Self-assembled DNA nanostructures with chemistry-enabled functionality are of great interest in nanobiotechnology. Herein, chemically modified DNA nanopores are designed to puncture cellular membranes and cause cytotoxicity. The nanopores are assembled from DNA oligonucleotides to form a 2 nm-high hydrophobic belt at one terminus. The belt is composed of charge-neutralized ethyl phosphorothioate (EP) groups which are required to decrease cell viability. The mode by which the pores achieve cell killing is elucidated with confocal microscopy. This study is the first to describe the interaction of DNA nanopores with cells. The work lays the foundation for the future development of cytotoxic agents with cancer type-specificity.Chemistry can play an important role in expanding the functional repertoire of DNA nanostructures. [1,2] Designed nanomaterials have been developed by equipping DNA scaffolds [2,3] with chemical linkages to spatially arrange nanoparticles, [4] fluorophores, [5] or proteins.[6] These DNA nanostructures have been mostly applied for cell-free applications but not for cell biology even though the latter field benefits from nanomaterials as demonstrated with canonical nucleic acids. [7,8] One class of chemically modified DNA nanostructures of potential in cell biology are membrane-spanning DNA nanopores. In general, engineered nanopores that facilitate transmembrane flux [9] can be used for cell permeabilization, drug delivery, [10] but also biosensing. [11][12][13] In the latter, label-free analytical strategy, individual molecules passing or binding inside a nanoscale pore are detected based on the associated changes in the ionic pore current. A wide range of analytes can be sensed, [11,14] and DNA can be sequenced by threading individual strands through the pore. [12,15] Nanopores have traditionally been constructed with re-engineered or de-novo protein scaffolds, or organic synthetic building blocks.[16]Nanopores composed of folded DNA are the most recent category. [17][18][19][20] Formed either by scaffold and staple strands [17] or short oligonucleotides, [18,19] the highly negatively charged DNA nanopores insert into hydrophobic bilayer membranes by chemical lipid anchors, whereby cholesterol, [17] porphyrin, [19] and a belt of EP tags [18] were successfully tested. In light of their established ability to span reconstituted membranes, we postulated that the pores could be adapted and exploited to puncture biological cell membranes. Our interest was spiked by the prospect of rationally designing DNA nanostructures for cell biological applications, such as gene transfection, drug permeabilization or targeted killing of diseased cells.Here we examine whether a membrane-spanning DNA nanopore can interact with cancer cells and potentially trigger cell death (Figure 1 a and b). Our nanopore was composed of a bundle of six DNA duplexes folded from six DNA strands (see Figure S1 in the Supporting Information). The hollow nanobarrel has a channel width of approximately 2 nm, an Figure 1. A membrane-...