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Polypeptide hybrid copolymers as selective micellar nanocarriers in nonaqueous media

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Polypeptide hybrid copolymers as selective micellar nanocarriers in nonaqueous media
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  See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/236630480 Polypeptide hybrid copolymers as selectivemicellar nanocarriers in nonaqueous media  Article   in  Colloid and Polymer Science · November 2009 DOI: 10.1007/s00396-009-2096-y CITATIONS 4 READS 34 5 authors , including: Some of the authors of this publication are also working on these related projects: Smart core-shell microgels as nanoparticle carriers for catalysis   View projectStructure and dynamics of phospholipid vesicles around the main phase transition   View projectGuillermo Orts-GilSpanish Foundation for Science and Technol… 95   PUBLICATIONS   361   CITATIONS   SEE PROFILE Sylvain François PrévostEuropean Synchrotron Radiation Facility 79   PUBLICATIONS   711   CITATIONS   SEE PROFILE Helmut SchlaadUniversität Potsdam 18   PUBLICATIONS   602   CITATIONS   SEE PROFILE Thomas HellwegBielefeld University 138   PUBLICATIONS   3,437   CITATIONS   SEE PROFILE All content following this page was uploaded by Guillermo Orts-Gil on 10 January 2017. The user has requested enhancement of the downloaded file.  This is an non-edited, pre-print version of the paper by Colloid and Polymer Science DOI 10.1007/s00396-009-2096-y 1 Polypeptide hybrid copolymers as selective micellar nanocarriers in non-aqueous media Guillermo Orts Gil, Sylvain Prévost, Magdalena Losik, Helmut Schlaad, and Thomas Hellweg  This is an non-edited, pre-print version of the paper by Colloid and Polymer Science DOI 10.1007/s00396-009-2096-y 2 Polypeptide hybrid copolymers as selective micellar nanocarriers in non-aqueous media Guillermo Orts Gil 1,2 , Sylvain Prevost 2,4 , Magdalena Losik 3 , Helmut Schlaad 3 ∗ , and Thomas Hellweg 5†   January 20, 2009 1 Bundesanstalt für Materialforschung und -prüfung (BAM - V.1), Unter den Eichen 87, 12205 Berlin, Germany 2 Stranski-Laboratorium f¨ur Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin, Germany 3 Max–Planck–Institut für Kolloid– und Grenzflächenforschung, Wissenschaftspark Golm, 14424 Potsdam, Germany 4 Hahn-Meitner-Institute, Glienicker Str. 100, 14109 Berlin, Germany 5 Universität Bayreuth, Physikalische Chemie I, Universitätsstr. 30, 95447 Bayreuth, Germany *Corresponding author; e-mail: Helmut.Schlaad@mpikg.mpg.de, phone: ++49-331- 5679514, Fax: ++49-331-5679502 †Corresponding author; e-mail: thomas.hellweg@uni-bayreuth.de, phone: ++49-921- 552768, Fax: ++49-921-552780 Abstract The self-assembly of polystyrene-block-poly(L-lysine) (PS-PLLys) copolymers with different block lengths has been studied in toluene. The obtained spherical micelles proved to be sensitive to size variation by addition of acids or bases. This was studied by following the effect of the addition of pyridine to the organic solutions using light and neutron scattering techniques. It is shown that pyridine induces a shrinking of the polystyrene chains in the micelle shell region decreasing the aggregates-solvent interface. Oppositely, the addition of benzoic acid leads to a swelling of copolymer micelles proportional to the molar fraction of polypeptide. This fact suggests a selective permeability of PS-PLLys micelles and the possibility to encapsulate organic compounds in toluene depending on their chemical nature.  This is an non-edited, pre-print version of the paper by Colloid and Polymer Science DOI 10.1007/s00396-009-2096-y 3 1 Introduction One of the most important features of amphiphilic block copolymers (BCP) is their ability to self-assemble and to form a plethora of different stuctures. This is true for bulk systems but also for solutions in selective solvents, show ing a similar behaviour to surfactants [1, 2, 3]. Also with respect to technical applications BCP’s are of increasing importance [4, 5, 6]. Another application is their use as templates in the synthesis of porous inorganic materials [7]. For some of these applications it would be advantageous to control the structuring in the BCP solutions. This goal can be achieved by controlling the packing parameter in the BCP solution. One approach to do it is mixing the BCP with surfactant in water [8, 9, 10, 11]. Other rather easy ways to control the packing parameter are given by variation total molecular weight, block compositions and length, molecular architecture and more recently by use of responsive blocks in the BCP [12, 13]. In this context there is a growing interest in the application of BCP comprising biological block (e.g. polypeptides) as selective nanocarriers [?]. Water is the most important solvent with respect to drug delivery. Hence, a lot of studies of block copolymers in solution were done using aqueous sys tems. Less is known about non-aqueous solutions [14]. In order to shed light on this topic the present contribution contribution deals with polypeptide based hybrid block copolymers in toluene. Poly(L-lysine) (PLLys) is an important water-soluble polypeptide which contains amine groups on the side chains. PLLys can adopt three different conformations i.e. random coil, _-helix and _-sheet depending on external parameters including pH, surfactant concentration, temperature, etc. [15]. In this paper we describe the self-assembled structures formed by PS-PLLys block copolymers in toluene and the selective encapsulation of basic and acidic compounds. 2 Experimental section 2.1 Sample preparation Previous studies concerning block copolymers composed of PS-PLLys demon strated that the molar ratio, as well as, the total number of monomer units play an important role  This is an non-edited, pre-print version of the paper by Colloid and Polymer Science DOI 10.1007/s00396-009-2096-y 4 determining the preferred structure in solution (micelles, vesicles, spheres, rod-like aggregates) [16] and the solubility in selective solvents [17]. Here, PS-PLLys copolymers with three different block lengths were synthesized by anionic polymerization and subsequent ring opening polymerization of N-carboxyanhydrides. For details of the synthesis and the characterization see [18, 16, 19, 17]. In table 1 the characteristics of the final products are listed. Table 1: Description of the three polystyrene-block-poly(L-lysine) copolymers object of study. The molecular weight (M w ) and the molar fraction of peptide monomer (x lys ), and the polydispersity index are given. Solutions of the copolymers were prepared by addition of the dry polymer powder in toluene (99%, Merck) up to a concentration of 0.1 wt.%. The solutions were sonicated 3 hours (Sonorex super RK 52 H, with a max. power of 240 W) at temperatures above the UCST of the polystyrene in toluene [20]. The obtained solutions were clear and stable. Based on dynamic light scattering (DLS) experiments, it was found that the outcome of preparation procedure was reproducible within experimental precision. Always the same particle size distribution was obtained. 2.2 Dynamic light scattering (DLS) Dynamic light scattering measurements were carried out at a temperature of 20 ◦ C using a setup consisting of an argon ion laser (lambda= 514.5 nm, P = 600 mW), a goniometer with fiber optic detector and two photoncounters (ALV, Langen, Germany). The signal is fed into a multiple-_ correlator (ALV-5000 Fast) operated in the cross-correlation mode.
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