Molecules or coatings with high selectivities, as antibodies or enzymes, are of great importance in chemistry, diagnostics, 1, 2 and biology. 3 However, these natural receptors are expensive or difficult to produce. Furthermore, since they are biomolecules their lifetime and applicability is limited. 4 Molecular imprinting is one technique that was developed to overcome these limitations. To generate imprints with certain selectivity, a prepolymer is simply polymerized in the presence of the desired target molecule (see Figure 1). 5− 7 When the polymer is cured, two things happen simultaneously. First, functional groups in the prepolymer orient toward their counteracting partners in the template. This complex formation has been theoretically investigated in several articles. 8− 10 Second, the polymer is cross-linked, resulting in “freezing” the orientation of the functional groups. This orientation remains even when the template is removed. As a result, the remaining cavities reproduce size, shape, and surface chemistry of the template molecules. As a consequence, molecules of the template species will be incorporated preferentially later on.

The resulting polymers are promising, since they are relatively cheap, straightforward to make, and remarkably robust. 11 Additionally, due to the high number of different monomers that are commercially available (more than 4000 polymerizable compounds), 12 their properties can be tuned. During the last years, the field of molecular imprinting has grown rapidly and become very broad. However, there are still entirely new fields where imprinted polymers have been used just recently. While molecularly imprinted polymers with great selectivities have been synthesized for small molecules, 13 imprinting with large macromolecules remains challenging. 14 This review includes recent advances that have been made in this field, focusing on the discussion of similarities and differences of applications and requirements concerning the imprinted polymers. This encompasses a broad overview of the topic, using the most important or recent illustrative examples.