Zero Order


General Update

Posted in Uncategorized by Amy Ross on July 23, 2010

A few things I’ve been up to lately:
-Still working on cell attachment with my hydrogels. I’m trying single-layer PEGDA hydrogels, but the results aren’t much of an improvement over the bilayer hydrogels I had been using. One of our summer rotation students thought the environment might be too dilute of nutrients for the cells to survive, as I had been swelling them in phosphate buffered saline. She suggested I should try swelling them in cell  media.  I thought it was worth a try, so I did that experiment this week.
When I assessed cell viability using MTS, I didn’t see a significant difference in cell attachment between the hydrogels swollen in media and the ones that weren’t.  However, it seemed like there were fewer cells on the bottom of the well  for the media group when I looked at them under the microscope.

Oh well, I’m trying something new this weekend that I’m excited about. I’ll tell you all about it soon!

-I’ve been learning  gel permeation chromatography (GPC). In short, chromatography applies to a broad range of techniques that separate materials based on a specific property. In the case of GPC, it’s size. All chromatography consists of two phases, a stationary phase (typically something solid) and a mobile phase (a liquid or a gas). The components of a mixture that have a greater affinity for the mobile phase will elute first; as affinity for the stationary phase increases, the elution time lengthens.

GPC is primarily used for polymers. Allow me to use this crude drawing (that looks a lot like the 1980’s Atari game Defender) to demonstrate how separation occurs.

The polymer solution (the red and blue shapes) is dissolved in a solvent, and injected into a column (the grey thing).  The shorter polymers (i.e., the red circle) get caught in the gaps of the column, and leave the column last. The larger polymers (the blue ellipse) are too large to fit in the gaps. They leave the column first. After leaving the column, a detector (there are several varieties) determines the properties of the polymer solution.

I used GPC to find the molecular weight of the polyacrylamide hydrogels I had made.   I got decent results once I increased my solution concentration.

-We’ve had several undergrads in our lab this summer, and they’re wrapping up their projects and will be headed back to school in a couple weeks.  I enjoyed teaching them things, and learned a few things from them as well. The place is going to be awfully quiet next month.

Have a great weekend. I’ll have more updates as warranted.

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2 Responses to 'General Update'

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  1. jonathan said,

    The research that appeared to spark an onslaught of modified applications was a Gel Permeation Chromatographic technique of fixing PIPA strands to glass beads and separating a mixture of dextrans, which was developed by Gewehr et al. They found that between the temperatures of 25-32 oC, the elution time of dextrans at different molecular weights exhibited a dependence on the temperature. Dextrans of the highest molecular weight eluted first since the PIPA chains exhibit hydrophilicity at temperatures below the LCST. As the temperature of the elution increased, when the chains behave in a more hydrophobic manner, the elution times increased for each of the analytes for the given range.Polymeric Columns, SPE & Bulk Media
    The trend generally applies over the entire temperature range, but there is a flattening of the curve before 25 °C and after 32 °C (the approximate LCST for this experiment). It is important to note that above the LCST, the PIPA acts as a typical nonpolar stationary phase that would be used in reverse-phased chromatography.

  2. jonathan said,

    There are also instances of the elution times increasing below 15 °C, which most likely can be attributed to the lower temperatures’ effects on mass transfer playing a more significant role on retention than the stationary phase behavior.Polymer GPC column
    this is also provide ample information as well as good quality servises This study showed that the resolution could essentially be tuned by adjusting the operating temperature. The scope of this study was limited to isothermal conditions and attaching polymer chains to glass beads. The results, however, were satisfying enough to inspire other investigations and modifications to create a more versatile stationary phase for the advancement of chromatography.


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