Continuous organelle separation in an insulator‐based dielectrophoretic device

Abstract

Heterogeneity in organelle size has been associated with devastating human maladies such as neurodegenerative diseases or cancer. Therefore, assessing the size‐based subpopulation of organelles is imperative to understand the biomolecular foundations of these diseases. Here, we demonstrated a ratchet migration mechanism using insulator‐based dielectrophoresis in conjunction with a continuous flow component that allows the size‐based separation of submicrometer particles. The ratchet mechanism was realized in a microfluidic device exhibiting an array of insulating posts, tailoring electrokinetic and dielectrophoretic transport. A numerical model was developed to elucidate the particle migration and the size‐based separation in various conditions. Experimentally, the size‐based separation of a mixture of polystyrene beads (0.28 and 0.87 μ$\umu $m) was accomplished demonstrating good agreement with the numerical model. Furthermore, the size‐based separation of mitochondria was investigated using a mitochondria mixture isolated from HepG2 cells and HepG2 cells carrying the gene Mfn‐1 knocked out, indicating distinct size‐related migration behavior. With the presented continuous flow separation device, larger amounts of fractionated organelles can be collected in the future allowing access to the biomolecular signature of mitochondria subpopulations differing in size.

Fine-Tuning the Characteristic of the Applied Potential To Improve AC-iEK Separations of Microparticles

“…On the AC hand, numerous reports exist on the use of electrode-based microsystemsalso known as electrode-based dielectrophoresis (eDEP)and AC fields, where the characteristics of the applied electrical voltages are varied . There are several reports on the use of AC electric fields in iEK systems, where separation mechanisms like absolute negative mobility (ANM), deterministic ANM, and deterministic ratchet migration , were used to demonstrate size-based separation of micron and submicron sized particles. However, there are very few reports on the use of low-frequency AC voltages in iEK systems. ,,,, Even in these studies, the effect of fine-tuning the different control parameters of the AC input voltage on the separation of similar particles or bioanalytes has not been investigated.…”

Numerical modeling reveals improved organelle separation for dielectrophoretic ratchet migration

“…The properties of Drp and Mfn relevant to the numerical model were their size and the EK mobility [42, 47]. The average sizes of Drp and Mfn were 1.82 and 0.62 µm, respectively.…”

“…The size was measured by dynamic light scattering using a Zetasizer Ultra instrument (Malvern Panalytical Inc.). The measured EK mobilities of Drp and Mfn were $$ - {\mathrm{\;}}5.34{\mathrm{\;}} \times {\mathrm{\;}}{10^{ - 9}}{\mathrm{\;}}$$and $$ - {\mathrm{\;}}2.39{\mathrm{\;}} \times {\mathrm{\;}}{10^{ - 9}}{\mathrm{\;}}{{\mathrm{m}}^2}/({\mathrm{V\;s}}$$), respectively, as the EK mobility was previously obtained from the migration velocity of mitochondria in a microfluidic platform with identical surface properties in the same buffer solution [42].…”

“…However, the continuous flow injection in the ratchet device for processing larger sample volumes has its limitations. When the pressure‐driven flow was dominating over the EK forces in the ratchet migration, the separation efficiency ( P , following our previous nomenclature)—a measure of how effectively a mixture of particles based on size is separated—was significantly reduced and affected the purity with which organelle subpopulations can be collected [42]. This phenomenon was observed at flow rates larger than 20 nL/min [42, 43].…”

Catalytic activity of glucose oxidase after dielectrophoretic immobilization on nanoelectrodes

“…DEP can be used to manipulate, classify, and sort cells [1]. Recently, more and more examples of DEP with smaller objects have been presented, for example, the separation of organelles [2] or the immobilization of virus particles [3] and even small dye molecules [4]. Proteins are also an interesting object for DEP, as there are many promising applications for DEP in protein separation, analysis or patterning and in biosensing [5,6].…”