1. Composite Silica:Polypeptide Nanoparticles*
07/16/96
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. Homopolypeptide Shell*
07/16/96
Fuzzballs
a silica interior and synthetic homopolypeptide exterior.
Silica (SiO2) core
typically 200 nm diameter
Optional
superparamagnetic
inclusion
Homopolypeptide Shell
typically 100 nm thick *

3. Why? The usual reasons for polymer-coated particles*
07/16/96
Why?
The usual reasons for polymer-coated particles
Stability studies, probe diffusion, standards, etc.
The better reasons for polypeptide-coated particles
Should allow excellent 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. *
07/16/96
Our Little Corner of the World: Silica-Homopolypeptide Composite Particles
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 *

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

6. SEM & TEM of Silica Particles

7. Synthesis of Magnetite – Fe3O4

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

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

10. TEM- Silica Coated Cobalt

11. Superparamagnetic Particles

12. Surface Functionalization

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

14. Synthesis of homopolypeptides

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

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

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

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

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

20. Not all initiators are active: crowding*
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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,

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. 3-(2-furoyl) quinoline-2-carboxaldehyde (ATTO-TAG™ FQ)
Avoiding crowding
3-(2-furoyl) quinoline-2-carboxaldehyde (ATTO-TAG™ FQ)
APTMS
AEAPTMS
MTMS
NH2
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. Hysteresis curve M -M
Magnetization
in opposite direction

28. SQUID- hysteresis plot of cobalt particles

29. SQUID- hysteresis plot of Co-PCBL

30. Formation of colloidal crystals
~ 0.5 m
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)*
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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. Fun supramolecular synthesize & Applies to optical devices,
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. Spectroscopic analysis of the crystal
/ nm
400
500
600
700
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
593 nm
568 nm
615 nm
Transmittance measured on monochromator-equipped microscope
Intensity
FWHM of line is ~ 16 nm, comparable to typical interference filters

34. *
07/16/96
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*
07/16/96
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. Silica coating N
NCA-monomer
crosslinking
Surface
Functionalization

39. HELIX COIL N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N