Aptamers

MeBioS Biosensors: Aptamer Research

In the last decade, synthetic ssDNA and RNA sequences known as aptamers have been used as biorecognition molecules for biosensor applications. Due to the specific 3D-folding of different sequences, aptamers are able to detect a wide range of targets. The ‘key-to-lock’ binding mechanism resembles the capture strategy of antibodies. Aptamers have some distinct advantages over antibodies, including the ease and low cost of production, the simplicity of chemical modification and their resistance to denaturation and degradation.

Conventionally, aptamers are selected from synthesis nucleic acid library using SELEX (Systematic Evolution of Ligands by Exponential enrichment) process. Briefly, a ssDNA or RNA pool with 10¹⁴ different sequences is incubated with targets. Some of the sequences will show affinity towards the target and form a complex. These bound sequences are selected by column chromatography or by filtration and then PCR amplified to generate a new enriched pool for further selection rounds. In general, 8 -15 rounds of affinity selection are needed to obtain aptamers with high affinity and selectivity.

A new trend in the aptamer research is the use of capillary electrophoresis (CE) as an alternative selection method to perform SELEX. In this new method, which is also called CE-SELEX, a mixture of ssDNA and targets is incubated and then injected onto a small separating column of the CE. The bound sequences are separated from unbound sequences under high voltage. The big advantages of CE-SELEX over the conventional SELEX are that this method provides very strong power of separation and selections are carried out in free solution, thus reducing the non-specific binding introduced by stationary support. This is why this new method is now profoundly investigated at our MeBioS Biosensor group.

We believe that rigorously selected aptamers are perfectly suited as biorecognition molecules in the development of so-called aptasensors. These aptasensors can then be utilized for a whole range of analytical applications, ranging from food quality and safety to medical diagnostics.