The review describes the use of biomaterials (polymeric biomaterials in particular) in the development of medical and biological products and devices, such as implants and endoprostheses; components of bioactive and pharmaceutical agents; carriers for bioengineering applications; sorbent agents and membrane systems used for the purification and separation of biological media; artificial biocatalysts, and general purpose biodegradable products. This review is provided with a short reference list of relevant monographs and reviews predominantly by Russian authors.

Two poly (vinyl pyrrolidone) (PVP) families with amino-acid residues (glycine, beta-alanine, gamma-aminobutiric acid and epsilon-aminocaproic acid) on the base of the co-polymer N-vinyl pyrrolidone and allyl-glycidyl ether (VP-AGE) and on the base of epoxidized PVP (EPVP) were synthesized. Static and dynamic light scattering measurements of these PVP derivatives in water showed that their structure/ behavior were similar to that of PVP. The bioreactivity was also similar to that of PVP. Further investigation of the immunoreactive properties of the derivatives in in vitro proliferation assays with fresh normal human peripheral blood lymphocytes and monocytes led to the determination of a costimulatory profile for each derivative in terms of polyclonal stimulation, specific antigen presentation, and immunoglobulin secretion. This profile allows the selection of an appropriate derivative as a carrier that would suit the immunoreactivity needs of the immobilized ligand.

Certain amphiphilic water-soluble polymers including amphiphilic derivatives of polyvinyl pyrrolidone (PVP) were found to be efficient steric protectors for liposomes in vivo. In this study, we have tried to develop synthetic pathways for preparing amphiphilic PVP and to investigate the influence of the hydrophilic/hydrophobic blocks on some properties of resulting polymers and polymer-coated liposomes. To prepare amphiphilic PVP with the end stearyl (S) or palmityl (P) residues, amino- and carboxy-terminated PVP derivatives were first synthesized by the free-radical polymerization of vinyl pyrrolidone in the presence of amino- or carboxy-mercaptans as chain transfer agents, and then modified by interaction of amino-PVP with stearoyl chloride or palmitoyl chloride, or by dicyclohexyl carbodiimide coupling of stearylamine with carboxy-PVP. ESR-spectra of the hydrophobic spin-probe, nitroxyl radical N-oxyl-2-hexyl-2-(10-methoxycarbonyl)decyl-4,4′-dimethyl oxazoline, in the presence of amphiphilic PVP demonstrated good accessibility of terminal P- and S-groups for the interaction with other hydrophobic ligands. Spontaneous micellization and low CMC values (in a low μmolar range) were found for amphiphilic PVP derivatives using the pyrene method. In general, S-PVP forms more stable micelles than P-PVP (at similar MW, CMC values for S-PVP are lower than for P-PVP). It was found that amphiphilic PVP incorporated into negatively charged liposomes effectively prevents polycation(poly-ethylpyridinium-4-vinylchloride)-induced liposome aggregation, completely abolishing it at ca. 10mol% polymer content in liposomes. Additionally, the liposome-incorporated PVP prevents the fluorescence quenching of the membrane-incorporated hydrophobic fluorescent label [N-(4-fluoresceinthiocarbamoyl)dipalmitoyl-PE] by the free polycation. PVP-modified liposomes were loaded with a self-quenching concentration of carboxyfluorescein, and their destabilization in the presence of mouse serum was investigated following the release of free dye. Amphiphilic PVP with MW between 1500 and 8000 provides good steric protection for liposomes. The degree of this protection depends on both polymer concentration and molecular size of the PVP block.

New controlled release water-soluble formulations of sorbic (2,4-hexadienoic) acid were prepared and their inhibitory activity on mycelium growth of Fusarium oxysporum f.sp. radicis-cucumerinum was evaluated. The new products are epoxidized polymers of polyvinylpyrrolidone (PVP) containing covalently bonded sorbic acid (polymeric esters of sorbic acid) and complexes of PVP with hydrogen bonded sorbic acid, characterized by controlled release of sorbic acid. It was shown that the polymeric complexes of sorbic acid with PVP were more effective fungicidal agents than sorbic acid polymeric esters. In all cases the activity of polymeric derivatives (esters and complexes) was increased by lowering the molecular weight of the polymeric carriers. Controlled release formulations of these polymeric derivatives are new promising products due to their low toxicity, wide range of efficient concentrations for application and ability to regulate lyophilicity. Our data contribute to the understanding of the action mechanism of various polymeric sorbic acid formulations and can result in products which are particularly suitable for food and feed protection applications.

Continuous wave (CW) electron paramagnetic resonance (EPR) studies of the 12-doxylmethyl stearic acid methyl ester (12-DOXYL) spin probe were made in the solutions of a triblock copolymer of acrylamide, vinylchloroethyl ether and an ester of the vinylchloroethyl ether with 2-[(2,6-dichlorophenyl)amino] benzene acetic acid, “dichlophenac” (DPH). Light scattering experiments show that the hydrophobic DPH group influences the clustering of the polymer in solution. The EPR evidence suggests that when the polymer is dissolved in buffer solutions of 12-DOXYL, the spin probe undergoes a partitioning between the solution, the polymer clusters and a minor third environment. The rate of the 12-DOXYL partitioning from the solution into the polymer cluster is fast compared with the time scale of the changes observed in light scattering and exhibits a dependence on the concentration of the polymer in solution and the pH. The 12-DOXYL environment in the polymer cluster is characterized as restricting 12-DOXYL to slow molecular motion with rotational correlation time τ=1.3×10−8s/rad and permitting relatively infrequent collisions between the 12-DOXYL molecules. The solution spectrum of the 12-DOXYL is dominated by the spin exchange narrowing expected for concentrated assemblies of the 12-DOXYL molecules, such as a micelle or bilayer. Partitioning of a hydrophobic spin probe in an aqueous solution is shown to be a sensitive measure of the presence of stabilizing hydrophobic regions in a polymer aggregate.

We describe the dynamics of new slow release formulations of plant growth regulators (PGR) in aqueous solution. The new PGR formulations are water-soluble copolymers derived from acrylamide and vinyl chloroethyl ether, containing side linkages of 1-naphthylacetic acid (NAA) and 3-indolbutyric acid (IBA). In discussing the results of the light scattering experiments we are interested primarily in the varying degree of the aromatic character of the side groups. The PGR system containing NAA hydrophobic side groups leads to the formation of interpolymeric micellar structures. The hydrodynamic radius, Rh, of the parent polymer, almost doubles by incorporating the NAA linkages, but it remains approximately the same when the NAA linkages are replaced by IBA side groups of less aromaticity. The scattering intensities and apparent hydrodynamic radii display a systematic decrease as a function of time due to the loss of the IBA linkages in alkaline conditions.

This paper describes the dynamics of new slow release formulations of plant growth regulator (PGR) 3-indolbutyric acid (IBA) in aqueous solution. The new PGR formulations are water-soluble copolymers derived from acrylamide and vinyl chloroethyl ether, containing side linkages of IBA, the latter being released after hydrolysis. From the observed photon correlation spectra of the polarized scattered light of the water-soluble PGRs, the distribution of relaxation times is computed by means of a direct Laplace transformation. The results of the light-scattering experiments suggest that the incorporation of the IBA groups does not affect the coil dimensions of the parent polymer. This behaviour is to be contrasted with a similar system containing hydrophobic side groups of 1-naphthylacetic acid that lead to the formation of interpolymeric micellar structures. The hydrodynamic radius R-h which is 42 Angstrom for the parent polymer (PF1), remains approximately the same for the different contents of the IBA polymeric ester considering the relative increase in size due to the increasing numbers of the IBA groups. In alkaline pH, the scattering intensities and apparent hydrodynamic radii display a systematic drop as a function of time due to the loss of the IBA linkages. However, such effects are negligible in neutral pH, in agreement with previous kinetic studies. (C) 1997 Elsevier Science Ltd. All rights reserved.

The stimulation of excised coleoptile elongation in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) caused by a low-molecular weight regulator released from the polyvinyl esters of 2,4-dichlorophenoxyacetic acid was studied. The specific relation between regulator concentration and polymer bioactivity depended on the chemical structure of the polymers. In particular, an increase in the content of acid residues in the polymers from 2.4 to 33.5 mol % led to a shift in the maximum stimulatory concentration from 10(-4) to 10(-3) M. The lower the rate of regulator release estimated by alkaline hydrolysis of polymers, the higher was the observed rise in stimulatory concentrations. It is proposed that the activity of the polymeric derivatives of plant growth regulators (phytoactive polymers) can be ranked according to the rate of their chemical hydrolysis in vitro.

This paper describes the dynamics of new slow release formulations of plant growth regulator (PGR) 1-naphthylacetic acid (NAA) in aqueous solution. The new PGR formulations are water-soluble copolymers derived from acrylamide and vinyl chloroethyl ether, containing side linkages of NAA the latter being released after hydrolysis. From the observed photon correlation spectra of the polarized scattered light of the water-soluble PGRs, the distribution of relaxation times is computed by means of a direct Laplace transformation. The results of the light scattering experiments suggest that the incorporation of the hydrophobic naphthyl group dramatically affects the conformation of the parent polymer. The interactions between the hydrophobic NAA groups lead to the formation of interpolymeric micellar structures. The hydrodynamic radius Rh which is 42 Å for the parent polymer (PFI), increases to 70 Å for the NAA polymeric ester with 1.94% mol content (PF2) and becomes 82 Å by increasing the amount of the hydrophobic substituent to 3.54 mol.% content (PF3). The scattering intensities and apparent hydrodynamic radii display a systematic drop as a function of time due to the loss of the NAA linkages and Rh becomes 58 Å for PF2 and 68 Å for PF3, 116 h after the preparation of the water polymeric solutions.

In conductometric studies, the dissociation constant for polymeric salts formed by biologically active amines (atropine, aminostigmine, pralidoxime) and the copolymer of N-vinylpyrrolidone with N-allylsulfamic acid was found to decrease in the listed order of the amines studied.

Polymeric esters of carboxyl-containing regulators of plant growth, 3-indolyl acetic, 3-indolyl butyric, 1-naphthyl acetic, 1-naphthoxy acetic, 2-naphthyl thioacetic, and 2,4-dichloro phenoxyacetic acids, were prepared by the reaction of their potassium salts with the copolymer of acrylamide and vinyl-2-chloroethyl ether in DMSO. The reactivity of the salt increases with a decrease in the strength of the acid.

Polymer derivatives of 1-aminocyclopropane-1-carboxylic acid (the plants grows and development regulator) have been synthesized by two methods: by interaction of trimethylsillyl derivatives of this acid with polyvinyl alconol and copolymers of maleic anhydride and by copolymerization of the methacryloyl derivative of the same acid ester with N-vinylpyrrolidone. Study of hydrolysis of polymers by the thin-layer chromatography method showed the character of the influence of their chemical structure on the separation of the low-molecular acid and correlation of the hydrolysis rate with biological activity of the polymers.