DNA Hydrogel-Based Biosensors for Circulating Tumor Cell and Extracellular Vesicle Detection: An Analytical Chemistry...

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.