Thermal drying synthesized density-tunable and high stability nonthiolated spherical nucleic acids for split aptamer...

Spherical nucleic acids (SNAs) have attracted considerable interest in designing biosensors. Our group recently developed a thermal drying method to fabricate SNAs with an ultrahigh density of cost-effective nonthiolated DNA containing a polyadenine block. In this study, functional properties of such SNAs in two types of biosensors were investigated using aptamer and hybridization-based model detection systems. For aptamer-based target recognition, we observed that a high DNA density on SNAs hindered target binding. To address this, short dilution strands were introduced to decrease probe density. Using oxytetracycline as a target, a plasmonic colorimetric sensor with a detection limit of 0.5 μM was achieved. For hybridization-based recognition, we identified key parameters for avoiding false positives in lateral flow assays (LFA) and demonstrated that high DNA density did not compromise sensitivity. Using genetically modified soybean MON87705 as a target, we developed a portable LFA platform by integrating loop-mediated isothermal amplification with CRISPR/Cas12a, achieving a detection limit of 0.08 wt%. Overall, this study provides specific guidance for the practical application of nonthiolated SNA probes in biosensors.