Science Behind Gels
Gels are semisolid, jelly-like pharmaceutical formulations that range widely in viscosity.
They are made from gelling agents that undergo a high degree of cross linking or association when dissolved or dispersed in the appropriate media.
These gelling agents confer the variety of different viscosities and properties of the specific gel.
Gelling agent examples:
It is important to know the properties of the specific gelling agent that you are using. There are temperature and pH considerations for correct gelling. Gelling agents also are available in a wide variety of polymer sizes, which produce gels of very different viscosities.
Some gelling agents only dissolve in a certain range of water temperature. They also may only disperse in a certain range of water temperatures. For example, MC only disperses in hot water. However, it only dissolves in cold water. To prepare a solution, the MC needs to be added first to hot water and stirred until it is well dispersed. Then, cold water can be added to dissolve the MC and form a gel.
Some gelling agents like carbomers need a pH adjustment once they are wetted in medium. This will help them gel and remain stable.
Many gelling agents are polymers and are available in different unit lengths or sizes. These sizes help determine viscosity of the gel.