Composite Silica:Polypeptide Nanoparticles Sibel Turksen, Brian Fong & Paul S. Russo

1. Composite Silica:Polypeptide Nanoparticles Sibel Turksen, Brian Fong & Paul S. Russo Macromolecular Studies Group Louisiana State University NSF, ACS, LSU Coates Fund Kasetsart University Bangkok, Thailand Thursday, November 18, 2004

2. Fuzzballs a silica interior and synthetic homopolypeptide exterior. Optional superparamagnetic inclusion Silica (SiO2) core typically 200 nm diameter Homopolypeptide Shell typically 100 nm thick

3. Why? The usual reasons for polymer-coated particles • Stability studies, probe diffusion, standards, etc. The better reasons for polypeptide-coated particles • Shouldallowexcellent shell thickness control. • Shell is rigid spacer for assembling silica spheres. • Astounding chemical versatility and functionality, including chirality. • Responsiveness and perfection of structures through reproducible helix-coil transitions. • Easily attach antibodies for recognition of cancer cells, easily attach cancer-killing lytic peptides, too. • When magnetic, good way to self-assemble all this functionality

4. Co-Si-homopolypeptide composite systems • Hierarchical structures • Homopolypeptide shell – PBLG, PCBL • (can be helix as shown, or coil?) • Superparamagnetic – Fe3O4 or Co core Mostly… unstructured, random coil polymers Our Little Corner of the World: Silica-Homopolypeptide Composite Particles

5. O H O H H O H O O H Si Si hydrolysis O H O H O O condensation Si Si O H O H O TEOS C H O H O O 2 5 N H O H 4 H O O H O H Stöber Silica-Stöber Synthesis Hydrolysis of tetraethyl orthosilicate (TEOS)

6. SEM & TEM of Silica Particles

7. Synthesis of Magnetite – Fe3O4

8. Dark:Magnetic inclusions (~ 10nm) Gray:Glassy SiO2 matrix TEM- Silica Coated Fe3O4 Magnetic silica particles

9. NH2(CH2)3Si(OH)2O– cit – + Co Cit– Co cit – + NH2(CH2)3Si(OH)3 NH2(CH2)3Si(OH)2O – cit – NH2(CH2)3Si(OH)2O – OH – O O O N N N OH – SiO2 + H2O TEOS, APS, EtOH Co Co Stöber reaction OH – OH – Superparamagnetic cobalt

10. TEM- Silica Coated Cobalt

11. Superparamagnetic Particles

12. Surface Functionalization

13. Homopolypeptides • PBLG • best understood homopolypeptide • semiflexible structure • helix-coil transition • PCBL • helix-coil transition @ 27 C in m-cresol

14. Synthesis of homopolypeptides

15. - + NH2RSi(OH)3 + N cit – N SiO2- Cobalt particles Superparamagnetic domain CBL-NCA, monomer Summary: Particle Preparation

16. Is the shell covalently attached? Almost certainly (By the way, the polypeptide conformation is mostly a-helix with some b-sheet)

17. TGA/DTA --Particles with ~ 23% by mass PBLG--Again, no evidence for binding of loose PBLG

18. Dynamic Light Scattering Bigger ones may diffuse slower (solvent viscosity effects)Flat plots indicate excellent, latex-like uniformity

19. Particle Characteristics • Silica Core Properties • Radius from DLS: 97 nm • Molar Mass: 4.5 x 109 • Surface area: 15.6 m2/g • PBLG Shell Properties • 78 nm. • ~90% solvent / 10% polymer. • Polymer density limited by crowding around initiator sites.

20. Unfortunately, the shell thickness was not controlled by [M]/[I]. Why not? Not all initiators are active: crowding Challenges: • Controlling initiator density • Attachment of ready-made polymers

21. Helix-coil Transition of PCBL Matsuoka, M., Norisuye, T., Teramoto, A., Fujita, H. Biopolymers, 1973, 12,1515-1532

22. Early attempts showed NO change in the size of the particles—as if the shells were not responding. We reasoned this might be due to overcrowding on the surface.

23. NH2 NH2 3-(2-furoyl) quinoline-2-carboxaldehyde (ATTO-TAG™ FQ) APTMS AEAPTMS MTMS Avoiding crowding 25% amino groups

24. Silica-homopolypeptide Composite Particles DLS of Si-PCBL particles in DMF

25. Helix-coil transition of Co-PCBL

26. It’s Alive! This plot shows polydispersity

27. M Magnetization -M Magnetization in opposite direction Hysteresis curve

28. SQUID- hysteresis plot of cobalt particles

29. SQUID- hysteresis plot of Co-PCBL

30. m ~ 0.5 m Formation of colloidal crystals Sufficiently dense suspensions assemble into colloidal crystals. With a size that matches that of visible light, diffraction results. Domains with different orientations result in different and quite pure colors.

31. Colloidal Crystals (PCBL Shell) Sufficiently dense suspensions assemble into colloidal crystals. With a size that matches that of visible light, diffraction results. Domains with different orientations result in different and quite pure colors. Helical homopolypeptide shell

32. Why Study? • Beautiful! • Fun supramolecular synthesize & characterize from nm to mm. • Applies to optical devices, • better lasers, pigment-free paint, • “smart colloids”, artificial muscle, • separations technology

33. 3.5 3.0 568 nm 2.5 2.0 593 nm 615 nm 1.5 1.0 0.5 0.0 400 500 600 700 l / nm Spectroscopic analysis of the crystal Transmittance measured on monochromator-equipped microscope Intensity FWHM of line is ~ 16 nm, comparable to typical interference filters

34. Achieving population inversion gets progressively harder for shorter wavelengths; lgreen < lred. E2 A12 B12 E1 l l

35. Conclusions • Facile synthesis & excellent uniformity • Responsive shell • Hierarchical structures, conformal transitions • Potential applications —optical devices, stationary phases for chiral separation, model particles, artificial muscles, medical treatments • Infinite variation with polypeptide chemistry

36. Future work • Helix-coil transition effect on magnetization • Crosslinking particles • Asymmetric particles • Application of different grafting techniques • Vapor deposition • Grafting onto • Controlling cobalt chains-rods • Investigation of colloidal crystals • Particles as probe diffusers

37. Crosslinking

38. N N N N N N N N N Silicacoating N Surface N N N Functionalization N N N N N N N N NCA-monomer crosslinking N N N N N N N

39. N N N N N N N N N N N N N N N N N N N N N HELIXCOIL N N N N N N N N N N N N N N N N N N N N N