CelLEVITAS: Label-free rapid sorting and enrichment of live cells via magnetic levitation

Abstract

Sorting methods that remove non-viable cells and debris, while retaining a high yield of viable cells, are crucial for many applications in biotechnology, genomics, tissue engineering and medicine. However, a significant challenge is gentle sorting of these different cell states based on very minute differences in density and magnetic signatures, without relying on any labels, tags or markers. Here, a new magnetic levitation-based technology, CelLEVITAS, is developed for the label-free sorting and enrichment of live cells. This work reports the first use of magnetic levitation for sorting of viable and non-viable cells within a microfluidic device and demonstrates extremely effective removal of dead cells and debris from heterogeneous samples. First, the levitation conditions for separating viable and non-viable cells under a magnetic field were fine-tuned. Levitation trajectories of live and dead cell states were then monitored in real-time, as cells magnetically focused to their corresponding levitation bands. CelLEVITAS successfully sorted and enriched live cells from a variety of input cell concentrations (100-200,000 cells/mL) and a variety of input purities (10-50%) into consistently high output purities (>80%). This method is sensitive, does not impair cell viability during sorting, and significantly increases the input sample viability up to 7-fold. Overall, this new magnetic levitation-based sorting strategy drastically reduces the processing time to a single-step, 30-minute sorting protocol and eliminates the manual pre-processing and labeling steps that are required for traditional flow cytometry techniques.

Magnetic Levitation and Sorting of Neoplastic Circulating Cell Hybrids

“…Compared to the murine hybrid cell line, mPBMCs had a lower levitation height at all the paramagnetic conditions tested (Figure 3a-c). mPBMC levitation heights also correlated with changes in the paramagnetic medium concentration, consistent with previous experiments and literature [21][22][23][24][25] . For instance, the average levitation height of mPBMCs cells was 226  58 m at 30 mM paramagnetic media (Figure 3a), and their heights increased to 295  75 m (Figure 3b) and 400  84 m (Figure 3c), at 50 mM and 80 mM paramagnetic media, respectively.…”

“…For instance, the average levitation height of mPBMCs cells was 226 ± 58 μm at 30 mM paramagnetic media ( Figure 3a ), and their heights increased to 295 ± 75 μm ( Figure 3b ) and 400 ± 84 μm ( Figure 3c ), at 50 mM and 80 mM paramagnetic media, respectively. According to the literature, dead cells or cell debris have a higher density compared to the live cells, thus they levitate at lower positions in the magnetic levitation system 21,23 . For all the samples tested, the wider distribution of mPBMCs relative to the freshly CHC population could be a result of dead cells or cell debris generated from the freeze thawing process during sample preparation.…”

“…The magnetic levitation device consists of laser-cut pieces of polymethyl methacrylate (PMMA), two permanent N52 neodymium bar magnets (K&J Magnetics) with the same poles facing each other, and custom-made mirrors [21][22][23][24] . A channel (1 mm in height) was placed between the magnets for static measurements.…”

Investigating influences of intravenous fluids on HUVEC and U937 monocyte cell lines using the magnetic levitation method

“…In particular, for critically ill patients, increased endothelial permeability, the existence of capillary leakage, blood volume expansion, or limited oxygen delivery might complicate treatment outcomes. 33–40 Hence, further investigations should be performed to clarify the cell-type-dependent influences of IV fluids.…”