Modular Assembly of Cell-targeting Devices Based on an Uncommon G-quadruplex Aptamer.

Aptamers are valuable tools that provide great potential to develop cost-effective diagnostics and therapies in the biomedical field. Here, we report a novel DNA aptamer that folds into an unconventional G-quadruplex structure able to recognize and enter specifically into human Burkitt's lymphoma cells. We further optimized this aptamer to a highly versatile and stable minimized version. The minimized aptamer can be easily equipped with different functionalities like quantum dots, organic dyes, or even a second different aptamer domain yielding a bi-paratopic aptamer. Although the target molecule of the aptamer remains unknown, our microscopy and pharmacological studies revealed that the aptamer hijacks the clathrin-mediated endocytosis pathway for its cellular internalization. We conclude that this novel class of aptamers can be used as a modular tool to specifically deliver different cargoes into malignant cells. This work provides a thorough characterization of the aptamer and we expect that our strategy will pave the path for future therapeutic applications.

Capture and Release (CaR): a simplified procedure for one-tube isolation and concentration of single-stranded DNA during SELEX.

Short biotinylated oligodeoxynucleotides immobilized on streptavidin-coated magnetic beads allow for convenient and rapid purification of single-stranded oligodeoxynucleotides from crude asymmetric PCR mixtures, facilitating the selection of DNA aptamers.

Light-controlled tools.

Spatial and temporal control over chemical and biological processes plays a key role in life, where the whole is often much more than the sum of its parts. Quite trivially, the molecules of a cell do not form a living system if they are only arranged in a random fashion. If we want to understand these relationships and especially the problems arising from malfunction, tools are necessary that allow us to design sophisticated experiments that address these questions. Highly valuable in this respect are external triggers that enable us to precisely determine where, when, and to what extent a process is started or stopped. Light is an ideal external trigger: It is highly selective and if applied correctly also harmless. It can be generated and manipulated with well-established techniques, and many ways exist to apply light to living systems--from cells to higher organisms. This Review will focus on developments over the last six years and includes discussions on the underlying technologies as well as their applications.

Label-free impedimetric aptasensor for lysozyme detection based on carbon nanotube-modified screen-printed electrodes.

We report on the direct electrochemical detection of aptamer-protein interactions, namely between a DNA aptamer and lysozyme (LYS) based on electrochemical impedance spectroscopy (EIS) technique. First, the affinity of the aptamer to LYS and control proteins was presented by using filter retention assay. An amino-modified version of the DNA aptamer-recognizing lysozyme was covalently immobilized on the surface of multiwalled carbon nanotube-modified screen-printed electrodes (MWCNT-SPEs), which were employed for measurements and have improved properties compared with bare SPEs. This carbon nanotube setup enabled the reliable monitoring of the interaction of lysozyme with its cognate aptamer by EIS transduction of the resistance to charge transfer (R(ct)) in the presence of 2.5 mM [Fe(CN)6]³â»/4⁻. This assay system provides a means for the label-free, concentration-dependent, and selective detection of lysozyme with an observed detection limit of 12.09 µg/ml (equal to 862 nM).

Plug and play with RNA.

Retooling RNA: RNA aptamers are high-affinity ligands that can be assembled with other structures to yield multivalent molecules. These properties have been addressed in two recent studies: One describes a GFP-like RNA reporter used to study the dynamics of endogenous RNA; the other study reports on an aptamer-templated assembly of multi-enzyme complexes in bacteria for the controlled production of secondary molecules (see picture).