DTT–Au NCs Interact with DNA to Form Raspberry‐Like Particles

Noble metal nanoclusters (NCs) have emerged as intriguing nanomaterials with widespread interest. Previously, it was shown that dithiothreitol (DTT)‐conjugated gold nanoclusters (Au NCs) respond to copper ions in aqueous solution. Here, it is shown that these DTT–Au NCs can interact with DNA by forming raspberry‐like particles. The raspberry‐like structures protect the capped DNA from enzymatic attack and show excellent biocompatibility. Moreover, these supramolecular complexes cross the plasma membrane of yeast cells and express green fluorescent protein encoded by the DNA, suggesting that DTT–Au NCs can serve as an efficient carrier for gene delivery.     

Dual‐Polymer‐Functionalized Nanoscale Graphene Oxide as a Highly Effective Gene Transfection Agent for Insect Cells with Cell‐Type‐Dependent Cellular Uptake Mechanisms

Efficient and safe gene transfection carriers, especially for hard‐to‐transfect cells, are urgently demanded in basic biological research and gene therapy applications. Many insect cell lines widely used in molecular cell biology exhibit relatively low transfection efficiencies when treated by conventional non‐viral agents. Herein, we develop a novel gene delivery vector by coating graphene oxide (GO) with both polyethylene glycol (PEG) and polyethylenimine (PEI), obtaining a dual‐polymer‐functionalized nanoscale GO (nGO‐PEG‐PEI) to transfect insect cells. While exhibiting remarkably reduced cytotoxicity compared with PEI, nGO‐PEG‐PEI, when used as the plasmid DNA transfection agent to treat Drosophila S2 cells, offers ≈7‐fold and ≈2.5‐fold higher efficiency compared with those achieved by using bare PEI and Lipofectamine 2000, a widely used commercial transfection agent, respectively. Interestingly, the advantages of nGO‐PEG‐PEI are even more dramatic when transfecting cells with lower‐quality linearized DNA. It is revealed that nGO‐PEG‐PEI/pDNA complexes enter insect cells via a unique pathway working even at a low temperature, rather different from their entry into mammalian adherent cells. Our results encourage the development of nano‐GO‐based gene carriers to treat special types of hard‐to‐transfect cells (e.g., insect cells), and indicate that nanomaterials would enter cells by cell‐type‐dependent mechanisms, which merit significantly more future attentions.     

From oleic acid-capped iron oxide nanoparticles to polyethyleneimine-coated single-particle magnetofectins

Various inorganic nanoparticle designs have been developed and used as non-viral gene carriers. Magnetic gene carriers containing polyethyleneimine (PEI), a well-known transfection agent, have been shown to improve DNA transfection speed and efficiency in the presence of applied magnetic field gradients that promote particle–cell interactions. Here we report a method to prepare iron oxide nanoparticles conjugated with PEI that: preserves the narrow size distribution of the nanoparticles, conserves magnetic properties throughout the process, and results in efficient transfection. We demonstrate the ability of the particles to electrostatically bind with DNA and transfect human cervical cancer (HeLa) cells by the use of an oscillating magnet array. Their transfection efficiency is similar to that of Lipofectamine 2000?, a commercial transfection reagent. PEI-coated particles were subjected to acidification, and acidification in the presence of salts, before DNA binding. Results show that although these pre-treatments did not affect the ability of particles to bind DNA they did significantly enhanced transfection efficiency. Finally, we show that these magnetofectins (PEI-MNP/DNA) complexes have no effect on the viability of cells at the concentrations used in the study. The systematic preparation of magnetic vectors with uniform physical and magnetic properties is critical to progressing this non-viral transfection technology.     

The influence of dust particle geometry on its charge and plasma potential

In this paper, a self‐consistent numerical model describing the behaviour of plasma around isolated highly charged dust particles with different shapes of rotation figures is presented. Dust particles in the form of a sphere, oblate ellipsoids (disk‐like particles), and elongated ellipsoids (rod‐like particles) are considered in the presence of an external electric field. Using the developed model, self‐consistent distributions of a space charge and plasma potential are obtained around non‐spherical dust particles. These distributions are carefully analysed by decomposing them in a series of Legendre polynomials. Decompositions of these distributions are compared with particles of different geometry. In addition, for different geometries of dust particles, the dependencies of the charge of a dust particle on geometry in the absence of an external field are investigated.     

Characterize the interaction between polyethylenimine and serum albumin using surface plasmon resonance and fluorescence method

Polyethylenimine (PEI) is a type of cationic polymer which is efficient in DNA transfer. The characters of PEI binding to bovine serum albumin and human serum albumin (HSA) were described by fluorescence quenching, surface plasmon resonance (SPR) and circular dichroism (CD) spectroscopy. The fluorescence quenching results showed that the binding processes occurred on the surface of the protein molecules. The accurate binding constants between PEI and the two proteins were obtained by SPR spectroscopy. The CD spectra results showed that the confirmations of the two proteins were affected with the addition of PEI.     

Facile Synthesis of Gd(OH)3‐Doped Fe3O4 Nanoparticles for Dual‐Mode T1‐ and T2‐Weighted Magnetic Resonance Imaging Applications

The facile hydrothermal synthesis of polyethyleneimine (PEI)‐coated iron oxide (Fe₃O₄) nanoparticles (NPs) doped with Gd(OH)₃ (Fe₃O₄‐Gd(OH)₃‐PEI NPs) for dual mode T₁‐ and T₂‐weighted magnetic resonance (MR) imaging applications is reported. In this approach, Fe₃O₄‐Gd(OH)₃‐PEI NPs are synthesized via a hydrothermal method in the presence of branched PEI and Gd(III) ions. The PEI coating onto the particle surfaces enables further modification of poly(ethylene glycol) (PEG) in order to render the particles with good water dispersibility and improved biocompatibility. The formed Fe₃O₄‐Gd(OH)₃‐PEI‐PEG NPs have a Gd/Fe molar ratio of 0.25:1 and a mean particle size of 14.4 nm and display a relatively high r₂ (151.37 × 10^?3m ^?1 s^?1) and r₁ (5.63 × 10^?3m ^?1 s^?1) relaxivity, affording their uses as a unique contrast agent for T₁‐ and T₂‐weighted MR imaging of rat livers after mesenteric vein injection of the particles and the mouse liver after intravenous injection of the particles, respectively. The developed Fe₃O₄‐Gd(OH)₃‐PEI‐PEG NPs may hold great promise to be used as a contrast agent for dual mode T₁‐ and T₂‐weighted self‐confirmation MR imaging of different biological systems.     

Fabrication of piezoelectric components for a tunable and efficient device for DNA delivery into mammalian cells

We fabricated three piezoelectric components (PZT) that can produce ultrasonic waves with various generated power in order to improve the delivery of DNA molecule and polymer/DNA complexes into cells. Two cationic polymers (PEI and PDMAEMA) were interacted with DNA to form nano-scaled DNA/polymer complexes with/without the help of PZT devices. The application of PZT devices under optimal conditions helped to avoid cytotoxicity and greatly increased the transfection (DNA delivery) efficiency of these complexes in mammalian cells. The cytotoxicity and transfection efficiency were found to be correlated with the PZT-generated power, waveforms and duration of ultrasonic treatment. There was no observable cytotoxicity in our experimental models and, a maximum transfection efficiency 700% greater than that of polymer/DNA complexes without applying ultrasound was achieved. The transfection efficiency of plain polymer/DNA complexes (without PZT treatment) corresponded to a 630-fold increase in comparison to the naked DNA. The waveforms of generated ultrasound greatly influenced the transfection efficiency, while cytotoxicity was not significantly affected. This means that, for optimal DNA delivery, duration of the peak voltage (V_max/Div) also plays a role. In addition, the generated waves from PZT do not cause dissociation of polymer/DNA complexes or a change in the particle sizes of these complexes. In conclusion, these results suggest that the operation of PZT devices can be a tunable/safe way to greatly improve DNA delivery for gene therapy.     

A Multi‐Thresholding Algorithm for Sizing out of Focus Particles

A methodology is presented that enables efficient acquisition of sufficient droplet information (e.g. diameter and aspect ratio) from images of in and out of focus droplets. The newly developed multi‐threshold algorithm is successfully implemented in the automatic particle/droplet image analysis (PDIA) system. Under the same optical hardware set‐up, and compared to the dual threshold methods [1], the multi‐threshold method increases the measurable/acceptable depth of field (DoF) of particles, especially for the small particles of diameters less than 50 μm (1098 pixels in this optical set‐up). When testing the 70 μm~110 μm and 100 μm~200 μm moving glass spheres, the dual threshold method can only detect 11%~29 % of the particles found by the multi‐threshold method. The multi‐threshold method is also capable of generating the aspect ratios of particles more accurately than dual threshold methods.     

Glass Transition Temperatures of Epoxy Modified with Pendent Nano‐Organic Rigid‐Rod Compounds

Pendent nanoscale organic rigid‐rod compounds are molecular fiber‐like materials that can be used to reinforce the polymer matrix. In this study, 4,4′‐diphenylmethane diisocyanate (MDI) was used to covalently connect a number of organic rigid‐rod compounds [4′‐hydroxyphenyl‐4‐hydroxy‐benzoate (HPHB), phenyl 4‐hydroxybenzoate (HPB), 4,4′‐isopropylidenediphenol (BSPA), and 2‐naphthol (NPT)] to the secondary hydroxyl groups of the epoxy resin. These reactions were monitored using Fourier transform infrared (FT‐IR) spectroscopy; the products were characterized using nuclear magnetic resonance (NMR) spectroscopy. The glass transition temperatures of the organic rigid‐rod compounds modified epoxy resins were investigated through differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Thermogravimetric analysis (TGA) was used to detect the values of Td and the thermal stabilities of the polymers.     

Spectroscopic and thermal studies on the inclusion of trans‐cinnamic acid and a number of its hydroxyl‐derivatives with α, β and γ‐cyclodextrins molecules

The inclusion compounds of α‐, β‐ and γ‐cyclodextrins (α‐CD, β‐CD and γ‐CD) with trans‐cinnamic acid (t‐CIA), 3‐hydroxy‐trans‐cinnamic acid (t‐3OHCIA), 4‐hydroxy‐trans‐cinnamic acid (t‐4OHCIA) and 3,4‐dihydroxy‐trans‐cinnamic acid (t‐3,4OHCIA) were prepared and characterized, in the solid state, by means of thermogravimetry and Raman spectroscopy. The effects of the inclusion process on the guest molecules and on the hydrogen bond interactions of the guest were studied by monitoring sensitive vibrational modes, such as CO, CC and ring C H stretching modes. By combining Raman and TG data with ab initio calculations and information from CSD database on similar compounds, inclusion geometries for the different compounds are proposed. The size of the host cavity and the maximization of host/guest hydrogen‐bonding contacts appear to be the main factors determining the inclusion geometries. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of electrostatic spray on human pulmonary epithelial cells

Aerosolization techniques for delivery of gene therapies to the lungs decrease activity of these treatments. The low transfection is attributed to loss in molecular integrity. Electrosprays can aerosolize DNA without structural loss. Electrospray affects on human pulmonary cells are unknown. This study is to assess toxicity, inflammatory response, and transfection of DNA mixtures delivered via electrospray to human pulmonary cells. EpiAirway? cells are cultured on air–liquid interfaces and simulate in vivo. All conditions examined (except PEI/DNA 10:1) showed no toxic or inflammation response. Transfection was not observed. In vitro results indicate that electrosprays have potential for administering DNA therapeutics pulmonarily.     

Enhanced Physiological Stability and Long‐Term Toxicity/Biodegradation In Vitro/In Vivo of Monodispersed Glycerolphosphate‐Functionalized Bioactive Glass Nanoparticles

Monodispersed bioactive glass nanoparticles (BGNs) have received much attention in various biomedical applications such as tissue regeneration, drug/gene delivery, bioimaging, and cancer therapy. However, the poor dispersion stability of BGNs in a physiological environment has limited their wide biomedical applications. The long‐term in vitro/in vivo toxicity and biodegradation of BGNs are also not clear. Monodispersed glycerolphosphate‐functionalized BGNs (GP‐BGN) are synthesized and their stability under physiological environment in vitro, and long‐term biodegradation behavior in vitro and in vivo are investigated herein. GP‐BGN shows significantly enhanced particles stability in physiological environment, good hemocompatibility and cellular biocompatibility, as well as high cellular uptake ability. GP‐BGN also exhibits long‐term biodegradation behavior in vitro/in vivo and negligible biotoxicity (tissue and blood toxicity). This study demonstrates that monodispersed surface‐functionalized BGNs could be used as biocompatible and biodegradable nanomaterials for long‐term safe bioimaging and disease therapy.     

Self‐Organization of Anisotropic and Binary Colloids in Thermo‐Switchable 1D Microconfinement

Anisotropic and binary colloids self‐assemble into a variety of novel supracolloidal structures within the thermo‐switchable confinement of molecular microtubes, achieving structuring at multiple length scales and dimensionalities. The multistage self‐assembly strategy involving hard colloidal particles and a soft supramolecular template is generic for colloids with different geometries and materials as well as their binary mixtures. The colloidal architectures can be controlled by colloid shape, size, and concentration. Colloidal cubes align in chains with face‐to‐face arrangement, whereas rod‐like colloids predominantly self‐organize in end‐to‐end configurations with their long axis parallel with the long axis of the microtubes. The 1D microconfinement imposed on binary mixtures of anisotropic and isotropic colloids further increases the diversity of colloid‐in‐tube structures. In cube–sphere mixtures, cubes may act as additional confiners, locking in colloidal sphere chains, while a “colloidal Morse code” is generated where rods and spheres alternate in the case of rod–sphere mixtures. The versatile confined colloidal superstructures including their thermoresponsive assembly and disassembly are relevant for the development of stimulus–responsive materials where controlled release and encapsulation are desired.     

Stabilization of the pesticide Fenitrothion toward O and N nucleophiles in the presence of cyclodextrins

The reaction of Fenitrothion with O and N nucleophiles (H₂O₂, NH₂OH, n‐butylamine and piperidine) was studied at 25 °C in water containing 2% 1,4‐dioxane in the presence of native cyclodextrins (α‐, β‐, and γ‐CD). For all the nucleophiles, the presence of CD produces reaction inhibition with saturation kinetics. The greatest effect in all cases is observed with β‐CD, and the greatest inhibition was observed for the reaction of Fenitrothion with H₂O₂ (81%), which is the most efficient nucleophile in promoting Fenitrothion degradation in homogeneous media. In the absence of CD, competition between the S_N2(P) and the S_N2(C) pathways was observed with piperidine as was reported before for the reaction with NH₂OH and n‐butylamine. The presence of β‐CD does not modify product distribution in the case of the reaction with NH₂OH and n‐butylamine, whereas there is an increase in S_N2(C) pathway when the nucleophile is piperidine. Copyright © 2014 John Wiley & Sons, Ltd.     

A single‐crystal Raman and infrared study of the nonlinear optical crystal MBANP

Single‐crystal Raman and polycrystalline thin‐film infrared measurements have been obtained for the polar organic nonlinear optical material 2‐(α‐methylbenzylamino)‐5‐nitropyridine (MBANP). For comparison, thin‐film polycrystalline infrared measurements were also made on 2‐(α‐methylbenzylamino)‐3,5‐dinitropyridine (MBADNP). The long wavelength electronic absorption was measured in several solvents and as a thin solid film. The Raman spectra are dominated by three intense bands attributed to vibrations of the ring, the NO₂ substituent, and the N H bond. The most intense scattering and absorption arose from the α_bb component of the polarisability tensor. This implies that the most significant contribution to the transition polarisability arises from the electronic transition near 383 nm, polarised along the b‐axis of the crystal. The strongest bands in the infrared spectra are also associated with the same three bands, consistent with the predictions of the effective conjugation coordinate (ECC) theory, implying efficient electron–phonon coupling (or electronic delocalisation) in the conjugated system. DFT calculations of vibrational wavenumbers and eigenvectors were used to assign relevant vibrational features and to derive useful information about the molecular structure. This single‐crystal material is also a strong candidate for an efficient laser Raman converter with a large wavenumber shift of 3404 cm⁻¹ and a high damage threshold. Copyright © 2010 John Wiley & Sons, Ltd.     

Sodium 1, 4‐dihydroxy‐9, 10‐anthraquinone‐ 2‐sulphonate interacts with calf thymus DNA in a way that mimics anthracycline antibiotics: an electrochemical and spectroscopic study

The anthracycline drugs, adriamycin and daunorubicin, efficient in the treatment of various human cancers, form strong intercalation complexes with DNA. The therapeutic efficiency and toxic properties of the drugs are associated with electron transfer processes, which correlate well with the redox behaviour of the compounds. Sodium 1,4‐dihydroxy 9,10‐anthraquinone‐2‐sulphonate (sodium quinizarin‐2‐sulphonate, NaLH₂) (Na‐Qz‐2S) is a molecule that resembles anthracycline drugs and has a simpler structure in comparison to these drugs. Two electrons in the course of chemical action reduce this molecule like the anthracyclines. Electrochemical methods were used to identify this process. UV‐Vis and fluorescence spectroscopy were used to analyse binding of the compound to calf thymus DNA. The binding constant and site size were evaluated for Na‐Qz‐2S and the same compared to that of the anthracyclines. Such comparisons are essential in order to understand whether the simpler hydroxy‐anthraquinones can be a substitute for anthracycline drugs in cancer chemotherapy. Copyright © 2009 John Wiley & Sons, Ltd.     

DNA Vector Polyethyleneimine Affects Cell pH and Membrane Potential: A Time-Resolved Fluorescence Microscopy Study

Polyethyleneimine (PEI) is one of the very efficient nonviral vectors being developed and tested for artificial gene transfer into target cells. One of its serious limitations is the significant cytotoxicity of the large amounts of free PEI in the mixtures of DNA and PEI used for transfection. To further investigate the cellular effects of free PEI, we have analyzed the PEI-induced alterations of various cell parameters such as membrane heterogeneity and fluidity, cytoplasmic pH, and plasma membrane potential in a variety of cells such as Swiss 3T3 fibroblast, Chinese hamster ovary, insect cells SF9, plant cell line BY2, and Saccharomyces cerevisae. Fluorescence probes such as Nile red, SNARF-1, and cyanine dye DiSC₂(3), coupled with the technique of picosecond time-resolved fluorescence microscopy, were used in estimating the above-mentioned cell parameters. It was found that the cell membranes were largely unperturbed by PEI. However, the cytoplasmic pH showed an increase of 0.1–0.4 units when the cells were treated with PEI. The plasma membrane potential was found to be depolarized in S. cerevisae and Swiss 3T3 cells. These results suggest that the cytotoxic effects of PEI may partly originate from inhibition of regulation of cytoplasmic pH and plasma membrane potential. Further, it is proposed that the resultant cell alterations favors the transfection process.     

Order and Defects in Ceramic Semiconductor Nanoparticle Superstructures as a Function of Polydispersity and Aspect Ratio

The supreme aim of nanoparticle‐based materials is to achieve new properties extending over the features of individual constituents. The emergence of cooperativity necessitates precise positioning and orientation of nanoparticle ensembles. Thus, it is important to understand and learn how to control self‐assembly processes of nanoparticles. Besides shape, the structural uniformity plays a key role for ordering in superstructures. Therefore, it is challenging to synthesize nanorods with narrow polydispersity. An analysis of the systematic variation of aspect ratio and polydispersity is missing. A series of zinc oxide nanorods is presented and it is shown that their formation resembles step‐polymerization with an amorphous precursor state as a monomer and polar ZnO particles as entities capable of growing. The width of nanorods is kept constant (15 nm) and the length is varied between 20 and 100 nm, as well as improving the polydispersity of the nanorod length from 36% to 10%. Best samples have been achieved by post‐preparative treatment using gradient centrifugation. A method has been developed for semiquantitative evaluation of orientational order. Ordering in structures formed by quasispherical particles is always low despite low polydispersity. For rod‐like nanoparticles with increasing aspect ratio, superstructure order depends on the occurrence of different defects, which correlate differently to nanoparticle polydispersity.     

Magnetic and relaxometric properties of polyethylenimine-coated superparamagnetic MRI contrast agents

Novel systems to be employed as superparamagnetic contrast agents (CA) for magnetic resonance imaging (MRI) have been synthesized. These compounds are composed of an iron oxide magnetic core coated by polyethylenimine (PEI) or carboxylated polyethylenimine (PEI-COOH). The aim of the present work was to prepare and study new nanostructured systems (with better or at least comparable relaxivities, R₁ and R₂, with respect to the commercial ones) with controlled, almost monodisperse average dimensions and shape, as candidates for molecular targeting. By means of atomic force microscopy (AFM) measurements we determined the average diameter, of the order of 200 nm, and the shape of the particles. The superparamagnetic behavior was assessed by SQUID measurements. From X-ray data the estimated average diameters of the magnetic cores were found to be 5.8 nm for PEI-COOH60 and 20 nm for the compound named PEI25. By NMR-dispersion (NMRD), we found that PEI-COOH60 presents R₁ and R₂ relaxivities slightly lower than Endorem^®. The experimental results suggest that these novel compounds can be used as MRI CA.     

Uniform Drug Loading into Prefabricated Microparticles by Freeze‐Drying

Microparticle‐based drug delivery is a promising technology for small volume bioassay platforms. The general utilization of the drug‐loaded microparticles in the in vitro bioassay platforms requires the drug loading method, which should impregnate the general drug types (e.g., water insoluble) with high payload into the variously designed microparticles. Loading the drug into the prefabricated microparticles using solvent evaporation satisfies the requirement. However, similar to the “coffee‐ring effect,” drugs are loaded in a seriously nonuniform manner, caused by the capillary flow during the evaporation process. Here, it is presented that the freeze‐drying is an efficient way to load uniform and high amount of the drug into the prefabricated microparticles. It is demonstrated that freezing solvent can block the capillary flow during the solvent removal process, improving the loading uniformity. The delivered amount of drugs is linearly proportional to the initial loading amount of drugs. Also, this drug loading method is shown to be applied to the various drug types and the prefabricated microparticles with different properties. Considering many challenges to suppress the “coffee‐ring effect” that induces nonuniform impregnation/deposition, the proposed concept can be applied not only for microparticle‐based drug delivery but also for uniform coating applications (e.g., thin‐film coating, DNA/protein microarray).