Gelatin Used for Drug Delivery

Concept:

  This activity is designed to illustrate how gelatin can be used as a medium for drug delivery.
 
Materials Needed:

• Knox® Gelatin, 21-grams
• Razor blade or other cutting implement
• Food coloring (blue works best)
• Distilled Water
• Baking pan or similar container
• Hot plate

Safety Considerations:

There are no safety hazards with materials used in this experiment. The pills may become moldy after storage for several days or more.  If that occurs, they should be disposed of in the trash.

Disposal:

All materials used in this experiment can be safely disposed of in the trash.

Procedure:

1. Prepare the Knox Gelatin® according to the directions on the package.
2. Add several drops of food coloring to the gelatin in the preparation. A dark color such as blue works best. The food coloring will be used to simulate a drug. More drops of food coloring increases the concentration of the simulated drug embedded in the gelatin matrix.
3. After the gelatin has solidified, prepare the simulated "pill." There are two methods you can use:
1. Cut the gelatin with a razor blade or knife.
2. Use a small circular-type cookie cutter to shape your pill.
4. Fill the baking pan or similar container with hot water. What else is happening?
5. Gently add one of the gelatin "pills" to the hot water.
6. The dye embedded in the gelatin matrix will slowly begin to diffuse out of the gelatin into the hot water.

Explanation:

Gelatin is a thermoreversible or cold-setting polymer. If the gelatin is not refrigerated or reheated, it will slowly convert back to a liquid. Because of this, a gelatin such as Jell-O® should remain refrigerated or it will become tasteless Kool-Aide®. Another popular dessert is Jell-O® instant pudding. It contains a modified food starch instead of gelatin. The instant pudding uses a heat-setting superabsorbing thickening polymer (the starch) to create its gelatinous texture.

The release of the blue embedded dye in the gelatin is for this same reason. In addition, the heat from the hot water promotes diffusion of the dye from the higher concentration of dye in the gelatin to the lower concentration of dye in the hot water. The dye eventually diffuses completely out of the gelatin over time which simulates the slow release of a drug from a pill.

Activities:"Doing" science by asking questions.

• Would the shape of your pill affect how fast the "drug" left? How could you test this idea?
• Does the concentration of the "drug" affect how fast it's released? Can you test your hypothesis?
• What if you covered your pill with something less "permeable" or soluble, or maybe just with more gelatin?
• Could you make a "gradient" pill where the concentration of your dye is different in the middle versus the outside? How could you do this? What differences would you expect if the center of your pill had more dye versus a pill with more dye near the outside?

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