In the presence of a template, desmetryn, commercial porous polypropylene membranes were photografted, using benzophenone as photoinitiator, with the functional monomer 2-acrylamido-2-methylpropanesulfonic acid and the cross-linker N,N′-methylenebis(acrylamide) in water. The influence of the polymerization conditions on membrane properties was studied by solute sorption analyses and membrane permeability measurements as well as electron spectroscopy for chemical analysis, FTIR spectroscopy, BET analysis, and scanning electron microscopy. It was found that molecularly imprinted polymer (MIP) membranes can be obtained which possess group affinity for the template and other triazine herbicides. Remarkably, the MIP membrane affinity for the template in buffer solution can be improved by the presence of salt during photograft copolymerization. This work presents the first successful example for molecular imprinting by in situ polymerization in water and on the surface of a commercially available synthetic polymer. The novel MIP membranes can be used in a fast preconcentration step, solid-phase extraction, by a simple microfiltration for the determination of herbicides in water. The possibility to introduce specific binding sites into porous membranes by surface imprinting polymerization without reducing their high permeabilities opens a general way to design new high-performance affinity membranes.

The amount of grafted poly(acrylic acid) on poly(methyl methacrylate) micro- and nanoparticles was quantified by conductometry, (13)C solid-state NMR, fluorophore labeling, a supramolecular assay based on high-affinity binding of cucurbit[7]uril, and two colorimetric assays based on toluidine blue and nickel complexation by pyrocatechol violet. The methods were thoroughly validated and compared with respect to reproducibility, sensitivity, and ease of use. The results demonstrate that only a small but constant fraction of the surface functional groups is accessible to covalent surface derivatization independently of the total number of surface functional groups, and different contributing factors are discussed that determine the number of probe molecules which can be bound to the polymer surface. The fluorophore labeling approach was modified to exclude artifacts due to fluorescence quenching, but absolute quantum yield measurements still indicate a major uncertainty in routine fluorescence-based surface group quantifications, which is directly relevant for biochemical assays and medical diagnostics. Comparison with results from protein labeling with streptavidin suggests a porous network of poly(acrylic acid) chains on the particle surface, which allows diffusion of small molecules (cutoff between 1.6 and 6.5 nm) into the network.

Hydrogels play an important role in the field of biomedical research and diagnostic medicine. They are emerging as a powerful tool in the context of bioanalytical assays and biosensing. In this context, this review gives an overview of different hydrogels and the role they adopt in a range of applications. Not only are hydrogels beneficial for the immobilization and embedding of biomolecules, but they are also used as responsive material, as wearable devices, or as functional material. In particular, the scientific and technical progress during the last decade is discussed. The newest hydrogel types, their synthesis, and many applications are presented. Advantages and performance improvements are described, along with their limitations.

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