DNA-functionalized nanomaterials for optical biosensors: Mechanisms, applications, and design perspectives

• Comparative review of six DNA-functionalized nanomaterial platforms. • Mechanistic insights into FRET, NSET, charge transfer, and colorimetry. • Application-oriented evaluation across ions, molecules, proteins, pathogens. • Critical analysis of design factors for sensitivity, stability, reproducibility. • Perspectives on translation toward clinical, food safety, and environmental use. Background: DNA-functionalized nanomaterials have emerged as a powerful platform for optical biosensing, where DNA's intrinsic molecular recognition imparts high sensitivity and selectivity. However, the integration of DNA with optically active nanomaterials introduces new opportunities and challenges in signal transduction, stability, and application-specific optimization. Despite growing interest in this hybrid field, a unified framework for evaluating and comparing different nanomaterial platforms in the context of DNA-guided sensing is lacking. This review addresses this gap by systematically analyzing the mechanisms and applications of DNA-functionalized optical biosensors. Results: We provide a comprehensive and critically integrated overview of DNA-functionalized nanomaterials across six major platforms: carbon dots, carbon nanotubes, metal nanoparticles, quantum dots, graphene quantum dots, and silicon-based nanoparticles. Each system is examined in terms of its optical sensing mechanisms, such as fluorescence, FRET, and colorimetric response, and its performance in detecting targets including metal ions, small molecules, nucleic acids, proteins, and pathogens. A direct comparison is presented based on practical criteria such as detection wavelength, detection range, functionalization efficiency, and biocompatibility. We further discuss recent applications in disease diagnostics, point-of-care testing, environmental monitoring, and food safety, along with challenges including signal reproducibility, surface DNA quantification, and stability in complex matrices. Significance: This review establishes a comparative foundation for evaluating DNA-guided optical biosensors and identifies emerging trends and design strategies across material classes. The insights provided are expected to inform the rational development of next-generation biosensors with enhanced precision, accessibility, and real-world applicability. This review aims to provide a comprehensive overview of the recent advancements and applications in optical biosensors utilizing DNA-functionalized nanomaterials.