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.

DNA nanotechnology offers a versatile toolbox for precise spatial and temporal manipulation of matter on the nanoscale. However, rendering DNA‐based systems responsive to light has remained challenging. Herein, we describe the remote manipulation of native (non‐photoresponsive) chiral plasmonic molecules (CPMs) using light. Our strategy is based on the use of a photoresponsive medium comprising a merocyanine‐based photoacid. Upon exposure to visible light, the medium decreases its pH, inducing the formation of DNA triplex links, leading to a spatial reconfiguration of the CPMs. The process can be reversed simply by turning the light off and it can be repeated for multiple cycles. The degree of the overall chirality change in an ensemble of CPMs depends on the CPM fraction undergoing reconfiguration, which, remarkably, depends on and can be tuned by the intensity of incident light. Such a dynamic, remotely controlled system could aid in further advancing DNA‐based devices and nanomaterials.