Michael J. Campolongo

Building plasmonic nanostructures with DNA

Plasmonic structures can be constructed from precise numbers of well-defined metal nanoparticles that are held together with molecular linkers, templates or spacers. Such structures could be used to concentrate, guide and switch light on the nanoscale in sensors and various other devices. DNA was first used to rationally design plasmonic structures in 1996, and more sophisticated motifs have since emerged as effective and versatile species for guiding the assembly of plasmonic nanoparticles into structures with useful properties. Here we review the design principles for plasmonic nanostructures, and discuss how DNA has been applied to build finite-number assemblies (plasmonic molecules), regularly spaced nanoparticle chains (plasmonic polymers) and extended two- and three-dimensional ordered arrays (plasmonic crystals).

DNA nanomedicine: Engineering DNA as a polymer for therapeutic and diagnostic applications

Abstract Nanomedicine, the application of nanotechnology to medicine, encompasses a broad spectrum of fields including molecular detection, diagnostics, drug delivery, gene regulation and protein production. In recent decades, DNA has received considerable attention for its functionality and versatility, allowing it to help bridge the gap between materials science and biological systems. The use of DNA as a structural nanoscale material has opened a new avenue towards the rational design of DNA nanostructures with different polymeric topologies. These topologies, in turn, possess unique characteristics that translate to specific therapeutic and diagnostic strategies within nanomedicine.

Novel DNA materials and their applications

Abstract The last two decades have witnessed the exponential development of DNA as a generic material instead of just a genetic material. The biological function, nanoscale geometry, biocompatibility, biodegradability, and molecular recognition capacity of DNA make it a promising candidate for the construction of novel functional nanomaterials. As a result, DNA has been recognized as one of the most appealing and versatile nanomaterial building blocks. Scientists have used DNA in this way to construct various amazing nanostructures, such as ordered lattices, origami, supramolecular assemblies, and even three‐dimensional objects. In addition, DNA has been utilized as a guide and template to direct the assembly of other nanomaterials including nanowires, free‐standing membranes, and crystals. Furthermore, DNA can also be used as structural components to construct bulk materials such as DNA hydrogels, demonstrating its ability to behave as a unique polymer. Overall, these novel DNA materials have found applications in various areas in the biomedical field in general, and nanomedicine in particular. In this review, we summarize the development of DNA assemblies, describe the innovative progress of multifunctional and bulk DNA materials, and highlight some real‐world nanomedical applications of these DNA materials. We also show our insights throughout this article for the future direction of DNA materials. WIREs Nanomed Nanobiotechnol 2010 2 648–669 This article is categorized under: 1 Diagnostic Tools > Biosensing2 Nanotechnology Approaches to Biology > Cells at the Nanoscale3 Implantable Materials and Surgical Technologies > Nanomaterials and Implants4 Nanotechnology Approaches to Biology > Nanoscale Systems in Biology

Crystalline Gibbs monolayers of DNA-capped nanoparticles at the air-liquid interface.

Using grazing-incidence small-angle X-ray scattering in a special configuration (parallel SAXS, or parSAXS), we mapped the crystallization of DNA-capped nanoparticles across a sessile droplet, revealing the formation of crystalline Gibbs monolayers of DNA-capped nanoparticles at the air-liquid interface. We showed that the spatial crystallization can be regulated by adjusting both ionic strength and DNA sequence length and that a modified form of the Daoud-Cotton model could describe and predict the resulting changes in interparticle spacing. Gibbs monolayers at the air-liquid interface provide an ideal platform for the formation and study of equilibrium nanostructures and may afford exciting routes toward the design of programmable 2D plasmonic materials and metamaterials.

Crystallization of DNA‐Capped Gold Nanoparticles in High‐Concentration, Divalent Salt Environments

The multiparametric nature of nanoparticle self-assembly makes it challenging to circumvent the instabilities that lead to aggregation and achieve crystallization under extreme conditions. By using non-base-pairing DNA as a model ligand instead of the typical base-pairing design for programmability, long-range 2D DNA-gold nanoparticle crystals can be obtained at extremely high salt concentrations and in a divalent salt environment. The interparticle spacings in these 2D nanoparticle crystals can be engineered and further tuned based on an empirical model incorporating the parameters of ligand length and ionic strength.

Adaptive DNA-based materials for switching, sensing, and logic devices

DNA-based materials that can adapt to their surroundings are of great interest for the development of next-generation switching, sensing, and logic devices. Through elaborate sequence design and chemical functionalization, numerous adaptive DNA-based materials have been developed that can reversibly switch conformations, act as dynamic sensors, perform logic operations, and even trigger macroscopic phase responses.

Three-Dimensional Structure and Thermal Stability Studies of DNA Nanostructures by Energy Transfer Spectroscopy

Structural changes and stability of DNA nanoarchitectures including Y-shaped DNA (see picture), dendrimer-like DNA, and DNA hydrogels are investigated. The results demonstrate the feasibility and flexibility of FRET and NSET (Forster resonance/ nanometal surface- energy transfer) in determining difficult-to-obtain 3D structures and characterizing the thermal responses of DNA nanoarchitectures in real time.

Size Effect on Failure of Pre-stretched Free-Standing Nanomembranes.

Free-standing nanomembranes are two-dimensional materials with nanometer thickness but can have macroscopic lateral dimensions. We develop a fracture model to evaluate a pre-stretched free standing circular ultrathin nanomembrane and establish a relation between the energy release rate of a circumferential interface crack and the pre-strain in the membrane. Our results demonstrate that detachment cannot occur when the radius of the membrane is smaller than a critical size. This critical radius is inversely proportional to the Young’s modulus and square of the pre-strain of the membrane.

Bio-Mediated Assembly of Ordered Nanoparticle Superstructures

Owing to their unique optical, electronic, magnetic, and catalytic properties, nanoparticles (artificial atoms) have attracted considerable research efforts across various disciplines, spanning chemistry, physics, biology, and materials science. Despite rapid progress in synthesis of nanoparticle over the past decades, it remains a challenge to rationally assemble these artificial atoms into well-defined architectures. Here, we review the latest developments in the utilization of biomolecules for building highly ordered nanoparticle assemblies. In particular, we discuss wet chemistry synthesis and bioconjugation of single crystalline nanoparticles, interaction energetics between biofunctionalized nanoparticles, and the recent achievement of bio-mediated, highly ordered nanoparticle superstructures.