Chad A Mirkin

Northwestern University, Evanston, Illinois, United States

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Publications (712)7223.71 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Shape-controlled synthesis of gold nanoparticles generally involves the use of surfactants, typically cetyltrimethylammonium (CTAX, X = Cl(-) , Br(-) ), to regulate the nucleation growth process and to obtain colloidally stable nanoparticles. The surfactants adsorb on the nanoparticle surface making further functionalization difficult and therefore limit their use in many applications. Herein, the influence of CTAX on nanoparticle sensitivity to local dielectric environment changes is reported. It is shown, both experimentally and theoretically, that the CTAX bilayer significantly reduces the refractive index (RI) sensitivity of anisotropic gold nanoparticles such as nanocubes and concave nanocubes, nanorods, and nanoprisms. The RI sensitivity can be increased by up to 40% by removing the surfactant layer from nanoparticles immobilized on a solid substrate using oxygen plasma treatment. This increase compensates for the otherwise problematic decrease in RI sensitivity caused by the substrate effect. Moreover, the removal of the surfactants both facilitates nanoparticle biofunctionalization and significantly improves their catalytic properties. The strategy presented herein is a simple yet effective universal method for enhancing the RI sensitivity of CTAX-stabilized gold nanoparticles and increasing their potential as transducers in nanoplasmonic sensors, as well as in catalytic and biomedical applications.
    Small 11/2015; DOI:10.1002/smll.201502449 · 8.37 Impact Factor
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    ABSTRACT: We report a strategy for creating a new class of protein transfection materials composed of a functional protein core chemically modified with a dense shell of oligonucleotides. These materials retain the native structure and catalytic ability of the hydrolytic enzyme β-galactosidase, which serves as the protein core, despite the functionalization of its surface with ∼25 DNA strands. The covalent attachment of a shell of oligonucleotides to the surface of β-galactosidase enhances its cellular uptake of by up to ∼280-fold and allows for the use of working concentrations as low as 100 pM enzyme. DNA-functionalized β-galactosidase retains its ability to catalyze the hydrolysis of β-glycosidic linkages once endocytosed, whereas equal concentrations of protein show little to no intracellular catalytic activity.
    Journal of the American Chemical Society 11/2015; DOI:10.1021/jacs.5b09711 · 12.11 Impact Factor
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    ABSTRACT: Electron microscopy (EM) represents the most powerful tool to directly characterize the structure of individual nanoparticles. Accurate descriptions of nanoparticle populations with EM, however, are currently limited by the lack of tools to quantitatively analyze populations in a high-throughput manner. Herein, we report a computational method to algorithmically analyze EM images that allows for the first automated structural quantification of heterogeneous nanostructure populations, with species that differ in both size and shape. This allows one to accurately describe nanoscale structure at the bulk level, analogous to ensemble measurements with individual particle resolution. With our described EM protocol and our inclusion of freely available code for our algorithmic analysis, we aim to standardize EM characterization of nanostructure populations to increase reproducibility, objectivity, and throughput in measurements. We believe this work will have significant implications in diverse research areas involving nanomaterials, including, but not limited to, fundamental studies of structural control in nanoparticle synthesis, nanomaterial-based therapeutics and diagnostics, optoelectronics, and catalysis.
    ACS Nano 11/2015; DOI:10.1021/acsnano.5b05968 · 12.88 Impact Factor
  • Guoliang Liu · Chuan Zhang · Jinsong Wu · Chad A Mirkin ·
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    ABSTRACT: Here we describe a general method for synthesizing multimetallic core-shell nanoclusters on surfaces. By patterning seeds at predesignated locations using scanning-probe block copolymer lithography, we can track shape evolution in nanoclusters and elucidate their growth pathways using electron microscopy. The growth of core-shell nanostructures on surface-bound seeds is a highly anisotropic process and often results in multimetallic anisotropic nanostructures. The shell grows at specific edge and corner sites of the patterned seeds and propagates predominately from the top hemisphere of the seeds.
    ACS Nano 11/2015; DOI:10.1021/acsnano.5b05191 · 12.88 Impact Factor
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    ABSTRACT: A method for modifying the external surfaces of a series of nanoscale metal-organic frameworks (MOFs) with 1,2-dioleoyl-sn-glycero-3-phosphate (DOPA) is presented. A series of zirconium-based nanoMOFs of the same topology (UiO-66, UiO-67, and BUT-30) were synthesized, isolated as aggregates, and then conjugated with DOPA to create stably dispersed colloids. BET surface area analysis revealed that these structures maintain their porosity after surface functionalization, providing evidence that DOPA functionalization only occurs on the external surface. Additionally, dye-labeled ligand loading studies revealed that the density of DOPA on the surface of the nanoscale MOF correlates to the density of metal nodes on the surface of each MOF. Importantly, the surface modification strategy described will allow for the general and divergent synthesis and study of a wide variety of nanoscale MOFs as stable colloidal materials.
    Angewandte Chemie International Edition 10/2015; DOI:10.1002/anie.201506888 · 11.26 Impact Factor
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    ABSTRACT: Chemical bonds are a key determinant of the structure and properties of a material. Thus, rationally designing arbitrary materials requires complete control over the bond. While atomic bonding is dictated by the identity of the atoms, nanoparticle superlattice engineering, where nanoparticle "atoms" are held together by DNA "bonds", offers a route to design crystal lattices in a way that nature cannot: through altering the oligonucleotide bond. Herein, the use of RNA, as opposed to DNA, is explored by synthesizing superlattices in which nanoparticles are bonded by DNA/DNA, RNA/RNA, and DNA/RNA duplexes. By moving beyond nanoparticle superlattices assembled only with DNA, a new degree of freedom is introduced, providing programmed responsiveness to enzymes and greater bond versatility. Therefore, the oligonucleotide bond can have programmable function beyond dictating the structure of the material and moves nanoparticle superlattices closer to naturally occurring biomaterials, where the line between structural and functional elements is blurred.
    Journal of the American Chemical Society 10/2015; DOI:10.1021/jacs.5b07908 · 12.11 Impact Factor
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    ABSTRACT: The concept of using cantilever-free scanning probe arrays as structures that can modulate nanoscale ink flow and composition with light is introduced and evaluated. By utilizing polymer pen arrays with an opaque gold layer surrounding the base of the transparent polymer pyramids, we show that inks with photopolymerizable or isomerizable constituents can be used in conjunction with light channelled through the pyramids to control ink viscosity or composition in a dynamic manner. This on-tip photo-modulated molecular printing provides novel chemically and mechanically controlled approaches to regulating ink transport and composition in real time and could be useful not only for rapidly adjusting feature size but also for studying processes including photoreactions and mass transport at the nanoscale, self-assembly, and cell-material interactions.
    Angewandte Chemie International Edition 09/2015; DOI:10.1002/anie.201505150 · 11.26 Impact Factor

  • Chemical Reviews 08/2015; 115(19). DOI:10.1021/acs.chemrev.5b00321 · 46.57 Impact Factor
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    ABSTRACT: By grafting multiple DNA strands onto one terminus of a polyester chain, a DNA-brush block copolymer that can assemble into micelle structure is constructed. These micelle spherical nucleic acids have a density of nucleic acids that is substantively higher than linear DNA block copolymer structures, which makes them effective cellular transfection and intracellular gene regulation agents. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Small 08/2015; 11(40). DOI:10.1002/smll.201501573 · 8.37 Impact Factor
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    ABSTRACT: Bottom-up assemblies of plasmonic nanoparticles exhibit unique optical effects such as tunable reflection, optical cavity modes, and tunable photonic resonances. Here, we compare detailed simulations with experiment to explore the effect of structural inhomogeneity on the optical response in DNA-gold nanoparticle superlattices. In particular, we explore the effect of background environment, nanoparticle polydispersity (>10%), and variation in nanoparticle placement (∼5%). At volume fractions less than 20% Au, the optical response is insensitive to particle size, defects, and inhomogeneity in the superlattice. At elevated volume fractions (20% and 25%), structures incorporating different sized nanoparticles (10-, 20-, and 40-nm diameter) each exhibit distinct far-field extinction and near-field properties. These optical properties are most pronounced in lattices with larger particles, which at fixed volume fraction have greater plasmonic coupling than those with smaller particles. Moreover, the incorporation of experimentally informed inhomogeneity leads to variation in far-field extinction and inconsistent electric-field intensities throughout the lattice, demonstrating that volume fraction is not sufficient to describe the optical properties of such structures. These data have important implications for understanding the role of particle and lattice inhomogeneity in determining the properties of plasmonic nanoparticle lattices with deliberately designed optical properties.
    Proceedings of the National Academy of Sciences 08/2015; 112(33):10292-10297. DOI:10.1073/pnas.1513058112 · 9.67 Impact Factor
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    ABSTRACT: Ribozymes are highly structured RNA sequences that can be tailored to recognize and cleave specific stretches of mRNA. Their current therapeutic efficacy remains low due to their large size and structural instability compared to shorter therapeutically relevant RNA such as small interfering RNA (siRNA) and microRNA (miRNA). Herein, a synthetic strategy that makes use of the spherical nucleic acid (SNA) architecture to stabilize ribozymes and transfect them into live cells is reported. The properties of this novel ribozyme-SNA are characterized in the context of the targeted knockdown of O(6)-methylguanine-DNA methyltransferase (MGMT), a DNA repair protein involved in chemotherapeutic resistance of solid tumors, foremost glioblastoma multiforme (GBM). Data showing the direct cleavage of full-length MGMT mRNA, knockdown of MGMT protein, and increased sensitization of GBM cells to therapy-mediated apoptosis, independent of transfection agents, provide compelling evidence for the promising properties of this new chemical architecture.
    Journal of the American Chemical Society 08/2015; 137(33). DOI:10.1021/jacs.5b07104 · 12.11 Impact Factor
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    ABSTRACT: We report a novel spherical nucleic acid (SNA) gold nanoparticle conjugate, termed the Sticky-flare, which enables facile quantification of RNA expression in live cells and spatiotemporal analysis of RNA transport and localization. The Sticky-flare is capable of entering live cells without the need for transfection agents and recognizing target RNA transcripts in a sequence-specific manner. On recognition, the Sticky-flare transfers a fluorophore-conjugated reporter to the transcript, resulting in a turning on of fluorescence in a quantifiable manner and the fluorescent labeling of targeted transcripts. The latter allows the RNA to be tracked via fluorescence microscopy as it is transported throughout the cell. We use this novel nanoconjugate to analyze the expression level and spatial distribution of β-actin mRNA in HeLa cells and to observe the real-time transport of β-actin mRNA in mouse embryonic fibroblasts. Furthermore, we investigate the application of Sticky-flares for tracking transcripts that undergo more extensive compartmentalization by fluorophore-labeling U1 small nuclear RNA and observing its distribution in the nucleus of live cells.
    Proceedings of the National Academy of Sciences 07/2015; 112(31). DOI:10.1073/pnas.1510581112 · 9.67 Impact Factor
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    ABSTRACT: Understanding the surface structure of metal nanocrystals with specific facet indices is important due to its impact on controlling nanocrystal shape and functionality. However, this is particularly challenging for halide-adsorbed nanocrystals due to the difficulty in analysing interactions between metals and light halides (for example, chloride). Here we uncover the surface structures of chloride-adsorbed, silver-coated gold nanocrystals with {111}, {110}, {310} and {720} indexed facets by X-ray absorption spectroscopy and density functional theory modelling. The silver-chloride, silver-silver and silver-gold bonding structures are markedly different between the nanocrystal surfaces, and are sensitive to their formation mechanism and facet type. A unique approach of combining the density functional theory and experimental/simulated X-ray spectroscopy further verifies the surface structure models and identifies the previously indistinguishable valence state of silver atoms on the nanocrystal surfaces. Overall, this work elucidates the thus-far unknown chloride-metal nanocrystal surface structures and sheds light onto the halide-induced growth mechanism of anisotropic nanocrystals.
    Nature Communications 07/2015; 6:7664. DOI:10.1038/ncomms8664 · 11.47 Impact Factor
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    ABSTRACT: Alloy nanoparticles are important in many fields, including catalysis, plasmonics, and electronics, due to the chemical and physical properties that arise from the interactions between their components. Typically, alloy nanoparticles are made by solution-based synthesis; however, scanning-probe-based methods offer the ability to make and position such structures on surfaces with nanometer-scale resolution. In particular, scanning probe block copolymer lithography (SPBCL), which combines elements of block copolymer lithography with scanning probe techniques, allows one to synthesize nanoparticles with control over particle diameter in the 2−50 nm range. Thus far, single-element structures have been studied in detail, but, in principle, one could make a wide variety of multicomponent systems by controlling the composition of the polymer ink, polymer feature size, and metal precursor concentrations. Indeed, it is possible to use this approach to synthesize alloy nanoparticles comprised of combinations of Au, Ag, Pd, Ni, Co, and Pt. Here, such structures have been made with diameters deliberately tailored in the 10− 20 nm range and characterized by STEM and EDS for structural and elemental composition. The catalytic activity of one class of AuPd alloy nanoparticles made via this method was evaluated with respect to the reduction of 4-nitrophenol with NaBH 4. In addition to being the first catalytic studies of particles made by SPBCL, these proof-of-concept experiments demonstrate the potential for SPBCL as a new method for studying the fundamental science and potential applications of alloy nanoparticles in areas such as heterogeneous catalysis.
    Journal of the American Chemical Society 07/2015; 137(28). DOI:10.1021/jacs.5b05139 · 12.11 Impact Factor
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    ABSTRACT: We report a template-based technique for the preparation of solution-dispersible nanorings composed of Au, Ag, Pt, Ni, and Pd with control over outer diameter (60–400 nm), inner diameter (25–230 nm), and height (40 nm to a few microns). Systematic and independent control of these parameters enables fine-tuning of the three characteristic localized surface plasmon resonance modes of Au nanorings and the resulting solution-based extinction spectra from the visible to the near-infrared. This synthetic approach provides a new pathway for solution-based investigations of surfaces with negative curvature.
    Nano Letters 07/2015; 15(8). DOI:10.1021/acs.nanolett.5b01594 · 13.59 Impact Factor
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    ABSTRACT: Herein, we report an example of entropy-driven crystallization behavior in DNA-nanoparticle superlattice assembly, marking a divergence from the well-established enthalpic driving force of maximizing nearest-neighbor hybridization connections. Such behavior is manifested in the observation of a non-close-packed, body-centered cubic (bcc) superlattice when using a system with self-complementary DNA linkers that would be predicted to form a close-packed, face-centered cubic (fcc) structure based solely on enthalpic considerations and previous design rules for DNA-linked particle assembly. Notably, this unexpected phase behavior is only observed when employing long DNA linkers with unpaired "flexor" bases positioned along the length of the DNA linker that increase the number of microstates available to the DNA ligands. A range of design conditions are tested showing sudden onsets of this behavior, and these experiments are coupled with coarse-grained molecular dynamics simulations to show that this entropy-driven crystallization behavior is due to the accessibility of additional microstates afforded by using long and flexible linkers.
    Nano Letters 06/2015; 15(8). DOI:10.1021/acs.nanolett.5b02129 · 13.59 Impact Factor
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    ABSTRACT: We report the design and synthesis of small molecules that exhibit enhanced luminescence in the presence of duplex rather than single-stranded DNA. The local environment presented by a well-known [Ru(dipyrido[3,2-a:2',3'-c]phenazine)L2 ](2+) -based DNA intercalator was modified by functionalizing the bipyridine ligands with esters and carboxylic acids. By systematically varying the number and charge of the pendant groups, it was determined that decreasing the electrostatic interaction between the intercalator and the anionic DNA backbone reduced single-strand interactions and translated to better duplex specificity. In studying this class of complexes, a single Ru(II) complex emerged that selectively luminesces in the presence of duplex DNA with little to no background from interacting with single-stranded DNA. This complex shows promise as a new dye capable of selectively staining double- versus single-stranded DNA in gel electrophoresis, which cannot be done with conventional SYBR dyes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - A European Journal 06/2015; 21(31). DOI:10.1002/chem.201502095 · 5.73 Impact Factor
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    ABSTRACT: Due to their size and tailorable physicochemical properties, nanomaterials are an emerging class of structures utilized in biomedical applications. There are now many prominent examples of nanomaterials being used to improve human health, in areas ranging from imaging and diagnostics to therapeutics and regenerative medicine. An overview of these examples reveals several common areas of synergy and future challenges. This Nano Focus discusses the current status and future potential of promising nanomaterials and their translation from the laboratory to the clinic, by highlighting a handful of successful examples.
    ACS Nano 06/2015; 9(7). DOI:10.1021/acsnano.5b03569 · 12.88 Impact Factor
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    ABSTRACT: The sequence-dependent cellular uptake of spherical nucleic acid nanoparticle conjugates (SNAs) is investigated. This process occurs by interaction with class A scavenger receptors (SR-A) and caveolae-mediated endocytosis. It is known that linear poly(guanine) (poly G) is a natural ligand for SR-A, and it has been proposed that interaction of poly G with SR-A is dependent on the formation of G-quadruplexes. Since G-rich oligonucleotides are known to interact strongly with SR-A, it is hypothesized that SNAs with higher G contents would be able to enter cells in larger amounts than SNAs composed of other nucleotides, and as such, cellular internalization of SNAs is measured as a function of constituent oligonucleotide sequence. Indeed, SNAs with enriched G content show the highest cellular uptake. Using this hypothesis, a small molecule (camptothecin) is chemically conjugated with SNAs to create drug-SNA conjugates and it is observed that poly G SNAs deliver the most camptothecin to cells and have the highest cytotoxicity in cancer cells. Our data elucidate important design considerations for enhancing the intracellular delivery of spherical nucleic acids. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Small 06/2015; 11(33). DOI:10.1002/smll.201500027 · 8.37 Impact Factor
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Publication Stats

67k Citations
7,223.71 Total Impact Points


  • 1992-2015
    • Northwestern University
      • • Department of Chemistry
      • • Nanoscale Science and Engineering Center (NSEC)
      Evanston, Illinois, United States
  • 2004-2014
    • Northwest University
      Evanston, Illinois, United States
  • 2006-2013
    • International Council on Nanotechnology
      INL, Minnesota, United States
    • Rushford Institute for NanoTechnology (RINTek)
      Rushford, Minnesota, United States
  • 2011
    • University of Virginia
      Charlottesville, Virginia, United States
    • University of New Mexico
      • Department of Chemical and Nuclear Engineering
      Albuquerque, NM, United States
    • University of Washington Seattle
      • Department of Chemistry
      Seattle, WA, United States
  • 2010
    • University of Münster
      • Institute of Geophysics
      Muenster, North Rhine-Westphalia, Germany
  • 2007
    • Johns Hopkins University
      • Department of Chemistry
      Baltimore, Maryland, United States
  • 2005
    • City Colleges of Chicago Harold Washington College
      Chicago, Illinois, United States
  • 2003-2005
    • University of Illinois, Urbana-Champaign
      • Department of Electrical and Computer Engineering
      Urbana, IL, United States
  • 1987-2003
    • University of Delaware
      • Department of Chemistry and Biochemistry
      Ньюарк, Delaware, United States
  • 1994
    • Western Illinois University
      • Department of Chemistry
      MQB, Illinois, United States
  • 1990-1992
    • Massachusetts Institute of Technology
      • Department of Chemistry
      Cambridge, Massachusetts, United States
  • 1986-1990
    • Pennsylvania State University
      • Department of Chemistry
      University Park, Maryland, United States