Is a real-time quantifiable liquid biopsy achievable using a microfluidic lab-on-chip ?

Abstract

An increasingly relevant functional measurement is a liquid biopsy to assist in the diagnosis of cancers. The existing approach for liquid biopsy is to utilize microfluidic chips for the isolation of circulating tumor cells (CTCs) or exosomes or extracellular vesicles (EV) from patient samples, and then for the analysis of the cargo contained inside the CTCs, exosomes or EVs. However, such an analysis does not provide a real-time liquid biopsy, since there is a long delay between the time of sample collection and the results from the analysis. Microfluidic chip-formats also provide the capability to mimic tissue functions from the analysis of small numbers of cells cultured in the chip. Analysis of the secreted molecules from such cells could provide a measurement of the secretome, which could be analogous to a liquid biopsy. A 3D structural organization of cells in microfluidic chips is usually in the form of organoids or spheroids. The analysis of organoids or spheroids is well-adapted for immunohistochemistry or ELISA-type identification of surface markers, but not for real-time analysis of secreted molecules since the fluid and molecules in the interior volume of the organoid or spheroid is not accessible in real-time. We have recently proposed an alternative novel design for a microfluidic chip format comprising 3D micro-niches that provide a real-time analysis of secretions produced directly from small numbers of cells. The microfluidic chip with 3D micro-niches then analyses the secretions from these monolayers in real-time (“secretome”). The microfluidic chip includes electronic biosensors that provide real-time measurement of secreted molecules. This short review concludes with a proposition for the means to utilize this novel microfluidic chip to function as a real-time and quantifiable diagnostic screening device to differentiate cancerous cells from healthy cells.