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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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In addition to its annual lectures, ChBE hosts a weekly seminar throughout the year with invited lecturers who are prominent in their fields. Unless otherwise noted, all seminars are held on Wednesdays in the Molecular Science and Engineering Building ("M" Building) in G011 (Cherry Logan Emerson Lecture Theater) at 4 p.m. Refreshments are served at 3:30 p.m. in the Emerson-Lewis Reception Salon.
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Robert Pelton - McMaster University, Canada
"Bioactive Paper Fabrication – Printing and Coating Filter Paper"
Filter paper offers a number of advantages as a support for biosensors including: a biomacromolecules friendly surface, a high surface area, capillary driven lateral flow, low background color and fluorescence. The literature contains many examples of hand fabricated filter-paper supported biosensors. However, there are challenges in converting hand pipetting and air drying to efficient roll-to-roll manufacturing. Herein we consider two examples: 1) The ink jet printing of sol-gel precursor solutions, giving enzymes entrapped silica domains in the paper; and, 2) the application of concentrated pullulan solutions to fabricate solvent resistant barriers in patterned microfluidic channels.
We recently reported on the multi-layer printing of sol-gel/enzyme bio-inks onto porous filter paper to create bioactive paper test strips. The method involves the printing of three inks: a polymer under layer; a sol-gel based silica layer, an acetyl cholinesterase (AChE) enzyme layer and finally a top layer of silica. Although the silica and enzyme solutions were printed sequentially, they formed a composite material within the porous paper network and coated only the fibers as a thin film of 35 ± 15 nm without filling the macropores. The silica coating on the cellulose fibers was sufficiently flexible to allow bending of the paper substrate, unlike traditional silica thin films. The protease assay results showed that the AChE became more protected as the amount of sol-gel derived silica printed on paper was increased. The top layer of sol-gel ink was found to play a critical role in protection against proteolysis, while the bottom layer of sol-gel ink was found to be necessary to prevent the potential inhibition of AChE by the cationic polymer (used as a capture agent for the product of the enzymatic reaction). Overall, the data show that ink-jet printed sol-gel materials form thin, protein entrapping films that are suitable for the production of printed biosensors. Our major issue with these systems is the blocking of the inkjet print heads with sol-gel precursor.
Although wax barriers are widely used to create paper-based microfluidic devices, wax can be breached by aggressive organic solvents and surfactant mixtures, often used with cell-based assays. We have shown that most liquids are blocked by a combination of a layer of pullulan-impregnated filter paper sandwiched between two wax layers. Observations of solvent-blocking pullulan lenses formed in glass capillary tubes support the explanation that pullulan solutions dry in paper to form lenses in the pores that physically block pullulan-insoluble solvents.
