Real-Time Detection of Tumor Cells during Capture on a Filter Element Significantly Enhancing Detection Rate

Abstract

Circulating tumor cells (CTCs) that enter the bloodstream play an important role in the formation of metastases. The prognostic significance of CTCs as biomarkers obtained from liquid biopsies is intensively investigated and requires accurate methods for quantification. The purpose of this study was the capture of CTCs on an optically accessible surface for real-time quantification. A filtration device was fabricated from a transparent material so that capturing of cells could be observed microscopically. Blood samples were spiked with stained tumor cells and the sample was filtrated using a porous structure with pore sizes of 7.4 µm. The possible removal of lysed erythrocytes and the retention of CTCs were assessed. The filtration process was observed in real-time using fluorescence microscopy, whereby arriving cells were counted in order to determine the number of CTCs present in the blood. Through optimization of the microfluidic channel design, the cell retention rate could be increased by 13% (from 76% ± 7% to 89% ± 5%). Providing the possibility for real-time detection significantly improved quantification efficiency even for the smallest cells evaluated. While end-point evaluation resulted in a detection rate of 63% ± 3% of the spiked cells, real-time evaluation led to an increase of 21% to 84% ± 4%. The established protocol provides an advantageous and efficient method for integration of fully automated sample preparation and CTC quantification into a lab-on-a-chip system.

Bio-Impedance Spectroscopy of Retained Cells Using a Micro-Perforated Sensing Membrane Filtrating Whole Blood Samples under High Flowrate

“…Previous studies published in the field of blood filtration focus on the complete recovery of the targeted biomarker with the aim of increasing the throughput by parallelizing devices. However, the scalability of these systems is questionable, as the size of the microfluidic systems is often tightly correlated to their capture efficiency [31,32]. Our approach to filtration significantly differs from this concept by focusing on a high-flow rate device combined with the use of electrical cell detection that does not require any extensive parallelization, thus alleviating scalability issues.…”