Acoustofluidic Separation of Proteins Using Aptamer-Functionalized Microparticles

Abstract

We propose an acoustofluidic method for the triseparation of proteins conjugated with aptamer-coated microparticles inside a microchannel. Traveling surface acoustic waves (TSAWs) produced from a slanted-finger interdigital transducer (SFIT) are used to separate the protein-loaded microparticles of different sizes via the TSAW-driven acoustic radiation force (ARF). The acoustofluidic device consists of an SFIT deposited onto a piezoelectric lithium niobate substrate and a polydimethylsiloxane (PDMS) microfluidic channel on top of the substrate. The TSAWs propagating on the substrate penetrate into the sample fluid flow, where the human protein-conjugated microparticles are suspended, inside the PDMS microchannel. The microparticles are subjected to the TSAW-driven ARF with varying magnitude depending on their size and thus flow along different streamlines, leading to triseparation of the proteins. In this work, we used two different-sized streptavidin-functionalized polystyrene (PS) microparticles to capture two kinds of aptamers (apt15 and aptD17.4), which were labeled with a respective biotin molecule at one end. The biotin ends of the aptamers were attached to the microparticles through streptavidin–biotin linkage, whereas the free ends of the aptamers were used to capture their target proteins of thrombin (th) and immunoglobulin E (IgE). The resultant PS–apt15–th and PS–aptD17.4–IgE complexes, as well as mCardinal2, were used for experimental demonstration of acoustofluidic triseparation of the human proteins. We achieved simultaneous separation of proteins of three kinds (th, IgE, and mCardinal2) for the first time via the TSAW-driven ARF in the proposed acoustofluidic device.

Residue-free acoustofluidic manipulation of microparticles via removal of microchannel anechoic corner

“…As shown in Fig. 5 , the elastic PS microspheres experience the most significant acoustic radiation force induced by travelling surface acoustic wave at κ ≈ 1.5 [10] , [12] . Despite the Mie scattering off both 5 μm ( κ ≈ 1.25) and 6 μm ( κ ≈ 1.5) PS microspheres, the 6 μm particles experience a relatively higher ARF.…”

“…We have previously demonstrated sorting of microparticles in the rectangular microchannel by avoiding the MAC region with the help of a sheath flow [5] , [9] , [10] , [39] . Being aware of the possibility of particles being stuck in the MAC region during the sorting process, in this work, we have proposed a residue and MAC-free approach to more efficiently deflect particles and exchange medium around them.…”

“…Ultrasonic surface acoustic wave (SAW)-driven microfluidics has experienced an unprecedented growth over the last decade for precise control of microfluidic flows and micro/nano-objects [1] , [2] , [3] , examples of which are manipulation of micro/nano-particles [4] , [5] , [6] , cells [7] , droplet [8] , [9] , biomolecules [10] , [11] , microorganisms [12] , [7] , and mixing [13] , [14] , [15] , pumping [16] , [17] , and atomization [18] , [19] of the fluids. In SAW-based acoustofluidic devices, SAWs are produced from an interdigital transducer (IDT) patterned on a piezoelectric substrate due to the inverse-piezoelectric effect when an alternating current (AC) signal with a resonant frequency is applied to the IDT.…”

Recent advances in acoustofluidic separation technology in biology

“…Reproduced from ref. 99 with permission from the American Chemistry Society. c Exosome separation from plasma samples using a multistage acoustofluidic device.…”

“…Afzal et al proposed an SIDT-generated TSAW device to separate three different types of proteins simultaneously based on the selective capture of proteins using aptamer-coated microparticles of different sizes (Fig. 6b ) 99 . Thrombin and IgE proteins were captured by two types of PS microparticles coated with apt15 and aptD17.4, respectively, while mCardinal2 proteins were unbound.…”