bio-materials - presentation

OBJECTIVES

At the end of this presentation, you will be coming to know about,

• What are Bio-materials?• What for they have been used?• Their vast application in Bio-medicine• Evolution of Bio-materials since 19th

century• Implement of advance technologies in

medicine

•Romans, Chinese, 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 and stainless steel being used for hip implants

HISTORY

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".

BIO-MATERIAL - Definition

Metals

Semiconductor Materials

Ceramics

Polymers

Synthetic BIOMATERIALS

Orthopedic screws/fixation

Dental Implants Dental Implants

Heart valves

Bone replacements

BiosensorsImplantable Microelectrodes

Skin/cartilageDrug Delivery Devices

Ocular implants

APPLICATIONS

•Bio-sugery(Implantation)

•Tissue Engineering

•Bio-aesthetics

•Drug delivery

•Bio-mechanics

•Immunology

•Skin grafting

Why Bio-materials?

• Bio-compatible• Bio-resorbable• Bio-degradable• Bio-inert (donot provoke harmful immune

response)• Bio-active (in replacing tissues and cells)• Similar chemical structures• Less Fatigue Fever

Biocompatibility is primarily a surface phenomenon …

BulkMaterial

Surface Layerof Material

Adsorbed layer ofwater, ions &

proteins

Cells inbiological

fluid

• The material does not provoke rejection bythe surrounding tissues and body as awhole.• Defined as the ability of a material toperform with an appropriate host responsein a specific application.

BIO-ACTIVE

The mechanism of new bone formation an bone bonding to a bioactive ceramic implant is illustrated at left. Immediatelyfollowing implantation, an ionexchange reaction takes placebetween the implant and thesurrounding body fluid during whichchemical species from the ceramicdiffuse into the fluid and vice versa.Over time, this results in the formation of chemically graded layers that become hydrocarbonate apatite, or new bone.

HOW DOES FATIGUE OCCURS

• Fatigue failure occurs through:– 1. Crack initiation– 2. Crack growth or propagation– 3. Final failure• Most components show no signs ofchange or damage prior to failure.

An Interdisciplinary Field

Bioengineers

Material Scientists

Immunologists

Chemists

Biologists

Surgeons

...

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

FIRST GENERATION

• “ad hoc” implants• specified by physicians using common and borrowed

materials• most successes were accidental rather than by design

EXAMPLES:

• gold fillings, wooden teeth, PMMA dental prosthesis• steel, gold, ivory, etc., bone plates• glass eyes and other body parts• dacron and parachute cloth vascular implants

INTRA-OCULAR LENS

3 basic materials used are – PMMA, acrylic, silicon

Vascular Grafts

SECOND GENERATION

•engineered implants using common and borrowed materials•developed through collaborations of physicians and engineers•built on first generation experiences•used advances in materials science (from other fields)

EXAMPLE:

• titanium alloy dental and orthopaedic implants• cobalt-chromium-molybdinum orthopaedic implants• UHMW polyethylene bearing surfaces for total joint replacements• heart valves and pacemakers

Artificial Hip Joints

•bioengineered implants using bioengineered materials•few examples on the market•some modified and new polymeric devices•many under development

THIRD GENERATION

EXAMPLE:

•tissue engineered implants designed to regrow rather than replace tissues•Integra LifeSciences artificial skin•Genzyme cartilage cell procedure•some resorbable bone repair cements•genetically engineered “biological” components (Genetics Institute and Creative Biomolecules BMPs)

Substitute Heart Valves

Evolution of Biomaterials

STRUCTURE

SOFT TISSUE REPLACEMENT

FUNCTIONAL TISSUE ENGINEERING CONSTRUCTS

Growth with Nerve Cells

Out of scientific curiosity, Zhang asked Holmes to test one of his self-assembling peptides for toxicity to nerve cells. Not only they were not toxic, they seemed to thrive in culture in the presence of a salt. With the salt, the peptides self-assembled into thin, wavy films that look a little like Saran Wrap. Under a microscope, the film contained a network of fibres.Further tests showed that nerve cells happily grew on these fibres. While no immune response or inflammation was seen when the peptides were injected into rat muscle tissue, they have not yet tested in the brain, spinal cord and peripheral nerves.

1 - Body Wide

2 - Body Nerve

 3 - Nerve Damage

4 - Severed Nerve

5 - Mesh in Place

6 - Mesh in Place Cut

7 - Nerve Growth 1

8 - Nerve Growth 2

9 - Nerve Growth 3

10 - Nerve Growth 4

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

What are some of the Challenges?

• To more closely replicate complex tissue architecture and arrangement in vitro

• To better understand extracellular and intracellular modulators of cell function

• To develop novel materials and processing techniques that are compatible with biological interfaces

• To find better strategies for immune acceptance