Dr. Alagiriswamy A A, (M.Sc, PhD, PDF)

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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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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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About Ceramics
Features
CARBON

• completely resorbable
• surface reactive
• nearly inert
• high corrosion
• wear resistance

• Pyrolytic carbons formed between 1000 to 24000
  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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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)
• Ceravitals 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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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 (800 - 1600 C)
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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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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, and thermo formation and welding Bone cement, intraocular lenses, contact lenses,
Not limited anyhow
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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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BONE CEMENT MIXING AND INJECTION
disadvantage - cause allergic reactions
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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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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)

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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
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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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• 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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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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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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• Send me your suggestions to
• a.alagiriswamy_at_gmail.com
• alagiriswamy_at_ktr.srmuniv.ac.in