Interaction of cationic amphiphilic drugs with lipid A: Implications for development of endotoxin antagonists

This report presents evidence for the interactions of several classes of cationic amphiphilic drugs including the phenothiazines, aminoquinolines, biguanides, and aromatic diamidines, with lipid A, the endotoxic principle of lipopolysaccharides. The interactions of the drugs were quantitatively assessed by fluorescence methods. The affinities of the drugs for lipid A parallel their endotoxin-antagonistic effects in the Limulus gelation assay. Dicationic compounds bind lipid A with greater affinity; the affinity of such molecules increases exponentially as a function of the distance between the basic moieties. The bis-amidine drug - pentamidine - examined in greater detail, binds lipid A with high affinity (apparent K-d: 0.12 mu M), and LPS, probably due to simultaneous interactions of the terminal amidine groups with the anionic phosphates on lipid A. The sequestration of endotoxin by pentamidine reduces its propensity to bind to cells, and the complex exhibits attenuated toxicity in biological assays. These results have implications in the development of therapeutic strategies against endotoxin-related disease states.

WATER-SOLUBLE AND AMPHIPHILIC POLYMERS .11. GRAFT-POLYMERIZATION OF ACRYLIC-ACID ON POLY(VINYL ALCOHOL)

The graft polymerization of acrylic acid(AA) on poly(vinyl alcohol) (PVAL) has been investigated by using either potassium persulfate (KPS) or ceric ammonium nitrate(CAN) as an initiator. In the case of KPS initiation, the formation of the graft polymer always lags behind the homopolymer formation. The graft polymer is separated by acetone, and the increase of reaction temperature favors the homopolymer formation at the early stage. In the case of CAN initiation, graft polymers with a high PAA content can hardly be obtained when the polymerization is performed under nitrogen and at < 0.06 mol/L HNO3 concentration. It has been found that incorporation of a small amount of oxygen in a protective nitrogen gas accelerates markedly the graft polymerization, and that the resulting graft polymers can not be separated by acetone precipitation technique in most cases. The Dalian nitrogen(containing 0.7% oxygen) is a good protective gas for CAN-initiated PVAL-AA graft polymerization.

WATER-SOLUBLE AND AMPHIPHILIC POLYMERS .6. A STUDY ON THE SURFACE-COMPOSITION OF CAST FILMS OF PST/PMAA AND PEO-PST-PEO BLOCK POLYMERS BY XPS

Thin films of PSt/PMAA and PEO-PSt-PEO block polymers were deposited on a polystyrene substrate by solution adsorption (with or without solvent treatment), and the film surfaces were characterized by means of XPS. Direct solvent - casting of PEO-PSt-PEO from benzene solutions resulted in PSt-rich surfaces, whereas PMAA richer surfaces were obtained for PSt/PMAA films cast from DMF solutions. Moreover, solvent treatment after casting had profound effect on the film surface composition. Treatment with water markedly increased the surface concentration of polar PEO segments. In the case of PSt-PMAA block polymers, the PSt content on the surface increased in the order of water < ethanol < cyclohexane < petroleum ether, the last-named giving films with almost pure PSt surface. It is well worth noticing that the bulk composition had little to do with the surface composition for both PSt/PMAA and PEO-PSt-PEO block polymers within the composition range investigated when subsequent solvent treatment was applied.

WATER-SOLUBLE AND AMPHIPHILIC POLYMERS .7. SYNTHESIS AND CHARACTERIZATION OF A NOVEL COMB-TYPE AMPHIPHILIC POLYMER PAMC16S

A novel comb-like amphiphilic polymer, poly (2-acrylamidohexadecylsulfonic acid) (PAMC16S), was synthesized by free radical polymerization of the corresponding amphiphilic monomer in 1,4-dioxane-water mixed solvents. Depending on the ratio of water/dioxane in the solvent, the reaction proceeded by either precipitation polymerization or micellar polymerization. The molecular weight of the polymer obtained under similar conditions decreased and subsequently increased with the increase of water content in the mixed solvent. The polyion nature of PAMC16S was confirmed by viscosity data of ethanolic solutions. In addition, the polymer was characterized by solubility, IR, TG and wide angle X-ray diffraction methods.

Phosphorylcholine based amphiphilic polymers for the solubilization of integral membrane proteins

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Stimuli-responsive Novel Amphiphilic Polymers for Chemical and Biomedical Applications

Amphiphilic polymers are a class of polymers that self-assemble into different types of microstructure, depending on the solvent environment and external stimuli. Self assembly structures can exist in many different forms, such as spherical micelles, rod-like micelles, bi-layers, vesicles, bi-continuous structure etc. Most biological systems are basically comprised of many of these organised structures arranged in an intelligent manner, which impart functions and life to the system. We have adopted the atom transfer radical polymerization (ATRP) technique to synthesize various types of block copolymer systems that self-assemble into different microstructure when subject to an external stimuli, such as pH or temperature. The systems that we have studied are: (1) pH responsive fullerene (C60) containing poly(methacrylic acid) (PMAA-b-C60); (2) pH and temperature responsive fullerene containing poly[2-(dimethylamino)ethyl methacrylate] (C₆₀-b-PDMAEMA); (3) other responsive water-soluble fullerene systems. By varying temperature, pH and salt concentration, different types microstructure can be produced. In the presence of inorganic salts, fractal patterns at nano- to microscopic dimension were observed for negatively charged PMAA-b-C60, while such structure was not observed for positively charged PDMAEMA-b-C60. We demonstrated that negatively charged fullerene containing polymeric systems can serve as excellent nano-templates for the controlled growth of inorganic crystals at the nano- to micrometer length scale and the possible mechanism was proposed. The physical properties and the characteristics of their self-assembly properties will be discussed, and their implications to chemical and biomedical applications will be highlighted.

Aggregation behaviour of hydrophobically modified poly(allylammonium) chloride

The behaviour of hydrophobically modified poly(allylammonium) chloride having octyl, decyl, dodecyl and hexadecyl side chains has been studied in aqueous solution using fluorescence emission techniques. Micropolarity studies using the I-1/I-3 ratio of the vibronic bands of pyrene show that the formation of hydrophobic microdomains depends on both the length of the side chain and the polymer concentration. The I-1/I-3 ratio of the polymers with low hydrophobe content (less than 5% mel) changes substantially when reaching a certain concentration. These changes are assigned to aggregation originating from interchain interactions. This behaviour is also confirmed by the behaviour of the monomer/excimer emission intensities of pyrene- dodecanoic acid used as a probe. For polymers having dodecyl side chains and hydrophobe contents higher than 10%, aggregates are formed independently of the polymer concentration. Anisotropy measurements show that microdomains resulting from the inter- and/or intramolecular interactions are similar to those observed for cationic surfactants. Viscosity measurements show that the coil dimensions are substantially decreased for the polymers having high hydrophobe contents, indicating intramolecular associations.

Développement de nouveaux polymères amphiphiles comme floculants versatiles pour le traitement de l’eau issue de l’industrie pétrolière

Les polymères hydrosolubles sont utilisés dans diverses industries pour permettre la floculation, soit une séparation solide-liquide de particules présentes en suspension colloïdale. Afin de réduire les impacts environnementaux de l’exploitation des sables bitumineux en Alberta, l’industrie est à la recherche de nouveaux moyens et procédés pour traiter les résidus miniers permettant de séparer les matières solides et de récupérer l’eau. L’objectif des travaux présentés est d’améliorer la floculation, la densification et la déshydratation de ces résidus miniers aqueux par de nouveaux polymères synthétiques. Des homopolymères d’acrylamide de différentes masses molaires ont été synthétisés pour étudier l’influence de la masse molaire sur l’efficacité de floculation. Le taux initial de sédimentation (TIS) est le paramètre qui fut utilisé afin de comparer l’efficacité de floculation des différents polymères. Il a été possible de confirmer l’importance de la masse molaire sur l’efficacité de floculation et de déterminer une masse molaire minimale d’environ 6 MDa pour des polyacrylamides, afin d’obtenir l’efficacité de floculation maximale de suspensions colloïdales principalement composées de kaolin. Afin d’étudier l’effet des charges sur l’efficacité de floculation, des polymères anioniques et cationiques ont été synthétisés. Une série de copolymères d’acrylamide et d’acide acrylique ont été synthétisés comme polymères anioniques et deux séries de copolymères ont été synthétisés comme polymères cationiques, soit des copolymères d’acrylamide et de chlorure de diallyldiméthylammonium et des copolymères de 4-vinyl pyridine et de 1-méthyl-4-vinyl pyridinium. Il a été démontré que les charges anioniques des polymères avaient peu d’influence sur l’efficacité de floculation et que leur comportement en présence de sels était différent de ce que prévoyait la littérature. Il a aussi été démontré que les charges cationiques des polymères n’améliorent pas l’efficacité de floculation. Par la suite, des séries de copolymères amphiphiles, avec des monomères d’acrylamide, de N-alkylacrylamides et d’acrylonitrile, ont été synthétisés, pour étudier l’effet du caractère amphiphile sur la déshydratation des résidus miniers. Le pourcentage de déshydratation nette est le paramètre qui fut utilisé afin de comparer l’efficacité de déshydratation des différents polymères. Il a été possible de développer des copolymères amphiphiles qui améliorent l’efficacité de déshydratation par rapport à des homopolymères d’acrylamide. Il ne fut pas possible de déterminer une tendance entre la balance hydrophile/hydrophobe des copolymères amphiphiles et l’efficacité de déshydratation.

Synthesis and aggregation behavior of four-arm star amphiphilic block copolymers in water

We report the first synthesis of amphiphilic four-arm star diblock copolymers consisting of styrene (STY) and acrylic acid (AA) made using reversible addition-fragmentation chain transfer (RAFT; Z group approach with no star-star coupling). The polymerization proceeded in an ideal living manner. The size of the poly(AA(132)-STYm)(4) stars in DMF were small and close to 7 nm, suggesting no star aggregation. Slow addition of water (pH = 6.8) to this mixture resulted in aggregates of 15 stars per micelle with core-shell morphology. Calculations showed that the polyAA blocks were slightly extended with a shell thickness of 15 nm. Treatment of these micelles with piperidine to cleave the block arms from the core resulted in little or no change on micelle size or morphology, but the polyAA shell thickness was close to 29 nm (33 nm is the maximum at full extension) suggesting a release of entropy when the arms are detached from the core molecule. In this work we showed through the use of star amphiphilic polymers that the micelle size, aggregation number, and morphology could be controlled.

In vivo evaluation of folate decorated cross-linked micelles for the delivery of platinum anticancer drugs

The biodistribution of micelles with and without folic acid targeting ligands were studied using a block copolymer consisting of acrylic acid (AA) and polyethylene glycol methyl ether acrylate (PEGMEA) blocks. The polymers were prepared using RAFT polymerization in the presence of a folic acid functionalized RAFT agent. Oxoplatin was conjugated onto the acrylic acid block to form amphiphilic polymers which, when diluted in water, formed stable micelles. In order to probe the in vivo stability, a selection of micelles were cross-linked using 1,8-diamino octane. The sizes of the micelles used in this study range between 75 and 200 nm, with both spherical and worm-like conformation. The effects of cross-linking, folate conjugation and different conformation on the biodistribution were studied in female nude mice (BALB/c) following intravenous injection into the tail vein. Using optical imaging to monitor the fluorophore-labeled polymer, the in vivo biodistribution of the micelles was monitored over a 48 h time-course after which the organs were removed and evaluated ex vivo. These experiments showed that both cross-linking and conjugation with folic acid led to increased fluorescence intensities in the organs, especially in the liver and kidneys, while micelles that are not conjugated with folate and not cross-linked are cleared rapidly from the body. Higher accumulation in the spleen, liver, and kidneys was also observed for micelles with worm-like shapes compared to the spherical micelles. While the various factors of cross-linking, micelle shape, and conjugation with folic acid all contribute separately to prolong the circulation time of the micelle, optimization of these parameters for drug delivery devices could potentially overcome adverse effects such as liver and kidney toxicity.

Organized Nanostructures of Thermoresponsive Poly(N-isopropylacrylamide) Block Copolymers Obtained Through Controlled RAFT Polymerization

Kontrolloidut radikaalipolymerointimenetelmät, kuten RAFT-polymerointi, ovat moderni tapa valmistaa polymeerejä säädellysti. RAFT-polymeroinnilla polymeerien ketjunpituutta, moolimassajakaumaa, mikrorakennetta (taktisuus, järjestys), koostumusta ja funktionaalisuutta kyetään hallitsemaan. Siten menetelmällä voidaan valmistaa uudenlaisia polymeeriarkkitektuureja, kuten blokki- ja tähtipolymeerejä, sekä hybridimateriaaleja ja biokonjugaatteja. Polymeeristen rakennuspalikoiden itsejärjestyminen, missä huolellisesti syntetisoidut polymeerit järjestyvät halutulla tavalla nanoskaalassa, on suosittu tutkimuskohde materiaalitieteessä. On huomattava, että blokkipolymeerien itsejärjestyminen on vielä suhteellisen nuori tutkimusaihe. Tämän hetkiset polymeeriset nanomateriaalit ovat suhteellisen yksinkertaisia luonnon luomuksiin verrattuina, tarjoten jatkuvasti uusia mahdollisuuksia seuraavan sukupolven polymeereille. Tässä työssä RAFT-polymeroinnilla syntetisoitiin amfifiilisiä di- ja triblokkikopolymeerejä sekä tutkittiin niiden järjestymistä nanorakenteiksi. Kaikissa blokkikopolymeereissä käytettiin lämpöherkkää poly(N-isopropyyliakryyliamidia). Siten polymeerit ja tutkitut materiaalit reagoivat lämpötilanmuutokseen ympäristössä eli ovat ns. ympäristöherkkiä. Työssä tutkittiin taktisuuden kontrollointia N-isopropyyliakryyliamidin RAFT-polymeroinnissa. Polymeerin taktisuutta sekä ketjunpituutta ja blokkijärjestystä säätämällä voitiin hallita polymeerin itsejärjestymistä vesiliuoksessa. Amfifiiliset polymeerit järjestyivät laimeissa vesiliuoksissa erilaisiksi misellirakenteiksi, muodostaen ns. mikrosäiliöitä. Tällaisilla polymeereillä odotetaan olevan sovelluksia esim. lääkeainevapautuksessa. Amfifiilejä käytetään myös esimerkiksi apuaineina pinnoitteissa ja kosmetiikassa. Kiinteässä tilassa tutkitut triblokkikopolymeerit muodostivat teoreettisesti ennustettuja morfologioita. Lämpöherkän materiaalin hydrogeelit toimivat suodatinmembraanina nanokokoluokassa. RAFT-polymeroinnilla syntetisoituja polymeereja voidaan sellaisenaan käyttää kultananopartikkeleiden päällystämiseen. Kultananopartikkelit ovat erittäin kiinostavia mm. niiden stabiilisuuden ja ainutlaatuisten pintaominaisuuksien vuoksi. Kun amfifiilisiä polymeerejä kiinnitettiin kultapartikkelin pinnalle, sen liuos- ja optisia ominaisuuksia voitiin säädellä pH:n ja lämpötilan avulla. Tällaisilla kultananopartikkeleilla on sovelluksia mm. diagnostiikassa, sensoreina ja solukuvauksessa.

Electroactive Aniline Pentamer Cross-Linking Chitosan for Stimulation Growth of Electrically Sensitive Cells

A new kind of electroactive polymers was synthesized by using aniline pentamer (AP) cross-linking chitosan (CS) in acetic acid/DMSO/DMF solution. UV-vis and CV confirmed the electroactivity of polymers in acidic aqueous solution. The amphiphilic polymers self-assembled into 200-300 nm micelles by dialysis against deionized water from the acetic acid buffer solution. Three samples with different weight percentages of AP were used to identify the relationship between the content of AP and the differentiation of rat neuronal pheochromocytoma PC-12 cells without external stimulation.

Synthesis and investigation of monoesters of polymaleic acids with azo-group

A series of amphiphilic polymers, monoesters of polymaleic acid containing ate-side groups (PMAN-A(n)Me) was synthesized by the reaction of alcohol(A,Me) with polymaleic anhydride (PMAN) for Langmuir-Blodgett assembly. The effects of the length of flexible spacer in the side chain on the pi-A isotherms and LB films were investigated. The UV-Vis and infrared linear dichroism spectra showed that the ate-side groups were highly oriented in PMAN-A(6)Me LB film deposited on silica or CaF2 substrate.