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Gel Diffusion Analysis STEM ED/CHM Nanotechnology 2011 Presented by Jennifer Welborn

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Background The delivery of nanoscale medicines to cells in the human body requires diffusion through tissues, organs and cell membranes 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 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 Understanding molecular diffusion through human tissues is important for designing effective drug delivery systems

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Introduction Measuring the diffusion of dyes in gelatin illustrates the transport of drugs in the extra-vascular space Measuring the diffusion of dyes in gelatin illustrates the transport of drugs in the extra-vascular space Gelatin is a biological polymeric material with similar properties to the connective extracellular matrix in tumor tissue Gelatin is a 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 Dyes are similar in molecular weight and transport properties to chemotherapeutics Their concentration can be easily determined simply by color intensity Their concentration can be easily determined simply by color intensity

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Analysis In The Classroom Groups can share data – model for repeated trials- all data can be combined onto one data table Provides for discussion of constants, outliers, statistical analysis ( basic– range, mean-- and advanced– standard deviation, etc.) Visual measurement = actual distance dye diffused Photo measurements can be used as is for comparison between dyes, or they can be used to calculate actual distance diffused using a ratio- provides opportunity to discuss use of tools to improve reduce error in measurement. Diffusion screen measurement X gel radius screen measurement = 32.5 mm Gel radius = 32.5 mm

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Image Analysis Method 1: –Measure the dye diffusion distance each day using a ruler. –Use graph paper to plot distance vs. time –The rate is the slope of the line. During the relatively short diffusion time (as in this lab), the relationship between distance and time is somewhat linear. A line of best fit may not have a y-intercept of 0 due to error.

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Measurement by Hand

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Image Analysis Method 2: Group Pictures by Color in date/time order Method 2: Group Pictures by Color in date/time order –Create a data table (paper or Excel)

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Pick one color to start Pick one color to start Load the first morning shot Load the first morning shot –Windows Photo Gallery or other image program

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Using the magnifier, expand the photo Using the magnifier, expand the photo Using a mm ruler, measure from the edge of the gel disk to the inner most edge of the diffusion for each color. Using a mm ruler, measure from the edge of the gel disk to the inner most edge of the diffusion for each color.

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

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

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

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Image Analysis Method 3 1.Download ADI software from: 2. Open one of your photos. Trim. Use the line tool and color along the line option to observe the change in RGB values along the line which illustrates the diffusion of the dye. 3. Repeat Step 2 with the other photos you took.

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Directions for Using ADI 1.Open a picture using analyzing digital images software 2.Use the trim option available to reduce processing speed

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4. Select Line tool under file options 5. Clicking on blue and red squares under adjust can fine tune placement of coordinate points. 6. Draw line. Note coordinates and color averages along line.

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Calculate Mean Percentage of Diffusion For the last time period measured and for each color of dye, calculate and record the mean percentage of diffusion Use: total distance traveled by dye in mm / 32.5 x 100 = ________%

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Questions 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 greater or poorer retention? Conversely, does fast diffusion mean greater or poorer retention? How could diffusion and retention be optimized? How could diffusion and retention be optimized? Is this the intuitive result? Is this the intuitive result?

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