Surface modification of cellulose acetate membrane for fabrication of microfluidic platforms for express extracellular vesicle-based liquid biopsy

A tumor-derived extracellular vesicle (EV) test is a promising early-stage cancer diagnostic and treatment monitoring tool. However, current methods that are used for EV isolation and detection are labor-intensive and often require expensive and sophisticated instruments. Additionally, the majority of these methods cannot selectively isolate tumor-associated protein enriched EVs among other non-specific EVs present in the sample. Membrane-based microfluidic fluorescence assays are simple, inexpensive, and sensitive methods for detection of biomolecules, which can be further improved through covalent bioconjugation of the molecular recognition elements onto the cellulose matrix. In this work we present a novel microfluidic device with an integrated membrane for EV-based liquid biopsy. Cellulose acetate is bioconjugated through two-stage protocol using 3aminopropyltriethoxysilane-glutaraldehyde linkage to covalently anchor anti-CD63 amino-modified aptamer. The functionalized cellulose surface is shown to selectively bind vesicles from cell culture media and human plasma. The reaction conditions and washing procedures are optimized to prevent non-specific binding of proteins, vesicles and oligonucleotides to the membrane matrix. The successful selective CD63+/EpCAM+ and CD63+/HER2+ EV detection is demonstrated in a membrane-based sandwich immunoassay. This membrane- based selective EV capture and labeling demonstrates applicability of this sensing platform for tumor-positive- vesicle detection that can be adapted to point-of-care testing and post treatment monitoring.