Microfluidic selection of aptamers using combined electrokinetic and hydrodynamic manipulation

This paper presents a microfluidic device that integrates the entire process of aptamer selection via bead-based biochemical in which affinity selected target-binding oligomers are electrokinetically transferred for amplification, while the amplification product is transferred back for affinity-selection via pressure-driven fluid flow. This hybrid oligomer manipulation leverages the advantages of both electrokinetic and pressure-driven oligomer manipulation by reducing the amount of flow control elements (e.g. valves) while avoiding exposure of the target to electric field induced, potentially structure altering, environmental conditions (e.g. pH). Efficient manipulation of reagents and reaction products is achieved through bead-based affinity selection and amplification, which, combined with hybrid transfer, allows integration of all steps of the SELEX process on a single chip. The microfluidic device is thus capable of closed-loop, multi-round aptamer enrichment without manual intervention or use of off-chip instruments, as demonstrated by selection of DNA aptamers against the protein IgE with high affinity (K_D = 12 nM) in a rapid manner (4 rounds in 10 hours).