Circulating tumor cells (CTCs) are distinct cancer biomarkers established in clinical settings for early cancer detection, metastasis progression, and minimal residual disease (MRD) monitoring. Despite numerous advances, comprehensive molecular characterization of CTCs remains extremely challenging due to their rarity and heterogeneity.

Here, we present a novel cotton microfluidic substrate (CMS) as an innovative biomedical matrix that efficiently isolates CTCs while facilitating in vitro CTC expansion, enabling further downstream analysis of these rare cells. CMS enabled both static and dynamic isolation of cells from the MCF-7 cancer cell line, as well as from the blood of head and neck squamous cell carcinoma (HNSCC) patients. The cell capture efficiencies were further compared with the clinically regulated OncoDiscover® Liquid Biopsy Test.

Furthermore, CMS served as a matrix on which the captured cancer cells were grown into 3D tumor models to study anti-cancer drug efficacy and multi-drug resistance (MDR) mechanisms. The design of the CMS employed two different surface chemistries—flattened and nanostructured surfaces—each conjugated with anti-EpCAM antibodies to evaluate CTC capture efficiency and 3D tumor growth dynamics.

The nanostructured surface was highly efficient in capturing CTCs and promoted 3D tumor spheroid formation, showing a five-fold increase in size from day 3 to day 10 of culture. Moreover, when treated with the anti-cancer drug cisplatin, an almost half reduction in tumor size was achieved within 24 hours, followed by a cytostatic threshold and the eventual acquisition of drug resistance within three days.

Conclusively, the CMS matrix exhibits potential for the further development of “tissue-on-chip” and “point-of-care” medical devices in cancer diagnostics, as well as for evaluating chemotherapeutic efficacy in drug discovery and development.