DNA Hydrogel-Based Biosensors for Circulating Tumor Cell and Extracellular Vesicle Detection: An Analytical Chemistry Perspective on Clinical Translation

Liquid biopsy enables noninvasive cancer detection through circulating tumor cells (CTCs) and extracellular vesicles (EVs), yet current technologies face challenges in sensitivity, specificity, and clinical scalability. DNA hydrogels-three-dimensional nucleic acid networks with sequence-programmable recognition and stimulus-responsive behavior-have emerged as promising platforms to address these limitations. This review critically evaluates DNA hydrogel-based biosensors for CTC and EV detection, encompassing design principles, functionalization strategies (aptamers, DNAzymes, nanomaterials), separation/enrichment approaches, and multimodal detection methods including electrochemical, optical, and magnetic resonance platforms. We introduce a unified Analytical Figures of Merit (AFoM) framework for standardized performance evaluation, define the Clinical-Analytical Translation Gap (CATG) to quantify performance degradation in clinical matrices, and present a systematic gap analysis revealing that fewer than 5% of studies report batch-to-batch reproducibility and over 80% lack validation in unprocessed clinical specimens. Despite remarkable programmability and multifunctional integration, DNA hydrogel biosensors require rigorous inter-laboratory reproducibility studies, systematic CATG characterization, head-to-head comparisons with FDA-cleared reference methods, and standardized analytical reporting before clinical translation can be realized.