Figure 3.

Examples of DNA nanostructures for in vitro and in vivo bioimaging. Fundaments of super-resolution microscopy technique (DNA-PAINT) (a) that exploits the complementarity of DNA sequences to provide transient binding of fluorescently labeled DNA strands to DNA docking strands protruding DNA-based nanostructures, adapted with permission from [96] and (b) multiplexing DNA Exchange Imaging (DEI) in complex biological samples, adapted with permission from [99]. Initially, different targets (T1,…Tn) are labeled with antibodies conjugated to orthogonal DNA strands (P1,…Pn) to forming imager strands (P1*, …Pn*). These imager strands can be rapidly and sequentially washed away by buffer exchange allowing efficient multiplexed in situ imaging. Hybridization chain reaction (HCR) in situ (c) provides also multiplexed imaging by exploiting the complementarity of RNA probes to mRNA targets triggering chain reactions to produce fluorescent amplified RNA-based polymers, adapted with permission from [70]. Reconfigurable DNA TDN (d) is able to detect intracellular ATP in living cells, adapted with permission from [109]. A fluorescently labeled DNA TDN (e) proved to be a powerful biocompatible imaging probe for brain tumor-targeting, following the cellular uptake in an in vitro BBB model and exhibits biodistribution in mice, adapted with permission from [113]. DNA octahedron (f) encapsulating quantum dots [119] and (g) DNA nanorods barcoded with AuNPs [120] were used as probes to imaging endocytic pathways by following the conjugated photomaterial during the cellular uptake in fixed cells. Adapted with permission from [119] and [120].