Transcript Slide 1

Dr. Alagiriswamy A A, (M.Sc, PhD, PDF)
Asst. Professor (Sr. Grade),
Dept. of Physics, SRM-University,
Kattankulathur campus,
Chennai
ABCs of Biomaterials
UNIT III
Lecture 4
Apr.05/10
July 17, 2015
1
Outline of the presentation
 CLASSIFICATION OF BIOMATERIALS
 Ceramics

Carbon, alumina (Nearly inert type)

Glass ceramics, Resorbable ceramics
 Polymers

Thermosetting

Thermoplastic
 Applications of biomaterials
 Biosensors
 Tissue engineering
July 17, 2015
2
About Ceramics
CARBON
 completely resorbable
 Pyrolytic carbons formed between 1000 to 24000 C.
 surface reactive
Vitreous carbon: - deposited with controlled grains
 nearly inert
0 C)
Low-temperature
isotropic
(LTI)
Carbons
(1500
 high corrosion
 good compatibility with bone, blood,
 wear resistance
 no foreign reactions found, high strength,
 elastic modulus close to bone, low fatigue issues
ALUMINA
 High-density alumina: - hip prostheses and dental implants (excellent
corrosion resistance, good biocompatibility, high wear resistance and
reasonable strength
 Strength, fatigue resistance and fracture toughness of polycrystalline alumina
are function of grain size and purity.
 Surface finishing, small grain size, biomechanically correct design, exact
implantation technique
July 17, 2015
3
GLASS CERAMICS
 Bioglass and Ceravital are two glass
ceramics,





fine-grained structure with excellent
mechanical/thermal properties, which are used in
implants.
Bioglass (composed of SiO2, Na2O, CaO and
P2O5)
Ceravital’s composition is similar to bioglass in
Sio2 content but differ in CaO,MgO,Na2O.
highly reactive to aqueous medium and
bioactive
Drawbacks:  brittleness, low fracture-resistance due to
mechanical weakness
July 17, 2015
4
RESORBABLE CERAMICS
The first resorbable implant substance - Plaster of Paris.
Problems with PP

variable resorption rates

poor mechanical properties.
Two types of orthophosphoric acid salt namely
•
- tricalcium phosphate (TCP)
• hydroxyapatite (HAP) :- Ca5(PO4)3(OH)
find widespread as resorbable Ceramics
July 17, 2015
5
BIOMEDICAL POLYMERS
 Elastomers are
 able to withstand large deformations
 return to their original dimensions after releasing
the stretching force.
 Plastics (more rigid materials)
 Thermoplastic
o Melted, reshaped, reformed
o polyolefins, Teflon (fluorinated hydrocarbons), Poly (methyl methacrylate
(PMMA), Polyvinyl chloride (PVC), Polycarbonate,
o nylon, polyester (Dacron ® )
 Thermosetting
o remelted and reused, but irreversible
o Butyl rubber, silicone rubber
July 17, 2015
6
Applications of bio-polymers
Polymer
Specific Properties
Biomedical uses
Polyethylene
Low cost, easy Possibility excellent electrical
insulation properties, excellent chemical resistance,
toughness and flexibility even at low temperatures
Tubes for various catheters,
hip joint, knee joint
Prostheses
Polypropylene
Excellent chemical resistance, weak permeability to
water vapors good transparency and surface
reflection.
Yarn for surgery, sutures
Tetrafluoroethylene
Chemical inertness, exceptional weathering and heat
resistance, nonadhesive, very low coefficient of
friction
Vascular and auditory
prostheses, catheters tubes
Polymethyl
methacrylate
Optical properties, exceptional transparency, Bone cement, intraocular
and thermo formation and welding
lenses, contact lenses,
July 17, 2015
7
ACRYLIC RESINS
Simple acrylates have relatively high toughness and strength.
The most widely used polyacrylate is poly (methyl methacrylate,PMMA).
The features of acrylic polymers are
 brittle in comparison with other polymers
 excellent light transparency (organic glass)
high index of refraction.
Contact lens, goggles,
bone cements,
July 17, 2015
8
BONE CEMENT MIXING AND INJECTION
disadvantage : - cause
allergic reactions
July 17, 2015
9
HYDROGELS
 Poly (hydroxyethyl methacrylate)
(PHEMA) is a rigid acrylic polymer
 when dry, but it absorbs water when
placed in aqueous solution and
changes into and elastic gel.
 Usually PHEMA Hydrogel takes up
approximately 40% water, and it is
transparent when wet.
 easily machined while dry, yet is very
pliable when wet, it makes a useful
contact lens material.
 soft, rubbery nature
 low or zero interfacial tension with surrounding
biological fluids and tissues
 Poly (hydroxyethyl methacrylate) (PHEMA)
July 17, 2015
10
POLYURETHANES
Cross Linked Polyurethanes:  common urethane linkage (-O-CO-NH-).
 long term surgical applications
 hydrophilic polymers
 microstructure domains : -mechanical/thermal properties
 non-cytotoxic (less damage to cells)
July 17, 2015
11
POLYAMIDES
HYDROGEN BONDS PLAY A MAJOR ROLE
Nylon tubes find applications in
catheters.
The coated nylon sutures find
wide biomedical applications.
Nylon is also utilized fabrication
of hypodermic syringes
July 17, 2015
12
BIOSENSORS
 A biosensor is an analytical device which converts a biological
response into an electrical signal.
The term 'biosensor' is often used to cover sensor devices used in
order to determine the concentration of substances and other
parameters of biological interest even where they do not utilize a
biological system directly.
July 17, 2015
13
Three so-called 'generations' of biosensors;
 First generation biosensors where the normal PRODUCT of the
reaction
diffuses to the transducer and causes the electrical response.
 Second generation biosensors which involve specific 'MEDIATORS'
between the reaction and the transducer in order to generate
improved response.
 Third generation biosensors where the REACTION itself causes the
response and no product or mediator
diffusion is directly
involved.
July 17, 2015
14
TISSUE ENGINEERING



Also known as regenerative medicine
restoring, maintaining, or enhancing tissue and organ
function
The three parts of tissue that regulate the performance
of a cell are



The cells themselves
Non-soluble factors within the extracellular matrix (ECM)
such as laminins, collagens, and other molecules
Soluble factors such as cytokines, hormones, nutrients,
vitamins, and minerals
July 17, 2015
15
An issue of TISSUE ENGINEERING
Implantable Devices –
vascular grafts, bone and cartilage
grafts
Extracorporeal devices artificial liver and artificial pancreas
Cell production and Cell growth skin cells, nerve regeneration
July 17, 2015
16
Send me your suggestions to

[email protected]

[email protected]
July 17, 2015
17