Gel Diffusion Experiment STEM ED/CHM Nanotechnology 2010.

Gel Diffusion Gel Diffusion ExperimentExperiment

STEM ED/CHMSTEM ED/CHM

Nanotechnology 2010Nanotechnology 2010

BackgroundBackground

The delivery of nanoscale medicines The delivery of nanoscale medicines to cells in the human body requires to cells in the human body requires diffusion through tissues, organs and diffusion through tissues, organs and cell membranescell membranes

This activity will explore the affect of This activity will explore the affect of particle size on diffusion ratesparticle size on diffusion rates

Understanding molecular diffusion Understanding molecular diffusion through human tissues is important through human tissues is important for designing effective drug delivery for designing effective drug delivery systems systems

IntroductionIntroduction

Measuring the diffusion of dyes in gelatin Measuring the diffusion of dyes in gelatin illustrates the transport of drugs in the illustrates the transport of drugs in the extra-vascular space extra-vascular space

Gelatin is a biological polymeric material Gelatin is a biological polymeric material with similar properties to the connective with similar properties to the connective extracellular matrix in tumor tissueextracellular matrix in tumor tissue

Dyes are similar in molecular weight and Dyes are similar in molecular weight and transport properties to transport properties to chemotherapeuticschemotherapeutics

Their concentration can be easily Their concentration can be easily determined simply by color intensitydetermined simply by color intensity

Experiment OverviewExperiment Overview

The diffusion of the dyes will be The diffusion of the dyes will be compared to demonstrate the effect of compared to demonstrate the effect of molecular weight on transport in tumors molecular weight on transport in tumors

Gelatin will be formed into cylindrical Gelatin will be formed into cylindrical shapes in Petri dishes and colored shapes in Petri dishes and colored solutions will be added to the outer ringsolutions will be added to the outer ring

Over several days the distance that the Over several days the distance that the dyes and particles penetrate into the dyes and particles penetrate into the gelatin cylinders will be measuredgelatin cylinders will be measured

Set-upSet-up

Collect materialsCollect materials– Petri DishesPetri Dishes– Food DyeFood Dye– SyringesSyringes– Paper CupsPaper Cups– GelatinGelatin– Crisco/Petroleum Crisco/Petroleum

JellyJelly– Baking PanBaking Pan

Prepare Gel CastPrepare Gel Cast– Determine water Determine water

needed for proper needed for proper coverage in pancoverage in pan

– Dissolve Gel into Dissolve Gel into warm water warm water (2Pks/Cup)(2Pks/Cup)

– Microwave for 90 Microwave for 90 Sec.Sec.

– Pour into pan and let Pour into pan and let set.set.

SetupSetup

Gel CastGel Cast– Cut circles in pan Cut circles in pan

w/metal cookie w/metal cookie cuttercutter

– Remove excessRemove excess– Move Gel Cast from Move Gel Cast from

pan and transfer to pan and transfer to Petri DishPetri Dish

– Smooth side Down!Smooth side Down!– Centered as best Centered as best

cancan

Adding DyeAdding Dye– Mix dyes in cupsMix dyes in cups– Inject one color/dishInject one color/dish– No dye on top of No dye on top of

CastCast– No seepage under No seepage under

castcast– Do not move dishes Do not move dishes

after dye insertedafter dye inserted

Collect Data and Collect Data and ObservationsObservations

Take Digital photosTake Digital photos– Same time each day and at same Same time each day and at same

intervalinterval 8:00 AM and again at 4:00 PM each day8:00 AM and again at 4:00 PM each day

– From approximately same height and From approximately same height and angleangle

– Helps to have a good background under Helps to have a good background under the Petri dishthe Petri dish

Data CollectionData Collection3 Food Dyes3 Food Dyes

Start

4 hours

Diffusion is first visible

Questions to considerQuestions to consider

Are the results expected? Are the results expected? Which dyes penetrated better?Which dyes penetrated better? Does that make sense? Does that make sense? Conversely, does fast diffusion mean Conversely, does fast diffusion mean

greater or poorer retention?greater or poorer retention? How could diffusion and retention be How could diffusion and retention be

optimized?optimized? Is this the intuitive result? Is this the intuitive result?

Gel Diffusion AnalysisGel Diffusion Analysis

Nanotechnology Institute Nanotechnology Institute 20102010

Image AnalysisImage Analysis

Method 1: Method 1: – Measure the dye penetration distance Measure the dye penetration distance

each day using a ruler.each day using a ruler.– Use graph paper to plot distance vs. timeUse graph paper to plot distance vs. time– The rate is the slope of the line. During the The rate is the slope of the line. During the

relatively short diffusion time (as in this relatively short diffusion time (as in this lab), the relationship between distance lab), the relationship between distance and time is somewhat linear. A line of best and time is somewhat linear. A line of best fit may not have a y-intercept of 0 due to fit may not have a y-intercept of 0 due to error. error.

Measurement by HandMeasurement by Hand

y = 0.2057x + 1.0715

0

2

4

6

8

10

12

14

16

18

0 20 40 60 80

Time

Dis

tan

ce

(m

m)

Image AnalysisImage Analysis

Group Pictures by Color in date/time Group Pictures by Color in date/time orderorder

– Create a data table (paper or Excel)Create a data table (paper or Excel)

6-1-0600 6-1-1800 6-2-0600 6-2-1800

Pick one color to startPick one color to start Load the first morning shotLoad the first morning shot

– Windows Photo Gallery or other image Windows Photo Gallery or other image programprogram

Using the magnifier expand the photoUsing the magnifier expand the photo

Using a mm ruler, measure from the Using a mm ruler, measure from the edge of the gel cast to the inner most edge of the gel cast to the inner most edge of the diffusion for each color. edge of the diffusion for each color.

Enter diffusion distances for each Enter diffusion distances for each color and time period in the color and time period in the appropriate column of your data appropriate column of your data tabletable

When finished your table might look When finished your table might look something like thissomething like this

Use the graphing wizard to complete the Use the graphing wizard to complete the project.project.

Important DetailsImportant Details When mixing dyes, red and yellow can be When mixing dyes, red and yellow can be

fairly concentrated. They tend to fade in the fairly concentrated. They tend to fade in the gel. The blue should not be concentrated- it gel. The blue should not be concentrated- it should be strong, but translucent. should be strong, but translucent.

Inject dye towards the outside of the petri Inject dye towards the outside of the petri dish, not towards the gel. Avoid getting dye dish, not towards the gel. Avoid getting dye on top or underneath gel. on top or underneath gel.

Try to use an even number of millimeters Try to use an even number of millimeters for the volume of dye. for the volume of dye.

The initial level of dye should not exceed ¾ The initial level of dye should not exceed ¾ of the way up the gel. of the way up the gel.

Photograph the gel: same time, same Photograph the gel: same time, same distance, same sequence. Keep camera distance, same sequence. Keep camera parallel to gel (do not tilt) to avoid parallax. parallel to gel (do not tilt) to avoid parallax.