Exosome-Based Liquid Biopsy in Biliary Tract Cancer: Nanotechnology-Enabled Strategies and Future Perspectives

Biliary tract cancer (BTC) remains a formidable clinical challenge owing to its asymptomatic early stages, anatomical complexity, and lack of reliable and noninvasive diagnostic tools. Although traditional tissue biopsy is often limited by invasiveness and sampling bias, liquid biopsy, particularly the analysis of tumor-derived exosomes, has emerged as a promising and clinically relevant alternative for early detection and longitudinal monitoring. Exosomes are specialized extracellular vesicles that sequester diverse molecular cargo including proteins, lipids, and nucleic acids, thereby reflecting the physiological state of their parental tumor cells. However, the clinical translation of exosomal biomarkers is often hindered by technical challenges in achieving high-purity isolation and ultrasensitive detection in complex biological matrices, such as blood and bile. To address these limitations, this review provides a comprehensive overview of recent advancements in nanotechnology-enabled platforms designed to overcome these challenges. First, we examined sophisticated nanostructured systems, such as immuno-magnetic nanoparticles and microfluidic nanoVelcro chips, for high-yield exosome enrichment. Subsequently, we investigated next-generation biosensing modalities with a focus on surface-enhanced Raman scattering for label-free molecular fingerprinting and CRISPR-Cas-integrated nanosensors for amplification-free nucleic acid detection. Significant emphasis has now been placed on the integration of artificial intelligence and deep learning algorithms, which have become indispensable for deciphering complex exosomal signatures to differentiate BTC from benign conditions such as cholangitis. Finally, we discuss the emerging clinical significance of bile-derived exosomes and remaining challenges in standardizing nanomedicine-based liquid biopsies for precision oncology. These integrated platforms could potentially redefine the BTC management paradigm by bridging the gap between advanced nanomaterials and clinical diagnostics.