Routine monitoring of microRNAs in salivary exosomes using a cellulose nanofiber sheet

Liquid biopsy is a promising approach for non-invasive disease monitoring, offering the potential for frequent sampling and early risk assessment. Among various biofluids, saliva is particularly well-suited for daily sampling due to its ease of collection and minimal invasiveness. Here, we present a cellulose nanofiber sheet as a novel platform for the rapid, low-volume recovery and stable storage of miRNAs associated with small extracellular vesicles in saliva. The sheet captures vesicles via its nanoscale porous networks and preserves their contents at room temperature, enabling efficient extraction of vesicle-associated miRNAs. Compared to ultracentrifugation, the method demonstrated superior miRNA recovery and required only 10 μL of saliva and less than 1 min of processing. Analysis of salivary miRNA profiles from healthy individuals and cancer patients revealed distinct expression patterns, enabling identification of candidate cancer-related miRNAs. Furthermore, daily saliva sampling during 20 days demonstrated the feasibility of longitudinal miRNA profiling and highlighted the effects of factors such as food intake. These findings underscore the potential of cellulose nanofiber sheets as a practical tool for salivary miRNA monitoring, with applications in personalized health management, early risk detection, and decentralized testing environments.