Velocity valleys enable efficient capture and spatial sorting of nanoparticle-bound cancer cells

Abstract

The development of strategies for isolating rare cells from complex matrices like blood is important for a wide variety of applications including the analysis of bloodborne cancer cells, infectious pathogens, and prenatal testing. Due to their high colloidal stability and surface-to-volume ratio, antibody-coated magnetic nanoparticles are excellent labels for cellular surface markers. Unfortunately, capture of nanoparticle-bound cells at practical flow rates is challenging due to the small volume, and thus low magnetic susceptibility, of magnetic nanoparticles. We have developed a means to capture nanoparticle-labeled cells using microstructures which create pockets of locally low linear velocity, termed velocity valleys. Cells that enter a velocity valley slow down momentarily, allowing the magnetic force to overcome the reduced drag force and trap the cells. Here, we describe a model for this mechanism of cell capture and use this model to guide the rational design of a device that efficiently captures rare cells and sorts them according to surface expression in complex matrices with greater than 10,000-fold specificity. By analysing the magnetic and drag forces on a cell, we calculate a threshold linear velocity for capture and relate this to the capture efficiency. We find that the addition of X-shaped microstructures enhances capture efficiency 5-fold compared to circular posts. By tuning the linear velocity, we capture cells with a 100-fold range of surface marker expression with near 100% efficiency and sort these cells into spatially distinct zones. By tuning the flow channel geometry, we reduce non-specific cell adhesion by 5-fold.

Profilierung zirkulierender Tumorzellen mit Apparaturen und Materialien der nächsten Generation

“…[83][84][85] CTCs,d ie mit magnetischen und mit anti-EpCAM-Antikçrpern beschichteten Nanopartikeln markiert sind, kçnnen entsprechend der Menge an einem Oberflächenantigen sortiert werden, von dem bekannt ist, dass es während der EMT abnimmt. Das Einfangen der Zellen mit Nanopartikeln funktioniert wegen der großen Zahl von Bindungsereignissen, die an der Oberfläche mçglich sind, gut;imkonkreten Fall stellt allerdings die geringe magnetische Suszeptibilität der Partikel eine Hürde dar.D aher wurden in den Chips X-fçrmige Mikrostrukturen erzeugt, durch die Regionen niedrigen Flusses entstehen (Abbildung 5B).…”

Materials and microfluidics: enabling the efficient isolation and analysis of circulating tumour cells

“…Whole blood, 114–118 RBC lysed blood, 117,118 or RBC lysed and WBC-depleted blood 117,119 was spiked with Ab-coated 114–116,118 or aptamer-coated 117,119 (discussed below) magnetic nanoparticles. The sample was infused through a series of microfluidic chambers, and an external magnetic field pulled both free magnetic nanoparticles and labelled CTCs onto the device surface.…”

“…This enabled selective recovery of CTCs with high EpCAM expression upstream and low EpCAM CTCs downstream. Comparatively, increasing chamber width incurred additional nonspecific artifacts, 116 while increasing chamber height could affect CTC recovery. 118 The magnetic ranking technology altered magnetic field strength to zonally select CTCs.…”

“…107 (C) A diagram of the Ephesia microfluidic technology, which aligns anti-EpCAM magnetic microbeads into solid supports for CTC isolation that can be released by removing the magnetic field. 33,60 (D) Velocity valley 114,116 and magnetic ranking 118 technologies for isolating magnetically labelled CTCs in zones of varying velocity or magnetic field strength, respectively, which provides phenotypic ranking of CTC antigen (e.g., EpCAM) expression in addition to enumeration. X-shaped microstructures reduce fluid velocity so magnetic forces can provide efficient CTC recovery.…”

Microfluidic Devices in the Fast‐Growing Domain of Single‐Cell Analysis

“…The magnetic nanoparticles attached to CTC were attracted to the channel bed and the other cells flow out. The CTCs in a similar fashion was isolated by Besant et al . However, these methods led to the aggregation of the isolated cells to the attracted site.…”