1. ABCs of Biomaterials 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
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2. 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
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3. About Ceramics CARBON ALUMINA completely resorbable surface reactive
Features
CARBON
completely resorbable
surface reactive
nearly inert
high corrosion
wear resistance
Pyrolytic carbons formed between 1000 to C.
Vitreous carbon: - deposited with controlled grains
Low-temperature isotropic (LTI) Carbons (15000 C)
good compatibility with bone, blood,
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
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4. 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
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5. thermally unstable (800 - 1600 C)
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
thermally unstable ( C)
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6. Toxicity, and irritations produced
BIOMEDICAL POLYMERS
Elastomers are
able to withstand large deformations
return to their original dimensions after releasing
the stretching force.
Plastics (more rigid materials)
Thermoplastic
Melted, reshaped, reformed
polyolefins, Teflon (fluorinated hydrocarbons), Poly (methyl methacrylate (PMMA), Polyvinyl chloride (PVC), Polycarbonate,
nylon, polyester (Dacron ® )
Thermosetting
remelted and reused, but irreversible
Butyl rubber, silicone rubber
Toxicity, and irritations produced
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7. Applications of bio-polymers
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, and thermo formation and welding
Bone cement, intraocular lenses, contact lenses,
Not limited anyhow
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8. 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,
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9. November 15, 2018November 15, 2018 BONE CEMENT MIXING AND INJECTION
disadvantage : - cause allergic reactions
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10. Poly (hydroxyethyl methacrylate) (PHEMA) is a rigid acrylic polymer
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)
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11. 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)
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12. POLYAMIDES November 15, 2018November 15, 2018
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
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13. 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.
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14. 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.
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15. Also known as regenerative medicine
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
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16. 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
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17. Send me your suggestions to a.alagiriswamy@gmail.com
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