DNA Hydrogel Plugs Immobilized in Microfluidic Channels with Improved Stability

Rebecca A. Zangmeister, Kimberly G. Olsen, David J. Ross, and Michael J. Tarlov

Process Measurements Division, Chemical Sciences and Technology Laboratory
National Institute of Standards and Technology, Gaithersburg, Maryland 20899

It has been previously demonstrated that DNA, modified on the 5' end with an acrylic acid group, can be incorporated into a polyacrylamide hydrogel matrix.  These types of DNA containing gels have recently been immobilized in plastic microfluidic channels through a photoinduced polymerization reaction.  The DNA oligomers retain activity, and are able to bind complementary target strands as they migrate through the gel plug under electrophoretic conditions.  Although preliminary studies have succeeded in the retention of DNA activity of immobilized probes, the lifetime of the polyacrylamide gel plugs rarely exceeded 30 minutes under continuous use.

The goal of recent experiments has been to increase the stability of the polyacrylamide gel plugs by the introduction of polymerization attachment points to the polymeric microchannel surfaces prior to gel plug formation.  UV/ozone treatment was used to increase the hydroxyl content on both top polymethylmethacrylate (PMMA) and bottom polycarbonate (PC) surfaces.  A methacrylate functionality, which can cross-link with the polyacrylamide gel, was introduced by reacting the hydroxyl terminated surfaces with Bind-Silane (3-Methacryloxypropyltrimethoxysilane).  Chemically modified surfaces were then exposed to polyacrylamide hydrogel polymerization conditions.  Contact angle measurements and FT-IR ATR spectra confirm the increase in polyacrylamide gel formation on PC and PMMA surfaces with the above described surface pretreatment.  Subsequent timed performance measurements on DNA containing gel plugs show that surface pretreatment can increase the lifetime of the gel plugs by 2.5 times on average.

The increase in gel plug stability allows for investigation into the percent activity, capture rate, and electrophoretic stringency of immobilized DNA within the polyacrylamide gel plugs.

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