In vitro diagnostics

In modern in-vitro diagnostics, clinical laboratories play a crucial role in detecting biomarkers in patient samples, necessitating both infrastructure and trained personnel. However, relying on a single biomarker often fails to provide comprehensive insights into diseases, given that similar symptoms can be associated with various disorders, each linked to different markers. Ongoing research aims to enhance diagnostic accuracy by developing robust multi-analytical systems, facilitating personalized medicine approaches. Bead-based assays present an elegant solution for sensitive, multiplexed clinical diagnostics. With their batch producibility and established surface modification processes, beads offer low variability. Additionally, using beads as solid support increases the surface-to-volume ratio, enhancing mass transport and analyte collection, thereby improving assay sensitivity. Incorporating microbeads into microfluidics simplifies and automates analytical steps, enabling the miniaturization of diagnostic protocols into Lab-on-a-Chip devices.

We have developed an electrokinetic microfluidic immunoassay system capable of rapidly detecting analytes on antibody-decorated beads and localizing their accumulation within confined regions in just 15 minutes. In our study, we applied this system to simultaneously analyze clinical concentrations of Neutrophil Gelatinase-Associated Lipocalin (NGAL) and Cystatin C (CysC) in serum, both crucial biomarkers for acute kidney injury (AKI). Our innovative approach involves integrating high-aspect-ratio, three-dimensional electrodes into a microfluidic channel, applying dielectrophoretic (DEP) forces to control the trajectory of antibody-decorated microbeads. This design efficiently retains beads against the fluid flow, ensuring robust on-chip analyte-to-bead binding. Specific electrokinetic forces tailored to the beads’ size are generated within the same channel, directing differently decorated beads to distinct readout regions on the chip. Our platform facilitates on-chip incubation for optimized analyte collection, enables the detection of multiple biomarkers, amplifies signals, and offers optical readout via a single fluorescence channel. This system represents a significant stride in achieving rapid and precise multiplexed immunoassays for clinical diagnostics. [1]

We are currently working on a point-of-care diagnostic tool to test multiple biomarkers of kidney failure. Our self-contained platform is the first of its kind, performing different fully-automatic homogeneous immunoassays. Microbead handling in microfluidics is commonly used to automate bioanalytical processes. Existing platforms, however, require additional steps like washes, liquid reagent delivery, or premixing with label molecules. We introduce a scalable platform that addresses these limitations, offering a rapid and sensitive system that leverages the advantages of bead-based immunoassays with a simple single-step protocol where the user only needs to inject the sample for multimarker analysis. Our system can test Cystatin C (CysC) and neutrophil gelatinase-associated lipocalin (NGAL) with minimal user intervention within 15 minutes. The levels of CysC directly correlate with the glomerular filtration rate, while spiking values of NGAL appear after tubular tissue damage. Simultaneous quantification of both markers gives insight into kidney health and the causes of injury. We are currently working on detection of kidney failure markers in urine and plasma samples from mice affected by polycystic kidney disease, in collaboration with the Laboratory of Developmental and Cancer Cell Biology (Constam Lab, EPFL).

[1] Thiriet, P.-E.; Medagoda, D.; Porro, G.; Guiducci, C. Rapid Multianalyte Microfluidic Homogeneous Immunoassay on Electrokinetically Driven Beads. Biosensors 2020, 10, 212.