Attachment of Motile Bacterial Cells to Prealigned Holed Microarrays

Construction of biomotors is an exciting area of scientific research that holds great promise for the development of new technologies with broad potential applications in areas such as the energy industry and medicine. Herein, we demonstrate the fabrication of prealigned microarrays of motile Escherichia coli bacterial cells on SiOx substrates. To prepare these arrays, holed surfaces with a gold layer on the bottom of the holes were utilized. The attachment of bacteria to the holes was achieved via nonspecific interactions using poly-l-lysine hydrobromide (PLL). Our data suggest that a single motile bacterial cell can be selectively attached to an individual hole on a surface and bacterial cell binding can be controlled by altering the pH, with the greatest occupancy occurring at pH 7.8. Cells attached to hole arrays remained motile for at least 4 h. These data indicate that holed surface structures provide a promising footprint for the attachment of motile bacterial cells to form high-density site-specific functional bacterial microarrays

Synthesis and Isolation of {110}-Faceted Gold Bipyramids and Rhombic Dodecahedra

Two {110}-faceted gold nanostructures—rhombic dodecahedra and obtuse triangular bipyramids—have been synthesized via a Ag-assisted, seed-mediated growth method. The combination of a Cl−-containing surfactant with a low concentration of Ag+ plays a role in the stabilization of the {110} facets. To the best of our knowledge, this is the first reported synthesis of a {110}-faceted bipyramid structure

The nature and implications of uniformity in the hierarchical organization of nanomaterials

In this Perspective, we present a framework that defines how to understand and control material structure across length scales with inorganic nanoparticles. Three length scales, frequently discussed separately, are unified under the topic of hierarchical organization: atoms arranged into crystalline nanoparticles, ligands arranged on nanoparticle surfaces, and nanoparticles arranged into crystalline superlattices. Through this lens, we outline one potential pathway toward perfect colloidal matter that emphasizes the concept of uniformity. Uniformity is of both practical and functional importance, necessary to increase structural sophistication and realize the promise of nanostructured materials. Thus, we define the nature of nonuniformity at each length scale as a means to guide ongoing research efforts and highlight potential problems in the field. nanomaterial | uniformity | colloidal crystal | dispersity | hierarch

Synthesis and Isolation of {110}-Faceted Gold Bipyramids and Rhombic Dodecahedra

Two {110}-faceted gold nanostructures—rhombic dodecahedra and obtuse triangular bipyramids—have been synthesized via a Ag-assisted, seed-mediated growth method. The combination of a Cl−-containing surfactant with a low concentration of Ag+ plays a role in the stabilization of the {110} facets. To the best of our knowledge, this is the first reported synthesis of a {110}-faceted bipyramid structure

Advancing the speed, sensitivity and accuracy of biomolecular detection using multi-length-scale engineering

Rapid progress in identifying disease biomarkers has increased the importance of creating high-performance detection technologies. Over the last decade, the design of many detection platforms has focused on either the nano or micro length scale. Here, we review recent strategies that combine nano- and microscale materials and devices to produce large improvements in detection sensitivity, speed and accuracy, allowing previously undetectable biomarkers to be identified in clinical samples. Microsensors that incorporate nanoscale features can now rapidly detect disease-related nucleic acids expressed in patient samples. New microdevices that separate large clinical samples into nanocompartments allow precise quantitation of analytes, and microfluidic systems that utilize nanoscale binding events can detect rare cancer cells in the bloodstream more accurately than before. These advances will lead to faster and more reliable clinical diagnostic devices

Epitaxy: Programmable Atom Equivalents

The programmability of DNA makes it an attractive structure-directing ligand for the assembly of nanoparticle (NP) superlattices in a manner that mimics many aspects of atomic crystallization. However, the synthesis of multilayer single crystals of defined size remains a challenge. Though previous studies considered lattice mismatch as the major limiting factor for multilayer assembly, thin film growth depends on many interlinked variables. Here, a more comprehensive approach is taken to study fundamental elements, such as the growth temperature and the thermodynamics of interfacial energetics, to achieve epitaxial growth of NP thin films. Both surface morphology and internal thin film structure are examined to provide an understanding of particle attachment and reorganization during growth. Under equilibrium conditions, single crystalline, multilayer thin films can be synthesized over 500 × 500 μm² areas on lithographically patterned templates, whereas deposition under kinetic conditions leads to the rapid growth of glassy films. Importantly, these superlattices follow the same patterns of crystal growth demonstrated in atomic thin film deposition, allowing these processes to be understood in the context of well-studied atomic epitaxy and enabling a nanoscale model to study fundamental crystallization processes. Through understanding the role of epitaxy as a driving force for NP assembly, we are able to realize 3D architectures of arbitrary domain geometry and size.United States. Air Force Office of Scientific Research (AFOSR FA9550-11-1-0275)United States. Air Force Office of Scientific Research (FA9550-12-1-0280)United States. Department of Defense (N00014-15-1-0043)United States. Department of Energy (Grant DE-SC0000989-0002)National Science Foundation (U.S.) (Award DMR-1121262