polymers in biomedicine introduction of polymers polymeric ... · • introduction of polymers •...
TRANSCRIPT
![Page 1: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/1.jpg)
Polymers in Biomedicine • Introduction of Polymers
• Polymeric Biomaterials
• Smart Biomaterials
• Polymer Drug Transporter
Prof. Dr. Tanja Weil, OCIII@UniUlm
![Page 2: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/2.jpg)
1. Definition Polymer
2
• Macromolecule consisting of repetition units
• Properties often more complex compared with small molecules (2 monomers are miscible, polymer consisting of these monomers not!)
![Page 3: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/3.jpg)
1. Polymers are Nanosized Objects
![Page 4: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/4.jpg)
• Polyesters Polylactic acid Polyhydroxyalkanoates • Proteins Silk Soy protein Corn protein (zein) • Polysaccharides Xanthan Gellan Cellulose Starch Chitin • Polyphenols Lignin Tannin • Lipids Waxes • Specialty polymers Shellac Natural rubber Nylon (from castor oil)
2. Overview over Nature’s Polymers
![Page 5: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/5.jpg)
1. How to Synthesize Polymers?
![Page 6: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/6.jpg)
20000 2000 4000 6000 m/z
6
Polymer: Polydisperse
Very long chains Short chains
Most abundand chain lengths
1. Polymers: Mixtures of Macromolecules
Polymer in solution: Statistical coil
Copolymer: Consists of two different monomers
![Page 7: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/7.jpg)
7
1. Molecular Weight of Polymers
• Synthetic polymers: Molecular weight distribution
(more than one molecular weight)
• Statistical distribution of molecular weight
• Average values
• Important features such as biodegradability depend
on the molecular weight
PDI: Polydispersity indey Commercial polymers Often very high (PDI: 3-10) MW of linear polymers In biomedicine: 104-106 g/mol
Number average molar mass
Weight average molar mass
![Page 8: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/8.jpg)
8
Solid State Properties
• Amorpous
Glas state, hard material, no order of the chains, chains are physically cross-
linked
• Semi-crystalline
Domains of high order are connected with domains of no order
• Crystallin
High degree of order (near and far-order)
![Page 9: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/9.jpg)
1. Composition of Polymers
9
Homopolymer
Copolymer
![Page 10: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/10.jpg)
1. Structures/ Topologies of Polymers
10
Linear
Branched
Star-shaped
Cross-linked
![Page 11: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/11.jpg)
1. “Perfect Polymers” = Dendrimers
![Page 12: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/12.jpg)
1. Overview over different Dendrimer Scaffolds
![Page 13: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/13.jpg)
1. Polymer versus Dendrimer
![Page 14: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/14.jpg)
B
B
B
B B
A
A A
B B
B
B B
B
A A
A
A A
A
B B B
B
B
B
B B B
B
B
B
A
A
A
A
A
A A
A
A
A
A
A B B
B B B B
B B
B B
B B
B B
B B B B
B B
B B
A
A
A
A
A
A
A
A
A A A A
A
A
A
A
A
A
A
A
A A A
F F F
F F F
F
F
F
F
F F
F F F
F
F F
F
F
F F
F
F
F
F
F
F
F
F
F F
F F
F F
F F
F F
F
F
F F
F
F
A
F F
1. Polymer versus Dendrimer
![Page 15: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/15.jpg)
15
2. Polymers as Biomaterials - Applications
• Dental Applications (Implants, Fillers,…)
• Cardiovascular and general surgery: Implants (bladder, skin, heart)
• Contact lenses
• Sensors, biochips, implants, microoptic devices
• Drugs
• Drug Transporter
![Page 16: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/16.jpg)
16
2. Very Brief: Biodegradation of Polymeric Materials
Material is not toxic and is resorbed/ degraded
Material releases toxic substances upon degradation
Material is not toxic and is not degraded
Encapsulation
Necrosis
Degradation and Resorption
Characteristics of an Interaction
e.g. Tissue Engineering
e.g. Metal implants, non-degradable polymers
polymer-coated sensors
![Page 17: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/17.jpg)
2. Biodegradable and Non-degradable Polymers
17
• Functional groups that can be cleaved
• Chemical Degradation
• Tissue Engineering / Drug Delivery
Biodegradable Non-Degradable
• Long term application in the body
(Carboxylic acid, alcohol)
![Page 18: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/18.jpg)
Biodegradation of Polymers
18
Hydrolysis is increased by
• High numbers of functional groups
• Low crystallization
• Low or no crosslinks
• High surface / volume ratio
• Mechanic stress
Hydrolysis is reduced by
• High molecular weight
• Low numbers of hydrophilic
groups
• Lipophilic polymers
• High crosslinking
![Page 19: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/19.jpg)
19
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
• Polymer is not degraded after implantation
• Low degree of structural changes
• Breakage due to (low degree of ) water adsorption
• Teflon
• Polyolefines (PE, PP)
• Acrylic polymers (PMMA, PDMAA)
• Inorganic polymers (PDMS)
( )n ( )n ( )n
PMMA
![Page 20: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/20.jpg)
Polyethylene (PE)
• Hydrophobic
• Semi-crystalline, can be soft or hard
• Transparent Catheters,
• Mechanically stable Implants, Plastics
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
![Page 21: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/21.jpg)
Polyethylen (PE)
• Soft, low density LDPE is used for tubings, packing material
• Highly branched polymer chains result in lower densities 0,915 g/cm3 und 0,935 g/cm3
(„LD“ means „low density“).
• Hard HDPE is used for producing more stable flasks etc.
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
• Implants: „Ultra High Molecular Weight Polyethylen (UHMWPE)“.
• Knee and finger joint implants
• If PE is used alone as acetabulum (Hüftgelenkpfanne), bone substance is
degraded after few years only (e.g. by attrition) nowadays mainly used in titane
inlets.
![Page 22: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/22.jpg)
Polyvinylchloride (PVC)
• Bags for blood, urine, nutrition media, gloves, tubings, catheters, blister packing
material as well as medical disposables.
• Advantages: good thermoformability, stiffness, flexibility, chemical resistance and
low allergic potential
• Disadvantage: Softeners such as phthalate, e.g. di-2-(ethylhexyl)-phthalate (DEHP)
and Di-n-octylphthalate (DnOP).
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
![Page 23: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/23.jpg)
• Di-2-(ethylhexyl)-phthalat (DEHP) and di-n-octylphthalat (DnOP) potentially teratogenic,
cancerogenic
• Medical usage: Ultrapure PVC with very low quantities of additives and impurities
• Flasks, medical devices (hard trays) can be sterilized
• Not suitable for long-term usage in the body
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
![Page 24: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/24.jpg)
24
Polytetrafluorethylene (PTFE, “Teflon”)
• Hydrophobic
• Chemically inert
• Thermally very stable
• Mechanically stable
“Gore-Tex”
Artificial blood vessels (low degree of protein adsorption)
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
![Page 25: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/25.jpg)
Polypropylene (PP)
• Nahtmaterial
• als Netze zur Überbrückung von Gewebedefekten
• zur Abdeckung von Leistenbrüchen etc..
• Membranen für Blutoxygenatoren und Nierendialyse,
• Fingergelenkprothesen, Herzklappen
• Einweg-Spritzen, Verpackungsmaterial
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
![Page 26: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/26.jpg)
Polystyrene (PS)
• Important packing material for medical articles, can be sterilized via γ-radiation
• Not so useful for reusable articles, which require sterilization by steam
• Transparent
• Cuvettes, petri dishes, blood tubings
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
![Page 27: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/27.jpg)
27
Biodegradable Polymers
Polymethylmetacrylate (PMMA, “Plexiglas”)
• Hydrophobic
• Glass state, amorphous (Tg > 100°C)
• Mechanically stable
• Transparent
Artificial Lenses (Eye)
MST-Devices (Copolymer)
• Bone cement and for dental prostheses or dental fillings
• Polymerization mixture together with monomer is hardened by light in the mounth
![Page 28: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/28.jpg)
28
Polyhydroxyethylmethacrylate (PHEMA)
• Hydrophilic
• Soft, gel-like (Tg < 25°C)
• Transparent
• Mechanically stable
Contact Lenses
(cross-linked copolymer)
Bladder catheter and coating for suture materials (“Nähmaterialien”)
2a. Non-Hydrolysable Smart Polymers & Hydrogels
![Page 29: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/29.jpg)
Poly-N-isopropylamide (PNIPAM)
• Hydrophilic/hydrophobic
• LCST – lower critical solution temperature (homopolymer: 32°C)
Hydrogel (cross-linked)
Cell cultivation, cell monolayers, tissue engineering
Drug Delivery
29
Responsive Polymer will be discussed in chapter 3 “Smart Polymers” in greater
details
2a. Non-Hydrolysable Smart Polymers & Hydrogels
![Page 30: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/30.jpg)
30
Polydimethylsiloxane (PDMS)
• Inorganic polymer
• Hydrophobic
• Soft, gel-like (Tg < -50°C)
Catheters, implants
Devices: Soft Lithography
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
![Page 31: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/31.jpg)
Polysiloxane
• Breast implants
• Long-term resistance against hydrolytic and enzymatic degradation
• No softeners, aging inhibitors or other materials that maintain elasticity required
• Drainage tubing, blood vessels, urethral tubes, catheters, tubing probes, dialysis and blood
transfusion tubes
• Artificial joints for fingers, wrists, toes, elbows, imprinting material for dental medicine,
artificial tendons, heart valves, respiratory bellows, artificial skin and bladder prostheses
2a. Non-Hydrolysable Polymers with low Tendency to Adsorb Water
![Page 32: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/32.jpg)
2b. Biodegradable Polymers with Low Tendency to Adsorb Water
32
• Polymer is degraded slowly after implantation
• Degradation starts at the surface of the material
• Morphology, crystalinity of the material has great impact on degradation
• Aromatic polyesters
• Polyamides
• Polyurethanes
![Page 33: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/33.jpg)
Polyurethane
• Construction of artificial blood vessels and blood vessel coatings
• Skin transplants, heart valves, dialysis membranes, tubings
• Polyethylene(oxide) chains with terminal amino groups are often grafted as side
chains to reduce the adsorption of the blood components.
2b. Biodegradable Polymers with Low Tendency to Adsorb Water
![Page 34: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/34.jpg)
Polyamide / Nylon
• Molecular weights between 10.000 bis 15.000
• Application as textile fibers and implants
n
2b. Biodegradable Polymers with Low Tendency to Adsorb Water
![Page 35: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/35.jpg)
35
Carboxylic acid + alcohol
2c. Water-Resorbing & Biodegradable Polymers
• Functional groups of the polymer backbone could be cleaved
• Degradation of the polymer chain into smaller chain segments
• Application: Tissue enmgineering, drug transport
![Page 36: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/36.jpg)
• Carbonyl bond to O
N
S
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
Thioester
2c. Biodegradable Polymers - Examples
![Page 37: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/37.jpg)
X C X'
O
R2R1
OH2
+ HX' R2X C OH
O
R1
Where X and X’= O, N, S
O C O
O
R2R1 NH C O
O
R2R1 NH C NH
O
R2R1
Carbonate Urethane Urea
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
2c. Biodegradable Polymers - Examples
![Page 38: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/38.jpg)
• Enzymatic degradation
• Hydrolysis (depend on main chain structure: anhydride > ester > carbonate)
– Homogenous degradation
– Heterogeneous degradation
Degradation proceeds in four steps:
• water sorption
• reduction of mechanical properties (modulus & strength)
• reduction of molar mass
• weight loss
2c. Water-Resorbing & Biodegradable Polymers
![Page 39: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/39.jpg)
2c. Water-Resorbing & Biodegradable Polymers
Polyglycolide (PGA) and Polylactide (PLA)
Self-degrading fibers
• Examples
– Polyglycolide (PGA)
– Polylactide (PLA)
– Copolymers thereof
O Cn
O
O Cn
O
CH3
![Page 40: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/40.jpg)
40
Poly-Glycolid-co-lactide (PGL)
• Degradable copolymer
• Hydrophilic
• Often cross-linked
Tissue Engineering, self-degrading
fibers
2c. Water-Resorbing & Biodegradable Polymers
![Page 41: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/41.jpg)
Summary: Not only the Polymer Structure is Important!
41
Hydrolysis is increased by
• High numbers of functional groups
• Low crystallization
• Low or no crosslinks
• High surface / volume ratio
• Mechanic stress
Hydrolysis is reduced by
• High molecular weight
• Low numbers of hydrophilic
groups
• Lipophilic polymers
• High crosslinking
![Page 42: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/42.jpg)
• Materials that have one or more properties that can be significantly changed in a
controlled fashion by external stimuli,
• Such as stress
• Temperature
• Moisture
• pH
• electric or magnetic fields
• Akustik sounds
• Example:
• pH-sensitive polymers are materials that change in volume when the pH of the
surrounding medium changes
3. “Smart” Biomaterials
![Page 43: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/43.jpg)
• Hydrogels are crosslinked network polymeric materials that are not soluble but
can absorb large quantities of water.
• These materials are soft and rubbery in nature, resembling living tissues in their
physical properties.
Hydrogels
http://www.youtube.com/watch?feature=endscreen&NR=1&v=TpvNEZCvk84 http://www.youtube.com/watch?v=pxIJdjizQes&feature=related
Many hydrogels are smart and respond to external stimuli
https://www.youtube.com/watch?v=iBZAwhxwHX0 https://www.youtube.com/watch?v=by53LP0Yu4c
![Page 44: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/44.jpg)
12/2/2016 44
![Page 45: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/45.jpg)
Definition of a Hydrogel
• Water insoluble, three dimensional network of
polymeric chains that are cross-linked by chemical or
physical bonding
• Polymers capable of swelling substantially in aqueous
conditions (eg. hydrophilic)
• Polymeric network in which water is dispersed
throughout the structure
12/2/2016 45
![Page 46: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/46.jpg)
Hydrogel Forming Polymers – Hydrophilc Polymers
O
H O O H
H O 2 C
O
O H O
N H
H O
O
O
O
H O O H
N a O 2 C
O
O
O
O
N H O
n
p o l y ( h y a l u r o n i c a c i d ) p o l y ( s o d i u m a l g i n a t e )
n
n
p o l y ( e t h y l e n e g l y c o l )
n
p o l y ( l a c t i c a c i d )
n
p o l y ( N - i s o p r o p y l a c r y l a m i d e )
Natural
Synthetic
![Page 47: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/47.jpg)
Characteristics of Hydrogels
• No flow when in the steady-state
• By weight, gels are mostly liquid but behave like solids
• Absorption of large quantities of water
– 1-20% up to 1000 times their dry weight
• Cross linkers within the fluid give a gel its structure
(hardness) and contribute to stickiness (tack).
![Page 48: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/48.jpg)
Hydrogels
Highly swollen hydrogels
• Cellulose derivatives
• Poly(vinyl alcohol)
• Poly(ethylene glycol)
Common structural features
• Many OH (or =O) groups to interact with
• Acidic environments hydrophillic swelling
48
O
n
Poly(ethylene glycol)
![Page 49: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/49.jpg)
• The polymer chains usually exist in the
shape of randomly coiled molecules.
• In the absence of Na+ ions the negative
charges on the carboxylate ions along
the polymer chains repel each other and
the chains tend to uncoil.
Polyacrylate Hydrogel
![Page 50: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/50.jpg)
• Water molecules are attracted to the
negative charges by hydrogen bonding
• The hydrogel can absorb over five
hundred times its own weight of pure
water but less salty water
Polyacrylate Hydrogel
![Page 51: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/51.jpg)
• When salt is added to the hydrogel, the chains start to change their shape and water
is lost from the gel
Polyacrylate Hydrogel
![Page 52: Polymers in Biomedicine Introduction of Polymers Polymeric ... · • Introduction of Polymers • Polymeric Biomaterials • Smart Biomaterials • Polymer Drug Transporter Prof](https://reader030.vdocuments.net/reader030/viewer/2022040610/5ed159104008b975c85575da/html5/thumbnails/52.jpg)
Hydrogel Swelling
• Swelling due to one or more highly electronegative atoms which results in charge
asymmetry favoring hydrogen bonding with water
• Because of their hydrophilic nature dry materials absorb water
• By definition, water must constitute at least 10% of the total weight (or volume)
for a materials to be a hydrogel
• When the content of water exceeds 95% of the total weight (or volume), the
hydrogel is said to be superabsorbant
12/2/2016 52