MRS Fall 2009: Monday afternoon, part 1
SS2.1 "Biosurface science" George Whitesides (Harvard)
His title changed slightly...
Specifically looking at quantitation in biology through three examples: mammalian cells, worms, and "cells in gels".
Taking from his earlier work on SAMs patterned by microcontact printing. Real cells look very different from dead cells on surfaces: how do cells sense things and move on surfaces? Why do they take on their stretched form? With mini arrays, an electrochemical pulse releases a stimulant, and one observes how the cells migrate. Through a large array, one can establish enough measurements to measure how cells behave through statistics of large numbers.
Now, worms, specifically C. elgans. It's got a 2-3 week lifespan, 0.5 mm long (easy to see), but still multicellular, and exhibits traits one associates with this such as locomotion. They've created a "lifespan on a chip", with each worm in a cell for its life. How are they held in place? They're not lassoed down. Here, worms are introduced into tapered chambers in PDMS; they load automatically and rapidly through flows control. When a worm blocks a tapered channel, it keeps further flow from going through and keeps it to one worm per channel. Their responses to chemical stimuli are measured by looking at their rate of undulation with time through some clever image processing.
Finally, "cell based assays on paper". The idea is that by working with a stack of filter papers, add "cells in gels" (hydrogels, here), then put in a mixture of nutrients and oxygen (or whatever it takes to keep the cells growing naturally). This can be put in a gradient of nutrients. After growth, the 3D matrix can be "sectioned" by pulling apart the sheets of filter paper. There are other details, selling points and variants, but that's the gist of it. I originally read about this in New Scientist. There seems to be some question about whether a fully developed, multi-cellular culture could be separated from the filter paper and still consider it "non-destructive" sectioning.
He ended with an "anti-peer review commercial" with the thought that the best and most interesting research is funded by corporations rather than government funding agencies.
My earlier comment about keeping it interesting and insightful: GW is great about that. The work from his group is consistently novel and does a great job of engaging his audience. To put it in economic terms, he's great value. And he keeps to time. Class act.
SS2.2 "Layer-by-layer assembly for increased sustainability of cell-based sensors Nancy Kelley-Loughnane (Wright-Patternson Air Force Research Lab, UES Dayton, Henry Jackson Foundation)
She presented on using regulatory ribonucleic structures as "ribo switches". These are regulatory RNA located in the 5' untranslated region of mRNA sequences to recognize and bind to small molecules and regulate the expression of downstream gene. They're making synthetic ribo switches. For example, theophylline synthetic riboswitch coupled to a GFP (Amphioxus GFPa1) with a high quantum efficiency. Right now, they're encapsulating them in E. coli and using LSCM to monitor their development with time.
SS2.3 "Biomimetic metallic electrodes for intracellular electrical measurements" Piyush Verma and Nick Melosh (Stanford)
Our ability to control flux across membranes is really primitive right now. What he envisions is "artificial membrane proteins". The "sharp stick" approach, putting something inorganic into a membrane leaves a gap between the probe and the membrane -- need to prevent that for accurate measurements.
They've developed "stealth probes" to prevent this which mimic the hydrophilic-hydrophobic-hydrophilic band at the cell membrane, that is creating a 1-2 nm thick hydrophobic band along a longer probe. The way to do it is to create a multi-layer inorganic surface that can penetrate the cell, but "it's more than just hydrophobic-hydrophilic interaction," he says. So he's created better interface for the gigaohm "patch clamps" to measure potentials within a cell, including a metallic post into a cell. The fabrication is pretty complex (multistep, anyway) right now. But he's shown 3 gigohm seal on a red blood cell. Cool.
SS2.4 "Improved limits of detection for localized surface plasmon resonance sensors by directed binding exclusively to the most sensitive regions" (whew!) Laurent Feuz (with Fredrik Höök) (Göteborg)
How to measure when only a few proteins are in solution and fewer adsorb? What's the best way for label-free detection? You need both a small adsorption pad and a small sensing field. What he's working with is surface plasmon resonance with about 12% sensitive gold area and 88% titania. Protein adhesion places were controlled by covering some areas with protein-repellant PEG. He saw faster binding with these modified sensors and a greater concentration of the protein of interest at the active areas.
His title changed slightly...
Specifically looking at quantitation in biology through three examples: mammalian cells, worms, and "cells in gels".
Taking from his earlier work on SAMs patterned by microcontact printing. Real cells look very different from dead cells on surfaces: how do cells sense things and move on surfaces? Why do they take on their stretched form? With mini arrays, an electrochemical pulse releases a stimulant, and one observes how the cells migrate. Through a large array, one can establish enough measurements to measure how cells behave through statistics of large numbers.
Now, worms, specifically C. elgans. It's got a 2-3 week lifespan, 0.5 mm long (easy to see), but still multicellular, and exhibits traits one associates with this such as locomotion. They've created a "lifespan on a chip", with each worm in a cell for its life. How are they held in place? They're not lassoed down. Here, worms are introduced into tapered chambers in PDMS; they load automatically and rapidly through flows control. When a worm blocks a tapered channel, it keeps further flow from going through and keeps it to one worm per channel. Their responses to chemical stimuli are measured by looking at their rate of undulation with time through some clever image processing.
Finally, "cell based assays on paper". The idea is that by working with a stack of filter papers, add "cells in gels" (hydrogels, here), then put in a mixture of nutrients and oxygen (or whatever it takes to keep the cells growing naturally). This can be put in a gradient of nutrients. After growth, the 3D matrix can be "sectioned" by pulling apart the sheets of filter paper. There are other details, selling points and variants, but that's the gist of it. I originally read about this in New Scientist. There seems to be some question about whether a fully developed, multi-cellular culture could be separated from the filter paper and still consider it "non-destructive" sectioning.
He ended with an "anti-peer review commercial" with the thought that the best and most interesting research is funded by corporations rather than government funding agencies.
My earlier comment about keeping it interesting and insightful: GW is great about that. The work from his group is consistently novel and does a great job of engaging his audience. To put it in economic terms, he's great value. And he keeps to time. Class act.
SS2.2 "Layer-by-layer assembly for increased sustainability of cell-based sensors Nancy Kelley-Loughnane (Wright-Patternson Air Force Research Lab, UES Dayton, Henry Jackson Foundation)
She presented on using regulatory ribonucleic structures as "ribo switches". These are regulatory RNA located in the 5' untranslated region of mRNA sequences to recognize and bind to small molecules and regulate the expression of downstream gene. They're making synthetic ribo switches. For example, theophylline synthetic riboswitch coupled to a GFP (Amphioxus GFPa1) with a high quantum efficiency. Right now, they're encapsulating them in E. coli and using LSCM to monitor their development with time.
SS2.3 "Biomimetic metallic electrodes for intracellular electrical measurements" Piyush Verma and Nick Melosh (Stanford)
Our ability to control flux across membranes is really primitive right now. What he envisions is "artificial membrane proteins". The "sharp stick" approach, putting something inorganic into a membrane leaves a gap between the probe and the membrane -- need to prevent that for accurate measurements.
They've developed "stealth probes" to prevent this which mimic the hydrophilic-hydrophobic-hydrophilic band at the cell membrane, that is creating a 1-2 nm thick hydrophobic band along a longer probe. The way to do it is to create a multi-layer inorganic surface that can penetrate the cell, but "it's more than just hydrophobic-hydrophilic interaction," he says. So he's created better interface for the gigaohm "patch clamps" to measure potentials within a cell, including a metallic post into a cell. The fabrication is pretty complex (multistep, anyway) right now. But he's shown 3 gigohm seal on a red blood cell. Cool.
SS2.4 "Improved limits of detection for localized surface plasmon resonance sensors by directed binding exclusively to the most sensitive regions" (whew!) Laurent Feuz (with Fredrik Höök) (Göteborg)
How to measure when only a few proteins are in solution and fewer adsorb? What's the best way for label-free detection? You need both a small adsorption pad and a small sensing field. What he's working with is surface plasmon resonance with about 12% sensitive gold area and 88% titania. Protein adhesion places were controlled by covering some areas with protein-repellant PEG. He saw faster binding with these modified sensors and a greater concentration of the protein of interest at the active areas.
Comment
© 2010 Created by Springer.
You need to be a member of JMS Network to add comments!
Join JMS Network