Block copolymerization of α-amino acid N-carboxyanhydride initiated by vinyl polymers having a terminal amino group and the characterization of the block copolymers

Poly(methyl methacrylate) and polystyrene having terminal amino groups were synthesized by the radical polymerization of those monomers in the presence of 2-mercaptoethylammonium chloride as a chain-transfer agent. By the terminal group analysis and the molecular weight determination of the polymers, 0.5–1.3 amino groups were found in a chain of poly(methyl methacrylate) and 0.5–2.5 amino groups in a chain of polystyrene. Using these polymers having a terminal amino group as an initiator, the block polymerization of α-amino acid N-carboxyanhydride (NCA) was carried out. In the polymerizations of Glu(OBzl) NCA and Lys(Z) NCA by the poly(methyl methacrylate) initiator, the terminal amino group underwent a nucleophilic addition reaction to NCA and initiated the polymerization, yielding A-B-type block copolymers in a high yield. The same was observed in the polymerizations of Gly(OBzl) NCA and Lys(Z) NCA by the polystyrene initiator. By eliminating the protecting groups of the side chains of the polypeptide segment, the block copolymers poly(methyl methacrylate)-poly(Glu), poly(methyl methacrylate)-poly(Lys), polystyrene-poly(Glu) and polystyrene-poly(Lys) were synthesized with little side reactions. The side chain amino groups of poly(Lys) segment in the poly(methyl methacrylate)-poly(Lys) block copolymers were sulphonated or stearoylated successfully.     

A Removable Polar Embedding Medium for Light Microscopy

A new plastic embedding medium for light microscopy is described. The monomer mixture consists of equal proportions by volume of acrylonitrile, dimethyl acrylamide and methyl methacrylate, and may be polymerized by exposure to ultraviolet light in the presence of benzoin methyl ether as catalyst. Dithiothreitol may also be added to the monomer mix to limit the degree of polymerization. The resulting polymer is soluble in dimethyl formamide.     

A removable polar embedding medium for light microscopy

A new plastic embedding medium for light microscopy is described. The monomer mixture consists of equal proportions by volume of acrylonitrile, dimethyl acrylamide and methyl methacrylate, and may be polymerized by exposure to ultraviolet light in the presence of benzoin methyl ether as catalyst. Dithiothreitol may also be added to the monomer mix to limit the degree of polymerization. The resulting polymer is soluble in dimethyl formamide.     

Grafting of oligosaccharides onto synthetic polymer colloids

A new method to form colloidally stable oligosaccharide-grafted synthetic polymer particles has been developed. The oligosaccharides, of weight-average degree of polymerization approximately 38, were obtained by enzymatic debranching of amylopectin. Through the use of a cerium(IV)-based redox initiation process, oligosaccharide chains are grafted onto a synthetic polymer colloid comprising electrostatically stabilized poly(methyl methacrylate) or polystyrene latex particles swollen with methyl methacrylate monomer. Ce(IV) creates a radical species on these oligosaccharides, which then propagates, initially with aqueous-phase monomer, then with the methyl methacrylate monomer inside the particles. Ultracentrifugation, NMR, and total starch analyses together prove that the grafting process has occurred, with at least 7.7 wt % starch grafted and a grafting efficiency of 33%. The surfactant used in latex preparation was removed by dialysis, resulting in particles colloidally stabilized with only linear starch as a steric stabilizer. The debranched starch that comprises these oligosaccharides is found to be a remarkably effective colloidal stabilizer, albeit at low electrolyte concentration, stabilizing particles with very sparse surface coverage.     

Synthesis, swelling behavior, and biocompatibility of novel physically cross-linked polyurethane-block-poly(glycerol methacrylate) hydrogels

Physically cross-linked novel block copolymer hydrogels with tunable hydrophilic properties for biomedical applications were synthesized by controlled radical polymerization of polyurethane macroiniferter and (2,2-dimethyl-1,3-dioxolane) methyl methacrylate. The block copolymers were converted to hydrogels by the selective hydrolysis of poly[(2,2-dimethyl-1,3-dioxolane) methyl methacrylate] block to poly(glycerol methacrylate). The block copolymerization has been monitored by monomer conversion and molecular weight increase as a function of time. It was observed that the polymerization proceeded with a characteristic "living" behavior where both monomer conversion and molecular weight increased linearly, with increasing reaction time. The resulting hydrogels were investigated for their equilibrium water content (EWC), dynamic water contact angles, swelling kinetics, thermodynamic interaction parameters, plasma protein adsorption, and platelet adhesion. Similar to our previous mechanically responsive hydrogels (Mequanint, K.; Sheardown, H. J. Biomater. Sci. Polym. Ed. 2005, 10, 1303-1318), the present results indicated that block copolymer hydrogels have excellent hydrophilicity and swelling behavior with improved modulus of elasticity. The equilibrium swelling was affected by the hydrolysis time, block length of poly(glycerol methacrylate), temperature, and the presence of soluble salts. Fibrinogen adsorption and platelet adhesion were significantly lower for the hydrogels than for the control polyurethane, whereas albumin adsorption increased for the hydrogels in proportion to the contents of poly(glycerol methacrylate). These hydrogels have potential in a number of biomedical applications such as drug delivery and scaffolds for tissue engineering.     

Modeling the spontaneous initiation of the polymerization of methyl methacrylate

The mechanism of the spontaneous initiation of the polymerization of methyl methacrylate (MMA) was investigated theoretically. The six minimum energy paths (MEP) of the possible reactions were calculated using the density functional theory (DFT) in conjunction with the B3LYP functional and 6-31G* basis set. The Diels-Alder initiation mechanism (path (I) and path (II)) with remarkably high energy barriers is not applicable to MMA. Four favorable paths were found (path (III), path (IV), path (V) and path (VI)), which are supporting the Flory mechanism. Path (V) has the lowest active energy. Therefore this path is considered as the main path for the spontaneous polymerization of MMA. Figure The mechanism of the spontaneous initiation of the polymerization of methyl methacrylate (MMA) was investigated theoretically. The six minimum energy paths (MEP) of the possible reactions were calculated using the density functional theory (DFT) in conjunction with the B3LYP functional and 6-31G* basis set.     

Cell-culturing characteristics of newly developed PHEMA microcarriers: their use with BHK21 cells.

Baby hamster kidney (BHK) fibroblasts, as model cells, have been proliferated on acrylic based microcarriers. Microcarriers were prepared by a novel suspension polymerization of acrylic monomers. Hydroxyethyl methacrylate was the basic monomer. Ethylene glycol dimethacrylate was used as the cross-linker. A hydrophobic comonomer, namely, methyl methacrylate, was included in order to adjust the hydrophilicity of the resultant matrix. An acrylic comonomer with positively charged tertiary amine groups, i.e., dimethylaminoethyl methacrylate, was also added in order to optimize the surface charge of the carriers. The adhesion, spreading, and growth characteristics of BHK cells on these novel beads were studied either in stationary or in submerged culture conditions. The results demonstrate that the cell attachment and growth can be controlled by changing the degree of charge and the hydrophilicity of the poly(hydroxyethyl methacrylate) matrix.     

Polyaniline as a support for urease immobilization

Polyaniline synthesized by chemical oxidative polymerization was used as an immobilization support for jack bean urease. Such immobilized enzyme has a good catalytic activity, storage stability, and reusability. Properties of free and immobilized urease were compared. Blends of polystyrene, cellulose acetate and poly(methyl methacrylate) with polyaniline were used for urease immobilization as well.     

Embedding Iliac Bone Biopsies at Low Temperature using Glycol and Methyl Methacrylates

A mixture of pure and anhydrous glycol methacrylate and methyl methactylate is used as an embedding medium for iliac bone biopsies. Infiltration is carried out at -20 C with the embedding medium and a cold inactivated catalyst-initiator system. Raising the temperature to 4 C initiates polymerization and limits the peak temperature of polymerization to 25 C. In this way, such thermolabile enzymes as osteoclastic acid phosphatase are preserved. After staining, sections are dehydrated in polyethylene glycol 400 30% in 2-propanol. This gives flat sections and improves staining properties.     

Transparent and luminescent ionogels composed of Eu3+‐coordinated ionic liquids and poly(methyl methacrylate)

We report here on transparent and luminescent ionogels that consist of ionic ternary europium (III) complexes and the inexpensive non‐toxic compound, poly(methyl methacrylate) (PMMA) and that were formed by dissolving these complexes in methacrylate (MMA) monomers followed by in situ polymerization. The resulting ionogels show a bright red emission under near‐UV light irradiation. Luminescence data confirm the energy transfer from terpyridine‐functionalized ionic liquid to Eu³⁺ ions. Copyright © 2015 John Wiley & Sons, Ltd.     

Glycol methacrylate as an embedding medium for bone

A simple and reliable procedure for embedding undecalcified trabecular bone tissue in noncommercial glycol methacrylate (GMA) has been developed. The embedding mixture includes a monomer, methacrylic acid hydroxyethyl ester; a copolymer, methacrylic acid butyl ester; a cross-linker, ethylene glycol dimethacrylate; a catalyst, Luperco; a chemical initiator (N,N-dimethylaniline) and, to avoid excessive elevation of temperature during polymerization, a heat moderator, alpha-terpinene. The appropriate proportions of these components have been selected to give specimens which can be easily sectioned with classical microtomes and which do not swell but spread evenly on a water surface. Since polymerization occurs at -4 C, the method allows demonstration of such enzymatic activities as acid and alkaline phosphatase and carbonic anhydrase. It provides excellent preservation of bone tissue and in studies of bone metabolism allows histomorphometry as well as visualization of fluorescent labeling and radioactive markers. The cost is significantly less than available commercial kits. In our hands glycol methacrylate is at present more useful than methyl methacrylate and is used in our laboratory for routine embedding of bone tissue.     

Immobilization of glucose oxidase in conducting graft copolymers and determination of glucose amount in orange juices with enzyme electrodes

Glucose oxidase was immobilized in conducting copolymers of three different types of poly(methyl methacrylate-co-thienyl methacrylate). Immobilization of enzyme was carried out by the entrapment in conducting polymers during electrochemical polymerization of pyrrole on the copolymer electrodes. Maximum reaction rate, Michaelis-Menten constants, temperature, pH and operational stabilities were determined for immobilized enzyme. The amount of glucose in orange juices of Turkey was investigated by using enzyme electrodes.     

Luminescence of Eu3+ ions in hybrid polymer‐inorganic composites based on poly(methyl methacrylate) and zirconia nanoparticles

Spherical nanoparticles of ZrO₂ with 2 and 10 mol% EuO_1.5 up to 20 nm size were prepared by the method of hydrothermal synthesis for luminescent functionalization of the polymer–inorganic nanocomposites based on poly(methyl methacrylate). Surface modification of oxide nanoparticles was carried out by 3‐(trimethoxysilyl)propyl methacrylate, dimethoxymethylvinyl silane and 2‐hydroxyethyl methacrylate to provide uniform distribution and to prevent agglomeration of nanosized filler in the polymer matrix. Polymer–inorganic composites were synthesized by in situ free radical polymerization in bulk. Structuring of ZrO₂‐EuO_1.5 nanoparticles in the poly(methyl methacrylate) was studied by very‐small‐angle neutron scattering. According to the results, the dependence of photoluminescent properties of ZrO₂‐EuO_1.5 nanoparticles on the content of lanthanide, the symmetry of the crystal field, surface treatment and the polymer matrix were established. A correlation was shown between Stark splitting in luminescence spectra of ZrO₂‐EuO_1.5 nanoparticles and their phase composition. Using MMT‐assay it was shown that composites based on poly(methyl methacrylate) and ZrO₂‐EuO_1.5 nanoparticles do not have cytotoxic properties, which makes it possible to use them as prosthesis materials with contrasted and luminescent imaging properties.     

Chitosan graft copolymer nanoparticles for oral protein drug delivery: preparation and characterization

Several novel functionalized graft copolymer nanoparticles consisting of chitosan (CS) and the monomer methyl methacrylate (MMA), N-dimethylaminoethyl methacrylate hydrochloride (DMAEMC), and N-trimethylaminoethyl methacrylate chloride (TMAEMC), which show a higher solubility than chitosan in a broader pH range, have been prepared by free radical polymerization. The nanoparticles were characterized in terms of particle size, zeta potential, TEM, and FT-IR. These nanoparticles were 150-280 nm in size and carried obvious positive surface charges. Protein-loaded nanoparticles were prepared, and their maximal encapsulation efficiency was up to 100%. In vitro release showed that these nanoparticles provided an initial burst release followed by a slowly sustained release for more than 24 h. These graft copolymer nanoparticles enhanced the absorption and improved the bioavailability of insulin via the gastrointestinal (GI) tract of normal male Sprague-Dawley (SD) strain rats to a greater extent than that of the phosphate buffer solution (PBS) of insulin.     

Methacrylate derivatives incorporating pyroglutamic acid

Methacrylates containing pyroglutamic acid were synthesized in good yields. Methyl alpha-pyroglutamyl methylacrylate (PyMM) and methyl alpha-pyroglutamidoundecanoyl methylacrylate (PyUM) give very fast photopolymerization rates both in homopolymerizations and with widely used commercial monomers N-vinyl pyrrolidinone (NVP) and hydroxyethyl methacrylate (HEMA). Soluble or cross-linked homopolymers can be obtained depending upon polymerization temperature. Pyroglutamic methacrylates polymerize without added initiator in the melt. Solution cast, photocured, and thermally cured coatings gave good to excellent adhesion to poly(ethylene terephthalate) and glass surfaces.     

Bone Embedding Technique with Inhibited Pmma Monomer

Unwashed inhibited thin and thick methyl methacrylate monomer was used for successful embedding of bone by increasing the quantity of benzoyl peroxide catalyst until the activity of the hydroquihone inhibitor was overwhelmed. Seven bones were embedded using 1, 2, 4, 6, 8, 10 or 12 grams of benzoyl peroxide per 100 milliliters of thick monomer. Two grams per 100 ml was found to be optimal. Higher concentrations resulted in uncontrolled polymerization while at 1 g/100 ml the solution remained liquid.     

Conjugation of a monoclonal antibody with a DTPA modified random copolymer of hydroxyethyl methylacrylate and methyl methacrylate

A new approach for covalent coupling diethylenetriaminepentaacetic acid (DTPA) molecules to a partially reduced monoclonal antibody utilizes a malemide modified copolymer of hydroxyethyl methylacrylate and methyl methacrylate (DTPA copolymer) prepared by the group transfer polymerization (GTP) method. An average of 6 DTPA molecules were incorporated per mol maleimeide DTPA copolymer and 1.5 mol maleimide DTPA copolymer per mol antibody. Maleimide DTPA copolymer modified antibody was intramolecularly cross-linked, reduced immunoactivity and had a high in vivo liver uptake.     

Synthesis, characterization, properties, and drug release of poly(alkyl methacrylate-b-isobutylene-b-alkyl methacrylate)

Polyisobutylene (PIB)-based block copolymers have attracted significant interest as biomaterials. Poly(styrene-b-isobutylene-b-styrene) (SIBS) has been shown to be vascularly compatible and, when loaded with paclitaxel (PTx) and coated on a coronary stent, has the ability to deliver the drug directly to arterial walls. Modulation of drug release from this polymer has been achieved by varying the drug/polymer ratio, by blending SIBS with other polymers, and by derivatizing the styrene end blocks to vary the hydrophilicity of the copolymer. In this paper, results are reported on the synthesis, physical properties, and drug elution profile of PIB-based block copolymers containing methacrylate end blocks. The preparation of PIB-poly(alkyl methacrylate) block copolymers has been accomplished by a new synthetic methodology using living cationic and anionic polymerization techniques. 1,1-Diphenylethylene end-functionalized PIB was prepared from the reaction of living PIB and 1,4-bis(1-phenylethenyl)benzene, followed by the methylation of the resulting diphenyl carbenium ion with dimethylzinc (Zn(CH(3))(2)). PIB-DPE was quantitatively metalated with n-butyllithium in tetrahydrofuran, and the resulting macroinitiator could initiate the polymerization of methacrylate monomers, yielding block copolymers with high blocking efficiency. Poly(methyl methacrylate-b-isobutylene-b-methyl methacrylate) (PMMA-b-PIB-b-PMMA) and poly(hydroxyethyl methacrylate-b-isobutylene-b-hydroxyethyl methacrylate) (PHEMA-b-PIB-b-PHEMA) triblock copolymers were synthesized and used as drug delivery matrixes for coatings on coronary stents. The PMMA-b-PIB-b-PMMA/PTx system displayed zero-order drug release, while stents coated with PHEMA-b-PIB-b-PHEMA/PTx formulations exhibited a significant initial burst release of PTx. Physical characterization using atomic force microscopy and differential scanning calorimetry of the formulated PMMA-b-PIB-b-PMMA coating matrix indicated the partial miscibility of PTx with the PMMA microphase of the matrix.     

Beta-sheet side chain polymers synthesized by atom-transfer radical polymerization

Silks are a widely studied class of naturally occurring structural proteins. Dragline spider silk, in particular, is considered to be nature's high-performance material due to its remarkable combination of strength and toughness. These mechanical properties stem from the protein secondary structure, a combination of well-defined beta-sheets in a less well-defined glycine-rich matrix. The translation of this structure into a synthetic polymer was the aim of this investigation. To achieve this, a peptide-based monomer containing the sequence alanine-glycine-alanine-glycine, a well-known beta-sheet-forming sequence found in silk, was synthesized. Using atom-transfer radical polymerization and a bifunctional initiator, a well-defined peptide-based polymer was prepared. This was then used as the macroinitiator for the polymerization of methyl methacrylate. The resulting well-defined triblock copolymer was analyzed using IR spectroscopy, which clearly showed beta-sheet secondary structure had been introduced.     

Alkaline and Acid Phosphatase Demonstration in Human Bone and Cartilage: Effects of Fixation Interval and Methacrylate Embedments

Human bone and cartilage specimens were evaluated for acid and alkaline phosphatase localization following varying fixation periods for fresh or frozen tissue. Formalin fixations of up to 183 hr were followed by embedment in methyl methacrylate; frozen tissue was examined either without fixation or following fixation for up to 1 hr and subsequent glycol or methyl methacrylate embedding. The humeral epiphysis of a young patient with osteogenic sarcoma showed optimum acid and alkaline phosphatase localization following fixation for periods up to 15 hr and embedding in methyl methacrylate. Frozen costochondral junction from a newborn with osteogenesis imperfecta type II showed optimum acid and alkaline phosphatase localization following 30 min fixation in formalin and embedding in methyl methacrylate or after 5 min fixation and embedding in glycol methacrylate.