UV Graft Polymerization of Polyacrylamide Hydrogel Plugs in Microfluidic Channels
Rebecca A. Zangmeister, Michael J. Tarlov
It has been previously demonstrated that DNA, modified on the 5' end with an acrylamide functionality, can be incorporated into a polyacrylamide hydrogel matrix. These types of DNA containing gels have recently been spatially immobilized in plastic microfluidic channels, creating selective DNA capture elements 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 exceed 25 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/O3 treatment was used to oxidize 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 oxidized surfaces with 3-methacryloxypropyltrimethoxysilane. Polyacrylamide was then UV grafted onto the chemically modified model surfaces. Contact angle measurements and FT-IR ATR spectra confirm polyacrylamide grafting on PC and PMMA surfaces with the above described surface pretreatment. The success of graft polymerization within the microchannel devices were evaluated using scanning electron miscroscopy (SEM) of delaminated devices and timed performance measurements which reveal that surface pretreatment of the microchannel walls can increase the lifetime of the gel plugs by 2.5 times on average.