Next-Generation Point-of-Care Cancer Detection: Bioelectronic Mapping of the Malignancy Spectrum

Abstract

Circulating tumor cells (CTCs) detach from primary tumors, enter the bloodstream, and contribute to disease progression through “metastasis”—the leading cause of cancer-related deaths. CTCs carry vital information about cancer progression; however, their capture and detection remain a major challenge for point-of-care (POC) cancer diagnostics, therapeutic monitoring, and prognostic assessment. This primarily arises from the lack of universal markers capable of isolating CTCs from blood and identifying their metastatic potential. In this work, we aim to advance next-generation POC cancer detection by developing a bioelectronic platform for mapping CTCs across their metastatic spectrum and establishing a novel core technology for their isolation and detection. To achieve this, we utilized in-vitro model of metastasis progression derived from the same cell lineage by varying the expression of Connexin 43 in MDA-MB-231 triple-negative breast cancer cells. In our work, via in-house developed single-cell force microscopy assay, we demonstrated that malignancy correlates with cellular biophysical properties. Highly malignant cells exhibited increased elasticity, cellular softening, and reduced adhesion forces up to ~150 nN, in contrary to cells with lower metastatic potential that showed cellular stiffening, viscous membrane character, and enhanced adhesion of ~350 nN, an almost 60% increase in adhesion strength. Notably, these differences were observed only when cells were in clusters, and the effect disappeared at single-cell state. A first of its kind measurement. Furthermore, we investigated real-time biomechanical responses to Docetaxel (DTX), a microtubule-targeting chemotherapeutic agent, across different metastatic states using Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). Treatment with 20 nM DTX increased cellular stiffness, with distinct response magnitudes and kinetics between the metastatic cell variants, which correlated with cell aggressiveness and malignancy levels. Additionally, we designed and fabricated a Dielectrophoretic Impedance Spectroscopy (DEPIS) array, with low-impedance and high-sensitivity using additive-manufacturing technology. This array was optimized through finite element analysis simulations to maximize efficiency for CTC capture and characterization in solution. Our results revealed an interplay between cancer cell biophysical and dielectric properties, which correlate with their metastatic states. Highly metastatic cells displayed membrane capacitances of 16.88 ± 3.24 mF m−2, higher than those of less metastatic subtypes with membrane capacitances below 14.3 ± 2.54 mF m−2. These capacitance variations corresponded to distinct crossover frequencies—an essential metric for cell sorting. Additionally, impedance measurements at 1 kHz revealed significant differences in double-layer capacitance among the metastatic subgroups, highlighting DEPIS as a non-invasive and rapid tool for CTC sorting, capture, and classification. Finally, we designed and developed a novel all-planar, high-performance organic electrochemical transistor (OECT) with high reproducibility, amplification (3.8 mS) and rapid response times (0.08 ms). Our OECT-based cancer biosensor revealed that cancer cells with different metastatic states modulate the drain current (IDS) differently. Cells with lower metastatic potential caused a greater attenuation of IDS up to 35% compared to 12% modulation with cells in the higher metastatic spectrum, correlating with their higher adhesion strength and lower membrane capacitance, as established in our previous studies. This work will pave the way for a next-generation POC platform for cancer detection. The unique cellular fingerprints identified can serve as biophysical and bioelectronic biomarkers for distinguishing and sorting CTCs. Our approach holds great promise for liquid biopsy-based cancer diagnostics and monitoring, offering a powerful tool for precision medicine applications