A Trachea‐Inspired Bifurcated Microfilter Capturing Viable Circulating Tumor Cells via Altered Biophysical Properties as Measured by Atomic Force Microscopy

Abstract

Circulating tumor cells (CTCs), though exceedingly rare in the blood, are nonetheless becoming increasingly important in cancer diagnostics. Despite this keen interest and the growing number of potential clinical applications, there has been limited success in developing a CTC isolation platform that simultaneously optimizes recovery rates, purity, and cell compatibility. Herein, a novel tracheal carina-inspired bifurcated (TRAB) microfilter system is reported, which uses an optimal filter gap size satisfying both 100% theoretical recovery rate and purity, as determined by biomechanical analysis and fluid-structure interaction (FSI) simulations. Biomechanical properties are also used to clearly discriminate between cancer cells and leukocytes, whereby cancer cells are selectively bound to melamine microbeads, which increase the size and stiffness of these cells. Nanoindentation experiments are conducted to measure the stiffness of leukocytes as compared to the microbead-conjugated cancer cells, with these parameters then being used in FSI analyses to optimize the filter gap size. The simulation results show that given a flow rate of 100 μL min(-1), an 8 μm filter gap optimizes the recovery rate and purity. MCF-7 breast cancer cells with solid microbeads are spiked into 3 mL of whole blood and, by using this flow rate along with the optimized microfilter dimensions, the cell mixture passes through the TRAB filter, which achieves a recovery rate of 93% and purity of 59%. Regarding cell compatibility, it is verified that the isolation procedure does not adversely affect cell viability, thus also confirming that the re-collected cancer cells can be cultured for up to 8 days. This work demonstrates a CTC isolation technology platform that optimizes high recovery rates and cell purity while also providing a framework for functional cell studies, potentially enabling even more sensitive and specific cancer diagnostics.

The Selection Strategy for Circulating Tumor Cells (CTCs) Isolation and Enumeration: Technical Features, Methods, and Clinical Applications

“…Similar positive findings by size-based CTC isolation were reported in melanoma [162][163][164], gastric cancer [76,165], prostate cancer [166,167], lung cancer [168][169][170], pancreatic cancer [103], liver cancer [127], sarcoma [171], and breast cancer [172]. Separation by physical properties, i.e., gravity, density gradients, using microfluidic technology [45,46,56,60,[173][174][175][176][177][178][179][180][181][182][183][184][185][186], or microfiltration [53,172,187,188] were also reported to be able to capture CTCs efficiently.…”

Microslit on a chip: A simplified filter to capture circulating tumor cells enlarged with microbeads

“…Also, there is less chance that a CTC will slip through the filter. Simulations showed that the fluidic pressure was almost 10 times less exerted in the microslit approach (Fig 4A) when comparing to a filter with 8 μm gaps spaced 100 μm apart (Fig 4B), which was modeled with similar geometry condition of the previous filter studies [23, 24]. In addition, as the number of captured cells increases, the tendency was not changed and more pressure increase on the cell membrane was exhibited in the filter type (Fig 4C and 4D).…”

Recent advances in microfluidic cell sorting techniques based on both physical and biochemical principles

“…In addition to size amplification, binding microparticles to cancer cells may also increase the stiffness of these cells, which has been confirmed by using the atomic force microscopy nanoindentation . Based on this principle, a tracheal carina‐inspired bifurcated microfilter and a Parsortix™‐like trapping pillar array were employed to isolate MCF‐7 cells coated with immunoparticles from whole blood samples with high efficiency and purity. To facilitate the labeling processes of CTCs, a microfluidic mixer composed of wavy ducts with sharp‐edged turns was fabricated to generate Taylor–Gortler vortex flows, which improve the interactions between cancer cells and anti‐EpCAM conjugated microbeads .…”