Novel cross-linked homogeneous polyacrylamide gels with improved separation properties: investigation of the cross-linker functionality

Complex polymer architectures through free-radical polymerization of multivinyl monomers

The construction of complex polymer architectures with well-defined topology, composition and functionality has been extensively explored as the molecular basis for the development of modern polymer materials. The unique reaction kinetics of free-radical polymerization leads to the concurrent formation of crosslinks between polymer chains and rings within an individual chain and, thus, free-radical (co)polymerization of multivinyl monomers provides a facile method to manipulate chain topology and functionality. Regulating the relative contribution of these intermolecular and intramolecular chain-propagation reactions is the key to the construction of architecturally complex polymers. This can be achieved through the design of new monomers or by spatially or kinetically controlling crosslinking reactions. These mechanisms enable the synthesis of various polymer architectures, including linear, cyclized, branched and star polymer chains, as well as crosslinked networks. In this Review, we highlight some of the contemporary experimental strategies to prepare complex polymer architectures using radical polymerization of multivinyl monomers. We also examine the recent development of characterization techniques for sub-chain connections in such complex macromolecules. Finally, we discuss how these crosslinking reactions have been engineered to generate advanced polymer materials for use in a variety of biomedical applications.

Nonvolatile copolymer compositions for fabricating gel element microarrays

By modifying polymer compositions and cross-linking reagents, we have developed a simple yet effective manufacturing strategy for copolymerized three-dimensional gel element arrays. A new gel-forming monomer, 2-(hydroxyethyl) methacrylamide (HEMAA), was used. HEMAA possesses low volatility and improves the stability of copolymerized gel element arrays to on-chip thermal cycling procedures relative to previously used monomers. Probe immobilization efficiency within the new polymer was 55%, equivalent to that obtained with acrylamide (AA) and methacrylamide (MA) monomers. Nonspecific binding of single-stranded targets was equivalent for all monomers. Increasing cross-linker chain length improved hybridization kinetics and end-point signal intensities relative to N,N-methylenebisacrylamide (Bis). The new copolymer formulation was successfully applied to a model orthopox array. Because HEMAA greatly simplifies gel element array manufacture, we expect it (in combination with new cross-linkers described here) to find widespread application in microarray science.

Use of protein-acrylamide copolymer hydrogels for measuring protein concentration and activity

We report the development and characterization of a polyacrylamide-based protein immobilization strategy for surface-bound protein assays, including concentration detection, binding affinity, and enzyme kinetics. Glutathione S-transferase (GST) fusion proteins have been labeled with an acrylic moiety and attached to acrylic-functionalized glass surfaces through copolymerization with acrylic monomer. The specific attachment of GST-green fluorescent protein (GFP) fusion protein was more than sevenfold greater than the nonspecific attachment of nonacrylic-labeled GST-GFP; 0.32 ng/mm(2) of surface-attached GST-GFP was detectable by direct measurement of GFP fluorescence and this lower detection limit was reduced to 0.080 ng/mm(2) using indirect antibody-based detection. The polyacrylamide-based surface attachment strategy was also used to measure the kinetics of substrate phosphorylation by the kinase c-Src. Michaelis-Menten kinetic constants for the reaction occurring in solution were K(m) = 2.7 +/- 1.0 microM and V(max) = 8.1 +/- 3.1 (arbitrary units). Kinetic values for the reaction utilizing surface-immobilized substrate were K(m) = 0.36 +/- 0.033 microM and V(max) = 9.7 +/- 0.63 and were found to be independent of the acrylamide concentration within the copolymer. Such a surface attachment strategy should be applicable to the proteomics field and addresses denaturation and dehydration problems associated with protein microarray development.