Amplification-free attomolar sensing of autism biomarkers with MINT-DNA dendrimer hybrids

Optimizing nano-bio interfaces to successfully combine the extreme sensitivity characteristic of SWCNT sensors with the ultimate selectivity provided by bio-molecules remains a major challenge, since covalent approaches can disrupt the SWCNT lattice and noncovalent chemistry yields kinetically unstable adducts. In this work, we address this challenge by connecting the macrocycles of mechanically interlocked SWCNTs (MINTs) to high-density DNA dendrimers, via thiol-ene covalent chemistry. This nanoscale design leverages the mechanical bond as a stable yet harmless connection between the SWCNTs and DNA dendrimers for signal amplification. The result is an amplification-free electrochemical biosensor for miRNA-27a with an outstanding limit of detection of 0.855 aM for the early and accurate detection of Autism Spectrum Disorder (ASD) biomarkers. The validity of the structural design is confirmed by the fact that the biosensor outperforms supramolecular analogues, SWCNTs, and conventional single-strand probes. It also exhibits excellent specificity, detecting miRNA-27a in the presence of interferents and successfully applied to clinical serum samples from autistic children, with results validated against the standard PCR technique. These findings confirm the platform's robustness under clinically relevant conditions and position it as a rapid, simple, efficient, and practical tool for miRNA-27a sensing, with strong potential for early ASD diagnosis and broader nucleic acid biomarker detection in complex biological matrices.