Post on 25-Feb-2016
description
BIODEGRADABLE POLYMER
Reporter: AGNES PurwidyantriStudent ID no: D0228005
Biomedical Engineering Dept.
Definition
Biodegradable A “biodegradable” product has the ability to break
down, safely, reliably, and relatively quickly, by biological means, into raw materials of nature and disappear into nature.
Biomaterial A biomaterial can be defined as a material intended to interface with biological systems to evaluate, treat, augment or replace any tissue, organ or function of the body [1].
Degradation time
Cotton rags 1-5 months Paper 2-5 months Rope 3-14 months Orange peels 6 months Wool socks 1 to 5 years Cigarette butts 1 to 12 years Plastic coated paper milk cartons 5 years Plastic bags 10 to 20 years Nylon fabric 30 to 40 years Aluminum cans 80 to 100 years Plastic 6-pack holder rings 450 years Glass bottles 1 million years Plastic bottles May be never
What is Polymer Degradation?
polymers were synthesized from glycolic acid in 1920s
At that time, polymer degradation was viewed negatively as a process where properties and
performance deteriorated with time.
Biodegradable Polymers as Medical Device Material
No need a second surgery for removal
More physiological repair
Avoid stress shielding Potential as the basis
for controlled drug delivery
Temporary sport during tissue recovery
Less invasive repair
BONE+PLATE
BONE PLATE
Time
Mec
hani
cal S
tren
gth
Degradable Polymer Plate
Natural Biodegradable Polymer
1. Polysaccharides Starch Cellulose
Chitin & Chitosan Hyaluronic acid Alginic acid
2. Polypeptides Collagen Gelatin
3. Bacterial Polyesters EXPENSIVE Poly-b-hydroxybutyrate (PHB)
Synthetic Biodegradable Polymer
Polymer with hydrolyzable backbones Poly-lactic acid (PLA) and its isomers
& copolymers Poly-glycolic acid (PGA) Poly-lactide-co-glycolide (PLGA) Poly-caprolactone (PCL) long
degradation time Polydioxanone
Polymers with carbon backbones Poly (vinyl alcohol) and poly
(vinyl acetate) Polyacrylates
Biodegradable Polymers
Carbonyl bond toONS
R1 C X
O
R2
OH2
R1 C OH
O
+ HX R2
Where X= O, N, S
R1 C O
O
R2
Ester
R1 C NH
O
R2
Amide
R1 C S
O
R2
A.
Where X = O, N, S
Ester Amide Thioester
X C X'
O
R2R1
OH2
+ HX' R2X C OH
O
R1
Where X and X’= O, N, S
B.
O C O
O
R2R1 NH C O
O
R2R1 NH C NH
O
R2R1
Carbonate Urethane Urea
C. R1 C X
O
C
O
R2
OH2
+R1 C OH
O
HX C
O
R2
R1 C NH
O
C
O
R2 R1 C O
O
C
O
R2
Imide Anhydride
Where X and X’= O, N, S
Biodegradable Polymers
Biodegradable Polymers
Acetal:
Hemiacetal:
Ether
Nitrile
Phosphonate
Polycyanocrylate
OH2 +C
O
H H
R' OHO C O
H
H
R R' R OH +
OC
CC C
C
OH
OH
OH
OH
OH OHC
CC C
OH
OH
OH
OH
H2O+
C==O
H
H2O
R C O C R'
H H
H HOH2
R C OH
H
H
R' C OH
H
H
+
R C R
C N
H
R C R
C O
H
NH2
R C R
C O
H
OH
OH2 OH2
RO P OR'
O
OR''
OH P OH
O
OR''
OH2 + +R OH OH R'
R C C C C R'
CN
C
OR''
CNH
H O C
OR'''
O
H
H
OH2R C C C
CN
C
OR''
H
H O
H
H
OH C R'
CN
C
OR'''
O
+
Degradation Mechanisms Enzymatic degradation Hydrolysis
(depend on main chain structure: anhydride > ester > carbonate)
Homogenous degradation Heterogenous degradation
Degradation Steps
Water-sorption
Reduction of mechanical properties (modulus & strength)
Molar mass
reduction
Loss of weight
Degradation Steps
Polymer Degradation by Erosion
Degradation Schemes
Surface erosion (poly(ortho)esters & polyanhydrides) Sample is eroded from the surface Mass loss is faster than the ingress of water
into the bulk Bulk degradation (PLA,PGA,PLGA, PCL)
Degradation takes place throughout the whole of the sample
Ingress of water is faster than the rate of degradation
Erodible Matrices or Micro/Nanospheres
(a)Bulk-eroding system
(b)Surface-eroding system
Comparison [7]
Properties PLA PS PVC PPYield Strength, MPa 49 49 35 35
Elongation, % 2.5 2.5 3.0 10
Tensile Modulus, GPa 3.2 3.4 2.6 1.4
Flexural Strength, MPa
70 80 90 49
Factors Influence the Degradation Behavior
Chemical Structure and Chemical Composition
Distribution of Repeat Units in Multimers
Molecular Weight Polydispersity Presence of Low Mw
Compounds (monomer, oligomers, solvents, plasticizers, etc)
Presence of Ionic Groups Presence of Chain
Defects Presence of Unexpected
Units Configurational
Structure
Morphology (crystallinity, presence of microstructure, orientation and
residue stress)
Processing methods & Conditions Method of Sterilization
Annealing Storage History
Site of Implantation Absorbed Compounds
Physiochemical Factors (shape, size)Mechanism of Hydrolysis (enzymes vs
water)
Poly(lactide-co-glycolide) (PLGA) [8]
Factors for Polymer Degradation Acceleration
More hydrophilic backbone. More hydrophilic endgroups. More reactive hydrolytic groups in the backbone. Less crystallinity. More porosity. Smaller device size.
Medical Applications of Biodegradable Polymers
Wound Management
• Staples• Sutures
• Clips• Surgical Meshes
• AdhesivesOrthopedic
Devices• Pins• Rods
• Screws• Tacks
• Ligament
Dental Applications
•Tissue regeneration membrane
• Void filler for after tooth extraction
Cardiovascular
applications Stents
Intestinal ApplicationAnastomosis
Ring
Drug, Gene Delivery System
Tissue Engineering
Tissue Engineering
PLLA, PCL, PGA, poly(glycolide) & poly[d,l-(lactide-co-glycolide)] have excellent biocompatibility and good mechanical properties and have been licensed by FDA for in vivo applications for tissue engineering scaffolds [2].
Cells are cultured on a scaffold to form a natural
tissue, and then the formed tissue is implanted in the
defect part in the patients. In some cases, a scaffold or a
scaffold with cells is implanted in vivo directly,
and the host’s body works as a bioreactor to construct new
tissues [3].
Gene Delivery System [4]
Poly(l-lysine)-based degradable polymers
Poly(β-amino ester)s-based degradable polymers
Polyphosphoester-based degradable polymers
Polyethylenimine modified with degradable polymers
Degradable polymers in siRNA delivery
Gene Delivery System
Barriers to gene delivery. Design requirements for gene delivery systems
include the ability to (I) package therapeutic genes, (II) gain entry into
cells,(III) escape from the endo-lysosomal pathway,(IV) affect DNA/vector release,(V)travelthrough the cytoplasm and into
the nucleus, and (VI) enable gene expression [5].
TSP50 was immobilized onto biodegradable
polymer fibers.ThenTSP50-immobilized polymer fibers
could selectivelyadsorb the anti-TSP50 [6].
Conclusion
Synthetic biodegradable polymers no immunogenicity
easier to be chemically modified &functionalized. The developing trends in the functionalization of
synthetic biodegradable polymers (1) Easier functionalization processes with mild
reaction conditions and without harmful effects on bulk
properties of polymers are pursued(2) Functionalization will be related to biomimetics(3) Promising potential for in vivo applications.
References
1. Nair LS,Laurencin CT. Biodegradable polymers as biomaterials. Prog Polym Sci. 2007;32:762–98
2 Rezwan K, Chen QZ, Blaker JJ, Boccaccini AR. Biodegradable and bioactive porous polymer/inorganic composite scaffolds for bone tissue engineering. Biomaterials 2006;27:3413–31
3. Place ES, George JH, Williams CK, Stevens MM. Synthetic polymer scaffolds for tissue engineering. Chem Soc Rev 2009;38:1139–51.
4. H. Tian et al. Progress in Polymer Science 37 (2012) 237–2805. Wong SY, Pelet JM, Putnam D. Polymer systems for gene delivery—
past, present, and future. Prog Polym Sci 2007;32:799–8376. Shi Q, Chen X, Lu T, Jing X. The immobilization of proteins on
biodegradable polymer fibers via click chemistry. Biomaterials 2008;29:1118–26
7. Mobley, D. P. Plastics from Microbes. 19948. Robert A. Miller, John M. Brady, Duane E. Cutright. Degradation rates
of oral resorbable implants (polylactates and polyglycolates): Rate modification with changes in PLA/PGA copolymer ratios. Journal of Biomedical Materials Research. Vol 11 issue 5 pages 711–719, September 1977
Thank you