(622a) Self-Assembly of Antibody-Polymer Conjugates into Novel Sensing Materials

Affinity biosensors based on antibody binding represent one of the most successful and widely investigated categories of protein materials, having yielded technologies as ubiquitous in the US today as home pregnancy tests and often forming the basis for efforts at the development of low cost diagnostics. The sensitivity of these materials is fundamentally limited by the density of binding sites on the material surface, with the possibility of an order of magnitude boost in sensitivity of a transformative increase in surface binding sites could be achieved.

Here, we show that such an increase in binding sites can be achieved through antibody self-assembly into three-dimensional nanostructured materials. Using a site-selective chemistry, bioconjguates are prepared of IgG antibody with the synthetic polymer poly(N-isopropylacrylamide) (PNIPAM). Lyotropic self-assembly of the materials leads to the formation of large lamellar nanostructures that can be observed by both X-ray scattering and transmission electron microscopy. Studies of the self-assembly as a function of bioconjguate concentration and polymer length provide insight into the phase behavior of the system. This is the first such demonstration of antibody self-assembly into large structured arrays.

Using a simple flow coating and crosslinking process, the antibody bioconjguates can be immobilized in nanostructured thin films on different substrates. These films show a 3-4 times higher capacity for protein G binding than adsorbed antibody monolayers. As the size of the binding protein is increased, however, the difference is reduced, presumably because the large binder has trouble penetrating the polymer channels within the protein nanostructure, indicating a need for additional engineering of nanostructure size and transport rates. In addition to this, ongoing work is focusing on developing protein materials from smaller engineered protein binders such as nanobodies.