EFFECT OF HYDROGEL NETWORK TOPOLOGY ON ANTIBODY- ANTIGEN BINDING AVIDITY

5There are fewer examples of highly specific stimuli-responsive gel materials. A hydrogel network that only responds in the presence of a specific biochemical marker would provide an enhanced degree of specificity and selectivity over traditional hydrogel materials. Model hydrogels that respond to a specific biochemical target have been studied; these materials typically take advantage of antibody-antigen binding, DNA-DNA complexation, or aptamer-aptamer interactions. 6-8 In most of these examples, gels are synthesized by copolymerization of an antibody- or aptamer-functionalized monomer with an acrylamide monomer, resulting in a random distribution of functionality throughout the polymer. Controlling the number and location of functional groups will allow for better measurement of the processes that govern gel formation/dissociation and will enable the formation of tailor-made gels by controlling the crosslink junction density and overall chain length. 9 Metal nanoparticles or star polymers can serve as the crosslink junction points within the gel network and can contain multiple functional groups per molecule, while end-functionalized poly(ethylene glycol) (PEG) chains can link these nanoparticles together. In this work, antibody-antigen binding interactions will be studied in order to determine how the binding avidity of polymer-tethered antibodies varies with increased or decreased junction point functionality. The resulting binding parameters can then be used to design highly selective target-responsive hydrogels. Experimental Materials and methods. All solvents and reagents were obtained from commercial sources and used as received unless otherwise stated. Functionalized linear and star poly(ethylene glycol)s were purchased from Nanocs. Prostaglandin E2 and anti-prostaglandin E2 were obtained from MP Biomedicals. Antibodies were reconstituted in phosphate buffer solution following packaged instructions to generate a stock solution. For surface functionalization, α-mercaptoundecyl-ω-amino poly(ethylene glycol) (HSPEG-NH2 Polymer Source, Mn = 2,400 g/mol) was used. Binding studies were carried out using a SensiQ biomolecular interaction analysis instrument (Nomadics, Inc.) equipped with unfunctionalized gold sensor chips. Buffer solutions and injection solutions were filtered and degassed prior to use.