Top-down synthesis of versatile polyaspartamide linkers for single-step protein conjugation to materials

Materials used in various biological applications are often modified with proteins to regulate biomolecular and cellular adhesion. Conventional strategies of protein conjugation accompany monovalent bifunctional protein linkers, which present several limitations in molecular synthesis and protein conjugation. Herein, we present a new strategy of preparing multivalent polyaspartamide linkers in a simple top-down manner, and also demonstrate that the resulting polymer linkers allow us to readily conjugate proteins to both organic and inorganic materials. The top-down synthesis of polyaspartamide linkers was performed by partially opening succinimidyl ring moieties of polysuccinimide (PSI) with the controlled number of nucleophiles reactive to photo-cross-linked hydrogel or gold-coated inorganic materials: (1) Poly(2-hydroxyethyl-co-2-methacryloxyethyl aspartamide) (PHMAA) presenting methacrylate was used to micropattern fibronectin or collagen on a hydrogel in order to regulate cell adhesion and growth area on a micrometer scale. (2) Poly(2-hydroxyethyl-co-2-mercaptoethyl aspartamide) (PHMCA) presenting thiol functional groups was used to link fibronectin to a gold-coated silicon microelectromechanical probe designed to measure cell traction force. Overall, these multivalent polyaspartamide protein linkers will greatly assist efforts to analyze and regulate the cellular adhesion to and phenotypic activities of a wide array of substrates and devices.