Polymers are typically large molecules comprised of repeating similar chemical units. Usually arranged in  a linear sequence, there are also examples of branched-chain polymers. In nature, examples include proteins, nucleic acids (DNA, RNA), and numerous other molecules. Plastics (polyurethanes) and polyesters represent synthetic versions of polymers.

Biopolymers are polymers produced from natural sources and are often biodegradable and non toxic. Examples include sugars, starches, etc. Biopolymers are produced by many living biological systems

	natural production from bacteria and other microorganisms
	plant / botanical sources
	(i.e. micro-organisms, plants and animals), or chemically synthesized from biological starting materials (e.g. sugars, starch, natural fats or oils, etc.).

Biopolymers represent the most abundant organic compounds in the biosphere and constitute the largest fraction of cells. Seven main classes of biopolymers are distinguished according to their chemical structures. This encyclopedia provides a throughout overview of the occurrence and metabolism of biopolymers. In addition, processes for biotechnological production, isolation from organisms and modification, material properties and technical applications in various areas such as, for example, in daily life products, medicine, pharmacy, food industry, agriculture, textile, chemical  and packaging industry are provided. The future perspectives of biopolymers are outlined.

Polymers and composites are widely used in medicine and dentistry as implantable or prosthetic materials, platforms for tissue engineering and in drug delivery formulations. Polymers can be degradable or non-degradable. Non-degradable systems include soft prosthetic applications as well as composite materials for drug delivery into the oral cavity. With the degradable systems, the materials can dissolve in a controlled manner into smaller components that can be eliminated as the body repairs and / or drug is released. Recent developments include synthesis of fluid monomers that can convert rapidly into strong biocompatible adhesive materials within seconds after injection into sites within the body, replacing and fixing damaged tissue such as bone and cartilage.

Table 1.  Biopolymers and Ceramics in Medical Devices

Medical Devices	Use	Biomaterials
Artificial hip, shoulder, elbow, wrist, etc.	Joint reconstruction	High-density alumina, metal-bioglass coatings Bioglass-metal fibre Polysulfone-carbon fibre
Bone plates, wires, screws	Fracture repair
Surgical nails	Align fractures
Spinal (Harrington) rods	Spinal curve correction
Artificial limbs	Limb replacement
Vertebrae spacers	Congenital defect correction	Al2O3
Spinal fusion	Vertebrae immobilizers	Bioglass
Mandible / alveolar bone	Improved denture fit	PTFE-bioglass, Porous Al2O3
Tooth implants	Replace damaged teeth	Al2O3, bioglass, etc.
Orthodontic anchors	repair dental deformities	Bioglass-coated Al2O3

Traditional Synthetic Implant Materials:

Alumina Ceramics -  currently used for orthopaedic and dental implants. It has been utilized in wear bearing environments such as the total hip replacements..

Metals - metals have useful properties including strength, toughness and malleability and are commonly used in medicine and dentistry as implantable or prosthetic materials. The metal titanium and a range of titanium alloys have received particular attention as dental and orthopaedic implants. These materials tend to be well received by the body, which may be at least partially due to the relatively non-reactive surfaces.

Glass - Glasses can be produced with widely different properties and offer unique possibilities as biomaterials.

Polymers and Tissue Engineering - polymers are inexpensive and more flexible than other materials.  Certain polymers exhibit toughness but also maintain the elasticity of a plastic. They can also be designed to have increased lubricity.

Flexible Alloy Muscles - a new synthetic alloy,  nitinol has had a unique impact on synthetic implants - it is an alloy that can remember "shape. It contracts when it’s heated, whereas standard metals usually expand when heated. It is also super-elastic and produces 100 times greater thermal movement (expansion, contraction) than standard metals. .

NanoScaffolding

NanoScaffolding is an extremely promising development is tissue re-growth and regeneration.  The technique (initially investigated by a group in Sheffield England) is also being studied by the U.S. military among others) and involves. The method employs nano-scaffolds: microscopic polymer structures upon which cells can grow, divide and re-create tissues and other more complex structures. The technique closely mimics the natural growth systems found in healthy cells and tissues.

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The nanoscaffold serves as a guide for cells to adhere to as they replicate, rapidly growing through and over the porous scaffold structure.  The U.S. military has reported success in the re-growth of fingertips, bladders and other organs, and there is tremendous promise for future techniques to repair damaged or even absent human organs.

Natural Biopolymers and Composite Materials

	Cellulose-Based Nanocomposites
	Soy Protein Plastics
	Bast Fibers
	Natural Fiber Composites
	Thermoset composites and Fiber Composites
	Natural Fiber—Rubber Composites
	Straw-Based composites
	Polylactide-biocomposites
	Cellulose Fiber-Reinforced Cellulose Esters: Biocomposites for the Future
	Lignin-Based Polymer Blends and Biocomposite Materials
	Soy Protein-based Plastics and Composites
	Bio-Polyurethanes