Aptamers are artificial nucleic acid ligands, specifically generated against certain targets, such as amino acids, drugs, proteins or other molecules. In nature they exist as a nucleic acid based genetic regulatory element called a riboswitch. For generation of artificial ligands, they are isolated from combinatorial libraries of synthetic nucleic acid by exponential enrichment, via an in vitro iterative process of adsorption, recovery and reamplification known as systematic evolution of ligands by exponential enrichment (SELEX). Thanks to their unique characteristics and chemical structure, aptamers offer themselves as ideal candidates for use in analytical devices and techniques. Recent progress in the aptamer selection and incorporation of aptamers into molecular beacon structures will ensure the application of aptamers for functional and quantitative proteomics and high-throughput screening for drug discovery, as well as in various analytical applications. The properties of aptamers as well as recent developments in improved, time-efficient methods for their selection and stabilization are outlined. The use of these powerful molecular tools for analysis and the advantages they offer over existing affinity biocomponents are discussed. Finally the evolving use of aptamers in specific analytical applications such as chromatography, ELISA-type assays, biosensors and affinity PCR as well as current avenues of research and future perspectives conclude this review.

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We assembled multilayer films of glucose oxidase (GOx) and horseradish peroxidase (HRP) coimmobilized together with polyelectrolyte layers on the surface of silica microparticles. The influence of different polyelectrolyte combinations on the immobilization and functionality of the enzymes was examined for several multilayer configurations. Precomplexation of the enzymes with a polyvinylpyridine-based polyamine allowed the stable adsorption of enzyme layers without affecting their catalytic activity. The efficiency of the sequential reaction between GOx and HRP on the surface of the colloids was quantitatively analyzed and rationalized in terms of the kinetic parameters of both enzymes and the reaction-diffusion kinetics of the system. In the optimized configuration, with GOx and HRP coimmobilized in the same layer, the overall rate of hydrogen peroxide conversion was around 2.5 times higher than for GOx and HRP in separate layers or for equivalent amounts of both enzymes free in solution.

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