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PubMed2004

Polymer-drug compatibility: a guide to the development of delivery systems for the anticancer agent, ellipticine.

To establish a method for predicting polymer-drug compatibility as a means to guide formulation development, we carried out physicochemical analyses of polymer-drug pairs and compared the difference in total and partial solubility parameters of polymer and drug. For these studies, we employed a range of biodegradable polymers and the anticancer agent Ellipticine as the model drug. The partial and total solubility parameters for the polymer and drug were calculated using the group contribution method. Drug-polymer pairs with different enthalpy of mixing values were analyzed by physicochemical techniques including X-ray diffraction and Fourier transform infrared. Polymers identified to be compatible [i.e., polycaprolactone (PCL) and poly-beta-benzyl-L-aspartate (PBLA)] and incompatible [i.e., poly (d,l-lactide (PLA)], by the above mentioned methods, were used to formulate Ellipticine. Specifically, Ellipticine was loaded into PBLA, PCL, and PLA films using a solvent casting method to produce a local drug formulation; while, polyethylene oxide (PEO)-b-polycaprolactone (PCL) and PEO-b-poly (d,l-lactide) (PLA) copolymer micelles were prepared by both dialysis and dry down methods resulting in a formulation for systemic administration. The drug release profiles for all formulations and the drug loading efficiency for the micelle formulations were also measured. In this way, we compared formulation characteristics with predictions from physicochemical analyses and comparison of total and partial solubility parameters. Overall, a good correlation was obtained between drug formulation characteristics and findings from our polymer-drug compatibility studies. Further optimization of the PEO-b-PCL micelle formulation for Ellipticine was also performed.

Antineoplastic Agents↗

PubMed2004

Transport of octreotide and evaluation of mechanism of opening the paracellular tight junctions using superporous hydrogel polymers in Caco-2 cell monolayers.

The purpose of this study was to investigate the mechanism of opening of tight junctions in Caco-2 cell monolayers using superporous hydrogel (SPH) and SPH composite (SPHC) polymers as permeation enhancers for peptide drug delivery. Moreover, the transport of octreotide across Caco-2 cell monolayers was assessed by application of SPH and SPHC polymers on Caco-2 cell monolayers. In these experiments, N,N,N-trimethyl chitosan chloride with 60% quaternization (TMC60) was used as a positive control for opening of tight junctions. Transepithelial electrical resistance (TEER) studies showed that all three polymers (TMC60, SPH, and SPHC) were able to decrease TEER values to approximately 30% of the initial values, indicating the ability of these polymers to open the tight junctions. Recovery TEER studies showed that the effects of the polymers on Caco-2 cell monolayers were reversible, indicating viability of the cells after incubation with polymers. Both SPH and SPHC (compared with TMC60) were able to increase the paracellular transport of octreotide by their mechanical pressures on tight junctions. The mechanistic studies showed that junctional proteins, including actin, occludin, and claudin-1, were influenced by application of SPH and SPHC polymers to the Caco-2 cell monolayers. SPH and SPHC induced clear changes in the staining pattern of all three proteins compared with the control, indicating that the expression of these proteins in the tight junctions was increased, most likely due to the mechanical pressure of the polymers on the junctional proteins.

Caco-2 Cells↗

PubMed2006

Vinyl polymers as non-viral gene delivery carriers: current status and prospects.

Since the first application of polymers as non-viral gene delivery systems in 1965 by Vaheri and Pagano using functionalised dextran (A. Vaheri and J. S. Pagano, "Infectious poliovirus RNA: a sensitive method of assay", Virology 1965, 27, 434-6), a large number of different polymers have been developed, studied and compared for application as DNA carriers. Vinyl-based polymers are one type of polymers that have gained considerable interest. The interest in developing this particular type of polymer is partly related to the straightforward way in which large amounts of these polymers can be prepared by radical (co)polymerisation. This opens up a path for establishing a wide range of structure-property relations using polymer libraries. The present review aims to give an overview of past and ongoing research using vinyl-based gene delivery systems. The application of cationic, neutral and zwitterionic polymers as DNA carriers is summarised and discussed. [structure: see text] Chemical structure of DEAE-functionalised dextran.

Animals↗

PubMed2004

Smart elastin-like polymers.

Elastin-like polymers are a new family of proteinaceous polymers. In these polymers converge a wide set of interesting properties that difficultly can be found together in other polymers. They are extremely biocompatible and show an acute smart and self-assembling behaviour. The increasing in complexity of the molecular design renders polymers showing combination of functionalities and complex performance. This is specially true nowadays where, taking into account their peptide nature, these polymers can be produced as recombinant proteins in genetically modified (micro)organisms. The absolute control and absence of randomness in the primary structure makes possible the realization of multifunctional polymers that can combine physical, chemical and biological functions in a desired fashion. It can be said that the molecular design is mainly limited by imagination and not by technique. This chapter is intended to show the molecular parameters that explain the smart behaviour finally observed and how the increase in complexity of the molecular designs leads to a richer behaviour of the polymer, as a way to show the enormous potential of this family in the development of advanced materials and systems for biomedicine and nanotechnology for the next decades.

Animals↗

PubMed1993

Hydrolysis of fish oils containing polymers of triacylglycerols by pancreatic lipase in vitro.

Fish oils containing different levels of polymers of triacylglycerols formed during autoxidation were incubated with pancreatic lipase to establish whether these polymers are substrates for lipase hydrolysis. With oils containing low amounts (less than 4%) of triacylglycerol polymers as substrates, both triacylglycerols and polymers of triacylglycerols were almost completely hydrolyzed, and fatty acid monomers and monoacylglycerols were the major lipid products. Under the same incubation conditions, some triacylglycerols remained intact when highly oxidized oils containing 20 or 30% triacylglycerol polymers were the substrate. The fatty acid composition of these residual triacylglycerols was almost identical to that of triacylglycerols present at the start of the assay. When fish oil containing 30% triacylglycerol polymers was incubated with the lipase, the component triacylglycerols and polymers of triacylglycerols were hydrolyzed at similar rates, and fatty acid dimers were detected as a product. It is concluded that the high molecular weight polymers of triacylglycerols present in oxidized fish oils can be hydrolyzed by pancreatic lipase in vitro.

Animals↗

PubMed2004

Synthetic polymers adsorbing bisphenol A and its analogues prepared by covalent molecular imprinting using bisphenol A dimethacrylate as a template molecule.

Synthetic polymers which can adsorb bisphenol A (BPA) and related compounds were prepared by a covalent molecular imprinting technique. BPA dimethacrylate, used as template molecule, was polymerized with a crosslinker, triethylene glycol dimethacrylate (TEGDMA) or trimethylol propane trimethacrylate (TRIM). After the polymerization treatment with dilute NaOH was used to cleave BPA from the polymers. For high recovery of BPA with low polymer matrix degradation, the hydrolysis conditions were determined to be treatment with 1.0 mol L(-1) NaOH for 48 h. The binding sites generated by the hydrolysis were evaluated by determination of the retentivity of BPA, BPA analogues, and other endocrine disruptors. The polymers strongly adsorbed compounds with two hydroxyl groups at the 4,4'-positions. Generally the TEGDMA-based polymers had stronger affinity than the TRIM-based polymers, although the TRIM-based polymer adsorbed steroidal hormones with two hydroxyl groups, for example 17 alpha-estradiol and 17 beta-estradiol, more strongly than the TEGDMA-based polymer, meaning that the crosslinkers affected the properties of the binding sites and, depending upon the target molecules, suitable crosslinkers should be chosen in this system.

Adsorption↗

PubMed2000

Study of the binding characteristics of molecular imprinted polymer selective for cefalexin in aqueous media.

A molecularly imprinted polymer was prepared using cefalexin as the template molecule and 2-(trifluoromethyl)acrylic acid as the functional monomer. The bulk polymer was ground, sieved and investigated in an equilibrium binding experiment to evaluate the binding characteristics of the cefalexin-imprinted polymer for a better understanding of the mechanisms of recognition in molecularly imprinted polymers. Scatchard analysis showed that two classes of binding sites were formed in the imprinted polymer under the concentration studied. The dissociation constants were estimated to be 0.14 mmol/L and 2.38 mmol/L. The polymer gave much higher binding capacity for cefalexin than the non-imprinted polymer with the same chemical composition. The selectivity was evaluated by distribution coefficients of cefalexin and other structurally similar compounds. The results showed that the imprinted polymer exhibited high affinity for cefalexin among the tested compounds.

Acrylates↗

PubMed2006

Polymer architecture and drug delivery.

Polymers occupy a major portion of materials used for controlled release formulations and drug-targeting systems because this class of materials presents seemingly endless diversity in topology and chemistry. This is a crucial advantage over other classes of materials to meet the ever-increasing requirements of new designs of drug delivery formulations. The polymer architecture (topology) describes the shape of a single polymer molecule. Every natural, seminatural, and synthetic polymer falls into one of categorized architectures: linear, graft, branched, cross-linked, block, star-shaped, and dendron/dendrimer topology. Although this topic spans a truly broad area in polymer science, this review introduces polymer architectures along with brief synthetic approaches for pharmaceutical scientists who are not familiar with polymer science, summarizes the characteristic properties of each architecture useful for drug delivery applications, and covers recent advances in drug delivery relevant to polymer architecture.

Animals↗

PubMed1995

Neutral polymers elicit, and antibodies to spectrin, band 4.1 protein and cytoplasmic domain of band 3 protein inhibit the concanavalin A-mediated agglutination of human erythrocytes.

Concanavalin A (Con A) is known to agglutinate human erythrocytes if the cells are pre-treated with a proteinase or neuraminidase. We report that untreated cells can also be made to agglutinate with the lectin if the lectin-bound cells are treated with anti-Con A antibodies, or if a neutral polymer such as serum albumin, polyvinylpyrrolidone or Ficoll is added. Thus, Con A falls in the category of 'incomplete' lectins. The polymer induces Con A-agglutinability without altering the receptor number, or deformability of the cells. If the polymer is sequestered within erythrocyte ghosts, Con A is unable to agglutinate them; but the presence of the polymer only on the outer surface (as in intact cells) or on both the surfaces permits agglutinability. Thus, the site of the polymer effect resides on the outer surface of the membrane. The polymer, however, is unable to induce agglutinability in erythrocyte vesicles, whose membrane lacks skeletal proteins. The result suggests a positive role for the membrane skeleton in the process of agglutination brought about by the polymer, as is true also for the agglutination of proteinase-treated cells. In order to obtain detailed information on the proteins participating in agglutination, monospecific antibodies to spectrins, band 4.1 protein, ankyrin and the cytoplasmic domain of band 3 protein were internalized in erythrocytes. It is found that anti-spectrin and anti-band 3 cytoplasmic domain, but not their Fab's, inhibit the Con A-mediated agglutinability partially, and anti-4.1 antibodies, as well as the Fab's, inhibit the agglutinability substantially. Anti-ankyrin, however, was without any effect. The results confirm a positive role for the membrane skeleton in the Con A-mediated agglutination of normal erythrocytes in the presence of a neutral polymer, or in proteinase treated cells. We also provide evidence for requirement of Mg-ATP in the agglutination process.

Adenosine Triphosphate↗

PubMed1996

Adsorption behaviour of amphiphilic polymers at hydrophobic surfaces: effects on protein adsorption.

The adsorption of four different amphiphilic polymers to a model surface has been studied, and the effects of the adsorbed amphiphiles on the subsequent adsorption of fibrinogen (Fg) and human serum albumin (HSA) at the surfaces were investigated. The amphiphilic polymers were one commercially available ABA block copolymer, Pluronic PE9400 (PE94), composed of poly(ethylene oxide) (A-blocks) and poly(propylene oxide) (B-block), and three graft copolymers, two with backbones of poly(styrene-co-acrylamide) (STY) and one with a backbone of poly(methyl methacrylate-co-ethylhexyl methacrylate) (ACRY). The backbones carried poly(ethylene oxide) (PEO) grafts. The model surface was a hydrophobic methylated silica surface (HMS). The amphiphilic polymers were adsorbed at the HMS surface from an ethanol/water solution. The adsorption process was monitored by ellipsometry. After rinsing with phosphate buffered saline (PBS), protein was added and the continued adsorption measured by ellipsometry. Surfaces modified by adsorption of the amphiphilic polymers were also characterized by contact angle measurements and X-ray photoelectron spectroscopy (XPS). According to these measurements the amphiphilic polymers adsorbed in significant amounts at the HMS surface. A limited study by atomic force microscopy (AFM), as well as the XPS measurements, suggests that both single molecules and micellar aggregates adsorb at the surface. ACRY and PE94 gave the highest levels of adsorption. As compared to the Pluronic block copolymer the graft copolymers were more strongly attached to the HMS surface, as shown by less desorption on rinsing with solvent. The ellipsometric results show that the adsorption of HSA and Fg at HMS surfaces containing preadsorbed amphiphilic polymer was significantly reduced as compared to the bare HMS surface. ACRY and PE94 showed the largest effects. Both polymers gave more than a 20-fold reduction of the Fg adsorption and a 10-fold reduction of the HSA adsorption. The STY polymers reduced the protein adsorption by a factor of 2-3.

Adsorption↗

PubMed1995

Concentration of BSA using a superabsorbent polymer: process evaluation.

A commercially available super absorbent polymer from Hoechst (Sanwet IM-5000-SG) was tested for the concentration of dilute solutions of bovine serum albumin (BSA). A systematic study was undertaken in order to evaluate the possibility of scaling-up the process. The polymer was first characterized by determining the swelling ratio (or mass increase) in aqueous solution as a function of time, temperature, pH, salt and polymer concentration. The swelling ratio was found to be independent of the polymer concentration, temperature (range 15-50 degree C), and pH (range 4-10), but decreased significantly with an increase in NaCL concentration. The polymer was capable of absorbing as much as 300-times its own weight in water, when using the most favorable conditions (0 mM NaCL). BSA was concentrated up to 3.5-times when using the appropriate polymer concentration. The recovery of protein was around 100% for concentration factors below 2.0, but decreased for higher concentration factors. As expected from the characterization results, higher amounts of polymer were needed to concentrate BSA solutions with higher salt concentrations. The performance of the process improved when using lower concentration BSA solutions (0.15 to 0.5 mg ml-1). The initial volume (10 to 500 ml) had a slight effect on the process due to a decrease in the rate of the absorption process. The concentration factor was predicted from the NaCL and polymer concentrations through a semi empirical model.

Hydrogen-Ion Concentration↗

PubMed1993

Sulfonic acid polymers are potent inhibitors of HIV-1 induced cytopathogenicity and the reverse transcriptases of both HIV-1 and HIV-2.

Four novel sulfonic acid polymers were evaluated for their in vitro HIV-1 and HIV-2 reverse transcriptase (RT) inhibitory activity and found to be equipotent against both RTs. The aromatic polymers demonstrated IC50 values that were approximately 10(3)-fold lower than those observed with the aliphatic polymers. Among the aromatic polymers, poly(4-styrenesulfonic acid) (PSS) (MW 8000; IC50 = 0.02 microgram/ml) was 3-fold more potent than poly(anetholesulfonic acid) (PAS) of approximately the same molecular weight range. The activity of PSS polymers increased in proportion to the size of the polymers and, relative to suramin, activity could be enhanced over 200-fold. These polymers also inhibited the cytopathic effect of HIV-1 at concentrations that were non-toxic to MT-4 cells. The potent RT inhibitory properties of these stable sulfonic acid polymers suggest that structure-activity studies are warranted to yield agents capable of inhibiting multiple stages of the viral process.

Animals↗

PubMed2005

Comparison of the mucoadhesive properties of various polymers.

In this study the mucoadhesive potential of nineteen different, most often referred mucoadhesive polymers was evaluated and characterized by adhesion time and total work of adhesion (TWA) of the polymer to porcine small intestinal mucosa. In addition, the influence of pH of the polymer and of method of drying on adhesion was evaluated. Aqueous polymer solutions were therefore adjusted to pH 3.0 and 7.0. Solutions were either dried by lyophilization (lyo.) or precipitated (pr.) in organic solvent and air-dried. Results of this study led to the following rank order of adhesion time: chitosan-4-thiobuthylamidine pH 3 lyo. >chitosan-4-thiobuthylamidine pH 6.5 pr.>polycarbophil-cysteine pH 3 lyo.>chitosan-4-thiobuthylamidine pH 6.5 lyo.>PAA450-cysteine pH 3 lyo.>pH 7 pr.>Carbopol 980 pH 7 pr.>Carbopol 974P pH 7 pr.>polycarbophil pH 7 pr.>980 pH 3 lyo. The rank order obtained for adhesion time was in agreement with the rank order obtained for total work of adhesion. The highest mucoadhesion was shown by thiolated polymers at pH 3.0, dried by lyophilization. In contrary, polyacrylates were most mucoadhesive in form of precipitated neutral sodium salts. Other tested polymers like natural polysaccharides, cellulose derivatives, polyvinylpirrolidone and polyethylenglycole, although previously reported as good mucoadhesives, showed low to almost no mucoadhesion. The pH of polymer and drying method were found to be important factors influencing the mucoadhesive potential of polymers.

Adhesiveness↗

PubMed2006

Polymer genomics: an insight into pharmacology and toxicology of nanomedicines.

Synthetic polymers and nanomaterials display selective phenotypic effects in cells and in the body signal transduction mechanisms involved in inflammation, differentiation, proliferation, and apoptosis. When physically mixed or covalently conjugated with cytotoxic agents, bacterial DNA or antigens, polymers can drastically alter specific genetically controlled responses to these agents. These effects, in part, result from cooperative interactions of polymers and nanomaterials with plasma cell membranes and trafficking of polymers and nanomaterials to intracellular organelles. Cells and whole organism responses to these materials can be phenotype or genotype dependent. In selected cases, polymer agents can bypass limitations to biological responses imposed by the genotype, for example, phenotypic correction of immune response by polyelectrolytes. Overall, these effects are relatively benign as they do not result in cytotoxicity or major toxicities in the body. Collectively, however, these studies support the need for assessing pharmacogenomic effects of polymer materials to maximize clinical outcomes and understand the pharmacological and toxicological effects of polymer formulations of biological agents, i.e. polymer genomics.

Animals↗

PubMed2006

Formation mechanism of nanotubes comprising layers of PbS nanoparticles in polymer-surfactant solutions.

The crystallization of PbS in aqueous solutions containing the surfactant sodium dodecyl sulfate (SDS) and hydrophilic polymers resulted in a novel type of metastable nanotubes, the walls of which consist of layers of ordered PbS nanoparticles, apparently separated by layers of surfactant molecules. Information on the mechanism of formation of these structures was obtained by focusing on the roles of the polymer, and of the insoluble lead dodecyl sulfate (Pb(DS)2) present in the system. TEM investigations of the early stages of crystallization revealed the coexistence of PbS and Pb(DS)2 precipitates, the latter being surprisingly important for nanotube formation, and allowed to follow the evolution of layered structures from combination of the two types of crystals. Six different hydrophilic polymers have been used, which interact with SDS with varying strengths. Surprisingly, and in contrast to previous hypotheses, layered nanostructures were observed in all polymer solutions, regardless of the strength of polymer-surfactant interactions. This indicates that, although the presence of a polymer is necessary, polymer-SDS interactions are not a driving force for the formation of the layered structures and nanotubes. On the contrary, the interactions between the polymer chains and the growing particles appear to be of the utmost importance. Results presented here can be interpreted in terms of two alternative mechanisms for layered nanostructure and nanotube formation.

Crystallization↗

PubMed2005

Hydrotropic polymer micelle system for delivery of paclitaxel.

Hydrotropic polymer micelle system has been developed for delivery of poorly water-soluble drugs such as paclitaxel. Hydrotropic polymers based on N,N-diethylnicotinamide were synthesized and used as a hydrophobic block for constructing amphiphilic block copolymers. The hydrotropic block copolymers self-assembled to form micelles in aqueous media. The size of the prepared polymer micelles was in the range of 30-50 nm, and increased to 100-120 nm after paclitaxel loading. The critical micelle concentrations (CMCs) of the block copolymers were higher by an order of magnitude than those of other typical polymer micelles, due to less hydrophobicity of the hydrotropic blocks. The drug loading capacity and physical stability of the polymer micelles were characterized and compared with those of other polymer micelles. The hydrotropic polymer micelles containing hydrotrope-rich cores showed not only higher loading capacity but also enhanced physical stability in aqueous media. They could be redissolved in aqueous media by simple vortexing and/or a mild heating. The hydrotropic polymer micelles provide an alternative approach for formulation of poorly soluble drugs.

Drug Delivery Systems↗

PubMed2001

Surface attached ultrathin polymer monolayers for control of cell adhesion.

BACKGROUND: Calcific degeneration is the major drawback of bioprostheses. None of the numerous preventive approaches omitted calcification. Previous studies showed that cellular surface seeding decreases calcium uptake in vitro but achievement of coverage remains problematic. A new approach is presented masking glutaraldehyde residues with a polymer layer allowing cell seeding. The aim of this study was to evaluate different polymers for suitability. METHODS: Ten polymers--covalently bound to glass--were tested for their ability to seed animal and human cells. Quality of coverage was evaluated by light and scanning electron microscopy, and polymers were characterized physicochemically. RESULTS: Quality of cellular growth was similar for canine and human cells. Five polymers allowed excellent surface coverage, two led to a decrease of cell adherence, and four to poor cellular growth. No correlation between molecular weight, thickness, hydrophilicity, or charge of the polymer and cell growth was found. CONCLUSIONS: Polymer monolayers can promote cellular growth but without correlation to physicochemical characteristics. Polymers covalently bound to biologic tissue appear to be a promising approach for achieving cellular coverage of biomaterials.

Animals↗

PubMed2002

Depletion-mediated red blood cell aggregation in polymer solutions.

Polymer-induced red blood cell (RBC) aggregation is of current basic science and clinical interest, and a depletion-mediated model for this phenomenon has been suggested; to date, however, analytical approaches to this model are lacking. An approach is thus described for calculating the interaction energy between RBC in polymer solutions. The model combines electrostatic repulsion due to RBC surface charge with osmotic attractive forces due to polymer depletion near the RBC surface. The effects of polymer concentration and polymer physicochemical properties on depletion layer thickness and on polymer penetration into the RBC glycocalyx are considered for 40 to 500 kDa dextran and for 18 to 35 kDa poly (ethylene glycol). The calculated results are in excellent agreement with literature data for cell-cell affinities and with RBC aggregation-polymer concentration relations. These findings thus lend strong support to depletion interactions as the basis for polymer-induced RBC aggregation and suggest the usefulness of this approach for exploring interactions between macromolecules and the RBC glycocalyx.

Animals↗