Gel Diffusion Experiment

1. Gel Diffusion Experiment STEM ED/CHM Nanotechnology Saturday Seminar Presented by Jennifer Welborn

2. Learning Goals In this activity, Saturday seminar participants will: • learn the concept of diffusion and its connection to frameworks • See how food dyes and gelatin are used to model the delivery of nanoscale medicines to cells in the human body

3. Diffusion and Teaching Standards This lab has content which is applicable to various disciplines/standards • Physical Science/Chemistry: particle motion theory • Biology: passive transport; cellular structure, etc. • Ecology/Environmental Science: environmental effects on living systems • Math: rates; proportions, data collection, measurement, precision/accuracy

4. Diffusion Diffusion– movement of a substance from a region of higher concentration to a region of lower concentration. Diffusion continues until equilibrium--- the concentration of a substance is equal throughout a space

5. Diffusion and Cells • Dissolved particles that are small or non-polar can diffuse through the cell membranes. • The process of diffusion is one of the ways in which substances like oxygen, carbon dioxide and water move into and out of cells. Carbon dioxide from the environment diffuses into plant cells

6. Background For Lab Activity • The delivery of nanoscale medicines to cells in the human body requires diffusion through tissues, organs and cell membranes • This activity will explore the affect of particle size on diffusion rates • Understanding molecular diffusion through human tissues is important for designing effective drug delivery systems

7. Background Continued • Measuring the diffusion of dyes in gelatin is a model for the transport of drugs in the extra-vascular space • Gelatin: biological polymeric material with similar properties to the connective extracellular matrix in tumor tissue • Dyes are similar in molecular weight and transport properties to chemotherapeutics

8. Experiment Overview • Gelatin was cut into cylindrical disks, placed in Petri dishes and colored solutions were added to the outer ring • The distance that the dye particles diffused into the gelatin disks is observed • The diffusion of the dyes is a model of the effect of molecular weight on movement of molecules in tumors

9. Collect materials Petri Dishes Food Dye Syringes/10 ml graduated cylinders Paper Cups Plain Gelatin Crisco/Petroleum Jelly Baking Pan Biscuit cutter Prepare Gel Disks Determine amount of water needed to fill up a pan to a depth of 1 cm. Dissolve gel into cold water (2Pks/Cup/200 ml) Microwave for 90 Sec. Pour into pan which has been coated with petroleum jelly and let set. Lab Prep

10. Gel Disks Cut disks--bisquit cutter Thin coating of Petroleum jelly on inside bottom of Petri dish Put gel disk –top side down and centered- on bottom of dish Gently press disk to secure Adding Dye Mix dyes in cups Inject one color/petri dish No dye on top of gel No seepage under gel Do not move dishes after dye inserted Lab Procedure

11. Important Details For Procedure • Make the dye solutions according to directions. • Inject dye towards the outside of the petri dish, not towards the gel. • Make sure there is a uniform coating of petroleum jelly on the bottom of the petri dish and the gel disk is firmly pressed down so no dye leaks under the gel.

12. Data Collection • Method 1-- By eye: measure (in mm) the distance each dye has diffused for each time interval. Record data in a data table or use excel spreadsheet • Method 2--Using a digital camera: take photos of each petri dish at the same time each day, from the same height and perpendicular to the gel (to avoid parallax)

16. Nano-medicine connection: Targeted Therapies • Nanoparticles diffuse into cancer cells and then heated in a magnetic field to weaken them. Chemotherapy is more effective on the weakened cells. • The dye in blue jeans or ballpoint pens has also been paired with gold nanoparticles to fight cancer. This dye, known as phthalocyanine, reacts with light. The nanoparticles take the dye directly to cancer cells while normal cells reject the dye. Once the particles are inside, scientists "activate" them with light to destroy the cancer. • Similar therapies have existed to treat skin cancers with light-activated dye, but scientists are now working to use nanoparticles and dye to treat tumors deep in the body. http://science.howstuffworks.com/life/human-biology/gold nanotech1.htm

17. The next 3 slides are from Professor Jonathan Rothstein’s presentation at the Nanotech summer institute. The full slide show along with the details of the gelatin experiment can be found at: • http://umassk12.net/nano/

18. Targeted Delivery to Tumors • Goal is to inject treatment far from tumor and have large accumulation in tumor and minimal accumulation in normal cells/organs.

19. Cancer Treatments • Tumor penetration is a key issue for successful chemotherapy

20. Nanoparticle use in Cancer Treatments • Because of their small size, nanoparticles can pass through interstitial spaces between necrotic and quiescent cells. • Tumor cells typically have larger interstitial spaces than healthy cells • Particles collect in center bringing therapeutics to kill the tumor from inside out.

21. Nanomedicine connection-youtube • Youtube video made by the Center for Hierarchical Manufactoring at UMASS, Amherst: • http://www.youtube.com/watch?v=bUvi5eQhPTc • 5:40-7:40 shows specific uses of diffusion of nano-scale particles in medicine. The rest of the video is AWESOME!

22. Additional Applications of this Lab • Fungal growth!  Kidding • Content– • Particle motion theory – temperature and concentration • Molecular weight (chromatography) • Diffusion of materials into and out of cells – connection to cancer tissue/therapy

23. Applications, Continued • Process Skills - Controlled experiments • precision/accuracy • Repeated trials • Measurement skills