Accurate and reliable biosensing is crucial for environmental monitoring, food safety, and diagnostics. Spatially reconfigurable DNA origami nanostructures are excellent candidates for the generation of custom sensing probes. Here we present a nanoscale biosensing device that combines the accuracy and precision of the DNA origami nanofabrication technique, unique optical responses of chiral plasmonic assemblies, and high affinity and selectivity of aptamers. This combination enables selective and sensitive detection of targets even in strongly absorbing fluids. We expect that the presented sensing scheme can be adapted to a wide range of analytes and tailored to specific needs.

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The DNA origami technique has emerged as one of the most versatile bottom-up nanofabrication methods due to its ability to construct well-defined complex three-dimensional nanostructures and guide assembly of functional nanoscale objects with unprecedented precision, high yields, and controlled stoichiometry. Nonetheless, limited compatibility with biologically relevant fluids and typical solvents utilized in nanofabrication often restricts applications of DNA origami-based assemblies and devices. Here we present an approach for coating DNA origami structures with silica. By careful adjustment of experiment parameters, we achieved reproducible growth of ultrathin silica shell in solution without agglomeration or deformation of DNA origami structures. The silica-coated structures are stable in water and exhibit an increased resistivity to nuclease-mediated degradation. In addition, the coated structures preserve their structural integrity in polar organic solvents. We anticipate that our results will aid further advancement of DNA origami techniques as the nanofabrication method.

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The defect in homologous recombination (HR) found in BRCA1-associated cancers can be therapeutically exploited by treatment with DNA-damaging agents and poly (ADP-ribose) polymerase (PARP) inhibitors. We and others previously reported that BRCA1-deficient tumors are initially hypersensitive to the inhibition of topoisomerase I/II and PARP but acquire drug resistance through restoration of HR activity by the loss of end-resection antagonists of the 53BP1/RIF1/REV7/Shieldin/CST pathway. Here we identify radiotherapy as an acquired vulnerability of 53BP1;BRCA1-deficient cells in vitro and in vivo. In contrast to the radioresistance caused by HR restoration through BRCA1 reconstitution, HR restoration by 53BP1 pathway inactivation further increases radiosensitivity. This highlights the relevance of this pathway for the repair of radiotherapy-induced damage. Moreover, our data show that BRCA1-mutated tumors that acquire drug resistance due to BRCA1-independent HR restoration can be targeted by radiotherapy.