Surface-Enhanced Raman Spectroscopy Aptasensors for Nucleic-Acid Detection: Advances, Challenges, and Future Perspectives.

Nucleic-acid biomarkers play pivotal roles in disease diagnosis, therapeutic monitoring, and precision medicine, creating an urgent demand for analytical platforms combining high sensitivity, molecular specificity, and rapid detection. Surface-enhanced Raman spectroscopy (SERS) integrated with aptamers, short single-stranded DNA or RNA oligonucleotides, has attracted considerable attention by coupling programmable molecular recognition with ultrasensitive plasmon-enhanced Raman detection. This review evaluates recent advances in aptamer-based SERS biosensors for nucleic-acid analysis, systematically examining sensing mechanisms, plasmonic substrate engineering, aptamer immobilization, signal-transduction pathways, and amplification approaches, including catalytic hairpin assembly, hybridization chain reaction, rolling circle amplification, and CRISPR-assisted systems. Recent developments in microfluidics, artificial intelligence-assisted spectral analysis, portable Raman instrumentation, and point-of-care platforms are assessed while distinguishing true aptamer-mediated sensing from conventional hybridization-based DNA detection. Rational hotspot engineering, deterministic nanogap architectures, and advanced amplification strategies have enabled detection from femtomolar to attomolar levels with improved selectivity, multiplexing, and reproducibility. Challenges including substrate variability, quantitative standardization, aptamer stability, biosafety, and clinical translation are discussed. Future directions toward standardized, intelligent, clinically deployable SERS platforms for next-generation molecular diagnostics and precision healthcare are proposed.