A Review on Synthetic Receptors for Bioparticle Detection Created by Surface-Imprinting Techniques-From Principles to Applications

The strong affinity of biological receptors for their targets has been studied for many years. Noncovalent interactions between these natural recognition elements and their ligands form the basis for a broad range of biosensor applications. Although these sensing platforms are usually appreciably sensitive and selective, certain drawbacks are associated with biological receptors under nonphysiological conditions in terms of temperature, pH, or ionic strength. Therefore, there are considerable efforts to mimic such molecular interactions with robust, synthetic receptors. Molecular imprinting is the best-known technique to obtain antibody mimics by synthesizing a polymer matrix in the presence of a template species, such as molecules or larger aggregates. Extraction of the template results in sterically and functionally adapted binding cavities in or on a porous matrix. Although in principle possible, the detection of larger bioparticles such as proteins, microorganisms, or cells remains challenging when using the classical MIP concept. To tackle inherent difficulties, extending the concept of molecular imprinting toward surface imprinting is a promising approach: Here, binding cavities are formed directly on the surface of a cross linked polymer layer, thus facilitating the removal of the templates. This article reviews the main surface-imprinting techniques and focuses on the implementation of surface-imprinted polymers (SIPS) into various biomimetic sensors and related applications. In addition, we provide an outlook on emerging research on surface imprinting and the development of biomimetic tools for diagnostic purposes.