Viral nanoparticles donning a paramagnetic coat: conjugation of MRI contrast agents to the MS2 capsid

A nanoparticle magnetic resonance imaging (MRI) contrast agent was developed by conjugation of more than 500 gadolinium chelate groups onto a viral capsid. The high density of paramagnetic centers and slow tumbling rate of modified MS2 capsids provided enhanced T1 relaxivities up to 7200 mM-1s-1 per particle. A bimodal imaging agent was generated by sequential conjugation of fluorescein and Gd3+ chelate. These results illustrate the potential for engineering natural protein assemblies to address bionanotechnology applications.     

Coating optimization of superparamagnetic iron oxide nanoparticles for high T2 relaxivity

We describe a new method for coating superparamagnetic iron oxide nanoparticles (SPIOs) and demonstrate that, by fine-tuning the core size and PEG coating of SPIOs, the T2 relaxivity per particle can be increased by >200-fold. With 14 nm core and PEG1000 coating, SPIOs can have T2 relaxivity of 385 s-1 mM-1, which is among the highest per-Fe atom relaxivities. In vivo tumor imaging results demonstrated the potential of the SPIOs for clinical applications.     

Noncovalent functionalization of carbon nanotubes with amphiphilic gd3+ chelates: toward powerful t1 and t2 MRI contrast agents

An amphiphilic gadolinium (III) chelate (GdL) was synthesized from commercially available stearic acid. Aqueous solutions of the complex at different concentrations (from 1 mM to 1 microM) were prepared and adsorbed on multiwalled carbon nanotubes. The resulting suspensions were stable for several days and have been characterized with regard to magnetic resonance imaging (MRI) contrast agent applications. Longitudinal water proton relaxivities, r1, have been measured at 20, 300, and 500 MHz. The r1 values show a strong dependence on the GdL concentration, particularly at low field. The relaxivities decrease with increasing field as it is predicted by the Solomon-Bloembergen-Morgan theory. Transverse water proton relaxation times, T2, have also been measured and are practically independent of both the frequency and the GdL concentration. An in vivo feasibility MRI study has been performed at 300 MHz in mice. A negative contrast could be well observed after injection of a suspension of functionalized nanotubes into the muscle of the leg of the mouse.     

Biodegradable Polysilsesquioxane Nanoparticles as Efficient Contrast Agents for Magnetic Resonance Imaging

Polysilsesquioxane (PSQ) nanoparticles are crosslinked homopolymers formed by condensation of functionalized trialkoxysilanes, and provide an interesting platform for developing biologically and biomedically relevant nanomaterials. In this work, the design and synthesis of biodegradable PSQ particles with extremely high payloads of paramagnetic Gd(III) centers is explored, for use as efficient contrast agents for magnetic resonance imaging (MRI). Two new bis(trialkoxysilyl) derivatives of Gd(III) diethylenetriamine pentaacetate (Gd‐DTPA) containing disulfide linkages are synthesized and used to form biodegradable Gd‐PSQ particles by base‐catalyzed condensation reactions in reverse microemulsions. The Gd‐PSQ particles, PSQ‐ 1 and PSQ‐ 2 , carry 53.8 wt% and 49.3 wt% of Gd‐DTPA derivatives, respectively. In addition, the surface carboxy groups on the PSQ‐ 2 particles can be modified with polyethylene glycol (PEG) and the anisamide (AA) ligand to enhance biocompatibility and cell uptake, respectively. The Gd‐PSQ particles are readily degradable to release the constituent Gd(III) chelates in the presence of endogenous reducing agents such as cysteine and glutathione. The MR relaxivities of the Gd‐PSQ particles are determined using a 3T MR scanner, with r₁ values ranging from 5.9 to 17.8 mMs^?1 on a per‐Gd basis. Finally, the high sensitivity of the Gd‐PSQ particles as T₁‐weighted MR contrast agents is demonstrated with in vitro MR imaging of human lung and pancreatic cancer cells. The enhanced efficiency of the anisamide‐functionalized PSQ‐ 2 particles as a contrast agent is corroborated by both confocal laser scanning microscopy imaging and ICP‐MS analysis of Gd content in vitro.     

The Coupled Thermal and Mechanical Influence on a Glassy Thermoplastic Polyamide: Nylon 6, 6 Under Vibro-Creep

The vibro-creep behavior of pure Nylon 6, 6 samples subjected to tensile-tensile cyclic loading conditions within the linear elastic region (25% of yield stress at 30 °C) was studied by examining their viscoelastic response. All tests were performed at controlled temperatures, and humidity was kept as low as possible. The test protocol included three frequencies and two amplitudes. The results from all tests show that vibro-creep behavior may be divided into three stages: (a) Primary thermally dominated regime (b) Transition or coupled regime (c) Tertiary damage dominated regime. The sample temperature was observed to rise 2–2.5 °C during the cyclic loading process, which significantly contributed to the early mechanical response of the sample. Two sets of quasi-static tests were completed at 30 °C and 32.5 °C to give references for vibro-creep effects. The relationship between engineering strain for the cyclic loading process (at 30 °C) and the quasi-static creep at 32.5 °C suggests the boundaries for different mechanisms dominating the vibro-creep behavior. This is also evident from the postmortem analyses of sample surfaces using AFM. Both the exterior sample surfaces and the interior cross-sectional surfaces were checked for the evolving damage. Mean roughness and dimensions of the cracks were measured in the damaged samples. Cracks of dimensions 2–4 m on the exterior surface and 1–2 m on the interior cross-sectional surface were observed in pure Nylon 6, 6 samples subjected up to 2 × 10⁶ cycles.     

Reflection from bound microbubbles at high ultrasound frequencies

Targeted contrast agents and ultrasound imaging are now used in combination for the assessment and tracking of biomarkers in animal models in vivo. These applications have triggered interest in the understanding and prediction of the ultrasound echoes from contrast agents attached to cells. This study describes the reflection enhancement due to microbubbles bound on a gelatin surface. The reflection enhancement was measured using ultrasound pulses at high frequency (40 MHz) and low pressure (38 kPa peak-negative pressure) allowing a linear approximation to be applied. The observed reflection coefficient increased with the number of microbubbles, until reaching saturation at 0.9 when the surface coverage fraction was 35%. A multiple scattering model assuming that the targeted microbubbles are confined within an infinitesimally thin layer appeared suitable in predicting the reflection coefficient even at very high surface densities. These results could permit the optimization of the sensitivity of high frequency ultrasound to targeted contrast agents.     

Biocompatible nanotemplate-engineered nanoparticles containing gadolinium: stability and relaxivity of a potential MRI contrast agent

In this article, we use a nanotemplate engineering approach to prepare biodegradable nanoparticles composed of FDA-approved materials and possessing accessible gadolinium (Gd) atoms and demonstrate their potential as a Magnetic Resonance Imaging (MRI) contrast agent. Nanoparticles containing dimyristoyl phosphoethanolamine diethylene triamine penta acetate (PE-DTPA) were prepared using 3.5 mg of Brij 78, 2.0 mg of emulsifying wax and 0.5 mg of PE-DTPA/ml from a microemulsion precursor. After the addition of GdCl3, the presence of Gd on the surface of nanoparticles was characterized using inductively coupled plasma atomic emission spectroscopy and Scanning Transmission Electron Microscopy (STEM). The in vitro relaxivities of the PE-DTPA-Gd nanoparticles in different media were assessed at different field strengths. The conditional stability constant of Gd binding to the nanoparticles was determined using competitive spectrophotometric titration. Transmetallation kinetics of the gadolinium ion from PE-DTPA-Gd nanoparticles with zinc as the competing ionic was measured using the relaxivity evolution method. Nanoparticles with a diameter of approximately 130 nm possessing surface chelating functions were made from GRAS (Generally Regarded As Safe) materials. STEM demonstrated the uniform distribution of Gd3+ on the surface of the nanoparticles. The thermodynamic binding constant for Gd3+ to the nanoparticles was approximately 10(18) M(-1) and transmetallation studies with Zn2+ yielded kinetic constants K1 and K(-1) of 0.033 and 0.022 1/h, respectively, with an equilibrium constant of 1.5. A payload of approximately 10(5) Gd/nanoparticle was achieved; enhanced relaxivities were observed, including a pH dependence of the transverse relaxivity (r2). Nanoparticles composed of materials that have been demonstrated to be hemocompatible and enzymatically metabolized and possessing accessible Gd ions on their surface induce relaxivities in the bulk water signal that make them potentially useful as next-generation MRI tumor contrast enhancement agents.     

Optical and magnetic resonance imaging of cell death and platelet activation using annexin a5-functionalized quantum dots

A quantum-dot-based nanoparticle is presented, allowing visualization of cell death and activated platelets with fluorescence imaging and MRI. The particle exhibits intense fluorescence and a large MR relaxivity (r1) of 3000-4500 mM-1 s-1 per nanoparticle due to a newly designed construct increasing the gadolinium-DTPA load. The nanoparticle is suitable for both anatomic and subcellular imaging of structures in the vessel wall and is a promising bimodal contrast agent for future in vivo imaging studies.     

Magnetically triggered clustering of biotinylated iron oxide nanoparticles in the presence of streptavidinylated enzymes

This work deals with the production and characterization of water-compatible, iron oxide based nanoparticles covered with functional poly(ethylene glycol) (PEG)-biotin surface groups (SPIO-PEG-biotin). Synthesis of the functionalized colloids occurred by incubating the oleate coated particles used as precursor magnetic fluid with anionic liposomes containing 14?mol% of a phospholipid-PEG-biotin conjugate. The latter was prepared by coupling dimyristoylphosphatidylethanolamine (DC(14:0)PE) to activated α-biotinylamido-ω -N-hydroxy-succinimidcarbonyl-PEG (NHS-PEG-biotin). Physical characterization of the oleate and PEG-biotin iron oxide nanocolloids revealed that they appear as colloidal stable clusters with a hydrodynamic diameter of 160?nm and zeta potentials of -?39?mV (oleate coated particles) and -?14?mV (PEG-biotin covered particles), respectively, as measured by light scattering techniques. Superconducting quantum interference device (SQUID) measurements revealed specific saturation magnetizations of 62-73?emu?g(-1) Fe(3)O(4) and no hysteresis was observed at 300?K. MR relaxometry at 3?T revealed very high r(2) relaxivities and moderately high r(1) values. Thus, both nanocolloids can be classified as small, superparamagnetic, negative MR contrast agents. The capacity to functionalize the particles was illustrated by binding streptavidin alkaline phosphatase (SAP). It was found, however, that these complexes become highly aggregated after capturing them on the magnetic filter device during high-gradient magnetophoresis, thereby reducing the accessibility of the SAP.     

PAMAM树状大分子磁共振成像造影剂的研究进展

树状大分子磁共振成像造影剂与小分子造影剂相比具有很高的质子弛豫增强及摩尔弛豫率,成像清晰度更好,有更长的血液循环时间等,因而具有十分乐观的应用前景.着重介绍了聚酰胺-胺(PAMAM)树状大分子钆螯合物造影剂的性质及应用研究情况.低代数(PAMAM-G2、G3、G4)树状大分子钆螯合物造影剂分子尺寸较小(小于6nm),相对而言可以迅速从肾排泄,能够作为肾功能性造影剂.高代数(PAMAM-G7、G8)树状大分子钆螯合物造影剂分子尺寸较大(大于12nm),可静脉注射用于血池造影剂,而PAMAM-G6大分子试剂可用于淋巴成像造影剂.对PAMAM树状大分子钆螯合物进行化学或生物学修饰,还可以使其具有肿瘤靶向性,并能作为钆中子捕获治疗(Gd-NCT)试剂.     

Short- and long-term stability of resonant quartz temperature sensors

A new miniaturized design of the thermosensitive quartz resonator (TSQR) using an NLC cut (yxl/ -31 degrees 30') with a fundamental frequency of 29.3 MHz was created in the Acoustoelectronics Laboratory of ISSPBAS for use in a wide temperature range (4.2 K to 450 K) as highly sensitive quartz temperature sensors (QTS). This paper presents the results of the investigations of the short- and long-term frequency stability of QTS. The short-term frequency stability of QTS was measured for averaging times up to 150 s at three constant temperatures: liquid helium (4.2 K), liquid nitrogen (77 K), and melting ice (0 degrees C). The short-term frequency stability is 6.8 * 10(-9) at 0 degrees C for t = 15 s, which permits a temperature sensitivity of 2 * 10(-4) K. The long-term stability (aging) was investigated at room temperature and at 80 degrees C for 500 days. The aging characteristics at 25 degrees C and 80 degrees C are compared. It was observed that the frequency change does not exceed 5 * 10(-7) after the 25th day of accelerated aging at 80 degrees C. This guarantees a reliable operation of the sensor, without additional calibration, for several years.     

Surface area and pore size characteristics of nanoporous gold subjected to thermal, mechanical, or surface modification studied using gas adsorption isotherms, cyclic voltammetry, thermogravimetric analysis, and scanning electron microscopy

Nitrogen adsorption/desorption isotherms are used to investigate the Brunauer, Emmett, and Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore size distribution of physically modified, thermally annealed, and octadecanethiol functionalized np-Au monoliths. We present the full adsorption-desorption isotherms for N(2) gas on np-Au, and observe type IV isotherms and type H1 hysteresis loops. The evolution of the np-Au under various thermal annealing treatments was examined using scanning electron microscopy (SEM). The images of both the exterior and interior of the thermally annealed np-Au show that the porosity of all free standing np-Au structures decreases as the heat treatment temperature increases. The modification of the np-Au surface with a self-assembled monolayer (SAM) of C(18)-SH (coverage of 2.94 × 10(14) molecules cm(-2) based from the decomposition of the C(18)-SH using thermogravimetric analysis (TGA)), was found to reduce the strength of the interaction of nitrogen gas with the np-Au surface, as reflected by a decrease in the 'C' parameter of the BET equation. From cyclic voltammetry studies, we found that the surface area of the np-Au monoliths annealed at elevated temperatures followed the same trend with annealing temperature as found in the BET surface area study and SEM morphology characterization. The study highlights the ability to control free-standing nanoporous gold monoliths with high surface area, and well-defined, tunable pore morphology.     

Wüstite-type Fe_(0.78)Mn_(0.22)O nanocubes:A new class for high-sensitive T_2-weighted magnetic resonance imaging agent

Wüstite-type Fe_(0.78)Mn_(0.22)O nanocubes,with a uniform size of～10 nm in edge length,have been synthesized by thermal-decomposition approach.The nanocubes exhibited superparamagnetic properties at room temperature,associated with a magnetization of 12.6 emu/g.These Fe_(0.78)Mn_(0.22)O nanocubes present transversal(r_2) and longitudinal(r_1) relaxivities of 325.9 and 0.518 mM~(-1) s~(-1) at 7 T for water protons.The ratio of the r_2/r_1(629.2) ranks them being the highest sensitivity(r_2/r_1) comparable to currently reported T2-weighted magnetic resonance imaging(MRI) agents.Meanwhile,the Fe_(0.78)Mn_(0.22)O nanocubes were functionalized and demonstrated to be biocompatible when attached to the surface of mesenchymal stem cells,therefore showing the promise as a new class of MRI agents in clinic applications.     

Functionalized Multi‐Wall Carbon Nanotubes for Lipase Immobilization

We examine the immobilization of lipase B from Candida antarctica on functionalized multi‐wall carbon nanotubes (MWCNTs) through physical adsorption. MWCNTs functionalized with carboxyl‐, amine‐ and ester‐ terminal groups on their surface are used as immobilization carriers. Dispersion of the nanotubes and the immobilization procedure take place in aqueous and low‐water media. High enzyme loadings are attained, up to 25% of the weight of the carbon nanotubes. These novel biomaterials are characterized though FT‐IR and Raman spectroscopy. The MWCNT–lipase bioconjugates exhibit high catalytic activity and increased storage and operational stability. The biomaterials retain more than 55% of their initial activity after 6 months at 4 °C, while they retain approximately 25% of their initial activity after 30 d of incubation in hexane at 60 °C. The catalytic behaviour of the immobilized enzyme depends on the terminal group of the carbon nanotubes, the concentration of the enzyme and the immobilization method employed.     

Surface functionalization of BiFeO<Subscript>3</Subscript>: A pathway for the enhancement of dielectric and electrical properties of poly(methyl methacrylate)–BiFeO<Subscript>3</Subscript> composite films

A novel two-phase composite film is prepared by the solvent casting method employing poly(methyl methacrylate) (PMMA) as polymer matrix and bismuth ferrite (BFO) as ceramic filler. The surfaces of BFO are functionalized by proper hydroxylating agents to activate their chemical nature. The structural analysis of the composite films confirms that the composites made up of functionalized BFO (BFO-OH) have a distorted rhombohedral structure. The morphological analysis shows that BFO-OH particles are equally distributed over the polymer matrix. The -OH functionality of BFO-OH is confirmed by FTIR. The dielectric and electrical studies at a frequency range from 100 Hz to 1 MHz reveal that PMMA-(BFO-OH) composites have enhanced dielectric constant as well as electrical conductivities, much higher than that of unmodified composites. According to the ferroelectric measurement result, the hydroxylated composite film shows a superior ferroelectric behavior than that of the unmodified one, with a remanent polarization (2P_r) of 2.764 μC/cm².     

Functionalization of mesostructured silica–carbon composites

A strategy for synthesizing highly functionalized porous silica–carbon composites made up of a sulphur- or nitrogen-doped carbon layer coating the pores of two mesostructured silica samples (i.e. SBA-15 and KIT-6) is presented. The synthesis scheme involves several steps: a) infiltration of the silica pores by sulphur-rich (thiophene) or nitrogen-rich (pyrrole) monomers, b) in situ polymerization of these precursors to form polythiophene or polypyrrole, and c) carbonization of the polymers. The resulting silica–carbon composites contain ∼25 wt % of carbonaceous matter and a large number of nitrogen and sulphur functional groups attached to the deposited carbon (up to 4.2 wt % of nitrogen and 6.1 wt % of sulphur). The structural characteristics of the parent silica are retained in the composite materials, which exhibit high surface area, large pore volume and a well-ordered porosity made up of uniform mesopores.     

Detection of surface and subsurface flaws in homogeneous and composite solids by resonant ultrasound

We used resonant ultrasound spectroscopy (RUS) to detect two types of flaws: a surface crack in a steel block and an interior void in a bilayered composite block. Detection is possible because cracks alter an object’s macroscopic vibration frequencies, which can be measured to better than 1 Hz in 1 MHz. The surface crack decreased the resonant frequencies up to 50%. The interior flaw in the adhesive joint between an aluminum alloy and a graphite-epoxy layer, increased resonant frequencies with increasing flaw size. We confirmed our measurements with finite-element and Ritz approximation calculations. Our study supports the use of RUS to detect cracks.     

Ultrasonic Nondestructive Evaluation of Cylindrical Samples with Surface Acoustic Waves

The paper reports experimental methodology and results of nondestructive evaluation and flaw imaging in cylindrical samples using surface acoustic waves (SAW) generated with conventional longitudinal wave transducers attached to the sample surface. A very thin layer of couplant (or even dry coupling) was used to provide efficient SAW generation in the direction normal to a cylinder element in the frequency range 5—15 MHz. A single B-scan mode was sufficient to inspect a total surface of cylindrical shafts of ceramic and metal engine valves. A delay of the processing time gate allowed us to analyze any of the successive SAW revolutions implementing a specific ``transmission B-scan' with a single probe. Amplitude and phase contrast of the B-scans obtained demonstrate the system capability to detect valve radius deviations of 1 μm and cracked flaws with sizes down to 30 μm.     

Ultrasonic Nondestructive Evaluation of Cylindrical Samples with Surface Acoustic Waves

Abstract

The paper reports experimental methodology and results of nondestructive evaluation and flaw imaging in cylindrical samples using surface acoustic waves (SAW) generated with conventional longitudinal wave transducers attached to the sample surface. A very thin layer of couplant (or even dry coupling) was used to provide efficient SAW generation in the direction normal to a cylinder element in the frequency range 5–15 MHz. A single B-scan mode was sufficient to inspect a total surface of cylindrical shafts of ceramic and metal engine valves. A delay of the processing time gate allowed us to analyze any of the successive SAW revolutions implementing a specific “transmission B-scan” with a single probe. Amplitude and phase contrast of the B-scans obtained demonstrate the system capability to detect valve radius deviations of ～ 1 μm and cracked flaws with sizes down to ～ 30 μm.     

Surface functionalization and structure characterizations of nanodiamond and its epoxy based nanocomposites

The aim of this study is the potential use of nanodiamond to make the lightweight and strong nanocomposites. Here, effects of size and surface modification of detonation nanodiamond (DND) on mechanical performance of epoxy based nanocomposites is presented. Our characterizations reveal that the process of functionalization not only removes the non-diamond content and impurities by significantly reducing DND's size but also introduces oxygen containing functional groups on its surface. The average size of functionalized DND aggregations could be decreased from 300 to 100 nm in contrast to pristine DND, which greatly benefits its homogeneous dispersion in epoxy matrix. In addition, strong chemical bonding among functionalized DND and epoxy resin due to functional groups leads to the formation of efficient interface. These interfaces overlap at high concentrations making a network which in turn significantly enhances the tensile properties. The enhancement in Young's modulus can reach up to 2.5 times higher than that of neat epoxy whereas the enhancement in tensile strength is about 1.5 times in functionalized DND/epoxy nanocomposites.