Antibiotic resistant bacteria not only affect human health and but also threatens the safety in hospitals and among communities. However, the emergence of drug resistant bacteria is inevitable due to evolutionary selection as a consequence of indiscriminate antibiotic usage. Therefore, it is necessary to develop a novel strategy by which pathogenic bacteria can be eliminated without triggering resistance. We propose a novel magnetic nanoparticle-based physical treatment against pathogenic bacteria, which blocks biofilm formation and kills bacteria. In this approach, multiple drug resistant Staphylococcus aureus USA300 and uropathogenic Escherichia coli CFT073 are trapped to the positively charged magnetic core-shell nanoparticles (MCSNPs) by electrostatic interaction. All the trapped bacteria can be completely killed within 30 min owing to the loss of membrane potential and dysfunction of membrane-associated complexes when exposed to the radiofrequency current. These results indicate that MCSNP-based physical treatment can be an alternative antibacterial strategy without leading to antibiotic resistance, and can be used for many purposes including environmental and therapeutic applications.

Owing to its high information density, energy efficiency, and massive parallelism, DNA computing has undergone several advances and made significant contributions to nanotechnology. Notably, arithmetic calculations implemented by multiple logic gates such as adders and subtractors have received much attention because of their well-established logic algorithms and feasibility of experimental implementation. Although small molecules have been used to implement these computations, a DNA tile-based calculator has been rarely addressed owing to complexity of rule design and experimental challenges for direct verification. Here, we construct a DNA-based calculator with three types of building blocks (propagator, connector, and solution tiles) to perform addition and subtraction operations through algorithmic self-assembly. An atomic force microscope is used to verify the solutions. Our method provides a potential platform for the construction of various types of DNA algorithmic crystals (such as flip-flops, encoders, and multiplexers) by embedding multiple logic gate operations in the DNA base sequences.

Target-oriented cellular automata with computation are the primary challenge in the field of DNA algorithmic self-assembly in connection with specific rules.

The Watson-Crick complementarity of DNA is exploited to construct periodically patterned nanostructures, and we herein demonstrate tile-based three dimensional (3D) multilayered DNA nanostructures that incorporate two design strategies: vertical growth and horizontal layer stacking with substrate-assisted growth. To this end, we have designed a periodically holed double-double crossover (DDX) template that can be used to examine the growth of the multilayer structures in both the vertical and horizontal directions. For vertical growth, the traditional 2D double crossover (DX) DNA lattice is seeded and grown vertically from periodic holes in the DDX template. For horizontal stacking, the DDX layers are stacked by binding the connector tiles between each layer. Although both types of multilayers exhibited successful formation, the observations with an atomic force microscope indicated that the DDX layer growth achieved with the horizontal stacking approach could be considered to be slightly better relative to the vertical growth of the DX layers in terms of uniformity, layer size, and discreteness. In particular, the newly designed DDX template layer provided a parallel arrangement between each domain with substrate-assisted growth. This kind of layer arrangement suggests a possibility of using our design scheme in the construction of other periodic structures.

DNA is an excellent and extraordinarily versatile building block that can be used to construct nanoscale objects and arrays of increasing complexity, and as a result, a considerable amount of progress has been made in DNA-directed molecular self-assembly. Here, we demonstrate the sequential fabrication of three-dimensional multilayered DNA nanostructures by utilizing single-strand and doublecrossover tile (DX) designs via substrate-assisted growth and multistep annealing methods. We used both layering and connector tiles to synthesize the base layer for both the single strand-based and DX tile-based designs. Layering without and with connector tiles was used to produce double-layer and multi-layer designs for single strandbased designs, but only layering tiles were used for the DX tilebased design. Connector tiles provided appropriate sticky-end sets to form the designed lattice structures. Atomic force microscopy revealed that the spacing between the tiles was in good agreement with the design scheme, but the heights of the multi-layered nanostructures were found to be slightly lower than expected due to suppression by the substrate. This kind of step-wise multi-layer assembly may produce a variety of spacings to incorporate different guest molecules or aid the attachment of various types of biomolecules and nanomaterials in parallel arrays along the layers. † Electronic supplementary information (ESI) available: Schematic diagram and DNA sequences for tiles forming single-, double-and multi-layers; height proles of multi-layer assembly; a 2% agarose gel image. See