Search

PDF file 3234K, Supplementary figures

XLSX file 43K, K562 induction of apoptosis in response TKI and cytokine treatment

XLSX file 50K, DAVID analysis of durably dephosphorylated peptides

XLSX file 206K, Statistically significant gene expression changes by Illumina microarray in TKI treated K562 cells

XLSX file 169K, Phosphoproteomic peptide identities and quantitative changes in response to drug HDP treatment

Boron neutron capture therapy (BNCT) is an encouraging therapeutic modality for cancer treatment. Prostate-specific membrane antigen (PSMA) is a cell membrane protein that is abundantly overexpressed in prostate cancer and can be targeted with radioligand therapies to stimulate clinical responses in patients. In principle, a spatially targeted neutron beam together with specifically targeted PSMA ligands could enable prostate cancer-targeted BNCT. Thus, we developed and tested PSMA-targeted poly(lactide

Adherens junctions (AJs) create spatially and mechanically discrete microdomains at the interfaces of cells. Using a mechanogenetic platform that generates artificial AJs with controlled protein localization, clustering, and mechanical loading, we report that AJs also organize proteolytic hotspots for γ-secretase with a spatially-regulated substrate selectivity that is critical in the processing of Notch and other transmembrane proteins. Membrane microdomains outside of AJs exclusively organize Notch ligand-receptor engagement (LRE-µdomain) to initialize receptor activation. Conversely, membrane microdomains within AJs exclusively serve to coordinate regulated intramembrane proteolysis (RIP-µdomain). They do so by concentrating γ-secretase and primed receptors while excluding full-length Notch. AJs induce these functionally distinct microdomains by means of cholesterol-dependent γ-secretase recruitment and size-dependent protein segregation. By excluding full-length Notch from RIP-µdomains, AJs prevents inappropriate enzyme-substrate interactions and suppresses spurious Notch activation. Ligand-induced ectodomain shedding eliminates size-dependent segregation, releasing Notch to translocate into AJs for processing by γ-secretase. This mechanism directs radial differentiative expansion of ventricular zone-neural progenitor cells in vivo and more broadly regulates the proteolysis of large cell-surface receptors like amyloid precursor protein. These findings suggest an unprecedented role of AJs in creating size-selective spatial switches that choreograph γ-secretase processing of multiple transmembrane proteins regulating development, homeostasis, and disease.

Adherens junctions (AJs) create spatially, chemically and mechanically discrete microdomains at cellular interfaces. Here, using a mechanogenetic platform that generates artificial AJs with controlled protein localization, clustering and mechanical loading, we find that AJs also organize proteolytic hotspots for γ-secretase with a spatially regulated substrate selectivity that is critical in the processing of Notch and other transmembrane proteins. Membrane microdomains outside of AJs exclusively organize Notch ligand-receptor engagement (LRE microdomains) to initiate receptor activation. Conversely, membrane microdomains within AJs exclusively serve to coordinate regulated intramembrane proteolysis (RIP microdomains). They do so by concentrating γ-secretase and primed receptors while excluding full-length Notch. AJs induce these functionally distinct microdomains by means of lipid-dependent γ-secretase recruitment and size-dependent protein segregation. By excluding full-length Notch from RIP microdomains, AJs prevent inappropriate enzyme-substrate interactions and suppress spurious Notch activation. Ligand-induced ectodomain shedding eliminates size-dependent segregation, releasing Notch to translocate into AJs for processing by γ-secretase. This mechanism directs radial differentiation of ventricular zone-neural progenitor cells in vivo and more broadly regulates the proteolysis of other large cell-surface receptors such as amyloid precursor protein. These findings suggest an unprecedented role of AJs in creating size-selective spatial switches that choreograph γ-secretase processing of multiple transmembrane proteins regulating development, homeostasis and disease.

Multifunctional magnetic nanoparticles have shown great promise as next-generation imaging and perturbation probes for deciphering molecular and cellular processes. As a consequence of multicomponent integration into a single nanosystem, pre-existing nanoprobes are typically large and show limited access to biological targets present in a crowded microenvironment. Here, we apply organic-phase surface PEGylation, click chemistry, and charge-based valency discrimination principles to develop compact, modular, and monovalent magnetofluorescent nanoparticles (MFNs). We show that MFNs exhibit highly efficient labeling to target receptors present in cells with a dense and thick glycocalyx layer. We use these MFNs to interrogate the E-cadherin-mediated adherens junction formation and F-actin polymerization in a three-dimensional space, demonstrating the utility as modular and versatile mechanogenetic probes in the most demanding single-cell perturbation applications.

Aberrant cleavage of Notch by γ-secretase is implicated in numerous diseases, but how cleavage is regulated in space and time is unclear. Here, we report that cadherin-based adherens junctions (cadAJs) are sites of high cell-surface γ-secretase activity, as well as sites of constrained physical space that excludes γ-secretase substrates having large extracellular domains (ECDs) like Notch. ECD shedding initiates drastic spatial relocalization of Notch to cadAJs, allowing enzyme-substrate interactions and downstream signaling. Spatial mutations by adjusting the ECD size or the physical constraint alter signaling. Dysregulation of this spatial switch promotes precocious differentiation of ventricular zone neural progenitor cells in vivo. We show the generality of this spatial switch for amyloid precursor protein proteolysis. Thus, cadAJs create spatially distinct biochemical compartments regulating cleavage events involving γ-secretase and preventing aberrant activation of receptors.

The ability to sense and manipulate the state of biological systems has been extensively advanced during the last decade with the help of recent developments in physical tools. Unlike standard genetic and pharmacological perturbation techniques – knockdown, overexpression, small molecule inhibition – that provide a basic on/off switching capability, these physical tools provide the capacity to control the spatial, temporal, and mechanical properties of the biological targets. Among the various physical cues, magnetism offers distinct advantages over light or electricity. Magnetic fields freely penetrate biological tissues and are already used for clinical applications. As one of the unique features, magnetic fields can be transformed into mechanical stimuli which can serve as a cue in regulating biological processes. However, their biological applications have been limited due to a lack of high-performance magnetism-to-mechanical force transducers with advanced spatiotemporal capabilities. In this account, we present recent developments in magnetic nano-tweezers (MNTs) as a high-performance tool for interrogating the spatiotemporal control of cells in living tissue. MNTs are comprised of force-generating magnetic nanoparticles and field generators. Through proper design and the integration of individual components, MNTs deliver controlled mechanical stimulation to targeted biomolecules at any desired space and time. We first discuss about MNT configuration with different force-stimulation modes. By modulating geometry of the magnetic field generator, MNTs exert pulling, dipole-dipole attraction, and rotational forces to the target specifically and quantitatively. We discuss the key physical parameters determining force magnitude, which include magnetic field strength, magnetic field gradient, magnetic moment of the magnetic particle, as well as distance between the field generator and the particle. MNTs also can be used over a wide range of biological time scales — By simply adjusting the amplitude and phase of the applied current, MNTs based on electromagnets allow for dynamic control of the magnetic field from microseconds to hours. Chemical design and the nanoscale effects of magnetic particles are also essential for optimizing MNT performance. We discuss key strategies to develop magnetic nanoparticles with improved force-generation capabilities with a particular focus on the effects of size, shape, and composition of the nanoparticles. We then introduce various strategies and design considerations for target-specific biomechanical stimulations with MNTs. One-to-one particle-receptor engagement for delivering a defined force to the targeted receptor and the small size of the nanoparticles are important. Finally, we demonstrate the utility of MNTs for manipulating biological functions and activities with various spatial (single molecule/cell to organisms) and temporal resolution (microseconds to days). MNTs have the potential to be utilized in many exciting applications across diverse biological systems spanning from fundamental biology investigations of spatial and mechanical signaling dynamics at the single-cell and systems levels to in vivo therapeutic applications.

This study was conducted to investigate the effects of upper thoracic joint mobilization technique using Kaltenborn-Evjenth concept on the range of cervical and thoracic motion and pain in patients with chronic neck pain. The subjects were divided into a thoracic joint mobilization group(n=7) and a conservative physical therapy group(n=7). Each of the groups received thoracic joint mobilization or conservative physical therapy three times a week lasted for four weeks. The measurements were performed for the range of thoracic segmental motion(SpinalMouse), the pain(visual analogue scale) and the range of cervical joint motion(Inclinometer, Dualer IQ). They were made four times: before experiment, at 2weeks, 4weeks, and 4weeks after experiment. Key word : Joint mobilization technique, Upper thoracic, Kaltenborn evjenth concept 요 약 본 연구는 만성 경부통증 환자에게 Kaltenborn-Evjenth concept에 기초한 상부흉추 관절가동술 적용이 경흉추 관절 가동범위와 통증에 미치는 영향을 알아보고자 하였다. Kaltenborn-Evjenth concept은 작은 진폭의 도수요법으로 관절낭이나 연부조직에 스트레스를 주지 않고 해당부위의 관절 또는 근육을 칼텐본 등급에 따라 정형도수치료를 하는 수기요법이다. 연구 대상자는 상부흉추 관절가동술군 7명과 보존적 물리치료군 7명으로 나뉘어 각각 주 3회, 4주간 흉추 관절가동술과 보존적 물리치료(온습포 치료, 간섭파, 초음파 치료)를 시행 받았다. 측정은 실험 전과 실험 2주, 실

Spatiotemporal interrogation of signal transduction at the single-cell level is necessary to answer a host of important biological questions. This protocol describes a nanotechnology-based single-cell and single-molecule perturbation tool, termed mechanogenetics, that enables precise spatial and mechanical control over genetically encoded cell-surface receptors in live cells. The key components of this tool are a magnetoplasmonic nanoparticle (MPN) actuator that delivers defined spatial and mechanical cues to receptors through target-specific one-to-one engagement and a micromagnetic tweezers (μMT) that remotely controls the magnitude of force exerted on a single MPN. In our approach, a SNAP-tagged cell-surface receptor of interest is conjugated with a single-stranded DNA oligonucleotide, which hybridizes to its complementary oligonucleotide on the MPN. This protocol consists of four major stages: (i) chemical synthesis of MPNs, (ii) conjugation with DNA and purification of monovalent MPNs, (iii) modular targeting of MPNs to cell-surface receptors, and (iv) control of spatial and mechanical properties of targeted mechanosensitive receptors in live cells by adjusting the μMT-to-MPN distance. Using benzylguanine (BG)-functionalized MPNs and model cell lines expressing either SNAP-tagged Notch or vascular endothelial cadherin (VE-cadherin), we provide stepwise instructions for mechanogenetic control of receptor clustering and for mechanical receptor activation. The ability of this method to differentially control spatial and mechanical inputs to targeted receptors makes it particularly useful for interrogating the differential contributions of each individual cue to cell signaling. The entire procedure takes up to 1 week.

Tools capable of imaging and perturbing mechanical signaling pathways with fine spatiotemporal resolution have been elusive, despite their importance in diverse cellular processes. The challenge in developing a mechanogenetic toolkit (i.e., selective and quantitative activation of genetically encoded mechanoreceptors) stems from the fact that many mechanically activated processes are localized in space and time yet additionally require mechanical loading to become activated. To address this challenge, we synthesized magnetoplasmonic nanoparticles that can image, localize, and mechanically load targeted proteins with high spatiotemporal resolution. We demonstrate their utility by investigating the cell-surface activation of two mechanoreceptors: Notch and E-cadherin. By measuring cellular responses to a spectrum of spatial, chemical, temporal, and mechanical inputs at the single-molecule and single-cell levels, we reveal how spatial segregation and mechanical force cooperate to direct receptor activation dynamics. This generalizable technique can be used to control and understand diverse mechanosensitive processes in cell signaling. VIDEO ABSTRACT.

Caspases are proteases involved in cell death, where caspase-3 is the chief executioner that produces an irreversible cutting event in downstream protein substrates and whose activity is desired in the management of cancer. To determine such activity in clinically relevant samples with high signal-to-noise, plasmon rulers are ideal because they are sensitively affected by their interparticle separation without ambiguity from photobleaching or blinking effects. A plasmon ruler is a noble metal nanoparticle pair, tethered in close proximity to one another via a biomolecule, that acts through dipole–dipole interactions and results in the light scattering to increase exponentially. In contrast, a sharp decrease in intensity is observed when the pair is confronted by a large interparticle distance. To align the mechanism of protease activity with building a sensor that can report a binary signal in the presence or absence of caspase-3, we present a caspase-3 selective plasmon ruler (C3SPR) composed of a pair of Zn0.4Fe2.6O4@SiO2@Au core–shell nanoparticles connected by a caspase-3 cleavage sequence. The dielectric core (Zn0.4Fe2.6O4@SiO2)-shell (Au) geometry provided a brighter scattering intensity versus solid Au nanoparticles, and the magnetic core additionally acted as a purification handle during the plasmon ruler assembly. By monitoring the decrease in light scattering intensity per plasmon ruler, we detected caspase-3 activity at single molecule resolution across a broad dynamic range. This was observed to be as low as 100 fM of recombinant material or 10 ng of total protein from cellular lysate. By thorough analyses of single molecule trajectories, we show caspase-3 activation in a drug-treated chronic myeloid leukemia (K562) cancer system as early as 4 and 8 h with greater sensitivity (2- and 4-fold, respectively) than conventional reagents. This study provides future implications for monitoring caspase-3 as a biomarker and efficacy of drugs.

The clinical experience with BCR–ABL tyrosine kinase inhibitors (TKI) for the treatment of chronic myelogenous leukemia (CML) provides compelling evidence for oncogene addiction. Yet, the molecular basis of oncogene addiction remains elusive. Through unbiased quantitative phosphoproteomic analyses of CML cells transiently exposed to BCR–ABL TKI, we identified persistent downregulation of growth factor receptor (GF-R) signaling pathways. We then established and validated a tissue-relevant isogenic model of BCR–ABL-mediated addiction, and found evidence for myeloid GF-R signaling pathway rewiring that profoundly and persistently dampens physiologic pathway activation. We demonstrate that eventual restoration of ligand-mediated GF-R pathway activation is insufficient to fully rescue cells from a competing apoptotic fate. In contrast to previous work with BRAFV600E in melanoma cells, feedback inhibition following BCR–ABL TKI treatment is markedly prolonged, extending beyond the time required to initiate apoptosis. Mechanistically, BCR–ABL-mediated oncogene addiction is facilitated by persistent high levels of MAP–ERK kinase (MEK)-dependent negative feedback. Significance: We found that BCR–ABL can confer addiction in vitro by rewiring myeloid GF-R signaling through establishment of MEK-dependent negative feedback. Our findings predict that deeper, more durable responses to targeted agents across a range of malignancies may be facilitated by maintaining negative feedback concurrently with oncoprotein inhibition. Cancer Discov; 4(2); 200–15. ©2013 AACR. This article is highlighted in the In This Issue feature, p. 131

The multivalent nature of commercial nanoparticle imaging agents and the difficulties associated with producing monovalent nanoparticles challenge their use in biology, where clustering of target biomolecules can perturb dynamics of biomolecular targets. Here, we report production and purification of monovalent gold and silver nanoparticles for their single molecule imaging application. We first synthesized DNA-conjugated 20 nm and 40 nm gold and silver nanoparticles via conventional metal-thiol chemistry, yielding nanoparticles with mixed valency. By employing an anion-exchange high performance liquid chromatography (AE-HPLC) method, we purified monovalent nanoparticles from the mixtures. To allow efficient peak-separation resolution while keeping the excellent colloidal stability of nanoparticles against harsh purification condition (e.g. high NaCl), we optimized surface properties of nanoparticles by modulating surface functional groups. We characterized the monovalent character of the purified nanoparticles by hybridizing two complementary conjugates, forming dimers. Finally, we demonstrate the use of the monovalent plasmonic nanoprobes as single molecule imaging probes by tracking single TrkA receptors diffusing on the cell membrane and compare to monovalent quantum dot probes.

The use of plasmon coupling in metal nanoparticles has shown great potential for the optical characterization of many biological processes. Recently, we have demonstrated the use of “plasmon rulers” to observe conformational changes of single biomolecules in vitro. Plasmon rulers provide robust signals without photobleaching or blinking. Here, we show the first application of plasmon rulers to in vivo studies to observe very long trajectories of single biomolecules in live cells. We present a unique type of plasmon ruler comprised of peptide-linked gold nanoparticle satellites around a core particle, which was used as a probe to optically follow cell-signaling pathways in vivo at the single-molecule level. These “crown nanoparticle plasmon rulers” allowed us to continuously monitor trajectories of caspase-3 activity in live cells for over 2 h, providing sufficient time to observe early-stage caspase-3 activation, which was not possible by conventional ensemble analyses.

Mergers and Acquisitions The crystallization of small molecules or polymers is often described in terms of a nucleation stage, where initial clusters form, followed by a distinct growth stage. Growth can come from the addition of unbound molecules, or through “Ostwald ripening” where larger crystals grow at the expense of smaller ones due to thermodynamic effects. Zheng et al. (p. 1309 ) studied the growth of platinum nanocrystals inside a transmission electron microscope using a special liquid cell, allowing observation of crystal growth in situ. Both monomer addition to growing particles and the coalescence of two particles were observed. The specific growth mechanism appeared to be governed by the size of each of the particles. The combination of growth processes makes it possible for an initially broad distribution of particles to narrow into an almost uniform one.

Synthetische magnetische Nanopartikel (MNP) werden in der Biomedizin immer haufiger als Sonden eingesetzt. Dies gilt besonders fur die Anwendung in der Kernspintomographie (Magnetic Resonance Imaging, MRI). Diese Nanopartikel sind von ahnlicher Grose wie biologische Funktionseinheiten. Deshalb und wegen ihrer einzigartigen magnetischen Eigenschaften eignen sie sich zur molekularen Bildgebung. Dieser Aufsatz gibt einen Uberblick zu neuartigen MNP-Sonden, mit denen biologische Ereignisse auf molekularer und zellularer Ebene empfindlich und spezifisch nachgewiesen werden konnen.

nanosheetcrystalsfromthe tungsten oxide rods. The reaction between the carbondisulfide and hexadecylamine generates in situ hydrogendisulfideandhexadecylisothiocyanateviaN-hexadecyldithio-carbamate as a transient species [Eq.(1); see also Figures S1and S2 in the Supporting Information], and subsequent

Nanoparticles have the potential to revolutionize current bio-medical diagnostic and therapeutic methods. For example, magnetic nanoparticles with unique superparamagnetism are emerging as next-generation probes for high performance magnetic resonance (MR) imaging. Their enhanced properties and nanoscale controllability in terms of size, composition, surface states, and magnetic spin structure have allowed for the highly sensitive and target-specific MR imaging of various biological systems including cancer detection, cell trafficking, and angiogenesis. On the other hand, viruses can be utilized as excellent delivery vehicles due to their facile cellular transfection and gene expression efficacies within their target cells. Such excellent properties of viruses offer promising prospects for gene therapy of genetic diseases and cancers, as well as for the genetic engineering of cells. Despite these prospects, a lack of understanding of their biological behaviors including in vivo migration, molecular recognition, gene delivery, and ultimate fate following their desired biofunctional applications limits their further development. There have been previous studies in the development of nanoparticle probing systems for viruses including virus-gold and virus-quantum dot nanoparticle systems. However, their utilization in the probing of viral gene delivery has not been investigated so far. Recently, Gd-based MR contrast agent-coated viruses were developed, but their functional behaviors including targetrecognition, cellular transfection, and gene delivery capabilities have not been demonstrated partly due to the intrinsically low sensitivity of Gd-based MR contrast agents. Our strategy is to hybridize the virus with magnetic nanoparticles into a single nanoparticle system with the dual-functional capabilities of target-specific MR imaging and gene delivery. Specifically, we fabricate hybrid nanoparticles of “enhanced green fluorescent protein (eGFP) promoter genecontaining adenovirus” and “manganese-doped magnetism engineered iron oxide (abbreviated as MnMEIO) nanoparticle”. As the viral gene delivery vector, we selected adenoviruses. Adenoviruses are known to be highly effective for transferring double-stranded DNAs to various cell types. Along with a gene delivery capability, adenoviruses possess targetspecificity to the cells with overexpression of Coxsackievirus B adenovirus receptor (CAR) which is known to facilitate the binding and intrusion of adenoviruses to the host cells. As the magnetic nanoparticle component we selected manganese-doped magnetism-engineered iron oxide (MnFe2O4, MnMEIO) nanoparticles, since it is known that MnMEIO exhibits exceptional MR contrast effects (R2 (=1/T2) value of 358 sec mM) and therefore is advantageous as probes for ultra-sensitive MR imaging. Briefly, the thermal reaction of manganese chloride (MnCl2) and iron tris(2,4-pentadionate) in hot organic solvents containing oleic acid and oleylamine capping molecules yielded hydrophobically capped MnMEIO nanoparticles. Their water-solubility and biocompatibility were attained by introducing 2,3-dimercaptosuccinic acids to the nanoparticle surface. Nanoparticles obtained were 12 nm with a high sizemonodispersity (r < 7%) and possessed single crystallinity, and a saturation magnetization value of 110 emu g (Mn+Fe). Hybridization of adenoviruses with MnMEIO nanoparticles was performed through a slight modification of a literature method, as follows. First, the capsid lysine residues of the adenoviruses were converted to maleimide groups by reacting them with sulfo-succinimidyl(4-N-maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC) cross-linkers. These groups were allowed to react with a large stoichiometric amount of MnMEIO nanoparticles, which resulted in the formation of adenovirus-MnMEIO hybrid nanoparticles by way of the nucleophilic addition of a surface thiol group of MnMEIO to the C O M M U N IC A IO N

© 2015 SIR. Purpose: To establish that a magnetic device designed for intravascular use can bind small iron particles in physiologic flow models. Materials and Methods: Uncoated iron oxide particles 50-100 nm and 1-5 μm in size were tested in a water flow chamber over a period of 10 minutes without a magnet (ie, control) and with large and small prototype magnets. These same particles and 1-μm carboxylic acid-coated iron oxide beads were likewise tested in a serum flow chamber model without a magnet (ie, control) and with the small prototype magnet. Results: Particles were successfully captured from solution. Particle concentrations in solution decreased in all experiments (P < .05 vs matched control runs). At 10 minutes, concentrations were 98% (50-100-nm particles in water with a large magnet), 97% (50-100-nm particles in water with a small magnet), 99% (1-5-μm particles in water with a large magnet), 99% (1-5-μm particles in water with a small magnet), 95% (50-100-nm particles in serum with a small magnet), 92% (1-5-μm particles in serum with a small magnet), and 75% (1-μm coated beads in serum with a small magnet) lower compared with matched control runs. Conclusions: This study demonstrates the concept of magnetic capture of small iron oxide particles in physiologic flow models by using a small wire-mounted magnetic filter designed for intravascular use.

Successful development of ultra-sensitive molecular imaging nanoprobes for the detection of targeted biological objects is a challenging task. Although magnetic nanoprobes have the potential to perform such a role, the results from probes that are currently available have been far from optimal. Here we used artificial engineering approaches to develop innovative magnetic nanoprobes, through a process that involved the systematic evaluation of the magnetic spin, size and type of spinel metal ferrites. These magnetism-engineered iron oxide (MEIO) nanoprobes, when conjugated with antibodies, showed enhanced magnetic resonance imaging (MRI) sensitivity for the detection of cancer markers compared with probes currently available. Also, we successfully visualized small tumors implanted in a mouse. Such high-performance, nanotechnology-based molecular probes could enhance the ability to visualize other biological events critical to diagnostics and therapeutics.

Anorganische Nanokristalle mit gezielt praparierten Formen und Abmessungen haben einzigartige, formabhangige Eigenschaften und sind als Bausteine zur Herstellung von Nanofunktionseinheiten von grosem Interesse. In diesem Aufsatz fassen wir die jungsten Entwicklungen bei der Formkontrolle von kolloidalen Nanokristallen zusammen, wobei der Schwerpunkt auf den wissenschaftlich und technologisch wichtigen Halbleiter- und Metalloxid-Nanokristallen liegt, die sich durch nichthydrolytische Synthesemethoden erhalten lassen. Viele ungewohnliche Strukturmotive wurden entdeckt, darunter Polyeder, Stabchen und Drahte, Scheiben und Prismen sowie komplexere Formen wie verzweigte Stabchen, Sterne, anorganische Dendrimere und Hanteln. Der gegenwartig favorisierte Mechanismus der Formkontrolle wird vorgestellt, ebenso wie richtungsweisende Studien zur Anordnung formkontrollierter Nanokristalle zu geordneten Ubergittern und zur Herstellung hochentwickelter Prototypen von Nanofunktionseinheiten.

The systematic assembly of nanoscale constituents into highly ordered superlattices is of significant interest because of the potential of their multifunctionalities and the discovery of new collective properties. However, successful observations of such superlattice-associated nanoscale phenomena are still elusive. Here, we present magnetic superlattices of Co and Fe 3 O 4 nanoparticles with multidimensional symmetry of either AB (NaCl) or AB 2 (AlB 2 ). The discovery of significant enhancement (≈25 times) of ferrimagnetism is further revealed by forming previously undescribed superlattices of magnetically soft–hard Fe 3 O 4 @CoFe 2 O 4 through the confined geometrical effect of thermally driven intrasuperlattice phase transition between the nanoparticulate components.

Inorganic nanocrystals with certain geometries exhibit unique shape dependent phenomena and subsequent utilization of them as building blocks for the key components of nanodevices is of huge interest. Architecture of these nanocrystals can be simply classified by their dimensionalities: zero-dimensional (0D) quantum dots including spheres, cubes, and tetrahedrons, one-dimensional nanorods and wires, two-dimensional (2D) nanodiscs and plates, and other advanced shapes such as rod-based multipods and nanostars. Among them, one-dimensional (1D) structures are of current interest in materials chemistry not only because they exhibit novel optical properties arising from dimensional anisotropy, but also because they can be utilized as key materials in addressable two-terminal circuits for nanodevice applications. We describe here the current studies on a variety of one-dimensional semiconductor and metal oxide nano-building blocks obtained by liquid phase colloidal synthetic methods. Several mechanisms and critical parameters for nanocrystal shape guiding processes are carefully examined. Once we understand the guiding laws of nanocrystals growth, many new nano-building blocks will easily be tailored for the discovery of novel phenomena and also further exciting advancement of nanoscience and nanotechnology.

The unique properties of magnetic nanocrystals provide them with high potential as key probes and vectors in the next generation of biomedical applications. Although superparamagnetic iron oxide nanocrystals have been extensively studied as excellent magnetic resonance imaging (MRI) probes for various cell trafficking, gene expression, and cancer diagnosis, further development of in vivo MRI applications has been very limited. Here, we describe in vivo diagnosis of cancer, utilizing a well-defined magnetic nanocrystal probe system with multiple capabilities, such as small size, strong magnetism, high biocompatibility, and the possession of active functionality for desired receptors. Our magnetic nanocrystals are conjugated to a cancer-targeting antibody, Herceptin, and subsequent utilization of these conjugates as MRI probes has been successfully demonstrated for the monitoring of in vivo selective targeting events of human cancer cells implanted in live mice. Further conjugation of these nanocrystal probes with fluorescent dye-labeled antibodies enables both in vitro and ex vivo optical detection of cancer as well as in vivo MRI, which are potentially applicable for an advanced multimodal detection system. Our study finds that high performance in vivo MR diagnosis of cancer is achievable by utilizing improved and multifunctional material properties of iron oxide nanocrystal probes.

Since inorganic nanocrystals exhibit unique shape-dependent nanoscale properties and can be utilized as basic building blocks for futuristic nanodevices, a systematic study on the shape control of these nanocrystals remains an important subject in materials and physical chemistry. In this feature article, we overview the recent progress on the synthetic development of symmetry-controlled colloidal nanocrystals of semiconductor and metal oxide, which are prepared through nonhydrolytic chemical routes. We describe their shape-guiding processes and illustrate the detailed key factors controlling their growth by examining various case studies of zero-dimensional spheres and cubes, one-dimensional rods, and quasi multidimensional structures such as disks, multipods, and stars. Specifically, the crystalline phase of nucleating seeds, surface energy, kinetic vs thermodynamic growth, and selective adhesion processes of capping ligands are found to be most crucial for the determination of the nanocrystal shape.

The structure, magnetism, and phase transition of core-shell type CoPt nanoparticles en route to solid solution alloy nanostructures are systematically investigated. The characterization of Co(core)Pt(shell) nanoparticles obtained by a "redox transmetalation" process by transmission electron microscopy (TEM) and, in particular, X-ray absorption spectroscopy (XAS) provides clear evidence for the existence of a core-shell type bimetallic interfacial structure. Nanoscale phase transitions of the Co(core)Pt(shell) structures toward c-axis compressed face-centered tetragonal (fct) solid solution alloy CoPt nanoparticles are monitored at various stages of a thermally induced annealing process and the obtained fct nanoalloys show a large enhancement of their magnetic properties with ferromagnetism. The relationship between the nanostructures and their magnetic properties is in part elucidated through the use of XAS as a critical analytical tool.

The surfactant-mediated shape evolution of titanium dioxide anatase nanocrystals in nonaqueous media was studied. The shape evolves from bullet and diamond structures to rods and branched rods. The modulation of surface energies of the different crystallographic faces through the use of a surface selective surfactant is the key parameter for the shape control.

Shape- and dopant-controlled magnetic semiconductor nanocrystals have been achieved by the thermolysis of nonpyrophoric and less reactive single molecular precursors under a monosurfactant system. Reaction parameters governing both the intrinsic crystalline phase and the growth regime (kinetic vs thermodynamic) are found to be important for the synthesis of various shapes of MnS nanocrystals that include cubes, spheres, 1-dimensional (1-D) monowires, and branched wires (bipods, tripods, and tetrapods). Obtained nanowires exhibit enhanced optical and magnetic properties compared to those of 0-D nanospheres. Proper choice of molecular precursors and kinetically driven low-temperature growth afford dopant controlled 1-D Cd1-xMn(x)S nanorods at high levels (up to approximately 12%) of Mn, which is supported by repeated surface exchange experiments and X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) analyses.

The multivalent nature of commercial quantum dots (QDs) and the difficulties associated with producing monovalent dots have limited their applications in biology, where clustering and the spatial organization of biomolecules is often the object of study. We describe here a protocol to produce monovalent quantum dots (mQDs) that can be accomplished in most biological research laboratories via a simple mixing of CdSe/ZnS core/shell QDs with phosphorothioate DNA (ptDNA) of defined length. After a single ptDNA strand has wrapped the QD, additional strands are excluded from the surface. Production of mQDs in this manner can be accomplished at small and large scale, with commercial reagents, and in minimal steps. These mQDs can be specifically directed to biological targets by hybridization to a complementary single stranded targeting DNA. We demonstrate the use of these mQDs as imaging probes by labeling SNAP-tagged Notch receptors on live mammalian cells, targeted by mQDs bearing a benzylguanine moiety.

Apoptotic caspases execute programmed cell death, where low levels of caspase activity are linked to cancer (KasibhatlaTseng, 2003). Chemotherapies utilize induction of apoptosis as a key mechanism for cancer treatment, where caspase-3 is a major player involved in dismantling these aberrant cells. The ability to sensitively measure the initial caspase-3 cleavage events during apoptosis is important for understanding the initiation of this complex cellular process; however, current ensemble methods are not sensitive enough to measure single cleavage events in cells. To overcome this, we describe a procedure to develop peptide-linked gold nanoparticles that have unique optical properties and can serve as beacons to visualize the apoptotic drug response in cancer cells at the single-molecule level. By thorough analyses of their trajectories, one can reveal early-stage caspase-3 activation in live cells continuously and with no ambiguity.

Apoptotic caspases execute programmed cell death, where low levels of caspase activity are linked to cancer (Kasibhatla & Tseng, 2003). Chemotherapies utilize induction of apoptosis as a key mechanism for cancer treatment, where caspase-3 is a major player involved in dismantling these aberrant cells. The ability to sensitively measure the initial caspase-3 cleavage events during apoptosis is important for understanding the initiation of this complex cellular process; however, current ensemble methods are not sensitive enough to measure single cleavage events in cells. To overcome this, we describe a procedure to develop peptide-linked gold nanoparticles that have unique optical properties and can serve as beacons to visualize the apoptotic drug response in cancer cells at the single-molecule level. By thorough analyses of their trajectories, one can reveal early-stage caspase-3 activation in live cells continuously and with no ambiguity.

Notch signaling is a key cell-to-cell communication mechanism during development and in normal tissue maintenance and cancer. Signals exchanged between neighboring cells via Notch can reinforce molecular differences which eventually direct the fate decision of individual cells. Despite increasing knowledge of these signaling events, little is known about how spatiotemporal dynamics of the receptor signaling across a cell influence the signal exchange. In this presentation, we introduce an advanced nano-probing system that mimics binary cell communication via Notch, while providing systematic spatiotemporal control of Notch signaling in live cells. This new nanosystem enabled simultaneous observation of Notch dynamics and signal activation with single molecule resolution in live cells for the first time. We envision this nano-probing system as a next generation force microscopy technology platform to quantify and control force-mediated biological processes at the subcellular level.

Precise control over interfacial chemistry between nanoparticles and other materials remains a significant challenge limiting the broad application of nanotechnology in biology. To address this challenge, we use “Steric Exclusion” to completely convert commercial quantum dots (QDs) into monovalent imaging probes by wrapping the QD with a functionalized oligonucleotide. We demonstrate the utility of these QDs as modular and non-perturbing imaging probes by tracking individual Notch receptors on live cells.