The document discusses synthetic biomaterials and polymers used in medicine. It provides definitions for biomaterials and biocompatibility. Biomaterials are materials designed for use inside the body, and their interaction with biological systems is studied. The document outlines commonly used biomaterial classes including metals, ceramics, polymers, composites and hydrogels. Examples are given of materials used for applications like orthopedic and dental implants, vascular grafts, and drug delivery devices. Key considerations for biomaterial selection like mechanical properties, biostability and biocompatibility are also summarized.

1. SYNTHETIC BIOMATERIALS
AND POLYMERS IN MEDICINE

2. Material Science Logic
Synthesis
+processing
Structure
Performance/Application
Properties
•Physical
•Biological

4. Biomaterials
• Biomaterials are materials that are designed for
in-vivo use
• The study of biomaterials focuses on
controlling/understanding the performance and
interaction of synthetic or modified biological
materials in biological systems, especially at the
interface between synthetic and biological
materials (biocompatibility)

5. A biomaterial is "any substance (other than drugs)
or combination of substances synthetic or natural
in origin, which can be used for any period of time,
as a whole or as a part of a system which treats,
augments, or replaces any tissue, organ, or
function of the body".
Biocompatibility — The ability of a material to
perform with an appropriate host response in a
specific application
Host Response — The response of the host
organism (local and systemic) to the implanted
material or device.

6. Definitions
• Biomaterial - Material for in-vivo use
• Biocompatible - No adverse affects on
biological system
• Bioinert - No interaction with biological system
• Bioerodable - Dissolves in biological system
over time

7. Keywords
 Metallic/glass/Polymeric/Ceramic/Composite
 Fracture/fatigue/creep/corrosion/degradation
 Tissue response/healing/biocompatibility/host
response/carcinogenicity
 Hard/soft tissue implants
 Vascular/Breast/Urological/Art. Organ
 Mucosal contacting …

8. Biomaterial Selection Parameters
Mechanical
Thermal/Electrical Conductivity
Diffusion
Water Absorption
Biostability
Biocompatibility

9. Biomaterial Selection Criteria
• Specific Surface Interactions
• Blood Contact
• Need to Bear a Load
• Structural Applications
• Degradation Propensity
• Permeability Responsiveness
• Solubility under Physiological Conditions
• Transparency Need
• Bioenvironmental Responsiveness

10. Some Commonly Used Biomaterials
Material Applications
Silicone rubber Catheters, tubing
Dacron Vascular grafts
Cellulose Dialysis membranes
Poly(methyl methacrylate) Intraocular lenses, bone cement
Polyurethanes Catheters, pacemaker leads
Hydogels Opthalmological devices, Drug Delivery
Stainless steel Orthopedic devices, stents
Titanium Orthopedic and dental devices
Alumina Orthopedic and dental devices
Hydroxyapatite Orthopedic and dental devices
Collagen (reprocessed) Opthalmologic applications, wound
dressings

11. Journals
 Biomaterials
 Biomaterials World News
 Materials Today
 Nature
 Journal of Biomedical Materials Research
 Cells and Materials
 Journal of Biomaterials Science
 Artificial Organs
 ASAIO Transactions
 Tissue Engineering
 Annals of Biomedical Engineering
 Medical Device Link
 … see: http://www.biomat.net/biomatnet.asp?group=1_5

12. A Little History on Biomaterials
• Chinese, Romans, and Aztecs used gold in dentistry over
2000 years ago, Cu not good.
• Ivory & wood teeth
• Aseptic surgery 1860 (Lister)
• Bone plates 1900, joints 1930
• Turn of the century, synthetic plastics came into use
– WWII, shards of PMMA unintentionally got lodged into
eyes of aviators
– Parachute cloth used for vascular prosthesis
• 1960- Polyethylene (PE) and stainless steel being used for
hip implants

13. Uses of Biomaterials
• Replace diseased part – dialysis
• Assist in healing – sutures
• Improve function – contacts
• Correct function – spinal rods
• Correct cosmetic – nose, ear
• Aid dx – probe
• Aid tx – catheter
• Replace rotten – amalgam
• Replace dead - skin

14. Problems/test for w Biomaterials
• Acute toxicity (cytotoxicity) arsenic
• Sub chronic/chronic Pb
• Sensitization Ni, Cu
• Genotoxicity
• Carcinogenicity
• Reproductive &/or developmental Pb
• Neurotoxicity
• Immunotoxicity
• Pyrogen, endotoxins

15. Evolution of Biomaterials
Structural
Functional Tissue
Engineering Constructs
Soft Tissue
Replacements

16. Biomaterials for Tissue Replacements
• Bioresorbable
vascular graft
• Biodegradable nerve
guidance channel
• Skin Grafts
• Bone Replacements

17. Biomaterials - An Emerging Industry
• Next generation of medical implants and
therapeutic modalities
• Interface of biotechnology and traditional
engineering
• Significant industrial growth in the next 15
years -- potential of a multi-billion dollar
industry

18. Synthetic Biomaterial Classes
• METALS: Co-Cr alloys, Stainless steels, Gold, Titanium
alloys, Vitallium, Nitinol (shape memory alloys) Uses:
orthopedics, fracture fixation,dental and facial
reconstruction,stents
• CERAMICS: Alumina, Zirconia, Calcium Phosphate,
Pyrolitic Carbon Uses: orthopedics, heart valves, dental
reconstruction
• COATINGS: Bioglasses, Hydroxyapatite, Diamond-like
carbon Uses: orthopedics, in-growth

19. Synthetic Biomaterial Classes cont.
• POLYMERS: Silicones, Gore-tex (ePTFE),
Polyethylenes(LDPE,HDPE,UHMWPE,) Polyurethanes,
Polymethylmethacrylate,Polysulfone, Delrin
Uses:orthopedics, artificial tendons,catheters, vascular
grafts, facial and soft tissue reconstruction
• COMPOSITES: CFRC, self reinforced, hybrids
Uses:orthopedics, scaffolds
• HYDROGELS: Cellulose, Acrylic co-polymers Uses:drug
delivery, vitreous implants,wound healing
• RESORBABLES: Polyglycolic Acid, Polylactic acid, polyesters
Uses: sutures,drug delivery, in-growth, tissue engineering

20. Metals
• Metals are (mostly) crystalline solids composed of
elemental, positively charged ions in a cloud of electrons
– Properties are a function of grain size, imperfections in
crystal structure
– Metals comprised of more than one element are alloys
– The surface of metals are often oxides, if inert leads to
protection, if active is corrosion
• Typical metal properties include:
– High melting points
– High stiffness and strength
– High conductivities
– isotropic properties

21. Why Use Metals as Biomaterials
• Properties and fabrication well known
• Stiff and strong
• Bioinert
• Joining technologies known
• Metals commonly used
– Titanium
– Stainless steel

22. Figure 4.1 These titanium-alloy joint replacements are an example of the many
applications for metal biomaterials for implantations. (from
http://www.spirebiomedical.com)

23. Ceramics
• Ceramics are compounds characterized by ionic or
covalent bonding
• Ceramics are generally crystalline, crystalline SiO2 is
quartz
• Glasses are the amorphous “ceramics” common glass is
amorphous SiO2
• Properties
– Properties function of grain size, imperfections in
crystal structure
– Many ceramics comprised of more than one compound
– Low conductivities (semi-conductors, insulators)
– Stiff and Brittle

24. Why Use Ceramics as Biomaterials
• Properties and fabrication well known
• Stiff and strong
• Bioinert
• Obvious fix for teeth and bones

28. Metals
Semiconductor
Materials
Ceramics
Polymers
Synthetic
BIOMATERIALS
Orthopedic
screws/fixation
Dental Implants Dental Implants
Heart
valves
Bone
replacements
Biosensors
Implantable
Microelectrodes
Skin/cartilage
Drug Delivery
Devices
Ocular
implants

29. Issues
• Understanding and controlling performance
– Physical
– Chemical
– Biological
• Relevant material performance is under biological
conditions
– 37 C, aqueous, saline, extracelluar matrix (ECM)
– Material properties as a function of time
• Initial negative biological response - toxicity
• Long term biological response – rejection
• Biology is a science of surfaces and interfaces
– Seldom (never) at equilibrium

30. Materials Lessons from Biology
• Polymer based
• Nanoscaled
• Energy efficient
• Self-healing
• Ecologically sound
• Self-improving
• Smart!
Biology represents a material/ part/system
strategy that works

33. A Brief Introduction of Polymer
A polymer is generally named based on the monomer it is synthesized from.
For example, ethylene is used to produce poly(ethylene) (PE). For both glycolic
acid and lactic acid, an intermediate cyclic dimer is prepared and purified, prior to
polymerization. These dimers are called glycolide and lactide, respectively.
Although most references in the literature refer to polyglycolide or poly(lactide),
you will also find references to poly(glycolic acid) and poly(lactic acid).
Poly(lactide) exists in two stereo forms, signified by d or l for dexorotary or
levorotary, or by dl for the racemic mix.
HOMOPOLYMER
(one monomer)

34. Polymers
• Terminology (contn):
– copolymer: polymers of two mer types
• random · · ·-B-A-B-A-B-B-A-· · ·
• alternating· · ·-A-B-A-B-A-B-A-· · ·
• block · · ·-A-A-A-A-B-B-B-· · ·
– heteropolymer: polymers of many mer types
COPOLYMER

35. Polymers Structure
Linear
Branched
Crosslinked

37. Polyurethanes
A urethane has an ester group and amide group bonded to the same carbon.
Urethanes can be prepare by treating an isocyanate with an alcohol.
RN C O ROH RNH C
O
OR
+
an isocyanate an alcohol a urethane
Polyurethanes are polymers that contain urethane groups.
O C N
CH3
N C O
toluene-2,6-diisocyanate
+ HOCH2CH2OH
ethylene glycol
C
O
NH
CH3
NH C
O
OCH2CH2O C
O
NH NH C
O
OCH2CH2O C
O
CH3
n
a polyurethane

39. I. Biodegradable Polymers
O
O
n O
O
n
O
O
O
O
n m
PGA
Tm= 225C
Tg = 36C
PPL
Tm= 80C
Tg = -24C
PCL
Tm= 61C
Tg = -60C
PLA
Tm= 180C
Tg = 60C
PLGA
Tg ~ 50 C
O
O
n
O
O
n

41. Synthetic Polymers
Biodegradable Synthetic
Polymers
• Poly(alkylene ester)s
• PLA, PCL, PLGA
• Poly(aromatic/aliphatic ester)s
• Poly(amide-ester)s
• Poly(ester-urethane)s
• Polyanhydrides
• Polyphosphazenes
Biostable Polymers
• Polyamides
• Polyurethanes
• Polyethylene
• Poly(vinylchloride)
• Poly(hydroxyethylmethacrylate)
• Poly(methylmethacrylate)
• Poly(tetrafluoroethylene)
• Poly(dimethyl siloxane)
• Poly(vinylalcohol)
• Poly(ethylenglycol)
Stimuli Responsive
 Poly(ethylene oxide-co-propilene oxide)
 Poly(methylvinylether)
 Poly(N-alkyl acrylamide)s
 Poly(phosphazone)s

52. Polymers: Biomedical Applications
• Polyethylene (PE)
– five density grades: ultrahigh, high, low, linear low and
very low density
– UHMWPE and HDPE more crystalline
– UHMWPE has better mechanical properties, stability
and lower cost
– UHMWPE can be sterilized

53. Polymers: Biomedical Applications
• UHMWPE: acetabular caps in hip implants and
patellar surface of knee joints
• HDPE used as pharmaceutical bottles, fabrics
• Others used as bags, pouches, tubes etc.

54. Artificial Hip Joints (UHMWPE)
http://www.totaljoints.info/Hip.jpg

55. Polymers: Biomedical Applications
• Polymethylmethacrylate (PMMA, lucite, acrylic,plexiglas)
– acrylics
– transparency
– tough
– biocompatible
• Used in dental restorations, membrane for dialysis, ocular
lenses, contact lenses, bone cements

56. Intraocular Lens
3 basic materials - PMMA, acrylic, silicone

57. Polymers: Biomedical Applications
• Polyamides (PA, nylon)
– high degree of crystallinity
– interchain hydrogen bonds provide superior mechanical
strength (Kevlar fibers stronger than metals)
– plasticized by water, not good in physiological
environment
• Used as sutures

58. Polymers: Biomedical Applications
• Polyvinylchloride (PVC) (monomer residue must be very
low)
– Cl side chains
– amorphous, hard and brittle due to Cl
– metallic additives prevent thermal degradation
• Used as blood and solution bags, packaging, IV sets,
dialysis devices, catheter, bottles, cannulae

59. Polymers: Biomedical Applications
• Polypropylene (PP)
– properties similar to HDPE
– good fatigue resistance
• Used as syringes, oxygenator membranes, sutures, fabrics, vascular
grafts
• Polyesters (PET)
– hydrophobic (beverage container PET)
– molded into complex shapes
• Used as vascular grafts, sutures, heart valves, catheter housings

60. Polymers: Biomedical Applications
• Polytetrafluoroethylene (PTFE, teflon)
– low coefficient of friction (low interfacial forces
between its surface and another material)
– very low surface energy
– high crystallinity
– low modulus and strength
– difficult to process
• catheters, artificial vascular grafts

61. Synthetic vascular grafts from W.L.Gore

62. Polymers: Biomedical Applications
• Rubbers
– latex, silicone
– good biocompatibility
• Used as maxillofacial prosthetics

63. Figure 4.3 This artificial heart valve is coated with Silizone, a biocompatible
material that allows the body to accept the implant. (from
http://www.sjm.com/devices/).

64. Polymers: Biomedical Applications
• Polyurethanes
– block copolymer structure
– good mechanical properties
– good biocompatibility
• tubing, vascular grafts, pacemaker lead insulation, heart assist
balloon pumps

65. Substitute Heart Valves

66. Polymers in the body