Design a Delayed-Release Tablet

Background Information for Teachers

Medication comes in many forms such as liquids, capsules, tablets, creams, drops, sprays, or injections (Figure 1). The main purpose of medication is to treat, cure, or prevent a disease in an individual. This is achieved by a chemical inside the drug, called the active ingredient, which interacts with the drug's target inside the body and thus has a certain effect on a person. For a drug to be effective, it has to be inside the body at the site of action for the correct time and duration. For example, a drug that is injected goes directly into the bloodstream whereas oral tablets pass through the digestive system and the active ingredient is then absorbed into the bloodstream. The active ingredient not only has to be at the right place at the right time, but it also has to have the right dosage. If the dosage of the drug is too low, it won't have the desired effect. If the dosage is too high, it could have harmful consequences and even be fatal!

Image Credit: Svenja Lohner, Science Buddies / Science Buddies
Figure 1. Medicine can take the form of capsules, tablets, or injections.

This is where drug delivery systems come in. A drug delivery system is a specific form of medication or a medical device that is able to control the rate, time, and place at which a certain drug is introduced into the body. A drug delivery system allows to specifically target where and when a drug is released inside the body. Many different drug delivery techniques have been developed. Among these are controlled-release drugs. These types of drugs release their active ingredient at a prespecified time.

One specific type of controlled-release drug is a delayed-release drug. Delayed-release drugs are medications, such as capsules or tablets, which do not immediately disintegrate when taken. Because of this, the active ingredient is released slowly in smaller portions, rather than immediately after being administered. This includes, for example, enteric-coated drugs that are designed to delay the release of the medication until the tablet has passed through the stomach. This prevents the active ingredient from being destroyed or inactivated by stomach fluids. The delayed release of the active ingredient is often achieved by coating or encapsulating the active ingredient in a polymer film that gradually dissolves over time, as shown in Figure 2.

Image Credit: Svenja Lohner, Science Buddies / Science Buddies
Figure 2. Delayed-release drugs are often encapsulated in polymers that dissolve over time.

Choosing the right encapsulation polymers with the right physical and chemical properties is crucial for designing delayed-release drugs. Polymers, which are large chains of many repeating subunits, can have very different properties depending on their molecular composition. This is why their properties have to be carefully tested. This includes testing not only the way in which the polymers dissolve in different solutions but also their toxicity in the human body as well as their interaction with the active drug ingredient.

In this lesson, students are challenged to design and build a delayed-release tablet, which will be made from different colored bath tablets and a variety of water-soluble plastics. Their task will be to create a tablet that releases each color from the bath tablets at a pre-determined time after it has been submerged in water. Before students start making their tablets, they will have to test the properties of each of the different materials they have been given, such as their dissolution behavior in water as well as other characteristics. As students design and build their delayed-release tablets, they will realize how the structure and properties of each of their materials influence their results. At the same time, students will get insight and exposure to drug formulation and development procedures.

Additional Background Links

• The New Control Group: Types of Controlled-release Drugs, from Orbis Bioscience
• Modified-Release Drug Products, from Access Pharmacy
• Enteric Coating, from Pharmapproach.com
• Water Soluble Films (PVOH), from the Polymer Properties Database
• Polymer Properties, from Polymer Science Learning Center

Prep Work (30 minutes)

1. Set up one table on which you put all the shared materials. Make sure this table is equally accessible to everyone. If you use heat sealers that need to be plugged in, place this table close to electrical power outlets but far away from any potential water spills.
2. Sort out the big colored bath tablets. You will only need small tablets for the students. Each group should get 10 small tablets of each color (yellow, red, blue). Put the tablets for each group into the small Ziploc bag and keep them separate from the rest of the materials.
3. Prepare the plastic materials for each group. Cut each material, or polymer, to the right size and label it with a number. Make sure the same material gets the same number for each group. Then place all the polymers and other building materials for each student group in a gallon-sized Ziploc plastic bag. Students should keep the materials in the bag when not in use to protect them from dissolving in case of potential water spills.
4. Make sure all student groups have access to a sink. To get reproducible results, use cold tap water so that the water is roughly the same temperature for each test.

Engage (20 minutes)

1. Tell students that in this lesson they will learn about medication, and about how drugs are made and the materials they are made of. Then show them the picture of the different tablets from the slideshow.

   What do you see in this picture?

   What do you notice when comparing all these different tablets?

   Have students describe how the various tablets look. They should notice that they all look different. The tablets come in different shapes, sizes, colors, and designs. They can come in the form of pressed powders, capsules with small tablets or powder in them, or gel capsules.

   Why do you think these tablets are all designed differently? For example, why do some have a plastic capsule, and some don't?

   Let students speculate about why the tablets are designed differently. Then continue to the next step.

2. Show students this time lapse video of different tablets dissolving:
   

   https://www.youtube.com/watch?v=4rY3X4xafs0

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3. Briefly review the video with the students.

   What did the video show?

   The video showed different types of tablets dissolving in water. This mimics the process of how tablets dissolve in our bodies.

   How was the dissolving behavior different or similar for all the tablets when submerged in water?

   Let students describe how the dissolving behavior of the tablets varied between each. Point out the differences between the pressed powder tablets and the tablet capsules.

   After watching the video, do you have more ideas about why tablets are designed differently?

   Guide students to conclude that, depending on its materials and how it is made, the tablet will behave differently inside the body. For example, it will dissolve fast or slow depending on whether the active ingredient is encapsulated/coated or not.

4. Explain to students that for a drug to be effective, it has to be inside the body at the right place for the right amount of time and in the right amount. To be able to achieve this, drug companies have developed so-called controlled-release drugs. These drugs are designed in a way that allows them to release their active ingredient at a prespecified time. A delayed-release drug, for example, is often coated with or encapsulated in a specific polymer film. The encapsulation, or polymer coating, protects the active ingredient from solving right away because the polymer first has to dissolve before the active ingredient can be released. Show the schematic of a delayed-release drug dissolving, which is provided in the slideshow, to support your explanations.

Explore

Explore Part 1: Material Testing and Selection (45 minutes)

Tell students that today they will design and build their own delayed-release tablet. But before they do that, they will first have to select the right materials to build their tablet.

1. Show students the colored bath tablets and the various plastic materials. Explain to them that the bath tablet will act as the active ingredient in their tablet. The active ingredient needs to be encapsulated in a polymer or plastic that prevents it from being released right away. They will be given various plastic materials and each one of them will vary in their properties. Their first task is to characterize, test, and select the materials that they are going to use to encapsulate their bath tablets. For these initial tests, they should use no more than a quarter from each of the material sheets. They need to keep the rest for designing and building their tablets later.
2. Divide students into groups of four. Then provide each group with the plastic cups, scissors, stopwatch, and gallon-sized Ziploc® bag filled with the building materials. Do not give them the bath tablets yet.
3. Instruct students to test each of the plastic materials (polymers) that they have in their gallon-sized Ziploc® bag. For the purpose of their tablet design, they will need to investigate the material properties of their given polymers (listed in Table 1) to find out which materials are best suited to build their delayed-release tablets.

4. Give student groups 20 minutes to investigate all of the plastic materials. Remind them to record their observations and results in their student worksheets.

Reflect

Reflect Part 1: Material Testing and Selection (20 minutes)

1. Once students have finished testing their materials, gather the class for a group discussion.

   What did you notice when testing all of your materials?

   Have students share their observations and results. Go through the results table with them and let them describe how the materials were different or similar based on their individual properties.

   Which material properties do you think are most important for your tablet design?

   Listen to students' replies. Remind students that the purpose of the material is to coat the active ingredient of the tablet to make a delayed-release drug. Thus, the material needs to be water-soluble in order to be able to release the active ingredient. Students might also mention that the material should be relatively tear resistant so that it doesn't rip during the building process.

   How did all of your materials react in water? How do their solubilities compare?

   Ask students to describe how the various materials reacted in water. Make a list of which polymers are water-soluble and which ones are not soluble in water. Optionally, you can discuss the dissolution reaction with your students in more detail, e.g. you could discuss if the polymer dissolution is a chemical reaction or a physical change.

   Based on your observations and results, which material(s) would you select for your tablet design?

   Students will probably name the water-soluble materials first. Have students explain why they would choose a particular material based on its properties. Then make a list of all the materials the students mention on the board.

2. Tell students that now that they have tested and selected their materials, they are ready to continue with the tablet design challenge. For their tablet design, students can use all the materials they have been provided with. They can also use more than one material to build their tablet.

Explore

Explore Part 2: Tablet Design and Building Challenge (60 minutes)

1. Have students go back into their groups of 4.
2. Introduce the tablet challenge to your students. Specify the requirements for their tablet design. Each group has to design and build one delayed-release tablet that has to meet the following design requirements:
   • They have to use one bath tablet of each color (yellow, red and blue) to make the tablet. The bath tablets can't be modified in any way. Note: you can also simplify the challenge by just using one or two different bath color tablets.
   • The final tablet has to be a single unit (made out of the three different color tablets) and needs to be fully enclosed.
   • When submerged in water, their tablet has to release each one of the colors (active ingredients) at a specific target time (Yellow: 30 seconds, Red: 1 minute 30 seconds, Blue: 3 minutes).
3. Provide each group with the prepared bath tablets. Then tell students that each group has 30 minutes to design and build one controlled-release tablet that meets all of these requirements. During that time, they should use the iterative design process (prototype, test, analyze, and refine) to find the optimal tablet design that meets all the specified requirements. Once they have optimized their tablet design, each group's tablet will be tested to find out which one performs the best. Make students aware of the scoring criteria . The tablet will be scored based on the accuracy of timing for color release.
4. Point students to the part of the student worksheet that explains how the tablet's performance will be scored. They can use this information to score their tablets during testing. Make sure students understand the scoring criteria.
5. Tell students that they will find more detailed instructions on their worksheets. Then give students 30 minutes to design and build their tablet. Remind them to test their tablet designs often. However, they should keep at least one bath tablet of each color along with enough plastic materials for their final tablet design. Point out to your students that:
   • They should keep their hands as well as their workspace dry and clean in order to not accidentally dissolve any water-soluble materials.
   • They should keep all their water-soluble materials in the Ziploc® bag to protect them from water spills.
   • They should use cold tap water for all their experiments so the temperature of the water they use for testing stays roughly the same throughout the experiment.
   • Once the 30 minutes are up, they need to have one controlled-release tablet ready to be tested.
6. Give students a 5-minute warning and then after 30 minutes have them stop their tablet production. Ask each student group to bring their controlled-release tablet as well as one cup filled with fresh water to a central table, where you will conduct the tablet competition. The competition will last for 5 minutes in total.
7. Execute the tablet competition following these steps:
   1. Verify that each team has its tablet as well as one cup of water assigned to them.
   2. All teams will test their tablets in parallel, one tablet per cup. Each team will be scoring their own tablet. Assign one student of each team to be responsible for dropping their tablet into the water cup. The remaining students will be in charge of timing the color release for their tablet and will need a Score Card to do so.
   3. Give students time to read through the scoring instructions briefly and provide them with a stopwatch. Assign one student in each team to operate the stopwatch. Alternatively, you can project a timer onto a screen for everyone to see. The timer should start at 0 and count upwards. Students can then look at this timer for scoring.
   4. All students hold their tablet above the water cup assigned to their team. After a countdown, give a starting signal and instruct students to start their stopwatches (or start the timer on the screen). At the same time, students will drop their tablet into the cup. As soon as the tablet hits the water's surface, the cup cannot be touched anymore.
   5. From the first moment the tablet hits the water surface, students need to carefully inspect the tablet inside their cup. As soon as they observe the tiniest bit of color being released from the tablet wrapping into the surrounding water (if the tablet dissolves inside the wrapping it does not count, yet), they should check the stopwatch (or timer) and write down the time on the scorecard. Note that the tablet can float or sink, so students should check the water surface as well (if the tablet floats) in case the color is released to the top and not the bottom.
   6. After 5 minutes (300 seconds), announce the end of the competition and ask students to stop their stopwatches (or stop the timer on the screen). Instruct each team to finish filling out their Score Card data (every color that has not been released until the end of the competition will be recorded as 5:00 min or 300s).
8. Finally, have teams calculate the final scores for each of the tablets based on the information on the individual Score Cards. Congratulate each team on their performance and announce the winner of the tablet design challenge. If there is a tie, the tablet with the color release closest to its respective release time wins.

Reflect

Reflect Part 2: Tablet Design and Building Challenge (20 minutes)

1. Gather your students for a class discussion. Ask students to share their observations and experiences from the tablet design challenge.

   What was difficult or easy about designing and building your controlled release tablet?

2. Have the winning team describe their specific tablet design. Let them explain which design features they think made their tablet perform the best. Then ask the other teams:

   How did your team's tablet perform during the competition? What would you do to improve your design next time?

3. Conclude the lesson by asking students to name three things that they have learned from today's lesson and the tablet design challenge.

Assess

You can use this quiz to assess student learning after the activity:

• Online quiz, assignable in any LMS
• Quiz (pdf) and answer key (pdf)

Make Career Connections

Discussing or reading about these careers can help students make important connections between the in-class lesson and STEM job opportunities in the real world.

Materials Scientist and Engineer

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Career Profile

Material scientists study all aspects of materials including their physical properties. Not only could they develop new polymer materials for drug delivery systems, but they could also create materials for other medical applications such as insulin pumps, medical patches, or implants like hip replacements or stents. Read more

Biochemist

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Career Profile

Biochemists study the chemistry of living processes. They need to know how our body functions and what effects certain chemicals have on our bodies. For example, they could search for chemicals that can be used to develop new drugs for a specific disease, or they could study what the most effective dosage of a particular drug is Read more

Lesson Plan Variations

• In this lesson, students focus primarily on the physical properties of the various plastic materials. Extend the investigation to include the chemical properties of the materials as well. Have students look into the molecular composition of the different polymers and let them investigate why some plastics are water-soluble and others are not.
• Explore other polymer applications in the medical field with your students, such as polymers in medical devices, polymer implants, or polymers for tissue engineering. Discuss with your students what properties these polymers need to have.
• Have students research actual controlled-release drugs. Ask them to find out how these particular drugs work, what they are used for, which diseases they treat, etc.