Work at physical chemistry and colloid science with bio-aspects

1. Work at physical chemistry and colloid science with bio-aspects Wageningen University Laboratory of physical chemistry and colloid science Dreijenplein 6, 6703 HB Wageningen, the Netherlands Frans.leermakers@wur.nl, Martien.cohenstuart@wur.nl

2. Laboratory of physical chemistry and colloid science • Strategic topic in phys. chem. and coll. sci. • Biophysical chemistry • Phys. chem. of food and biotechnology • Polymers at interfaces • Environmental physical chemistry Approach: -systematic experiments with a focus on understanding (we prefer to use model systems) -theoretical modeling directed to understand experiments

3. 1. Self-assembly of pluronic 121  polymersomes • PEOn-PPOm-PEOn surfactants form unstable vesicles for n ~5 and m~60 (L121) • We stabilize the vesicles by a PETA network and obtain stable nanocapsules with tunable size • Below you see such capsules filled by fiber-forming protein. AFM images F. Li, T. Ketelaar, A.T.M. Marcelis, F.A.M. Leermakers, M.A. Cohen Stuart, E.J.R. Sudholter "Stabilization of polymersome vesicles by an interpenetrating polymer network" Macromolecules 40 (2007) 329-333.

4. 2. SCF modeling of self-assembly • Lipid membranes in bulk and at interfaces • bending moduli, structure and thermodynamics • Vesicles in bulk and at interfaces • Protein-like inclusions in membranes We like to work on -pores in membranes -interaction of polycation with negatively charged membrane -asymmetric interaction of objects with membrane -steady-state membrane systems -vesicle to micelle transition by way of adding surfactants to lipids R.A. Kik, F.A.M. Leermakers, J.M. Kleijn "Molecular modeling of lipid bilayers and the effect of protein-like inclusions" Phys. Chem. Chem. Phys. 7 (2005) 1996-2005.

5. 3. Self-consistent field modeling • Core-shell particles with PE corona • Janus micelles composed of tri-block copolymers An-Bm-Cn with A, C hydrophilic B hydrophobic We like to work on: -fluctuation in micelle size  driving force -self-assembly driven by electrostatic interactions -understand the formation of tubular vesicles -do more work on micellar shape transitions in micelles with PE corona

6. 4. Micelles formed by attraction of + and - charges • Generic idea is make micelles with water soluble compounds by mixing • anionic block and neutral block Mn-Am • cationic block and neutral block Pn-Bm • when cAB > 0 Janus micelles can form PAA42-b-PAAm47 P2MVP42-b-PEO446 I.K. Voets, A. de Keizer, P. de Waard, P.M. Frederik, P.H.H. Bomans, H. Schmalz, A. Walther, S.M. King, F.A.M. Leermakers, M.A. Cohen Stuart "Double-faced micelles from water-soluble polymers" Angew. Chem. Int. 45 (2006) 6673-6676.

7. 5. Protein-copolymer complexes + - - - + + + • Enzyme encapsulation,targeting, controlling activity + + + + + + + - - enzyme - + + + - - - + + enzyme - - + - - + - - + - - - + + PAA-PAM + lysozym: light scattering

8. 6. Micelles made by complexation with reversible polymers • Metal-bisligand coordination complexes are self-assembled supramolecules that have residual (negative) charge. • Admixing with oppositely charged copolymers gives hierarchical self-assembly Cryo-TEM images of coacervate core micelles formed in the mixed systems a), f- = 0.5 PMVP41-PEO204/ Zn-L2EO4 b), f- = 0.5 A-B-A/ Zn-L2EO4 mixed system. f- is the negative charge fraction in the mixed system. A-B-A=polyaminoacid block copolymer, A = neutral block, B = positively charged block Yan, Y.; Besseling, N. A. M.; de Keizer, A.; Marcelis, A. T. M.; Drechsler, M.; Cohen Stuart, M. A. Angew. Chem. Int. Ed. 2007, 46, published on line Feb.2, 2007

9. 7. Brushes: experiments and SCF models • Brushes as anti-fouling surfaces PEO, polysacharide (sweet) • Polydisperse polymer brushes • Proteins in polyelectrolyte brushes F.A.M. Leermakers, M. Ballauff, and O.V. Borisov “On the mechanism of uptake of globular proteins by polyelectrolyte brushes: a two-gradient self consistent field analysis” Langmuir 2007 in print

10. 8. Polypeptide synthesis by yeast cells

11. 8. Tri-block copolyelectrolytes from yeast -available on gram scale -homo-disperse, chiral and pure -pH responsive gel formation (driven by b-sheet formation)

12. 9. Measurements of forces by colloid probe AFM • We have an interest in measuring forces on the nanoscale -depletion forces -in non-adsorbing polymer systems -in equilibrium polymer systems -deformation of vesicles (nano-capsules) -electrostatic interactions, -polymer mediated forces -effect of surface modification. EHUT + some DHUT Silica+C18 cyclohexane W. Knoben, N.A.M. Besseling, M.A. Cohen Stuart "Long-range depletion forces induced by associating small molecules" Phys. Rev. Lett. 97 (2006) 068301/1-4.

13. 10. Summary experimental • SCF-modeling (and a little bit MC simulations) • Strong in thermodynamic analysis • Strong in electrified interfaces • Scattering (light, neutrons, xrays) • Reflectometry (dynamic adsorption studies) /ellipsometry • Calorimetry • AFM including colloidal probe • Titrations and other analytical tools, surface characterisation • Microscopy (light, confocal, TEM …) • NMR • Langmuir trough

14. 10. Summary systems • Self-assembly in aqueous systems based on • hydrophobic driving force • electrostatic driving force • metal-ligand mediated assembly • with help of polymer network • Applications are bio-inspired • responsive systems • preference to study equilibrium systems • interest in steady state conditions • Open eye for applications