Biomaterials, the Nanobiointerface, and Surface
Transcription
Biomaterials, the Nanobiointerface, and Surface
Biomaterials, the Nanobiointerface, and Surface Modification Strategies Buddy D. Ratner University of Washington Engineered Biomaterials (UWEB), Department of Bioengineering, Department of Chemical Engineering, University of Washington, [email protected] An NSF Engineering Research Center Nanotechnology (and nanoscience) continue to grow in prominence Where did nano/bio ideas come from? How are they relevant to biocompatibility? How can we use nano ideas for biomaterials? Biointerface and biosurface The roots roots of of nanotechnology: nanotechnology: The 1770 Ben Franklin 1890 Agnes Pockels 1920 Irving Langmuir / Katherine Blodgett 1940+ Pauling / Watson & Crick 1959 Richard Feynman 1970 Helmut Ringsdorf 1986 Binnig and Rohrer 2000 Bill Clinton Modern nano ideas The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws… Richard Feynman, 1959 What went on in the intervening years? Imagine the possibilities… Bill Clinton, CalTech, 2000 The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws… Richard Feynman, 1959 The molecular biologists and molecular bioengineers have been busy! (1960s - 2000) Imagine the possibilities… Bill Clinton, CalTech, 2000 Rube Goldberg Simplified Pencil Sharpener Open window (A) and fly kite (B). String (C) lifts small door (D) allowing moths (E) to escape and eat red flannel shirt (F). As weight of shirt becomes less, shoe (G) steps on switch (H) which heats electric iron (I) and burns hole in pants (J). Smoke (K) enters hole in tree (L), smoking out opossum (M) which jumps into basket (N), pulling rope (O) and lifting cage (P), allowing woodpecker (Q) to chew wood from pencil (R), exposing lead. Emergency knife (S) is always handy in case opossum or the woodpecker gets sick and can't work. Biological Triggers of Cell Functions hormone (more than 1000 such G protein receptors have been identified) Adenylyl Cyclase G protein receptor cell membrane hormone binding triggers conformational change cytosol G protein activated G protein ATP cAMP an important second messenger Nature: the ultimate nanoengineer Soong, et al. Science, 290, 1555 (2000) Schematic diagram of the F1-ATPase biomolecular motor-powered nanomechanical device. The device consisted of (A) a Ni post (height 200 nm, diameter 80 nm), (B) the F1-ATPase biomolecular motor, and (C) a nanopropeller (length 750 to 1400 nm, diameter 150 nm). The device (D) was assembled using sequential additions of individual components and differential attachment chemistries. Ned Seeman - DNA architechures Artist’s conception Marlaria protozoa invade red cells in a similar manner “Rules” common to nanotechnology and molecular biology • “Bottom up” fabrication (molecules up) • self assembly • supramolecular structure • self replication (J. Rebek, etc) • a new applied physics - quantum tunneling - diffusions and flows • integrated use of soft and hard matter • engineering with kT noise • surface science principles • hydrophobicity / interfacial properties Scaling relationships - nano to macro µm flow Protein DNA 20µm 10-9 m 10-9 m - 10-5 m 20µm Uncoated Coated 10-5 10 m Implant device Array device Nanogen 10-5 m - 10-2 m 10-2 m So, how does “nano” connect to “macro-biomaterials?” Coat the device with a nanometerdimension film. Coat the device with proteins. USING NANO CONCEPTS IN DESIGNING BIOMATERIALS Introduction to modern biomaterials -How can nanotechnology help? Surfaces of biomaterials In 50 years since the first biomaterials (as we know them today) were developed, the field has evolved into a $100 billion endeavor that saves lives and improves the quality of life for millions. B-17 Common Medical Implants Finger joint Breast implant Heart valve CNN Hip joint Artificial heart http://www.usc.edu/dept/biomed/ bme490.981/artificial_heart.htm Intraocular lens (IOL) Success in Biomaterials after ~50 years of research and development: W O R L D W I D E • IOLs (>7,000,000/yr) (PMMA, silicone) • Hip and knee Prostheses (>600,000/yr) (titanium, steel, PE) • Vascular Grafts (>300,000/yr) (Teflon, Dacron) • Heart Valves (>200,000/yr) (carbon, fixed tissue) • Percutaneous Devices (>100,000/yr) (titanium, silicone) • Stimulatory Electrodes (>100,000/yr)(platinum, iridium) • Catheters (millions/yr)(silicone, PVC, PEU, Teflon) • Stents (>2,500,000/yr)(stainless steel) U.S. healthcare market (1998) > $1 trillion Millions of lives saved / The quality of life improved for millions more how well do biomaterials really work? • IOLs (25%-50% reoperation rate) • Hip and knee Prostheses (still a 10-15 yr lifetime) • Vascular Grafts (no healing) • Heart Valves (calcification or thrombosis) • Percutaneous Devices (no seal) • Stimulatory Electrodes (electrode encapsulation) • Catheters (thrombosis, infection; 1,000’s of deaths/yr) • Stents (clotting and closure) • Contact lenses (discomfort and eye injury) • Dental Implants (loosening) Problems of much concern, but also, An opportunity… Why the complication rate? What can we do about it? A central premise of the biomaterials field has been: The surface dictates the biological reaction BIOMATERIAL How does the surface dictate healing? Biocompatible Biomaterials Healing: Encapsulation and Isolation 1. 8. Biomaterial injury The biomaterial is encapulated and isolated Biomaterial Biomaterial 2. protein adsorption neutrophil fibronectin laminin GAG TSP? SPARC? ECM: collagen Biomaterial 7. 3. cell interrogation fibroblast monocyte / macrophage 4. release In conjunction with ECM molecules... 6. Communication to fibroblasts release Growth and attachment inhibitors and stimulators PDGF FGF interleukins TGF or EGF TNF 5. Giant cell formation at the Implant surface -- frustrated phagocytosis SEM of tissue surrounding subcutaneous device in rat: 6 weeks after implant PTFE device loose connective tissue- From K. Ward, Isense Corp dense foreign body capsule e th n k eo s a rg su An operational definition of “biocompatibility“ The foreign body reaction no adhesion between implant and the capsule circa, 2001 thin walled capsule Ti PET PEU Implant C PLA PDMS PE f f o ed body l l Wa the m fro The implant, after approximately 1 month, is found within a thin, relatively acellular, collagenous sac. The reaction site is quiescent. What is the similarity between all these widely different materials? Ti PDMS PEU PET C PLA PE They all have uncontrolled interfacial proteins! • HYPOTHESIS • Can we conclude that surface properties do not matter? Not a good conclusion: • Biology uses surfaces and interfaces, too. • All in vitro biomaterials directly exploit surfaces Nature does it’s work at interfaces and surfaces: e c a Lipid membrane f ur s e ul (Proteins Sugars Water) cell ec l o m Collagen and other extracellular matrix proteins Medical device (biomaterial) (the molecules assemble to form a surface) www.cellsalive.com http://cellbio.utmb.edu/cellbio/membrane_intro.htm#Architecture Biology’s Surface Tricks 1. Complexity 2. Recognition • • • • enzyme-substrate antibody-antigen DNA-RNA-protein lectin-carbohydrate 3. Assembly (order) • collagen • cell wall • supramolecular structure 4. Mobility 5. Optical sense Surface Modification: the rationale surface Unchanged: bulk - mechanical properties - configuration - surgeon handling characteristics - manufacture Only alter the surface zone to influence: biocompatibility other performance parameters Surface Modification Methods • Plasma treatment and deposition • radiation grafting • chemical reaction of the surface • ozonolysis • photoreaction • ion implantation • ion etching • solvent cast films • surface active modifiers (low and high MW) • metalization • self assembly • micro-contact printing • immobilization of biomolecules UWEB How biomaterials heal now! Biomaterial The foreign body reaction Biomaterials healing in the future Biomaterial A reconstruction of the anatomy! Normal wounds heal this way. Why not our biomaterials? University of Washington Engineered Biomaterials (UWEB) UWEB Vision Statement ... ... to to evolve evolve engineered engineered biomaterials biomaterials that, that, by by emulating emulating nature’s nature’s own own mechanisms, mechanisms, control control with with precision precision the the interaction interaction of of biology biology with with synthetic synthetic materials. materials. This This leads leads to: to: •• biomaterials biomaterials that that heal heal and/or and/or function function in in an an improved improved manner manner •• improved improved diagnostics diagnostics •• aa new new intellectual intellectual frontier frontier as as aa platform platform for for our our educational educational and and outreach outreach efforts. efforts. Can mechanistic biology be reduced to a clockwork model (the province of the engineer)? an NSF Engineering Research Center University of Washington Engineered Biomaterials (UWEB) research team effort industry education UWEB is… • Biomaterials that heal (engineered biomaterials) • Improved diagnostics 20 professors and 100 students focused on biology at surfaces twenty six companies in partnership to advance biomaterials a focused effort to bring more students, and more diverse students, into engineering and science So how can we get around this foreign body reaction? The Central UWEB Strategy •stealth materials and non-fouling materials Use where necessary •Prevent non-specific interactions Always! •Encourage specific interaction Engineered surfaces An Engineered Biomaterial • the biology is well understood (the correct receptor interaction) • molecules in defined orientation, conformation stabilized • bland, non-interactive regions between receptors? (pattern the surface chemistry) 10 nm Medical device A focus on the interface: The Basic Repertoire of Surface Analysis Methods x-rays . . . . . ... electrons primary ions + + + ESCA SIMS .. .. ..-secondary .. ions + Macintosh II Macintosh II laser AFM detector θ lever Macintosh II Contact angle H T AL E ST A strategy for non-fouling (stealth) surfaces Poly(ethylene glycol) or Poly(ethylene oxide) (PEO) (O-CH2CH2)n PEO surfaces are found to resist protein and cell pickup Our monomers are glymes, e.g. tetraglyme: CH3 (O-CH2CH2)4 O-CH3 A 20 nm coating Advantages of Plasma Deposits • • • • • • • • • • • dry processing rapid pin-hole free conformal can be done on continuous basis tenacious adhesion to the substrate many possible chemistries many possible substrates monomer costs are negligible sterile product much precendent Plasmas -- Unique Monomers and Unique Surface Chemistries Thin film deposition “Monomer” Methane Tetrafluorethylene Benzene Methanol Ethylene oxide Tetraglyme Acrylic acid Allylamine Hydroxyethyl methacrylate N-vinyl pyrrolidone mercaptoethanol Film Characteristics Hydrocarbon, diamond Fluoro, hydrophobic graphitic polar Rigid, polar Non-fouling -COOH-rich Amine-rich Hydrogel, hydroxyl hydrogel Sulfur-containing H Fibrinogen Adsorption to Plasma Polymerized Tetraglyme on FEP T AL E ST Absorbed Fbgn (ng/cm 2 ) 160 140 UWEB 116 120 100 80 60 Teflon control Various glyme coatings 40 20 0 0 A 1.6 3.7 6.3 6.4 B C D E A (EtOH)FEP 0 Data of T. Horbett, V. Pan and B. Ratner Pseudomonas aeruginosa attachment and growth Growth Mode: Net Accumulation of colony forming units (CFU) 160 140 Glass Glymes Cyclics 120 % change in number of CFU 100 80 60 40 20 0 Gls 1 Gls 2 Mono 1 Tri 1 Tri 2 Tetra Tetra Diox 12cr4 15cr5 15cr5 5w 20w 5w 20w Data of E. Johnston, J. Bryers and B. Ratner Photopatterning of RFGD Films UV Cast Expose Develop UV Re-expose Analyze Re-develop Polymerize Methylobacterium extorquens AM on patterned tetraglyme Upon seeding 70 hrs. later Data of Yael Hanein, Karl Boehringer, Vickie Pan and Buddy Ratner Methylobacterium extorquens AM on patterned tetraglyme 0 70 hrs. Images taken every 2 hrs. Data of Yael Hanein, Karl Boehringer, Vickie Pan and Buddy Ratner 2 Monocyte Density (cells/mm ) Monocyte adhesion to plasma polymerized tetraglyme 2000 R2=0.983 1500 1000 500 5, 10, 20 W 0 0 50 100 40, 60, 80 W; FEP 150 200 250 300 350 400 Adsorbed Fibrinogen (ng/cm2) Mingchao Shen, et al. Histology of tissues surrounding implants Tetraglyme Implant FEP Implant 60 50 Fibrous 40 Capsule 30 Thickness (um)20 10 0 FEP Tetraglyme Skin side Muscle side Collagenous Tissues M. Shen, et al. Conclusion We believe non-fouling surfaces to be necessary, but not sufficient, for biomaterials that heal. UWEB The Clues to Healing Materials that “heal” without a capsule... Hydroxyapatite (bone) 5 µm porous structures fine fibers Kukobo Titanium (bone) Tyrosine polycarbonate? RGD peptides? Molecules always present in healing wound sites SPARC Osteopontin Thrombospondin Fibronectin Fibrinogen Laminin V UWEB “Rosetta Stones” -- read the code and learn how nature heals! 5 µm pores Made by microsphere templating (A. Marshall) Porous materials have been examined for toxicology and endotoxin Crystalline surface of packed 60µm beads (oblique view) Porous pHEMA templated with a crystalline array of 60µm beads Electrospinning of fibro-porous materials “skinny fibers” Capsule Thickness µm (mm) 55 45 35 25 15 5 -5 0 5 10 15 20 25 FiberDiameter(mm)µm Joan Sanders, et al. Turn on specific reactions Matricellular Proteins ECM SPARC Tenacin Osteopontin Thrombospondin Cells Osteopontin coating is a normal part of implant healing: ePTFE subcutaneous implants 7 days 28 days Osteopontin stains brownish-red Giachelli, et al. Osteopontin-Immobilized PolyHEMA (Lysine-Immobilized control) 50 m 50 m Lysine-Immobilized PolyHEMA, explanted after 28 days OPN-Immobilized PolyHEMA, explanted after 28 days BV Score = 1 BV Score = 3 Data of Stephanie Martin, Cecelia Giachelli and Buddy Ratner Vascular density and capsule thickness of foreign body capsules in control and TSP2-null mice (4 week implantation) genotype Thrombospondin normal mice Thbs2+/+ Thrombospondin knockout mice material vessels/capsule Capsule thickness facing dermis (µm) body wall (µm) PDMS 10±10 55±8 24±3 Ox-PDMS 12±8 58±7 25±4 PDMS 100±20 91±7 36±5 Ox-PDMS 90±14 95±8 38±5 Thbs2-/- Data of Kyriakides, Leach, Hoffman, Ratner and Bornstein Proc. Natl. Acad. Sci. USA 96, 4449-4454. How can we deliver these “healing” signals on real world medical devices? Molecular templating is a possibility... Proteins on mica CH 2O H O Coat with sugar Deposit plasma film Glue to glass O H H O O O H HOC H2 O H O O H O H CF3 CF CF2 CF CF CF2 CF CF CF CF2 C CF3 CF2 CF CF Peel off mica/ dissolve proteins Do the pits recognize the template protein? Galen Shi, et al. Nature, 398, 593-597(1999) A hypothesis for the recognition mechanism Imprinted Binding Pocket CHO O H HOC O CH 2 O O OH HO OH O OH HO HO OH O OH H H OH H N HOCH O OH Ser O OH HO O OH O Lys Glu Template Protein O HO O OH N CH OH H N His Tyr HO OH O H O H O CH HO O H N Asn Examples illustrating the fidelity of the imprint to reproduce the template template TEM image of the imprint AFM 3 nm 1 m E. coli Glutamine Synthetase (MW 600 KD) 14 nm 20 nm E. coli 1 m Distribution (%) imprint 20 15 10 5 0 5 10 15 Diameter (nm) 20 Surface Topography (AFM) of Protein Imprints 45 nm 4 nm 6.5 nm 14 nm 5 nm 3 nm Albumin Fibrinogen (MW 66 KD) (MW 340 KD) 0 20 nm 0 20 nm 200 200 0 0 400 200 400 BSA IMP 600 nm 400 200 Fbgn IMP 400 600 nm Microcontact printing (µCP) silicon coat with resist and expose Silicon resist Silicon Silicon PDMS Silicon PDMS develop resist Silicon PDMS etch Silicon PDMS strip Silicon silanize coat with PDMS strip from silicon ink the stamp protein thiol silane polymer stamp a surface Visualization of Protein Recognition: AFM BSA SA monolayer Stamp PDMS PDMS Stamp Mica SA stamping SA Biotin-10nm Au AFM Mica BSA backfill Adsorbed protein Pattern ? Biotin-BSA-Au Incubation Template imprinting Imprint Imprint Imprint SA SA/BSA co-adsorption H Shi, B. Ratner, M. Garrison, Pat Stayton, Sandro Ferari 10 nm Au-biotin bound to adsorbed SA - AFM 150 100 nm 20 0 10 0 50 20 10 20 30 0 50 100 0 150 m 30 40 m 40 Nature, 398, 593-597(1999) The proteins on mica are disordered -- this is a sub-optimal template! binding site Now Desired Imprint Question: Control at the nanoscale? binding site How will we analyze ordered proteins at interfaces? • static secondary ion mass spectrometry SIMS primary ions + + + .. .. ..-secondary .. ions + Macintosh II + Static SIMS spectrum of a fibrinogen film counts/10 2 3 P, R 2.5 V, D 2 1.5 S F, W 1 0.5 0 50 E, K H L H D M 70 Y F 90 R R M E m/z 110 F W Y 130 150 Each letter indicates an amino acid Mantus and Ratner Y PC PCA Principal Components Analysis •PC1: direction of the greatest variance •PC2: orthogonal axis defining the next greatest of variance •Scores: projection of the samples onto the new PC axes •Loadings: direction cosines of the matrix rotation 2 ......... . ....................... ... .. 1 C P matrix rotation X PCA Distinguishes ToF-SIMS Spectra 0.06 PC 2 (19%) Hemoglobin IgG 0.04 Fibronectin γ-Globulins 0.02 Myoglobin BSA 0 Papain Transferrin -0.02 Collagen Lactoferrin Fibrinogen -0.04 Cytochrome c Lysozyme -0.06 -0.08 -0.15 -0.1 -0.05 0 0.05 0.1 PC 1 (53%) Proteins adsorbed onto mica from 100 µg/mL solutions Matt Wagner and Dave Castner Controlling and measuring antibody orientation Effect of pH on protein charge distribution Isoelectric point of IgG1, their fragments, and hCG+ IEP of Fc Isoelectric Point (IEP) of antibody IEP of Fab Mouse monoclonal anti-hCG I.E.P. 6.8 Fab Fc 8.5 6.1 + 2 + 2 dipole Dipole moment Fab Fab - 2 2 + + + + Human chorionic gonadotropin (hCG) Fc Hua Wang, S. Jiang Linking SIMS spectra to protein structure • Information on anti-hCG structure from the protein data bank can tell us relative composition of amino acids in Fab and Fc: Amino acid composition ratio Fab/Fc 3.5 TYR 3 2.5 GLY SER 2 ARG LEU 1.5 THR 1 0 CYS VAL ASP ILE 0.5 ALA MET GLN PRO GLU LYS T R P ASN PHE HIS The SIMS Experiment fab fragment anti-hCG on C11NH2 N N N N N N N N N N H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 anti-hCG on Au (111) fc fragment anti-hCG on C15COOH H O O C H O O C H O O C H O O C H O O C H O O C H O O C H O O C H O O C H O O C Multivariate analysis of SIMS data scores plot from PCA of Fab and Fc fragments PC2(16.32%) 0.03 0.02 0.01 0 -0.01 -0.02 -0.03 -0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04 P C 1 ( 7 9 . 5 7 % ) fc fragment on Au fab fragment on Au Loadings Loadings plot for PC1 (67.94%) form PCA 0.8 0.6 0.4 0.2 0 -0.2 -0.4 86.097: Leu/Ile 70.0668: Val, Pro, 84.084: Leu/Ile, Lys Arg 72.08: Val 44.05: Ala, Lys 60.45: Ser 44.013: Asn 59.049: Arg 120.08: Phe 110.07: His 73.06: Asn 74.06: Thr 72.047: Ala, 71.01: Ser Thr 87.06: Asn 147.04: Tyr m/z Hua Wang, S. Jiang Applying the PCA model to anti-hCG anti-hCG on C11NH2 sco res plot from PCA of ant i-hCG 00 .04 PC2(16.32%) 00 .03 00 .02 00 .01 anti-hCG on Au (111) 0 -00 .01 -00 .02 -00 .03 -00 .04 -00 .05 00 .1 00 .15 00 .2 00 .25 00 .3 00 .35 00 .4 PC1 (79.57%) ant i-hC G on C 11NH2 S A M s ant i-hC G on Au sur face anti-hCG on C15COOH ant i-hC G on C 15C OOH SAMs PCA analysis of the SIMS spectra show differences among anti-hCGs with different orientations. dipole Fab Fab N N N N N N N N N N H2 H2 H2 H2 H2 H2 H2 H2 H2 H2 Fc IgG molecule H O O C H O O C H O O C H O O C H O O C H O O C H O O C H O O C H O O C H O O C Using this alignment, monoclonal antibodies to specific domains on osteopontin can be used to align the OPN. These can then be used as templates for imprinting. data from Hua Wang (in collaboration with Shaoyi Jiang, Chemical Engineering Department) Adenovirus Nature knows how to order proteins and deliver protein signals. Adenoviruses are icosahedral particles. The capsid (protein coat) is built up from 252 capsomers (T=25), of which 240 are hexavalent and 12 (situated at the apices) are pentavalent. A "penton fibre"projects from each apex. http://www.uct.ac.za/depts/mmi/stannard/adeno.html What are the implications of template recognition surfaces? Immobilized biomolecules on “real” medical devices have the following limitations: Hip prosthesis Coat with nanopits for a key recognition protein Implant in bone The device concentrates the body’s protein •Low stability •Expensive •Hard to sterilize •Prone to contamination •Complex regulatory position Heals into bone A sugar-coated medical device. The patient’s own proteins are used for healing. The Hallmarks of an Engineered Biomaterial 1. We know which reaction we want to control 2. We know the recognition events to control it 3. We will inhibit non-specific interactions Nano and Surface skills that will be needed: non-fouling, immobilization, orientation, mimic, pattern, analysis WHAT WILL THE FUTURE HOLD? Biomaterials (2001-2020) Precison nano-surfaces (2010-2040 Tissue Engineering (2005-2050) Regenerative medicine (2020+ ) “The art of medicine consists in amusing the patient while nature cures the disease.” Voltaire (1694-1778) J. Donoghue, Brown University UWEB 2002