Protein Microspheres for Stimulating Bone Regeneration A. Scruggs, G. Farrar and A. W. Morgan Summer Objectives 1. Synthesize albumin microspheres for.

Protein Microspheres for Stimulating Bone Regeneration

A. Scruggs, G. Farrar and A. W. Morgan

Summer Objectives1. Synthesize albumin microspheres for enhancing bone

marrow regeneration

2. Crosslink the protein with a reducing sugar such as ribose

3. Identify an enzyme to enable controlled degradation of the microspheres to release the protein

NSF-Virginia Tech-REU DMR-0552661 on Field-Responsive Materials: 2008 Research Highlight

Akia ScruggsRising senior in ChemistryNorfolk State University

GPA: 3.2Hometown: Columbus, OH

Akia ScruggsRising senior in ChemistryNorfolk State University

GPA: 3.2Hometown: Columbus, OH

Protein microspheresprepared in a water-in-oil

emulsion

Middle Schoolers in VT’sNSF Summer ScienceProgram, mentored by

REU students, conduct science

experiments and prepare their

demonstration projects

NSF-Virginia Tech-REU DMR-0552661 Field-Responsive Materials and Young Scientist Experience

NSF-Virginia Tech-REU DMR-0552661 Field-Responsive Materials

2008 Field-Responsive MaterialsSummer undergraduates

Middle School Young Scientists

Virginia Tech’s materials’ REU features mentored research, education in

communications and scientific ethics, an introductory short course on polymers,

team-building skills, picnics, a talent show, an end-of summer symposium and science

and engineering projects with Middle Schoolers.

Well-defined Amphiphilic Polymer-coated Magnetite Nanoparticles Judy S. Riffle (Virginia Tech), DMR-0312046, in collaboration with Richey M. Davis, (Virginia Tech)

Fe3O4 H3N+S Si O

OO

S

+NH3

S+NH3 x y

H

Fe3O4

Dynamic structuresIn a hydrophobic lipid membrane

In hydrophilicmedia

The diameters of the amphiphilic nanoparticles can be estimated from DLVO theory combined with experimental magnetite sizes from TEM. Then colloidal stability in water can be predicted from the half-lives for doublet formation. Long t1/2 values correspond to predictions of long-standing colloidal stability. Select examples of these complexes are sufficiently hydrophilic to maintain colloid stability in water, yet sufficiently hydrophobic to interact with hydrophobic areas in cell membranes.

We have synthesized a systematic series of polymer-magnetite nanoparticles to determine how molecular parameters of polymeric amphiphilic coatings affect interactions with select cell membranes. Magnetite nanoparticles coated with a poly(propylene oxide-b-ethylene oxide) diblock copolymer (block MWs of 3300 g/mole PPO and 2600 g/mole PEO) inhibit the drug resistance that develops in cancer cells, likely by interacting with membrane-bound proteins via the hydrophobic copolymer block. Rhodamine accumulation in the cells mimics how chemotherapy drugs can enter cancer cells. Thus, high dye accumulation in the cells indicates that the multi-drug resistance P-glycoprotein pump has been partially inactivated.

Amphiphilic Polymer-coated Magnetite Nanoparticles Interact with Cancer Cell Membranes

Judy S. Riffle (Virginia Tech), DMR-0312046, in collaboration with Alexander V. Kabanov and Tatiana Bronich (University of Nebraska Medical Center)

Michelle Gasko, toxicology grad student at UNMC while on an internship at VT

Polymer-coated Magnetite Nanoparticles have High NMR RelaxivitiesJudy S. Riffle and Richey M. Davis (VA Tech), DMR-0602932, in collaboration with Tim

St. Pierre and Robert Woodward, School of Physics, University of Western Australia, Perth

0

50

100

150

200

0 0.5 1 1.5 2 2.5

5.6kPPO-7.2kPEO-40%mag5.6kPPO-3.8kPEO-37%mag3.3kPPO-4.8kPEO-56%mag3.3kPPO-2.6kPEO-34%magFerridex-R2

y = 105.36x R2= 0.99356

y = 125.4x R2= 0.9958

y = 142.16x R2= 0.98181

y = 355.11x R 2= 0.97647

y = 80.947x R2= 0.99993

R2 (

s-1

)

Fe Concentration (mmol)

Polymer%

MagnetiteR2 (s-1)

5.6kPPO-

7.2kPEO40 105

5.6PPOk-

3.8kPEO37 125

3.3kPPO-

4.8kPEO56 142

3.3kPPO-

2.6kPEO34 355

Ferridex - 81

Transverse NMR relaxivities of magnetite nanoparticles are very sensitive to the block lengths and hydrophobic-hydrophilic relationships of their polymer coatings, and it is not yet clear why this is so. High relaxivities are associated with faster MRI diagnostics and the opportunity to reduce the concentration of contrast agents. Select PPO-b-PEO coatings yield relaxivities four times higher than current commercial sources.

Materials World Network for the Study of Macromolecular FerrofluidsJudy S. Riffle and Richey M. Davis (VA Tech), DMR-0602932, in collaboration with Tim

St. Pierre and Robert Woodward, School of Physics, University of Western Australia, Perth

Left to right, front row, Nikorn Pothayee (VT), Annette Tyler (UWA), back row, Tim St. Pierre (UWA), Rob Woodward (UWA), Phil Huffstetler (VT), Thompson Mefford (former VT student, now Ass’t Prof, Clemson), Matt Carroll (UWA), Jon Goff (VT), Judy Riffle (VT)

Working group meeting with VA Tech and UWA: held in conjunction with the 6th International Conference on Scientific and Clinical Applications of Magnetic Carriers, May, 2008, Vancouver, CA

We presented 10 papers!