Visual enumeration of circRNA in serum using a biserrate DNA-modified AuNP SPR probe

This study developed a 60 nm biserrate DNA-modified Au nanoparticle (AuNP) platform for rapid circRNA detection using dark-field microscopy (DFM). Compared with other Au nanostructures, spherical AuNPs exhibited superior stability and sensitivity, achieving a detection limit of ∼0.02 fM for circHECTD1 within 40 min, representing about a 100-fold improvement in sensitivity over the qPCR method for this target. This approach enables fast, cost-effective, and highly sensitive circRNA analysis without PCR amplification.