Collagen

Collagen is a protein with unique chemistry and specific function. In the proper form, collagen has many responsibilities in the body - such as aiding cellular activity and providing an organized matrix in skin. An understanding of collagen's chemical, physical, and biological properties will help clinicians utilize collagen technology effectively in their wound care protocols.

Collagen is a natural biomaterial present in all animals. In the proper form, collagen has biological properties which provide function and integrity to body tissues.

Collagen's Role in Healing

Collagen molecule chemistry

Collagen in the Body

  • A structural protein with unique chemistry.
  • Provides structure and integrity to most body tissues.
  • Distribution and orientation reflects tissue function.
  • Must be in the proper form to elicit biological functions.

Molecules self assemble into fibers

Collagen in the Proper Form

  • Chemistry consists of helical and nonhelical domains.
  • Molecules must be complete to provide appropriate biological response.
  • Self-assembled molecules form fibers and aggregates.
  • Intact fibers cause cell growth, activity, and migration.
  • Aggregates have specific binding sites for cells and cell­ binding proteins in the body.
  • Functional aggregates result in strong, healthy tissues

Fibers from aggregates

  • Aggregates have specific binding sites for cells and cell­ binding proteins in the body.
  • Functional aggregates result in strong, healthy tissues

Aggregates become skin tissue

Human and Bovine Collagen

  • Human collagen varies because producing exact duplicates may be biologically uneconomical.
  • Composition of collagen in bovine is within the rang e of variance of collagen duplicated in human tissues.
  • Amino acid chain sequences are similar.

Human and Bovine Collagen

Transmission electron microscopy illustrates that the structure of bovine collagen fibrils presented in textbooks (left) closely resembles the structure of fibrils found in dressings containing collagen in the proper form ( right)

Bovine Collagen

These fibrils are 0.5 µm in diameter with repeat structural units that result in periodic striations

Collagen in Proper Form

These fibrils are 0.5 µm in diameter. Fibrils self assemble to form fibers and aggregates.

Collagen vs. Non-Collagen

Collagen has specific chemistry, fibrillar structure, and aggregate structure. In the proper form, collagen has functional and biological properties which are lacking in improper collagen and other materials.

Collagen: 20 weeks ar 20x magnification

When in the proper form, collagen is replaced by newly deposited collagen (blue) in the body

Collagen in the Proper Form

  • Contains complete molecules.
  • Contains fibrils with banding pattern.
  • Forms aggregates 9 with rope-like structure.
  • Has structural and biological properties of native collagen

Collagen composite: 20 weeks at 20x magnification

Produces a response that is similar to non­ collagen materials. There is a lack of newly deposited collagen (blue) and a presence of foreign body giant cells (purple).

Collagen in Improper form

  • Fails to meet scientifically accepted definition of collagen.
  • Has irregular structure, resembling that of n on-collagen materials.
  • Exhibits biological responses that are analogous to non -collagen materials.
  • Lacks functional properties of collagen

Alginate: 20 weeks at 20x magnification

Other materials can cause foreign body responses

Other Materials

  • Lack biological form and function.
  • Provides an artificial environment .
  • These non -collagen mate rials are not natural to the human body.

Collagen Aggregates & Structure

Collagen in the proper form has an ordered structure

Proper Form

Fibers self assemble into aggregates which resemble rope-like structures


Improper Form

Soluble collagen: Lacks nonhelical domains, forms disorganized fibrils

Insoluble Collagen: No ordered structural matrix.


Other materials

Simple hydrogel: Lacks any organized structure


Glossary

  • Aggregate: A mass or assemblage.
  • Amino Acid: Any organic compound containing an amino and a carboxyl group.
  • Alginate: A salt of alginic acid , which is extracted from marine kelp. Calcium, sodium, and ammonium alginates have been used as foam, clot, or gauze for absorbable surgical dressings.
  • Collagen: The most prevalent protein in the anima l kingdom responsible for the structure and integrity of most tissues. A protein containing domains of triple-helical conformation . Characterized by repetitive Gly­ X-Y sequences where glycine is in every third residue, and stabilize d by praline and hydroxyproline residues. A protein that participates in formation of extra­ cellular aggregates which are primarily supporting elements.
  • Collagen Fibrils: Delicate fibrils of collagen in connective tissue, usually cemented together in wavy bundles.
  • Hydrogel: A gel that has water as its dispersion medium.
  • Protein: Any of a group of com­ plex organic compounds which contain carbon, hydrogen, oxy­ gen, nitrogen, and usually sulfur, and which are widely distributed in plants and animals. Twenty different amino acids are com manly found in proteins. and each protein has a unique, genetically defined amino acid sequence which determines its specific shape and function.