Nano-biosensors for circulating tumor markers: advancing liquid biopsy toward precision cancer diagnostics.

Early detection of cancer remains a major challenge in oncology. Circulating tumour markers (CTMs), including circulating tumour cells, circulating tumour DNA, exosomes, microRNAs, and tumour-associated proteins, offer a minimally invasive strategy for monitoring tumour dynamics through liquid biopsy. However, their clinical translation is limited by low abundance, heterogeneity, and instability in body fluids. Recent advances in nanotechnology have enabled the development of highly sensitive and specific nano-biosensors that address many of these barriers. This review highlights the current progress in CTM detection using electrochemical, optical, plasmonic, and microfluidic-integrated platforms. Advanced nanomaterials such as graphene, carbon nanotubes, noble metal nanoparticles, quantum dots, and nanozymes are discussed for their roles in signal amplification, surface functionalization, and biomarker selectivity. Special focus is placed on lab-on-a-chip and wearable biosensors for multi-marker, point-of-care testing. To amplify the signals associated with nanobiosensors, various technologies, such as surface functionalization, aptamer and antibody functionalization, and nanozymes, have been integrated with the nanobiosensors.