Enzymatic and anaerobic degradation of amylose based acrylic copolymers, for use as matrices for drug release

The aim of this investigation is the use of starch for effective colon-targeted drug delivery. To this end, high-amylose starch-based copolymers were tested as matrices for drug delivery. Ethyl methacrylate (EMA) was grafted onto a high-amylose starch (A). Copolymer synthesis and characterization as well as other experiments to test the enzymatic resistance and the capacity for fermentation of these products by colonic bacteria were carried out. Finally, tablets developed with our copolymers were tested to observe the dissolution behaviour of a model drug and a model protein. Our findings indicate that large quantities of grafted PEMA are not necessary to obtain high enzymatic resistance. Fermentation experiments indicate that the carbohydrate of A-EMA copolymers is susceptible to fermentation in spite of the EMA coating around the amylose backbone and that these materials could favour colon-targeted delivery.     

The use of acrylic acid-co-nylon substrates for immobilizing enzymes

A number of poly(acrylic acid)-co-nylon graft copolymers were prepared. Two approaches were used. The first involved the direct, radiation-induced grafting of acrylic acid onto the nylon, while the second involved the hydrolysis of polyacrylonitrile-co-nylon graft copolymers. All the resulting poly(acrylic acid)-co-nylon graft copolymers coupled large amounts of protein when the carbodimides CMC and EDAC were used as coupling agents. However, when the enzymes β-galactosidase and trypsin were immobilized, the retention of activity was relatively low. A number of reasons for this effect can be postulated, some of which were investigated. From the evidence, it would appear that the major reason is that the carboxylic acid groups are fixed to a “rigid” backbone, which allows them to interact with the enzyme after the establishment of an initial covalent attachment. Additionally, with acid phosphatase, it was observed that the enzyme interacted with immobilized carboxylic acid groups before coupling occurred.     

The use of modified acrylic copolymers for the preparation of immunoadsorbents

Summary Copolymer beads from acrylonitrile and ethyl either butyl acrylate or vinyl acetate, with amino, hydroxyl or carboxyl groups were activated with glutaraldehyde or water-soluble carbodiimide and coupled to human serum albumin. The obtained immunoadsorbents were applied to the isolation of anti-human albumin anibody from rabbit antiserum. Among the 22 studied copolymers only a few showed satisfactory effectiveness for immunoaffinity chromatography, similar to that noted for immunoadsorbents from commerical polymers.     

Evaluation of molecularly imprinted membranes based on different acrylic copolymers

Polyacrylonitrile and its copolymers with different functional monomers (itaconic acid, acrylic acid and acrylamide) were synthesized via water-phase precipitation polymerization in order to prepare molecularly imprinted polymer (MIP) membranes with recognition properties for the flavonoid naringin (NR). Membranes were prepared by phase inversion technique using dimethylformamide (DMF) as the solvent and adding naringin as template molecule to the casting solution. For comparison, membranes without template (blank) were prepared and tested. All MIP membranes showed high specific binding capacity; among them, the membrane prepared with the copolymer containing acrylamide as functional group, showed the highest binding capacity. Blank membranes only showed non-specific binding. The bound template was totally recovered and regenerated membranes maintained their initial binding capacity after reuse.     

Catalytic aminolysis of acrylic copolymers in solution and in the melt. I. Mechanism and kinetics

The aminolysis of poly(styrene-co-methyl acrylate) (SMA) by octadecylamine was studied in solution and in the melt at temperatures around 200°C. This reaction is rather slow, so several types of catalysts were tested to accelerate it. The most efficient is 2-pyridone, a compound in tautomeric equilibrium with 2-hydroxypyridine. A mechanism of the catalytic reaction is proposed whereby the tautomeric nature of the catalyst plays a key role in a very important step of the reaction, namely the proton transfer. This mechanism is confirmed by the kinetic data determined in a 1,2,4-trichlorobenzene solution and in the melt. In addition, it was found that the kinetic data obtained in both media are very close, indicating no significant difference of local polarity in the two reaction media. Data also show only a minor effect due to difference in viscosity. Finally, the question of the homogeneity of the molten medium is discussed.     

Blends of bisphenol-A polycarbonate and acrylic polymers: II. PC/acrylic copolymers as a new route for compatibilization

An acrylic polymer containing acid and anhydride units, referred to as reactive polyglutarimide (RPGI), has been used to react with PC. The reaction has been previously determined as an acidolysis of the carbonate bond which breaks the PC chain in two parts. One of those two parts remains free while the other one is grafted on the acrylic backbone. We have found that the anhydride units could also react with the carbonate bonds. In this case the PC macromolecule would also be broken in two parts, which would, however, both be grafted on the acrylic backbone. The reaction has been performed in solution in order to keep good contact between the reacting units. The influence of temperature and concentration on the grafting ratio has been studied. The best experimental conditions were determined in order to obtain a grafted copolymer where the acrylic backbone only supports, on the average, one PC side chain through acid reaction or two PC chains through anhydride reaction. Indeed, these two types of reactions could not be isolated. The efficiency of this copolymer as emulsifier has been studied in solution cast blends as well as in melt mixed blends. The copolymer strongly affects the microstructure in solution cast blends where films containing 30 wt % of PC have become transparent. However, the dispersed phase size of solvent cast blends could be highly influenced by the casting conditions related to solvent trapping. In melt mixed samples, the copolymer also reduces significantly the dispersed phase size, but no transparent blends have been observed so far. These results were compared with those given in the literature describing the efficiency of a synthesized copolymer which has a more complicated structure. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 735–747, 1997     

Blends of styrene/acrylic acid copolymers and acrylic polymers

The miscibility of a series of styrene/acrylic acid copolymers with various polyacrylate and polymethacrylate homopolymers, as well as a series of styrene/methyl methacrylate copolymers, has been investigated. According to the binary interaction model, the miscibility diagram for styrene/acrylic acid copolymers with styrene/methyl methacrylate copolymers indicates that acid and ester groups interact endothermically. The phase behavior of the homopolymers also implies this. The analysis ignores the association and self-association observed for the polymer blends and the low-molecular-weight analogs used to model them. The heat of mixing of low-molecular-weight analogs depended greatly on both composition and acid structure.     

Crystallization of branched polymers. I. Ethylene–vinyl acetate and ethylene–acrylic acid copolymers

The following quantities were measured on a number of ethylene–vinyl acetate (EVA) and ethylene–acrylic acid (EAA) copolymers: (1) the small-angle x-ray scattering invariant, (2) the overall density, and (3) the crystallinity. Assuming a two-phase structure, the separate values of the densities of the crystalline and amorphous regions can be calculated from these data. Of these, the crystalline density is compared with the value obtained from the lattice constants. A systematic difference is observed which is ascribed to the presence of comonomeric side groups in the crystalline regions. For the EVA and EAA samples, their concentration is at least 0.3 and 0.5 times the overall concentration, respectively. The amorphous densities are found to be higher than the values calculated from completely amorphous copolymers by extrapolation procedures.     

Epoxy functional copolymers as biospecific adsorbents for purification of enzymes

The affinity chromatographic characteristics of some chemically modified copolymers based on glycidyl methacrylate have been evaluated. The copolymers were modified by means of reaction of suitable ligands with epoxy groups. Purification of pencillin acylase was carried out using these matrices as the stationary phase in the chromatographic column. Effect of the nature of the ligands and pH on the binding and desorption efficiency of the enzyme was evaluated.     

Triplet energy transfer to polymer matrices—I. Transfer at 77 K in a series of copolymers

The life-time of phosphorescence emission from triphenylene and coronene suspended in a range of styrene/methyl methacrylate copolymers has been measured at 77 K. It has been concluded that the polymer matrix quenches the triplet state of the polycyclic aromatics, presumably by an energy transfer mechanism.     

Comb-like copolymers as self-coating,low-viscosity and high-resolution matrices for DNA sequencing

Comb-like copolymers with a polyacrylamide backbone and poly(N,N-dimethylacrylamide) grafts were prepared, as a way to combine the superior sieving properties of polyacrylamide with the self-coating properties of polydimethylacrylamide. These matrices function well in the absence of a capillary coating, and achieve separation performances for single-stranded DNA that are comparable to those of state-of-the-art long-chain linear polyacrylamide. Structural parameters such as the grafting density and the polymer molecular mass were varied, and good performance appears to be achieved with a relatively large range of parameters. Surprisingly, excellent separation is achieved even with matrices that have a viscosity as low as 200 mPa/s. A discussion of the physics underlying this behavior is provided.     

Block copolymers of ethylene. I. Butadiene

Block copolymers of ethylene and butadiene have been prepared to study their properties. The method of preparation of polybutadiene, polyethylene, and block copolymers of ethylene and butadiene with n-butyl lithium-tetramethyl ethylene diamine complex is outlined. Kinetic studies have been reported elsewhere and these are assessed to determine that suitability of the system to produce monodispersed “living” chains so that simple correlations between physical properties and molecular weight can be made. The properties were somewhat restricted by the 1,2-microstructure of the butadiene block.     

Catalytic aminolysis of acrylic copolymers in solution and in the melt. II. Comparison between styrenic and ethylenic copolymers

The aminolysis of poly(styrene-co-methyl acrylate) (SMA) by octadecylamine in solution and in the melt has been reported in Part I. We now have studied the aminolysis of poly(ethylene-co-methyl acrylate) (EMA) with the same amine in the melt and compared the two sets of data in this paper. With EMA, the data confirmed and precised the catalytic mechanism proposed in Part I. The best tautomeric catalysts are the ones which form an eight-atom ring structure with the ester and amine groups. With EMA aminolysis is faster than with SMA because of the steric hindrance of phenyl groups in SMA. But EMA aminolysis remains a rather slow reaction. In a corotating twin-screw extruder the conversion was only around 4% at 220°C with a mean residence time of 150 s. It was also shown that the EMA/octadecylamine/catalyst system, like the SMA system, is homogeneous in the molten state at temperatures around 200°C.     

A study of water-sorption characteristics of filled acrylic copolymers

Water-sorption properties of hydrophilic acrylic copolymers with a 3D network structure, filled with biodegradable components, were studied. The effect of pressure and pH of the swelling medium on the water absorption by the filled copolymers was analyzed.     

Thermodynamics of plasticized triblock copolymers. I. Theory

The thermodynamic theory of bulk ABA copolymers developed by Leary and Williams is extended to copolymer–solvent systems. Free energy expressions are derived for five hypothetical phase-separated morphologies and evaluated specifically for a polymer with approximately 25% of the A component. The separation temperature, T_s, at which a given morphology will be in equilibrium with a homogeneous mixture, is also evaluated. The major result is the prediction of the T_s(?S) depression, where ?s is the solvent fraction. Depression is maximized when δ_S is equidistant between δ_A and δ_B, but becomes rapidly less when δ_S is outside the δ_A–δ_B range. Morphological favoritism is independent of ?_S and δ_S (model does not apply to preferential precipitation), with a planar microstructure being favored along with microstructures containing domains of B in continuous A for the 25% A polymer.     

Coupling of acrylic polymers and collagen by use of a water-soluble carbodiimide. I. Optimization of reaction conditions

A means of coupling synthetic polymers of biomedical interest with collagen under mild conditions was investigated as a part of preliminary studies in the development of a biomedical adhesive. The coupling agent, 1-cyclohexyl-3-[2-morpholinyl-(4)-ethyl]carbodiimide, provides a covalent bond between the acrylic polymer and collagen. The variables affecting the establishment of this bond in solution are concentration of the carboxylic group on the acrylic polymer, concentration of the acid-soluble collagen, concentration of the coupling agent, pH, and time of reaction. Optimum values of these variables have been obtained experimentally.     

Algebraic structure of fermion density matrices. I

In this paper we define the algebraic structure of a reduced fermion density matrix. We relate the algebraic structure to certain symmetry properties of the reduced density matrix.     

Silver sorption on acrylic copolymers functionalized with amines. Equilibrium and kinetic studies

The sorption capacity of three weak base ion exchangers based on acrylic copolymers functionalized with ethylenediamine, triethylenetetramine and N, N- dimethylamino propylamine for Ag(I) ions was evaluated. Adsorption experiments were carried out by batch method. The effect of pH, crosslinking degree of copolymers, amount of sorbent, initial ion concentration, contact time and temperature was studied. The parameters which characterize the retention process were estimated using Langmuir and Freundlich isotherm models, the best fitting being for the first model. Kinetic data were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion models. Experimental data were in good agreement with the pseudo second order.