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1.  Label-free capture of breast cancer cells spiked in buffy coats using carbon nanotube antibody micro-arrays 
Nanotechnology  2016;27(13):13LT02.
We demonstrate the rapid and label-free capture of breast cancer cells spiked in buffy coats using nanotube-antibody micro-arrays. Single wall carbon nanotube arrays were manufactured using photo-lithography, metal deposition, and etching techniques. Anti-epithelial cell adhesion molecule (EpCAM) antibodies were functionalized to the surface of the nanotube devices using 1-pyrene-butanoic acid succinimidyl ester functionalization method. Following functionalization, plain buffy coat and MCF7 cell spiked buffy coats were adsorbed on to the nanotube device and electrical signatures were recorded for differences in interaction between samples. A statistical classifier for the ‘liquid biopsy’ was developed to create a predictive model based on dynamic time warping to classify device electrical signals that corresponded to plain (control) or spiked buffy coats (case). In training test, the device electrical signals originating from buffy versus spiked buffy samples were classified with ~100% sensitivity, ~91% specificity and ~96% accuracy. In the blinded test, the signals were classified with ~91% sensitivity, ~82% specificity and ~86% accuracy. A heatmap was generated to visually capture the relationship between electrical signatures and the sample condition. Confocal microscopic analysis of devices that were classified as spiked buffy coats based on their electrical signatures confirmed the presence of cancer cells, their attachment to the device and overexpression of EpCAM receptors. The cell numbers were counted to be ~1—17 cells per 5 µl per device suggesting single cell sensitivity in spiked buffy coats that is scalable to higher volumes using the micro-arrays.
doi:10.1088/0957-4484/27/13/13LT02
PMCID: PMC5065025  PMID: 26901310
carbon nanotube; micro-arrays; cancer cells; buffy coats; fine needle aspirates; circulating tumor cells
2.  A synergistic approach to the design, fabrication and evaluation of 3D printed micro and nano featured scaffolds for vascularized bone tissue repair 
Nanotechnology  2016;27(6):064001.
3D bioprinting has begun to show great promise in advancing the development of functional tissue/organ replacements. However, to realize the true potential of 3D bioprinted tissues for clinical use requires the fabrication of an interconnected and effective vascular network. Solving this challenge is critical, as human tissue relies on an adequate network of blood vessels to transport oxygen, nutrients, other chemicals, biological factors and waste, in and out of the tissue. Here, we have successfully designed and printed a series of novel 3D bone scaffolds with both bone formation supporting structures and highly interconnected 3D microvascular mimicking channels, for efficient and enhanced osteogenic bone regeneration as well as vascular cell growth. Using a chemical functionalization process, we have conjugated our samples with nano hydroxyapatite (nHA), for the creation of novel micro and nano featured devices for vascularized bone growth. We evaluated our scaffolds with mechanical testing, hydrodynamic measurements and in vitro human mesenchymal stem cell (hMSC) adhesion (4 h), proliferation (1, 3 and 5 d) and osteogenic differentiation (1, 2 and 3 weeks). These tests confirmed bone-like physical properties and vascular-like flow profiles, as well as demonstrated enhanced hMSC adhesion, proliferation and osteogenic differentiation. Additional in vitro experiments with human umbilical vein endothelial cells also demonstrated improved vascular cell growth, migration and organization on micro-nano featured scaffolds.
doi:10.1088/0957-4484/27/6/064001
PMCID: PMC5055473  PMID: 26758780
3D printing; vascularized bone; nanomaterials; perfusable channel; stem cells; endothelial cells
3.  Effect of surface coating of KYb2F7:Tm3+ on optical properties and biomedical applications 
Nanotechnology  2016;27(38):385601.
This project aims to provide an insight on the effects of biocompatible polymers on the optical properties and the nanoparticle-cell interaction of KYb2F7:Tm3+ nanocrystals that exhibit strong near infrared (NIR) fluorescence. KYb2F7:Tm3+ nanocrystals were synthesized with a diameter of 20–30 nm and surface modified with poly(ethylene glycol), Pluronic® F-127, and poly(N-vinylpyrrolidone), due to the associated advantages. Some of these include biocompatibility and biodistribution in the instance of agglomeration and hydrophobicity as well as the addition of a targeting agent and drug loading by further functionalization. Despite the decrease in fluorescence intensity induced by the surface modification, thulium’s emission fingerprint was easily detected. Moreover, surface modified KYb2F7:Tm3+ nanocrystals failed to induce a toxic response on endothelial cells following a 24 h uptake period up to concentrations of 100 μg ml−1. In vitro toxicity and confocal imaging have demonstrated the versatility of these NIR fluorescence nanocrystals in biomedical imaging, drug delivery, and photodynamic therapy.
doi:10.1088/0957-4484/27/38/385601
PMCID: PMC4999246  PMID: 27518385
lanthanide ions; rare Earth ions; near infrared imaging; contrast agents; surface modification
4.  The effect of cryoprotection on the use of PLGA encapsulated iron oxide nanoparticles for magnetic cell labeling 
Nanotechnology  2013;24(12):125101.
Magnetic PLGA nanoparticles are a significant advancement in the quest to translate MRI-based cell tracking to the clinic. The benefits of these types of particles are that they encapsulate large amounts of iron oxide nanocrystals within an FDA-approved polymer matrix, combining the best aspects of inert micron-sized iron oxide particles, or MPIOs, and biodegradable small particles of iron oxide, or SPIOs. Practically, PLGA nanoparticle fabrication and storage requires some form of cryoprotectant to both protect the particle during freeze drying and to promote resuspension. While this is a commonly employed procedure in the fabrication of drug loaded PLGA nanoparticles, it has yet to be investigated for magnetic particles and what effect this might have on internalization of magnetic particles. As such, in this study, magnetic PLGA nanoparticles were fabricated with various concentrations of two common cryoprotectants, dextrose and sucrose, and analyzed for their ability to magnetically label cells. It was found that cryoprotection with either sugar significantly enhanced the ability to resuspend nanoparticles without aggregation. Magnetic cell labeling was impacted by sugar concentration, with higher sugar concentrations used during freeze drying more significantly reducing magnetic cell labeling than lower concentrations. These studies suggest that cryoprotection with 1% dextrose is an optimal compromise that preserves monodispersity following resuspension and high magnetic cell labeling.
doi:10.1088/0957-4484/24/12/125101
PMCID: PMC5026304  PMID: 23459030
5.  Temperature dependence of DNA translocations through solid-state nanopores 
Nanotechnology  2015;26(23):234004.
In order to gain a better physical understanding of DNA translocations through solid-state nanopores, we study the temperature dependence of λ-DNA translocations through 10 nm-in-diameter silicon-nitride nanopores, both experimentally and theoretically. The measured ionic conductance G, the DNA-induced ionic-conductance blockades ΔG and the event frequency Γ all increase with increasing temperature while the DNA translocation time τ decreases. G and ΔG are accurately described when bulk and surface conductances of the nanopore are considered and access resistance is incorporated appropriately. Viscous drag on the untranslocated part of the DNA coil is found to dominate the temperature dependence of the translocation times and the event rate is well described by a balance between diffusion and electrophoretic motion. The good fit between modeled and measured properties of DNA translocations through solid-state nanopores in this first comprehensive temperature study, suggest that our model captures the relevant physics of the process.
doi:10.1088/0957-4484/26/23/234004
PMCID: PMC4503867  PMID: 25994084
solids-state nanopores; temperature dependence; DNA translocations; nanopore conduction model
6.  Combinatorial approaches to evaluate nanodiamond uptake and induced cellular fate 
Nanotechnology  2016;27(8):085107.
Nanodiamonds (NDs) are an emerging class of engineered nanomaterials that hold great promise for the next generation of bionanotechnological products to be used for drug and gene delivery, or for bio-imaging and biosensing. Previous studies have shown that upon their cellular uptake, NDs exhibit high biocompatibility in various in vitro and in vivo set-ups. Herein we hypothesized that the increased NDs biocompatibility is a result of minimum membrane perturbations and their reduced ability to induce disruption or damage during cellular translocation. Using multi-scale combinatorial approaches that simulate ND-membrane interactions, we correlated NDs real-time cellular uptake and kinetics with the ND-induced membrane fluctuations to derive energy requirements for the uptake to occur. Our discrete and real-time analyses showed that the majority of NDs internalization occurs within 2 h of cellular exposure, however, with no effects on cellular viability, proliferation or cellular behavior. Furthermore, our simulation analyses using coarse-grained models identified key changes in the energy profile, membrane deformation and recovery time, all functions of the average ND or ND-based agglomerate size. Understanding the mechanisms responsible for ND-cell membrane interactions could possibly advance their implementation in various biomedical applications.
doi:10.1088/0957-4484/27/8/085107
PMCID: PMC4889219  PMID: 26820775
nanodiamonds; course grained simulation; cell-based sensing
7.  Carbon Nanoelectrodes for Single-Cell Probing 
Nanotechnology  2015;26(18):185101.
Carbon nanoelectrodes with tip diameters ranging from tens to hundreds of nm are fabricated by pyrolitic deposition of carbon films along the entire inner surfaces of pulled-glass pipettes. The pulled end of each glass pipette is then etched to expose a desired length (typically, a few µm) of carbon pipe. The carbon film provides an electrically conductive path from the nanoscopic carbon tip to the distal, macroscopic end of the pipette, bridging between the nanoscale tip and the macroscale handle, without a need for assembly. We used our nanoelectrodes to penetrate into individual cells and cell nuclei and measured the variations in the electrode impedance upon cell and nucleus penetration as well as the electrode impedance as a function of cell penetration depth. Theoretical predictions based on a simple circuit model were in good agreement with experimental data.
doi:10.1088/0957-4484/26/18/185101
PMCID: PMC4508198  PMID: 25876625
carbon nanopipettes (CNP); nano; probe; electrode; biosensing; cell; single; electrochemical methods
8.  Rose Bengal-decorated silica nanoparticles as photosensitizers for inactivation of gram-positive bacteria 
Nanotechnology  2010;21(6):065102.
A new type of photosensitizer, made from Rose Bengal (RB)-decorated silica (SiO2–NH2–RB) nanoparticles, was developed to inactivate gram-positive bacteria, including Methicillin-resistant Staphylococcus aureus (MRSA), with high efficiency through photodynamic action. The nanoparticles were characterized microscopically and spectroscopically to confirm their structures. The characterization of singlet oxygen generated by RB, both free and immobilized on a nanoparticle surface, was performed in the presence of anthracene-9,10-dipropionic acid. The capability of SiO2–NH2–RB nanoparticles to inactivate bacteria was tested in vitro on both gram-positive and gram-negative bacteria. The results showed that RB-decorated silica nanoparticles can inactivate MRSA and Staphylococcus epidermidis (both gram-positive) very effectively (up to eight-orders-of-magnitude reduction). Photosensitizers of such design should have good potential as antibacterial agents through a photodynamic mechanism.
doi:10.1088/0957-4484/21/6/065102
PMCID: PMC4836856  PMID: 20061596
9.  Nanoscale Electron Transport Measurements of Immobilized Cytochrome P450 Proteins 
Nanotechnology  2015;26(15):155102.
Gold nanopillars, functionalized with an organic self-assembled monolayer, can be used to measure the electrical conductance properties of immobilized proteins without aggregation. Measurements of the conductance of nanopillars with cytochrome P450 2C9 (CYP2C9) proteins using conducting probe atomic force microscopy demonstrate that a correlation exists between the energy barrier height between hopping sites and CYP2C9 metabolic activity. Measurements performed as a function of tip force indicate that, when subjected to a large force, the protein is more stable in the presence of a substrate. This agrees with the hypothesis that substrate entry into the active site helps to stabilize the enzyme. The relative distance between hopping sites also increases with increasing force, possibly because protein functional groups responsible for electron transport depend on the structure of the protein. The inhibitor sulfaphenazole, in addition to the previously studied aniline, increased the barrier height for electron transfer and thereby makes CYP2C9 reduction more difficult and inhibits metabolism. This suggests that P450 Type II binders may decrease the ease of electron transport processes in the enzyme, in addition to occupying the active site.
doi:10.1088/0957-4484/26/15/155102
PMCID: PMC4791957  PMID: 25804257
Cytochrome P450; Electron Transfer; Nanopillars; Biomolecular Electronics; Conductivity; Conducting Probe Atomic Force Microscopy
10.  Detection of DNA hybridizations using solid-state nanopores 
Nanotechnology  2010;21(33):335102.
We report an experimental study of using DNA translocation through solid-state nanopores to detect the sequential arrangement of two double-stranded 12-mer hybridization segments on a single-stranded DNA molecule. The sample DNA is a trimer molecule formed by hybridizing three single-stranded oligonucleotides. A polystyrene bead is attached to the end of the trimer DNA, providing a mechanism in slowing down the translocation and suppressing the thermal diffusion, thereby allowing the detection of short features of DNA by standard patch-clamp electronics. The electrical signature of the translocation of a trimer molecule through a nanopore has been identified successfully in the temporal traces of ionic current. The results reported here represent the first successful attempt in using a solid-state nanopore as an ionic scanning device in resolving individual hybridization segments (or ‘probes’) on a DNA molecule.
doi:10.1088/0957-4484/21/33/335102
PMCID: PMC4811674  PMID: 20657045
11.  Tunable graphene quantum point contact transistor for DNA detection and characterization 
Nanotechnology  2015;26(13):134005.
A graphene membrane conductor containing a nanopore in a quantum point contact (QPC) geometry is a promising candidate to sense, and potentially sequence, DNA molecules translocating through the nanopore. Within this geometry, the shape, size, and position of the nanopore as well as the edge configuration influences the membrane conductance caused by the electrostatic interaction between the DNA nucleotides and the nanopore edge. It is shown that the graphene conductance variations resulting from DNA translocation can be enhanced by choosing a particular geometry as well as by modulating the graphene Fermi energy, which demonstrates the ability to detect conformational transformations of a double-stranded DNA, as well as the passage of individual base pairs of a single-stranded DNA molecule through the nanopore.
doi:10.1088/0957-4484/26/13/134005
PMCID: PMC4400256  PMID: 25765702
12.  Dielectrophoretic Stretching of DNA Tethered to a Fiber Tip 
Nanotechnology  2015;26(12):125501.
In this work, we studied the stretching of λ phage DNA molecules immobilized on an optical fiber tip attached to a force sensitive tuning fork under AC electric fields. We designed a two electrodes stretching system in a small chamber: one is a gold-coated optical fiber tip electrode, and the other is a gold-coated flat electrode. By applying a dielectrophoretic force, the immobilized λ DNA molecules on the tip are stretched and the stretching process is monitored by a fluorescent microscope. The DNA stretching in three-dimensional space is optimized by varying electrode shape, electrode gap distance, AC frequency, and solution conductivity. By observing the vibrational amplitude change of a quartz tuning fork, we measured the effects due to Joule heating and the dielectrophoretic force on the tethered DNA molecules in solution. This work demonstrates a method to manipulate and characterize immobilized λ DNA molecules on a probe tip for further study of single DNA molecules.
doi:10.1088/0957-4484/26/12/125501
PMCID: PMC4411638  PMID: 25741602
DNA stretching; DNA manipulation; fluorescence imaging; dielectrophoretic force
13.  An investigation into the feasibility of myoglobin-based single-electron transistors 
Nanotechnology  2012;23(39):395705.
Myoglobin single-electron transistors were investigated using nanometer-gap platinum electrodes fabricated by electromigration at cryogenic temperatures. Apomyoglobin (myoglobin without heme group) was used as a reference. The results suggest single electron transport is mediated by resonant tunneling with the electronic and vibrational levels of the heme group in a single protein. They also represent a proof-of-principle that proteins with redox centers across nanometer-gap electrodes can be utilized to fabricate single-electron transistors. The protein orientation and conformation may significantly affect the conductance of these devices. Future improvements in device reproducibility and yield will require control of these factors.
doi:10.1088/0957-4484/23/39/395705
PMCID: PMC4802369  PMID: 22972432
14.  Silk-regulated hierarchical hollow magnetite/carbon nanocomposite spheroids for lithium ion battery anodes 
Nanotechnology  2015;26(11):115603.
Hierarchical olive-like structured carbon-Fe3O4 nanocomposite particles composed of a hollow interior and a carbon coated surface are prepared by a facile, silk protein-assisted hydrothermal method. Silk nanofibers as templates and carbon precursors first regulate the formation of hollow Fe2O3 microspheres and then they are converted into carbon in a reduction process into Fe3O4. This process significantly simplifies the fabrication and carbon coating processes to form complex hollow structures. When tested as anode materials for lithium-ion batteries, these hollow carbon-coated particles exhibite high capacity (900 mAh g−1), excellent cycle stability (180 cycles) and rate performance due to their unique hierarchical hollow structure and carbon coating.
doi:10.1088/0957-4484/26/11/115603
PMCID: PMC4356645  PMID: 25706314
Fe3O4; olive-like hollow structures; silk nanofiber; energy storage; anode material
15.  Fabrication and characterization of gold nano-wires templated on virus-like arrays of tobacco mosaic virus coat proteins 
Nanotechnology  2012;24(2):025605.
The rod-shaped plant virus tobacco mosaic virus (TMV) is widely used as a nano-fabrication template, and chimeric peptide expression on its major coat protein has extended its potential applications. Here we describe a simple bacterial expression system for production and rapid purification of recombinant chimeric TMV coat protein carrying C-terminal peptide tags. These proteins do not bind TMV RNA or form disks at pH 7. However, they retain the ability to self-assemble into virus-like arrays at acidic pH. C-terminal peptide tags in such arrays are exposed on the protein surface, allowing interaction with target species. We have utilized a C-terminal His-tag to create virus coat protein-templated nano-rods able to bind gold nanoparticles uniformly. These can be transformed into gold nano-wires by deposition of additional gold atoms from solution, followed by thermal annealing. The resistivity of a typical annealed wire created by this approach is significantly less than values reported for other nano-wires made using different bio-templates. This expression construct is therefore a useful additional tool for the creation of chimeric TMV-like nano-rods for bio-templating.
doi:10.1088/0957-4484/24/2/025605
PMCID: PMC4787025  PMID: 23220929
16.  Directed surface attachment of nanomaterials via coiled-coil-driven self-assembly 
Nanotechnology  2012;23(49):495304.
Numerous nanoscale devices and materials have been fabricated in recent years using a variety of biological scaffolds. However, the interfacing of these devices and materials into existing circuits and ordered arrays has proved problematic. Here, we describe a simple solution to this problem using self-assembly of the peptide coiled-coil heterodimer ACID:BASE to immobilize M13 bacteriophage particles to specific locations on a patterned gold surface. Surface plasmon resonance demonstrated that free ACID peptides will assemble onto a surface derivatized with BASE. We then displayed the ACID peptide on the pIX coat protein of M13 and showed that these phage particles permit formation of the coiled-coil resulting in specific surface attachment. The ACID:immobilized BASE affinities appear to be similar for free peptide and phage-displayed ACID. Finally, we fabricated two gold electrodes, separated by a 200 nm gap, coated one of them with BASE and showed that this allows localization of the M13:ACID onto the functionalized electrode.
doi:10.1088/0957-4484/23/49/495304
PMCID: PMC4785676  PMID: 23154792
17.  Electrochemical annealing of nanoporous gold by application of cyclic potential sweeps 
Nanotechnology  2015;26(8):085602.
An electrochemical method for annealing the pore sizes of nanoporous gold is reported. The pore sizes of nanoporous gold can be increased by electrochemical cycling with the upper potential limit being just at the onset of gold oxide formation. This study has been performed in electrolyte solutions including potassium chloride, sodium nitrate and sodium perchlorate. Scanning electron microscopy images have been used for ligament and pore size analysis. We examine the modifications of nanoporous gold due to annealing using electrochemical impedance spectroscopy, and cyclic voltammetry and offer a comparison of the surface coverage using the gold oxide stripping method as well as the method in which electrochemically accessible surface area is determined by using a diffusing redox probe. The effect of additives adsorbed on the nanoporous gold surface when subjected to annealing in different electrolytes as well as the subsequent structural changes in nanoporous gold are also reported. The effect of the annealing process on the application of nanoporous gold as a substrate for glucose electro-oxidation is briefly examined.
doi:10.1088/0957-4484/26/8/085602
PMCID: PMC4350776  PMID: 25649027
18.  PHYSICAL MODEL FOR RECOGNITION TUNNELING 
Nanotechnology  2015;26(8):084001.
Recognition tunneling (RT) identifies target molecules trapped between tunneling electrodes functionalized with recognition molecules that serve as specific chemical linkages between the metal electrodes and the trapped target molecule. Possible applications include single molecule DNA and protein sequencing. This paper addresses several fundamental aspects of RT by multiscale theory, applying both all-atom and coarse-grained DNA models: (1) We show that the magnitude of the observed currents are consistent with the results of non-equilibrium Green's function calculations carried out on a solvated all-atom model. (2) Brownian fluctuations in hydrogen bond-lengths lead to current spikes that are similar to what is observed experimentally. (3) The frequency characteristics of these fluctuations can be used to identify the trapped molecules with a machine-learning algorithm, giving a theoretical underpinning to this new method of identifying single molecule signals.
doi:10.1088/0957-4484/26/8/084001
PMCID: PMC4353715  PMID: 25650375
recognition tunneling; multiscale dynamics; thermal fluctuations; hydrogen bond; coarse-grain simulations; chemical analysis; support Vector Machine
19.  Challenges in DNA motion control and sequence readout using nanopore devices 
Nanotechnology  2015;26(7):074004.
Nanopores are being hailed as a potential next-generation DNA sequencer that could provide cheap, high-throughput DNA analysis. In this review we present a detailed summary of the various sensing techniques being investigated for use in DNA sequencing and mapping applications. A crucial impasse to the success of nanopores as a reliable DNA analysis tool is the fast and stochastic nature of DNA translocation. We discuss the incorporation of biological motors to step DNA through a pore base-by-base, as well as the many experimental modifications attempted for the purpose of slowing and controlling DNA transport.
doi:10.1088/0957-4484/26/7/074004
PMCID: PMC4710574  PMID: 25642629
single-molecule; DNA sequencing; nanopores
20.  Targeting multiple types of tumors using NKG2D-coated iron oxide nanoparticles 
Nanotechnology  2014;25(47):475101.
Iron oxide nanoparticles (IONPs) hold great potential for cancer therapy. Actively targeting IONPs to tumor cells can further increase therapeutic efficacy and decrease off-target side effects. To target tumor cells, a natural killer (NK) cell activating receptor, NKG2D, was utilized to develop pan-tumor targeting IONPs. NKG2D ligands are expressed on many tumor types and its ligands are not found on most normal tissues under steady state conditions. The data showed that mouse and human fragment crystallizable (Fc) -fusion NKG2D (Fc-NKG2D) coated IONPs (NKG2D/NPs) can target multiple NKG2D ligand positive tumor types in vitro in a dose dependent manner by magnetic cell sorting. Tumor targeting effect was robust even under a very low tumor cell to normal cell ratio and targeting efficiency correlated with NKG2D ligand expression level on tumor cells. Furthermore, the magnetic separation platform utilized to test NKG2D/NP specificity has the potential to be developed into high throughput screening strategies to identify ideal fusion proteins or antibodies for targeting IONPs. In conclusion, NKG2D/NPs can be used to target multiple tumor types and magnetic separation platform can facilitate the proof-of-concept phase of tumor targeting IONP development.
doi:10.1088/0957-4484/25/47/475101
PMCID: PMC4356627  PMID: 25371538
nanoparticles; ovarian cancer; lymphoma; NKG2D; MICA; Rae-1
21.  Electronic detection of dsDNA transition from helical to zipper conformation using graphene nanopores 
Nanotechnology  2014;25(44):445105.
Mechanical manipulation of DNA, by forced extension, can lead to a structural transformation of double-stranded DNA (dsDNA) from a helical form to a linear zipper-like form. By employing classical molecular dynamics and quantum mechanical non-equilibrium Greens function-based transport simulations, we show the ability of graphene nanopores to discern different dsDNA conformations, in a helical to zipper transition, using transverse electronic conductance. In particular, conductance oscillations due to helical dsDNA vanish as dsDNA extends from helical to zipper form as it is transported through the nanopore. The predicted ability to detect conformational changes in dsDNA, via transverse electronic conductance, can widen the potential of graphene-based nanosensors for DNA detection.
doi:10.1088/0957-4484/25/44/445105
PMCID: PMC4244269  PMID: 25325530
22.  Highly stable polymer coated nano-clustered silver plates: A multimodal optical contrast agent for biomedical imaging 
Nanotechnology  2014;25(44):445104.
Here we present a new optical contrast agent, based on silver nanoplate clusters embedded inside a polymer nano matrix. Unlike nanosphere clusters, which have been well studied, nanoplate clusters have unique properties due to the different possible orientations of interaction between the individual plates, resulting in a significant broadening of the absorption spectra. These nanoclusters were immobilized inside a polymer cladding, so as to maintain their stability and optical properties under in vivo conditions. The polymer coated silver nanoplate clusters show a lower toxicity, compared to the uncoated nanoparticles. At high nanoparticle concentrations, cell death occurs mostly due to apoptosis. These nanoparticles were used for targeted fluorescence imaging in a rat glioma cell line by incorporating a fluorescent dye into the matrix, followed by conjugation of a tumor targeting F3 peptide. We further used these nanoparticles as photoacoustic contrast agents in vivo, to enhance the contrast of the vasculature structures in a rat ear model. We observed a contrast enhancement of over 90%, following nanoparticle injection. It is also shown that these NP’s can serve as efficient contrast agents, with specific targeting abilities, for broadband multimodal imaging, usable for diagnostic applications and extendable into use as therapeutic agents as well.
doi:10.1088/0957-4484/25/44/445104
PMCID: PMC4244271  PMID: 25325364
Polymer Nanoparticles; Silver Nanoplates; Metal Nanocluster; Fluorescence Imaging; Photoacoustic Imaging
23.  Stem Cell-mediated Delivery of SPIO-loaded Gold Nanoparticles for the Theranosis of Liver Injury and Hepatocellular Carcinoma 
Nanotechnology  2014;25(40):405101.
The treatment of liver injuries or hepatocellular carcinoma (HCC) with has been hindered by the lack of efficient drug delivery. Even with the help of nanoparticles or other synthetic delivering agents, a large portion of the dose is still sequestered in the reticuloendothelial system (RES). As an alternative, adipose-derived mesenchymal cells (AD-MSCs), which have the capability of homing to the injured liver, can be used as a unique carrier for theranostic agents. Theranostic agents must have the capacity for being non-toxic to host cells during transportation, and for timely activation once they arrive at the injury sites. In this study, we loaded AD-MSCs with superparamagnetic iron oxide-coated gold nanoparticles (SPIO@AuNPs) and tested their effects against liver injury and HCC in cells and in mice. SPIO@AuNP is a non-toxic MRIactive contrast agent that can generate heat when irradiated with near-infrared laser. Our results showed that SPIO@AuNPs were successfully transfected into AD-MSCs without compromising either cell viability (P > 0.05) or cell differentiability. In vivo MRI imaging and histologic analysis confirmed the active homing of AD-MSCs. Upon laser irradiation, the SPIO@AuNPloaded AD-MSCs could thermally ablate surrounding HCC tumor cells. SPIO@AuNP–loaded AD-MSCs proved a promising theranostic approach for injured liver and HCC.
doi:10.1088/0957-4484/25/40/405101
PMCID: PMC4414337  PMID: 25211057
stem cell; SPIO; gold nanoparticle; MRI; liver
24.  Thrombin-Inhibiting Nanoparticles Rapidly Constitute Versatile and Detectable Anticlotting Surfaces 
Nanotechnology  2014;25(39):395101.
Restoring an antithrombotic surface to suppress ongoing thrombosis is an appealing strategy for treatment of acute cardiovascular disorders such as erosion of atherosclerotic plaque. An antithrombotic surface would present an alternative to systemic anticoagulation with attendant risks of bleeding. We have designed thrombin-targeted nanoparticles that bind to sites of active clotting to extinguish local thrombin activity and inhibit platelet deposition while exhibiting only transient systemic anticoagulant effects. Perfluorocarbon nanoparticles (PFC NP) were functionalized with thrombin inhibitors (either PPACK or bivalirudin) by covalent attachment of more than 15,000 inhibitors to each PFC NP. Fibrinopeptide A ELISA demonstrated that thrombin-inhibiting NPs prevented cleavage of fibrinogen by both free and clot-bound thrombin. Magnetic resonance imaging confirmed that a layer of thrombin-inhibiting NPs prevented growth of clots in vitro. Thrombin-inhibiting NPs were administered in vivo to C57BL6 mice subjected to laser injury of the carotid artery. NPs significantly delayed thrombotic occlusion of the artery, whereas an equivalent bolus of free inhibitor was ineffective. For thrombin-inhibiting NPs, only a short-lived (~10 minutes) systemic effect on bleeding time was observed, despite prolonged clot inhibition. Imaging and quantification of in vivo antithrombotic NP layers was demonstrated by magnetic resonance imaging (MRI) of the PFC NP. 19F MRI confirmed colocalization of particles with arterial thrombi, and quantitative 19F spectroscopy demonstrated specific binding and retention of thrombin-inhibiting NPs in injured arteries. The ability to rapidly form and image a new antithrombotic surface in acute vascular syndromes while minimizing risks of bleeding would permit a safer method of passivating active lesions than current systemic anticoagulant regimes.
doi:10.1088/0957-4484/25/39/395101
PMCID: PMC4238071  PMID: 25200815
Thrombosis; Nanomedicine; MRI; Nanoparticles
25.  Enhanced blood-brain barrier transmigration using a novel Transferrin-embedded fluorescent magnetoliposome nanoformulation 
Nanotechnology  2014;25(5):055101.
Blood-brain barrier (BBB) is considered as the primary impediment barrier for most of drugs. Delivering therapeutic agents to brain is still a big challenge by now. In our study, a dual mechanism, receptor mediation combining with external non-invasive magnetic force, was incorporated together into ferrous magnet-based liposome for BBB transmigration enhancement. The homogenous magnetic nanoparticles (MNPs) with size of ~ 10 nm were synthesized and confirmed by TEM and XRD respectively. The classical magnetism assay showed presence of characteristic superparamagnetic property. These MNPs encapsulated in PEGylated fluorescent liposomes as magneto liposomes (ML) showed mono-dispersion ~ 130±10 nm diameter by dynamic laser scattering (DLS) using lipid-extrusion technique. Remarkably, this magnetite encapsulation efficiency of nearly 60% was achieved. And the luminescence and hydrodynamic size of ML was stable for over two months under 4 degree. Additionally, the integrity of ML structure remained unaffected through 120 rounds circulation mimicking human blood fluid. After biocompatibility confirmation by cytotoxicity evaluation, these fluorescent ML was further embedded with Transferrin and applied to in vitro BBB transmigration study in presence or absence of external magnetic force. Comparing with only by magnetic force- or Transferrin receptor-mediated transportation, their synergy resulted in 50–100% increased transmigration without affecting the BBB integrity. Consequently, confocal microscopy and iron concentration in BBB-composed cells further confirmed the higher cellular uptake of ML particles due to synergic effect. Thus, our multi-functional liposomal magnetic nanocarriers possess great potential in particles transmigration across BBB and may have bright future in drug delivery to brain.
doi:10.1088/0957-4484/25/5/055101
PMCID: PMC4520325  PMID: 24406534
Magnetic nanoparticles (MNPs); Magneto liposome (ML); Blood-brain barrier (BBB); Fluorescence; Transferrin; transmigration

Results 1-25 (161)