|Title||Magnetically Responsive Negative Acoustic Contrast Microparticles for Bioanalytical Applications|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||Ohiri, KA, Evans, BA, C Shields, IV, W, Gutierrez, RA, Carroll, NJ, Yellen, BB, López, GP|
|Journal||Applied Materials & Interfaces|
Separation with biofunctional magnetic beads is the current gold standard for the capture, isolation, and downstream manipulation of many target analytes because of their ease-of-use and prevalence. This well-understood approach has had far-reaching implications in a variety of research efforts, including positive and negative selection strategies for debulking cellular suspensions,(1-4) establishing a platform for fundamental in vitro studies,(5) and the organization of single cells on magnetophoretic arrays.(6-9) Despite significant benefits such as low cost, ease of use, and broad applicability of magnetic manipulation, traditional magnetic separation relies on a single force that generally fails to robustly sort nonlabeled or weakly diamagnetic materials. This causes difficulty separating magnetic targets from each other (e.g., multiplex targeting, removal of unbound magnetic beads prior to cell culture) or from concentrated nonmagnetic solutions (e.g., whole blood separation).(10) Additionally, magnetic separation can lead to the entrainment of contaminating species into collection ports or a decrease in throughput of the separation mechanism. Acoustic separation, however, overcomes these limitations by applying a differential force on particles or cells in suspension based on their inherent mechanical properties, or acoustic contrast factor. Consequently, we have engineered a new class of magnetic, negative acoustic contrast particles (mNACPs), Figure 1a) that undergo positive magnetophoresis (Figure 1b) and negative acoustophoresis(11, 12) (i.e., by migrating to the pressure antinodes of a standing wave) in water (Figure 1c). These particles enable new combinations of acoustic and magnetic manipulation for microfluidic separations, assays, and other applications such as colloidal assembly.