Gel Diffusion Experiment
STEM ED/CHM
Nanotechnology Saturday Seminar
Presented by Jennifer Welborn
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

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
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
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
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

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

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
Lab Prep

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 Procedure

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
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.
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)
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

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/
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.
Cancer Treatments
• Tumor penetration is a key issue for successful chemotherapy
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.
Nanomedicine connectionyoutube
Youtube video made by the Center for
Hierarchical Manufactoring at UMASS,
Amherst:
 http://www.youtube.com/watch?v=bUvi5e
QhPTc
 5:40-7:40 shows specific uses of diffusion
of nano-scale particles in medicine. The
rest of the video is AWESOME!

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
Applications, Continued
 Process
Skills
- Controlled experiments
- precision/accuracy
- Repeated trials
- Measurement skills