23rd May 2017

AptaBasics: Aptamer Selection

At Aptamer Group we can select and identify novel aptamers to specific targets in as little as 12 weeks. To select an aptamer we screen our aptamer library of about 1015 molecules, isolating monoclonal aptamers with the required affinity and selectivity for the customer nominated target of interest.

The selection process begins when the target molecule is introduced to the aptamer library. The solution is incubated to allow aptamer-target complexes to form. After this, bound and unbound aptamers are separated. The bound aptamers are then eluted from the target and amplified. This cycle is repeated, reducing the number of aptamers present and leaving only the best suited aptamers.

A diagram illustrating the cycle that aptamer selection goes through.

The aptamer selection cycle.

As the selection rounds progress the number of different aptamers present reduces as they compete to bind to the target. Depending on the size of the target molecule, it may be possible for multiple aptamers to bind to a single target. Because of this we adjust conditions to optimise selection.

As aptamer selection progresses, stringency measures are introduced to help reduce the diversity of the pool and increase the specificity of the remaining aptamers. The conditions of the solution which the aptamer and target are in can significantly affect ligand binding. We use the matrix conditions of the intended end application to influence the measures that are introduced during selection.

 

In the later rounds we can introduce counter-selection to ensure that the aptamer is specific to the customer target requirements. Counter-selection provides the opportunity to monitor aptamer binding to either closely related species or to components of the matrix that will be present in the end-use situation for the aptamer.

Next week we have a case study showing how our aptamer selection can differentiate between two very closely related molecules.

If you want to discuss aptamer selection for you and your work please call 01904 567 790 or email info@aptamergroup.co.uk