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BIOCOMPATIBLE POLYMERS: BIOCOMPATIBLE POLYMERS: DESIGN, FUNCTION AND USES,
R. James ChristieOct. 4, 2008Utsunomiya Girls High School
Biomaterials: Materials that Function with Living Organismswith Living Organisms
Materials that imitate natural functionArtificial organs bone Artificial organs, bone, tissue BiosensorsBiosensorsDrug delivery vehicles
artificial virus
Types of Biomaterials
metals
Source: Dentainium.com
polymersceramics
Source: totalhipreplacement.com
Biomaterials Are Widely Used
Source: http://www.uweb.engr.washington.edu/research/tutorials/introbiomat.html
What is a Biocompatible Polymer?
A “plastic” that is tolerated by living organismsorganismsMany forms are man‐madePossible properties:
Implantable solidpCoated SurfaceInjectable liquidInjectable liquid
Possible characteristicsD t i iti t i Does not initiate immune responseControls cell adhesionControlled water content
What are Polymers?
Polymers: Large molecules made up of small repeating units “poly” = many “mer” = unitsrepeating units. poly = many, mer = units“Plastics”
Single molecule: “monomer” Two molecules: “mono” = one“mer” = unit
“dimer”“di” = two
“ ” itrepeat “mer” = unitrepeat attachment of monomers
Polymer molecule
Natural Polymerschemical structures:
Proteins:H2N CH C OH
Ochemical structures:
Source: Protein Data Bank
C
O
2
CH3
DNA:NH
CN
C
CC
HC
N
NH2N
OCH2HO 2
C CC
OC
H
HH
HHO
Complex sugars (polysaccharides):
PO
O-
O-
OH
guaninep g (p y )
O
H
HO
OH
OHMost natural
polymers are high i b
Source: Dr. Ronald E. Hurlbert H
HO
HO
HHHin carbon, oxygen
and nitrogen
Synthetic Biocompatible Polymers
M d i
CH2CH
H2C
CH
H2C
CHCH2
CH
OH OH OH OH Man‐made in laboratories
OH OH OH OH
poly(vinyl alcohol)
High oxygen and/or nitrogen
OCH2
H2C
O
H2C
CH2
O
/ gcontentSterile products
CH3 CH3 CH3
poly(ethylene glycol)
Sterile productsC
CH2
C
CH2
C
CO NH
CO NH
CO NH
H2CCH
CH
OH
O NH
H2CCH
OH
O NH
H2CCH
OH
CH3 CH3 CH3
poly(N-2-hydroxypropyl methacrylamide)
Examples of Biocompatible Polymer A li tiApplications
1) Growing cell sheets
2) Tissue scaffolds
3) Wildlife vaccination
4) Treating genetic disease4) Treating genetic disease
Biocompatible Polymer for Tissue Culture
37 oC 32 oC37 C 32 Ccollapsed structure
expanded structure
Poly(N‐isopropylacrylamide) “PIPAAm”
structure structure
PIPAAm changes properties at different temperatures
How could this property be used for medical applications?
Growing Cell Sheets Using PIPAAm
PIPAAmpolymer
surface surface surface1) coat surface 2) apply live cells 3) allow cells to grow
37 oC)with polymer
) pp y 3) g
4) reducet t
32 oCtemperature
Source: Prof. TeruoOkano
surface5) harvest cells
Cells can be grown outside of the body
Examples of Cell Sheets
heart (cardiac) cells skin (epithelial) cellsSource: http://www.ptei.org/interior.php?pageID=171
Cell sheets have great potential to
treat many
skin cell graft on patient
yinjuries/diseases
Biocompatible Polymer Tissue Scaffolds
Poly(lactic acid) “PLLA”
live cells
1) Prepare a cast of desired shape
2) Apply live cells 3) Allow cells to grow
Cells grow over scaffold to create live tissueo des ed s ape
Growing a New Ear
Source: Institute of Science & Technologyin Medicine Keele University
Damaged earRehabilitated ear
Source: Prof. YongniamYan
Source: Wake Forest School of MedicineSource: Stelios Arcadiou
Seed cells onto scaffold
Grow cells Harvest ear
Biocompatible Polymers for Wildlife VaccinationVaccination
?
40 meters
H t i t ild bi t di t ?How to vaccinate wild bison at a distance?
Vaccine Delivery to Animals
Solution: “Biobullets”
“Sugar” bulletsAir rifle delivery
Bullet penetrates target , degrades e de e yand releases contents
Vaccine Carrier: Hydrogel
Bison vaccine = live bacteriaNeed aqueous environmentN d lid t t t l i t bi b ll t
?Need a solid structure to place into biobullet
Solution = HYDROGELSolution = HYDROGELHydro = waterGel = semi‐solid
How to load live bacteria i t b ll t?into bullet?
reaction
Polymer solution
Connected polymer chains
Solid gel
Vaccine Encapsulation/Bullet Loading
liquid solid
Hydrogels can be formed in biobulletsHydrogels contain live vaccine within high water environment
Result: Vaccination Worked!
80% of vaccinated bison protected against brucellosis
Higher calf birth rate
Treating Genetic Diseases
disease source disease effect
CELLCELLCELLCELL
DNA RNA protein
nucleus
Genetic disease can be treated by:Genetic disease can be treated by:1) altering DNA2) preventing RNA formation2) preventing RNA formation3) preventing protein formation
siRNA Therapy Strategy
siRNA = “killer” RNA”
Source: The Nobel Committee for Physiology or Medicine
siRNA therapy inhibits protein formation
Formation of siRNA Nanocarrier
Oppositely charged polymers associate into organized structuresPolymers designed contain specific properties
E l ( th l l l) h bi tibilitE.g.: poly(ethylene glycol) enhances biocompatibilityThiol groups generate reversible crosslinks
Analysis of Efficacy
Monitor the formation of 2 proteinsMonitor the formation of 2 proteinsInhibit one, then determine expression ratioA ifi i l iRNA l d d i l i hibi % Artificial siRNA‐loaded particle inhibits >50% protein expression
Conclusions
Biocompatible polymer properties can be changed to meet specific requirementschanged to meet specific requirementsBiocompatible polymers improve quality of lif life
tools to treat injury and disease
You will probably use a biocompatible in your lifetime!
About Me
H C l
Crater Lake
Hometown: Central Point, Oregon, USA
Population = 17,000
Rogue River rafting
Education
Ashland, OR
‐ B S 2000 Biochemistry Southern Oregon University
Colorado Rocky Mountains
‐ B.S. 2000, Biochemistry, Southern Oregon University‐Ph.D. 2006, Chemistry, Colorado State University‐Current research appointment: Kataoka Lab, pp ,University of Tokyo
Why Become a Scientist?Knowledge of “how stuff works”Knowledge of how stuff worksCreate commodities that improve the quality of life for allOpportunity to meet many interesting people pp y y g p pduring studies/researchTravel opportunitiesTravel opportunities
What does it take to become a What does it take to become a scientist?
CuriosityCuriosityAbility to learnInterest in academicsInterest in academicspatience