New polymeric biomaterial interfaces for biosensor applications

Abstract

To fabricate living cell-based immunological sensors, we have examined two PEO-based biomaterials that can be patterned to generate cellular array templates: poly(allylamine)-g- poly(ethylene glycol) graft-copolymer and poly(ethylene glycol) dimethacrylate hydrogel. Poly(allylamine)-g-poly(ethylene glycol) polycation graft-copolymers were designed, synthesized, and characterized in order to combine bio-functionality with patternability on charged polyelectrolyte multilayer surfaces. Polymer-on-polymer stamping (POPS) techniques were used to create micron scale patterned regions on negatively charged multilayer surfaces via direct stamping of these graft copolymers. The long PEG side chains effectively resisted adsorption of antibodies or other proteins, and created a bio-inert area when patterned by POPS. On the other hand, desired proteins can be covalently attached to the graft copolymer by introducing proper coupling agents. Arrays of proteins were produced by either simple adsorption or coupling of proteins onto the graft copolymer patterned surfaces. The protein arrays were utilized as templates in fabricating cellular arrays of non-adherent B cells.

(cont.) Poly(ethylene glycol) dimethacrylate hydrogel precursors were photopolymerized into 3D rmicrowell array templates via micromolding. After the floors of microwells were decorated with antibodies, hydrogel microwell array templates were employed in fabrication of cellular arrays. The topology of microwells facilitates the positioning of cells inside microwells and improves the binding stability of cells with protection from mechanical agitations. T cell arrays fabricated on hydrogel microwell array templates were tested as living cell- based immunological sensors. B cells were settled uniformly on T cell arrays to establish contacts between B and T cells over a large area. A level of T cell activation by target peptides were quantified using calcium sensitive fura dyes. A large set of individual T cell response data was acquired from a single T cell array and utilized to obtain average dose-response behavior of T cells. Average T cell responses were suitable as quantitative signal of a living cell-based immunological sensor. In addition, a potential application of T cell arrays in high throughput assay of individual T cell responses was investigated.

(cont.) Analysis of calcium oscillation frequency of individual T cells revealed that there is no clear correlation of calcium oscillation frequency with target peptide dose in this experiment.