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Biological systems have a tendency to adsorb nonspecifically onto a solid substrate, thus reducing the efficacy of the interface being used in biorecognition. This nonspecific adsorption is a common problem in the development of biosensors as it typically reduces the efficacy of the sensor platform. In this manuscript we report the synthesis of an oligo(ethylene glycol) (OEG) containing ATRP (atom transfer radical polymerization) thiol initiator and demonstrate the role of this initiator in preventing nonspecific adsorption of IgG antibodies on chemically functionalized gold electrode surfaces using cyclic voltammetry. A new synthetic route for the synthesis of the new ATRP thiol initiator in high yields has been reported. Surface initiated poly(acrylic acid) brushes grown off the gold surface with modified OEG containing and conventional ATRP thiol initiators were chemically modified with 2,4-dinitrophenyl (DNP) groups. Amperometric studies were carried out on gold electrodes modified with DNP-PAA brushes using DNP-specific and nonspecific IgG antibodies. The cyclic voltammograms of an osmium redox mediator recorded over time suggest that the chemical modification of the gold electrodes with DNP-PAA brushes using the OEG-containing ATRP initiator is much more effective in preventing nonspecific adsorption of antibodies than polymer brushes grown from the conventional initiator. Finally, we confirmed these results with the quartz crystal microbalance (QCM) technique by quantitatively evaluating the adsorption of nonspecific IgG antibodies on DNP-PAA functionalized QCM surfaces. The use of this modified ATRP thiol initiator to chemically functionalize macro/microelectrode surfaces will help develop reproducible, reliable, and robust electrochemical biosensors with minimized nonspecific adsorption. [ABSTRACT FROM AUTHOR]

Environmentally benign supercritical carbon dioxide (scCO2) has been utilized as an “ecologically responsible” solvent for a wide variety of applications. However, nonpolar scCO2is generally a very poor solvent for polar polymers which limits its use as a processing solvent in high resolution photolithography. In this paper, we report the synthesis of fluorinated scCO2compatible additives and demonstrate their utility to help dissolve polar polymers in scCO2. We have designed and synthesized a series of quaternary ammonium salts (QAS) as scCO2additives. The ability of these salts to assist in the dissolution of model acidic and protected polar polymers has been compared. For our studies we have chosen three different polar reference polymers. Addition of millimolar quantities of the QAS to the scCO2solvent helped to dissolve the protected model polymer under moderate supercritical conditions. To explicitly investigate the interactions between the QAS additive and the various functionalities on the polymers we have carried out computational simulations using a fully atomistic force field adapted from optimized potentials for liquid simulations (OPLS). These studies combining both theory and experiment showed that the architecture of the cation and the basic nature and size of the anion are crucial in designing more efficient additives. Finally, on the basis of these findings we report the lithographic evaluation of a standard commercially available polymer photoresist using an appropriate scCO2compatible QAS additive after development in scCO2. Well-resolved, negative-tone patterns as small as 100 nm were obtained by e-beam exposure, indicating the excellent potential of using scCO2as the processing solvent in the presence of the QAS additives to form high-resolution structures. [ABSTRACT FROM AUTHOR]