Group Presentation #2

Craig Milroy

(4/29/10)

(I) Py-HA electrode coating

• Objective: increase in vivo longevity of neural probes by minimizing glial scarring & general immune response.

• so far: coat Py-HA on electrochemically active portion of

electrode surface implant evaluate immune response.

(www. http://www.neuronexus.com/Products/ResearchProducts/MicroelectrodeArray/ProbePackages/ASeries/tabid/140/Default.aspx)

(I) Py-HA electrode coating

• next steps:

(1) GM-HA or GM-heparin coating (UV polymerization) of entire probe surface, including electrode sites and non-conducting parts (Leach protocol).

(2) incorporate anti-inflammatory drug release.

(www. http://www.neuronexus.com/Products/ResearchProducts/MicroelectrodeArray/ProbePackages/ASeries/tabid/140/Default.aspx)

(1) Diffusionbased

(2) Biodegrable conjugated matrix

(3) Electro-stimulated release

(I) Py-HA electrode coating

Delivering anti-inflammatory agents

(1) Diffusion of nanoparticles• (GM)HA + poly-aspirin nanoparticles (or layers)

(2) Biodegradable gel-matrix containing drugs• (Mix GMHA with) HA-polyaspirin conjugate

(3) Enzyme-mediated release• Ppy doped with aspirin, coated with PyHA, GMHA, etc.• (a) oxidoreductase enzymes mediate (b) electron

transfer to Ppy & (c) convert ox. Ppy to re. Ppy, causing (d) release of doped aspirin.

Selection of anti-inflammatory agents

Uhrich, Biomacromolecules 2005, 6, 359-367.

mycobacteria colon inflammation, ulcerative collitus

Mw of polymerSolubility, degrad. rate

Reaction efficiency (solvent, yield)Degrad. rate

For doping / nanoparticles

For conjugation with HA

Key steps for “diffusion-based”

• Disperse poly(aspirin) nanoparticles in GMHA prior to crosslinking – MW- dependent water solubility.– Loading requirements/limitations.

• Characterize release profile – MW-dependent diffusivity of polyaspirin. – swelling characteristics of gel.

GMHA

(Leach, Schmidt. Mat Res soc symp proc Vol EXS-1, 2004)

Electrochemically mediated release

• Fundamental hurdle: identify relevant enzyme

ascorbate peroxidase: REDUCES H2O2 (transfers electrons from ascorbate to peroxide, producing dehydroascorbate and water as products)

horseradish peroxidase:

H2O2 + 2AH2 HRP C 2H2O + 2AH*

Involves both oxidation and reduction, but generation of reactive species as well

IDEAS…….

Implantable electrode/biosensor platform

• Enzyme specific for NO from activated astrocytes?

• Direct reduction of doped Ppy?

• Tethered enzyme?

• Use of melanin?

(1) Entrapped enzyme (2) Tethered enzyme

(II) PLGA meshes • Objective: introduce nanoscale surface features on

biomimetic materials to optimize cell-material interactions.

• so far: coating PLGA mesh with Py, amino-Py, and carboxy-Py; electro-stimulation, cell fixing/staining, visualization.

• next steps: bioactive molecule conjugation (laminin, fibronectin), melanin.

• other applications:

coating Py on other polymers (e.g. polysulfone, cellulose acetate) for surface oxidation to prevent biofouling.

(III) PPy-PU

• Background: restore function to damaged myocardium; skeletal myoblasts do not electrically couple with mycocardium and do not express connexin.

• Objective: synthesize electrically conductive elastomer to enable propagation of cardiac electrical signals across damaged gap junction.

• so far: emulsion polymerization (Py in-situ within PU), cyto-compatible, amorphous (Chris Broda, Benjamin Harrison).

Wang Y, GA Sotzing, RA Weiss. “Preparation of conductive Py-PU composite foams by in- situ polymerization of Py”. Chemistry of Materials 20:7 (2008); 2574-82.

(III) PPy-PU

• next steps…polymer processing to achieve:fibrous form (electrospinning, injection, extrusion)

porous form (gas bubbling, salt leaching)

for cardiac/neural application (potential Will Wagner collab.)

(IV) OTHERS…..

• extensions of Natalia’s or Jessica’s projects (organic-inorganic materials interface)

• systems analysis of cell behavior• melanin• biodegradable scaffolds (with new post-doc)?

ORGANIC-INORGANIC INTERFACES

Speaker:  Andrew Dattelbaum Technical Staff Member, Center for Integrated Nanotechnologies, Los Alamos National Laboratory

• Title:  Luminescent Silica Nanocomposite Materials for Biological Sensing and Imaging

• Abstract:   Luminescent nanocomposite silica materials may be used in a variety of sensing and imaging applications.  Silica is an ideal matrix for fluorescence applications because it is optically transparent and provides a rigid, chemically inert framework that acts to protect and immobilize sensing materials. Several examples will be presented of how nanocomposite silica materials can be applied for sensing of proteins in solution or imaging in cells.  In particular, the talk will focus on 1) the preparation and characterization of bulk single-walled carbon nanotube silica composite materials for biosensing applications and 2) functionalized silica-based nanoparticles for far-red-to-near infrared fluorescence imaging in cells. For this work, the use of various fluorescence and spectroscopic techniques will be discussed, including Raman and fluorescence spectroscopy as well as confocal and wide-field imaging techniques, to characterize the nanocomposite silica materials.

(III) Electrode Studies

mount electroactive PyHA gel on electrode surface (carbon paste, ITO)

i) so far: ii) electrochemical biosensors • immobilize enzymes within hydrogel (Giuseppe-Elie)• connect to metal electrode via PPy redox mediators. • p(HEMA) for gel, copolymerized with phosphoylcholine

(PC) and PEG for biocompatibility, • Enzyme and mediator tethered by “monomerization”

reactions with acryloyl(PEG) NHS ester that links lysine residues in

• PPy for “interference shielding”