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 *

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 *

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 *

* 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 *

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

SEM & TEM of Silica Particles

Synthesis of Magnetite – Fe3O4

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

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

TEM- Silica Coated Cobalt

Superparamagnetic Particles

Surface Functionalization

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

Synthesis of homopolypeptides

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

Is the shell covalently attached? * 07/16/96 Is the shell covalently attached? Almost certainly (By the way, the polypeptide conformation is mostly a-helix with some b-sheet) *

* 07/16/96 TGA/DTA --Particles with ~ 23% by mass PBLG --Again, no evidence for binding of loose PBLG *

Dynamic Light Scattering * 07/16/96 Dynamic Light Scattering Bigger ones may diffuse slower (solvent viscosity effects) Flat plots indicate excellent, latex-like uniformity *

Particle Characteristics * 07/16/96 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. *

Not all initiators are active: crowding * 07/16/96 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 *

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

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.

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

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

Helix-coil transition of Co-PCBL

It’s Alive! This plot shows polydispersity

Hysteresis curve M -M Magnetization in opposite direction

SQUID- hysteresis plot of cobalt particles

SQUID- hysteresis plot of Co-PCBL

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.

Colloidal Crystals (PCBL Shell) * 07/16/96 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 *

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

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

* 07/16/96 Achieving population inversion gets progressively harder for shorter wavelengths; lgreen < lred. E2 A12 B12 E1 l l *

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 *

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

Crosslinking

Silica coating N NCA-monomer crosslinking Surface Functionalization

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