Collagens are a large family of proteins found within the extracellular matrix (ECM), and are an important constituent of many tissues in humans and other vertebrates. Gelatin is a heat-denatured product of collagen, and hydrolyzed gelatin (also known as collagen peptide) can be prepared via enzymatic hydrolysis or heating.

Collagen and gelatin demonstrate excellent biocompatibility and biodegradability because they are derived from the animal body. In addition, each of these components has functions useful for medical fields, and have therefore been widely used from basic research to clinical applications.

Most cells express collagen binding proteins (e.g. Integrin) on their surface; therefore, collagen shows impressive cell attachment.

Some types of cells can efficiently grow and differentiate by recognizing collagen molecules. Taking advantage of this property, collagen is being used as a superior raw material in medical devices including artificial skin and bone grafts. In addition, it has recently been used as a culture substrate for tissue formation from stem cells.

Collagen solutions can readily form gels by adjusting the salt concentration to physiological conditions and incubating at 37°C. Therefore, it is possible to culture cells in or on collagen gel. Collagen gel has been used as a research tool for a long time. In addition, it has recently been applied to medical uses such as transplantation and as a carrier for cell therapy.

It is known that the cell adhesiveness of gelatin is not strong. However, gelatin can strongly bond with fibronectin, which is a cell adhesion molecule existing in blood or in culture medium. Therefore, it is possible to achieve high cell adhesion in culture devices by gelatin coating.

Gelatin solution has sol-gel transition type-temperature responsivity. Thus, it can form a gel on cooling and can be liquefied upon heating. This reversible reaction is the most unique function of gelatin and is used for various applications.

Gelatin can readily dissolve in water and some kinds of organic solvents. In addition, it has several amino and carboxyl groups and can therefore be easily modified with various chemical reagents.

Some types of gelatin show high viscosity. Therefore, it is possible to alter the viscosity of medical drugs to achieve optimal effects by adding gelatin.

Gelatin is a hydrophilic colloid displaying a protective colloidal property. It can be thus used to inhibit the flocculation of hydrophobic colloids.

Materials that can be easily processed into various shapes are a need of the ever-demanding medical field, especially for regenerative medicine. Both, collagen and gelatin have good formability and have been applied to various uses including bone grafts, artificial skin, DDS carrier, etc. Recently, innovative techniques like 3D printing and electrospinning have been employed to achieve a new degree of control over the shape and formability of systems containing collagen and gelatin. Thus, it is expected that further innovative tools will be created using these materials.

Collagen peptide have been used as pharmaceutical additives since a long time. They show very low viscosity and do not gel even at a high concentration. In the near future, they could be a promising material for cell therapy and regenerative medicine.