ligands; Methacrylates; Methylmethacrylate; Nitrogen; Polymerization; Reducing Agents; Salts
PubMed: 36234849
DOI: 10.3390/molecules27196312 -
British Medical Journal Feb 1972Experiments were carried out on dogs in an attempt to identify the mechanisms underlying the systemic hypotension associated with the application of acrylic cement...
Experiments were carried out on dogs in an attempt to identify the mechanisms underlying the systemic hypotension associated with the application of acrylic cement substances to raw bone surfaces, as in reconstructive hip surgery. Intravenous injection of the liquid component of such cements (monomeric methylmethacrylate) into six dogs produced a significant fall in blood pressure together with an increase in heart rate and cardiac output. This seemed to be due to peripheral vasodilatation caused directly by the monomer and not through the release of histamine. Absorption of free monomer from the mixed cement into the systemic circulation at operation is likely to have the same effect. Precautionary measures can be taken and groups of patients who are especially at risk can be identified, thus reducing the hazards of total hip replacement.
Topics: Acrylic Resins; Animals; Blood Pressure; Bone Cements; Cardiac Output; Cardiovascular System; Central Venous Pressure; Dogs; Heart Rate; Hip Joint; Injections, Intravenous; Liver Circulation; Methylmethacrylates; Perfusion; Vasodilator Agents
PubMed: 5008662
DOI: 10.1136/bmj.1.5796.349 -
Molecules (Basel, Switzerland) Sep 2022In this research, a new biodegradable and eco-friendly adsorbent, starch-grafted polymethyl methacrylate (St-g-PMMA) was synthesized. The St-g-PMMA was synthesized by a...
In this research, a new biodegradable and eco-friendly adsorbent, starch-grafted polymethyl methacrylate (St-g-PMMA) was synthesized. The St-g-PMMA was synthesized by a free radical polymerization reaction in which methyl methacrylate (MMA) was grafted onto a starch polymer chain. The reaction was performed in water in the presence of a potassium persulfate (KPS) initiator. The structure and different properties of the St-g-PMMA was explored by FT-IR, 1H NMR, TGA, SEM and XRD. After characterization, the St-g-PMMA was used for the removal of MB dye. Different adsorption parameters, such as effect of adsorbent dose, effect of pH, effect of initial concentration of dye solution, effect of contact time and comparative adsorption study were investigated. The St-g-PMMA showed a maximum removal percentage (R%) of 97% towards MB. The other parameters, such as the isothermal and kinetic models, were fitted to the experimental data. The results showed that the Langmuir adsorption and pseudo second order kinetic models were best fitted to experimental data with a regression coefficient of R = 0.93 and 0.99, respectively.
Topics: Adsorption; Free Radicals; Gentamicins; Hydrogen-Ion Concentration; Kinetics; Methacrylates; Methylene Blue; Methylmethacrylates; Polymerization; Polymethyl Methacrylate; Spectroscopy, Fourier Transform Infrared; Starch; Water; Water Pollutants, Chemical
PubMed: 36144579
DOI: 10.3390/molecules27185844 -
British Medical Journal (Clinical... Sep 1981
Topics: Bone Cements; Bone Neoplasms; Fracture Fixation, Internal; Fractures, Spontaneous; Humans; Methylmethacrylates
PubMed: 6791732
DOI: 10.1136/bmj.283.6294.748 -
Oral Diseases Jul 2016Candida-induced denture stomatitis is a common debilitating problem among denture wearers. Previously, we described the fabrication of a new denture material that...
OBJECTIVE
Candida-induced denture stomatitis is a common debilitating problem among denture wearers. Previously, we described the fabrication of a new denture material that released antifungal drugs when immersed in phosphate buffered saline. Here, we use more clinically relevant immersion conditions (human saliva; 37°C) and measure miconazole release and bioactivity.
MATERIALS AND METHODS
Disks were prepared by grafting PNVP [poly(N-vinyl-2-pyrrolidinone)] onto PMMA [poly(methylmethacrylate)] using plasma initiation (PMMA-g-PNVP) and then loaded with miconazole. Drug-loaded disks were immersed in 10-100% human saliva (1-30 days). Miconazole release was measured and then tested for bioactivity vs miconazole-sensitive and miconazole-resistant Candida isolates.
RESULTS
HPLC was used to quantify miconazole levels in saliva. Miconazole-loaded disks released antifungal drug for up to 30 days. Higher drug release was found with higher concentrations of saliva, and, interestingly, miconazole solubility was increased with higher saliva concentrations. The released miconazole retained its anticandidal activity. After immersion, the residual miconazole could be quenched and the disks recharged. Freshly recharged disks displayed the same release kinetics and bioactivity as the original disks. Quenched disks could also be charged with chlorhexidine that displayed anticandidal activity.
CONCLUSIONS
These results suggest that PMMA-g-PNVP is a promising new denture material for long-term management of denture stomatitis.
Topics: Adult; Antifungal Agents; Candida; Chlorhexidine; Delayed-Action Preparations; Dental Materials; Dentures; Dose-Response Relationship, Drug; Drug Carriers; Female; Gentamicins; Humans; Male; Methylmethacrylates; Miconazole; Middle Aged; Polymethyl Methacrylate; Pyrrolidinones; Saliva
PubMed: 26855200
DOI: 10.1111/odi.12456 -
In Vivo (Athens, Greece) 2006Despite a large number of previous studies, the mechanism of free radical interaction between vitamin E (VE) (alpha-, beta-, gamma- and delta-tocopherol) and ascorbate...
Despite a large number of previous studies, the mechanism of free radical interaction between vitamin E (VE) (alpha-, beta-, gamma- and delta-tocopherol) and ascorbate or flavonoids as coantioxidants remains unclear. VE, particularly alpha-tocopherol, shows less antioxidant activity against peroxyl radicals, suggesting that VE possesses functions that are independent of its antioxidant/radical-scavenging activity. The synergistic antioxidant effect of VE or L-ascorbyl 2,6-dibutyrate (ASDB, an ascorbate derivative) with the flavonoids (-)-epicatechin (EC) and (-)-epigallocatechin gallate (EGCG) was investigated using the induction period method in the polymerization of methyl methacrylate initiated by thermal decomposition of benzoyl peroxide (an oxygen-centered radical, PhCOO*) under nearly anaerobic conditions. For delta-tocopherol, a synergistic antioxidant effect was observed in the presence of both EC and EGCG, whereas antioxidant activity for alpha-, beta- and gamma-tocopherol was decreased by addition of EC and EGCG. This suggested that the partial regeneration between VE and flavonoids may depend on the chemical structure of VE, i.e., monomethyl, dimethyl, or trimethyl tocol. The regeneration of delta-tocopherol, a monomethyl tocol, by flavonoids may be due to the lower steric effect of tocol. For ASDB, regeneration of vitamin E, which is well-known for a VE/ascorbate mixture, was not observed, possibly due to the anaerobic experimental conditions. The radical interaction between VE and EC, EGCG or ASDB suggests reactivity of VE with biological systems.
Topics: Anaerobiosis; Antioxidants; Ascorbic Acid; Benzoyl Peroxide; Calorimetry, Differential Scanning; Catechin; Flavonoids; Free Radical Scavengers; Free Radicals; Kinetics; Methylmethacrylate; Molecular Structure; Polymers; Tocopherols; Vitamin E
PubMed: 17203774
DOI: No ID Found -
Journal of General Internal Medicine Feb 2017
Topics: Adenocarcinoma; Aged, 80 and over; Fatal Outcome; Humans; Lung Neoplasms; Male; Methylmethacrylate; Prostheses and Implants; Radiography, Thoracic; Terminal Care; Tomography, X-Ray Computed; Tuberculosis, Pulmonary
PubMed: 27488968
DOI: 10.1007/s11606-016-3828-6 -
Korean Journal of Ophthalmology : KJO Dec 1992The most important problem in the transplantation of artificial cornea is the extrusion of keratoprosthesis. So we performed this study to know the conditions to keep...
The most important problem in the transplantation of artificial cornea is the extrusion of keratoprosthesis. So we performed this study to know the conditions to keep the keratoprosthesis as long as possible after animal experiment with experimental keratoprosthesis of various material and structure. We concluded from the results that silicone barrier could not prevent the retroprosthetic membrane, and fluorosilicone was not adequate material as an optic. And the following conditions are required to maintain keratoprosthesis as long as possible; optic made of PMMA, retention plate made of PTFE with 0.6 mm thick, anterior direction of optic, large optic, intralamellar suture technique. Furthermore we postulated that enzymatic theory is more appropriate than aseptic necrosis theory about the extrusion of keratoprosthesis.
Topics: Animals; Cornea; Corneal Transplantation; Methylmethacrylate; Methylmethacrylates; Polytetrafluoroethylene; Prostheses and Implants; Prosthesis Design; Rabbits
PubMed: 1301447
DOI: 10.3341/kjo.1992.6.2.55 -
The Iowa Orthopaedic Journal 2020Exposure to methyl methacrylate vapor (MMA) presents an occupational risk to orthopedic surgeons and ancillary personnel in the operating room. The purpose of this study...
BACKGROUND
Exposure to methyl methacrylate vapor (MMA) presents an occupational risk to orthopedic surgeons and ancillary personnel in the operating room. The purpose of this study was to identify a disposable face mask to reduce MMA organic vapor inhalation in the operative suite.
METHODS
First, the effectiveness of MMA vapor filtration was determined in the laboratory. A section of activated carbon impregnated filter face mask (Model 8514, 3M Inc.) was exposed to 150 ppm MMA vapor and MMA ppm of filtered air was monitored until MMA vapor was detectable. The face mask was then worn as directed in the operating room during routine cement mixing during total knee arthroplasty to determine the exposure to MMA vapors during the procedure both with and without the activated carbon impregnated filter face mask.
RESULTS
The activated carbon impregnated face mask was effective in reducing MMA vapor inhalation to non-detectable levels for up to 40 minutes in the laboratory at steady-state exposure of 150 ppm MMA vapor as well as throughout cement mixing and curing in the operative suite during routine total knee arthroplasty.
CONCLUSIONS
An activated carbon impregnated face mask offers a solution for the orthopedic surgeon and supporting personnel who wish to limit their exposure to MMA vapors due to health concerns..
Topics: Air Pollutants, Occupational; Arthroplasty, Replacement, Knee; Bone Cements; Humans; Inhalation Exposure; Masks; Methylmethacrylate; Occupational Exposure; Operating Rooms; Quality Improvement
PubMed: 32754006
DOI: No ID Found