Recently developed methods for constructing protein biosensors can be categorized broadly into two types: (i) monolithic
three-dimensional (3D) surfaces with a large amount of immobilization sites, such as carboxymethylated dextran [2,3], polymer
brushes formed by surface initiated polymerization [4,5], and other hydrogel-based surfaces [6–10], and (ii) 3D surfaces fabricated with
micro/nano-structures to regulate the accessibility of immobilized
proteins. The 3D surfaces based on polymer matrices could dramatically increase the protein immobilization density by providing a
large amount ofbinding sites owing to their 3D architecture.