Surface initiated‐atom transfer radical polymerization of a sugar methacrylate on gold nanoparticles

For development of surface‐functionalized gold nanoparticles (GNPs) as cellular probes, we report herein the synthesis of glycoconjugates of GNPs with cyclic sugar methacrylate, 2‐lactobionamidoethyl methacrylate (LAMA). The strategy involves the attachment of an initiator on the nanoparticle surface followed by surface initiated‐atom transfer radical polymerization (SI‐ATRP) of LAMA. SI‐ATRP of LAMA was achieved by reacting a mixture of copper (I) bromide (CuBr), 2,2′‐bipyridine (bpy) and initiator‐bound GNPs in methanol at 20 °C for 12 h. The resultant GNP glycoconjugates were characterized using Fourier‐transform infrared (FT‐IR) spectroscopy, X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The FT‐IR spectra of GNP glycoconjugates show IR peaks characteristic of LAMA demonstrating the formation of a LAMA layer on the GNPs' surface. The XPS spectrum of glycoconjugates shows signals due to the presence of carbon (C1s, 288 eV) and oxygen (O1s, 536 eV) along with gold (Au 4f, 100 eV; Au 4p, 743 eV). The increase in diameter of GNPs from 13 to 25 nm measured by SEM further confirms the presence of a LAMA layer on the surface of the GNPs. Considering the biological importance of glycoconjugates, such as cell recognition, cell adhesion and cell growth regulation, the method described herein would be beneficial in many areas such as pathogen detection and biosensors. Copyright © 2008 John Wiley & Sons, Ltd.     

Design,synthesis and preclinical evaluations of (s)-2-((s)-1-benzyl-2,5-dioxopyrrolidin-3-yl)-3-(4-isopropylphenyl)-2-methylpropanal (succ-5) as cardioprotective,hepatoprotective and lipid lowering molecule. in-vivo and in-silico approaches

In this study, the newly synthesized compound (Succ-5) was analyzed through spectral methods, seen for potential receptor targets via molecular docking, and pre-clinically evaluated for therapeutic effects and safety profile using biochemical and histopathological techniques. The biochemical analysis included assessment of cardiac biomarkers, hepatic enzymes, and lipid profiles, while histopathology included evaluation of cardiac and liver tissues. The toxic dose was determined pre-clinically, followed by dividing albino rats into five treatment groups (each having n = 6). The control group received oral saline for eight days. The 5-FU (5-Fluorouracil) group received oral saline for 8 days and 5-FU (150 mg/kg I.P.) on day 5. The atenolol group was administered with atenolol (20 mg/kg) for 8 days and 5-FU (150 mg/kg I.P.) on day 5. Two groups of rats were administered with the test compound (Succ-5) at doses of 5 mg/kg I.P and 10 mg/kg I.P (for 8-days), followed by 5-FU (150 mg/kg I.P.) on day 5. Elevated serum levels of CK-MB (creatinine kinase myocardial band), cTnI (troponin I), LDH (lactate dehydrogenase), lipid profile, and selected liver enzymes including ALP (alkaline phosphatase), ALT (alanine transaminase), AST (aspartate aminotransferase), BT (bilirubin total) and BD (direct bilirubin) were associated with 5-FU toxicity. After administration of the test compound at the mentioned doses, these biomarkers significantly decreased. Likewise, histological examination revealed 5-FU damaged the heart and hepatic tissues, which were also considerably recovered following administration of the test compound. Immunohistochemistry of heart tissue also revealed the low expression of COX-2 and TNF-α in Succ-5 treated groups compared to toxic group. Dose-response evaluation showed that a dose of 10 mg/kg provided better results than 5 mg/kg. The analysis of binding energy values computed via docking simulations showed that Succ-5 interacts with the human beta2-adrenergic G protein-coupled receptor with a slightly stronger affinity than calcium channel T-type. In conclusion, the histological and biochemical findings revealed that the test compound had significant cardioprotective, hepatoprotective, and lipolytic effects in the 5-FU-induced toxicity.     

Gold nanoparticle–antibody conjugates for specific extraction and subsequent analysis by liquid chromatography–tandem mass spectrometry of malondialdehyde-modified low density lipoprotein as biomarker for cardiovascular risk

Oxidized low-density lipoproteins (OxLDLs) like malondialdehyde-modified low-density lipoprotein (MDA-LDL) play a major role in atherosclerosis and have been proposed as useful biomarkers for oxidative stress. In this study, gold-nanoparticles (GNPs) were functionalized via distinct chemistries with anti-MDA-LDL antibodies (Abs) for selective recognition and capture of MDA-LDL from biological matrices. The study focused on optimization of binding affinities and saturation capacities of the antiMDA-LDL-Ab-GNP bioconjugate by exploring distinct random and oriented immobilization approaches, such as (i) direct adsorptive attachment of Abs on the GNP surface, (ii) covalent bonding by amide coupling of Abs to carboxy-terminated-pegylated GNPs, (iii) oriented immobilization via oxidized carbohydrate moiety of the Ab on hydrazide-derivatized GNPs and (iv) cysteine-tagged protein A (cProtA)-bonded GNPs. Depending on immobilization chemistry, up to 3 antibodies per GNP could be immobilized as determined by ELISA. The highest binding capacity was achieved with the GNP-cProtA-Ab bioconjugate which yielded a saturation capacity of 2.24 ± 0.04 μg mL⁻¹ GNP suspension for MDA-LDL with an affinity K_d of 5.25 ± 0.11 × 10⁻¹⁰ M. The GNP-cProtA-antiMDA-LDL bioconjugate revealed high specificity for MDA-LDL over copper(II)-oxidized LDL as well as native human LDL. This clearly demonstrates the usefulness of the new GNP-Ab bioconjugates for specific extraction of MDA-LDL from plasma samples as biomarkers of oxidative stress. Their combination as specific immunoextraction nanomaterials with analysis by LC–MS/MS allows sensitive and selective detection of MDA-LDL in complex samples.     

Gold nanoparticles enhance the X-ray-induced degradation of human centrin 2 protein

In the war against cancer, radiotherapy is a prominent tool but counterbalanced by the fact that it also induces damages in healthy tissues. Nanotechnologies could open a new possibility to decrease these side effects. In particular, gold nanoparticles (GNPs) could be used as radio-sensitizers. As the role of proteins in the processes leading to cell death cannot be neglected, their radio-sensitization by GNPs is of great interest. This is particularly true in the case of the human centrin 2 protein, which has been proposed to be involved in DNA repair processes. To investigate this effect, we quantified for the first time the degradation of this protein in a gold colloidal solution when submitted to X-rays. We showed that the X-ray-induced degradation of the human centrin 2 protein is enhanced 1.5-fold in the presence of GNPs, even though no covalent bond exists between protein and GNPs. Among the conditions tested, the maximum enhancement was found with the higher GNP:protein ratio of 2×10⁻⁴ and with the higher X-ray energy of 49 keV.     

Fractionation and characterization of gold nanoparticles in aqueous solution: asymmetric-flow field flow fractionation with MALS, DLS, and UV–Vis detection

Asymmetrical-flow field flow fractionation (AFFF) separates constituents based on hydrodynamic size and is emerging as a powerful tool for obtaining high-resolution information on the size, molecular weight, composition, and stability of nanoscale particles in liquid media. We employ a customized AFFF system combining on-line detectors for multi-angle light scattering, dynamic light scattering, and UV–Vis absorption. Our objective is to develop optimized measurement protocols for the characterization of gold nanoparticles (GNPs), which are widely utilized in biomedical research and other nanotechnology applications. Experimental conditions have been optimized by controlling key parameters, including injection volume and solids concentration, mobile phase composition, membrane type and pore size, and ratio of channel-to-cross-flow rates. Individual citrate-stabilized GNP components (nominally 10, 20, 30, 40, and 60 nm) and GNPs functionalized with polyethylene glycol were separated from multicomponent GNP mixtures by AFFF and subsequently characterized. We discuss the effects due to variations in measurement parameters and GNP surface modification on observed retention, recovery, and peak resolution.     

Effect of size and protein environment on electrochemical properties of gold nanoparticles on carbon electrodes

We studied the electrochemical properties of gold nanoparticles (GNPs) and their complexes with proteins using square-wave voltammetry. Effect of the nanoparticle size and detection procedure was explored upon the oxidation of GNPs on a glassy carbon electrode (GCE). For pre-characterized GNPs of 13, 35 and 78 nm diameter, the oxidation peak potential was + 0.98, + 1.03 and + 1.06 V vs. Ag/AgCl, respectively. The conjugation of GNPs with four different proteins was verified by UV–Vis spectroscopy and atomic force microscopy indicated the formation of protein shells around GNPs. This process hampered the oxidation of GNPs on bare GCE causing pronounced decrease in the current response by an average factor of 72. GCE modification with carbon nanotubes weakly influenced the sensitivity of GNP detection but resulted in a 14.5-fold signal increase averaged for all GNP–protein complexes. The acidic dissolution and electrodeposition of GNPs or their complexes adsorbed on GCE allowed superior signal amplification directly proportional to nanoparticle size. The results are useful for the optimization of voltammetric analysis of GNP–protein complexes and can be extended to the characterization of other metal nanostructures and their complexes with biological components.     

Melt extrudate swell behavior of graphene nano-platelets filled-polypropylene composites

The extrudate swell ratios of polypropylene (PP) composite melts filled with graphene nano-platelets (GNPs) were measured using a capillary rheometer within a temperature range of 180–230 °C and apparent shear rate varying from 100 to 4000 s⁻¹ in order to identify the effects of the filler content and test conditions on the melt die-swell behavior. It was found that the values of the extrudate swell ratio of the composites increased with increasing apparent shear rate, with the correlation between them obeying a power law relationship, while the values of the extrudate swell ratio decreased almost linearly with rise in temperature. The values of the melt extrudate swell ratio increased approximately linearly with increasing shear stress, and decreased roughly linearly with an increase of the GNP weight fraction. In addition, the extrudate swell mechanisms are discussed from the observation of the fracture surface of the extrudate using scanning electronic microscopy. This study provides a basis for further development of graphene reinforced polymer composites with desirable mechanical performance and good damage resistance.     

Novel conducting poly(3,4-ethylenedioxythiophene) – Graphene nanocomposites with gigantic dielectric properties and narrow optical energy band gap

Novel nanocomposites, consisting of conducting poly(3,4-ethylenedioxythiophene) [PEDOT] and graphene nanoplatelets [GNPs], were successfully synthesized by in-situ chemical-oxidative polymerization of 3,4-ethylenedioxythiophene [EDOT] using ammonium peroxydisulfate as an oxidizing agent. The formation of PEDOT and its incorporation onto the surface of GNPs were confirmed by scanning electron microscopy, Fourier-transform infrared-spectroscopy, and X-ray diffraction. The optical energy band gap, E_g^opt, was determined by UV–Vis spectroscopy. Dielectric constant and loss as well as AC electrical conductivity, σ_AC, were determined in the frequency range from 10 Hz to 8 MHz. The PEDOT-GNP nanocomposites were found to have extremely large dielectric constant, ε′, significantly high σ_AC, and narrow E_g^opt values. In particular, PEDOT-GNP nanocomposite with 10 wt% GNP has a gigantic dielectric constant of the order of 9 × 10⁵ at 1 kHz and a narrow optical energy band gap of 1.26 eV. The ε′ values (10⁸ to 10⁵ in the frequency range from 10 Hz to 5 MHz) of PEDOT-10 wt% GNP are the highest among those reported in the literature for carbon based polymer nanocomposites. The massive quantity of micro-capacitors formed in the nanocomposites, prior to the creation of conductive networks, leads to the gigantic dielectric properties. The ε′ and σ_AC values of PEDOT-10 wt% GNP nanocomposite were about 90 and 400 times larger than those of pure PEDOT. Our method should be particularly promising in the development of new materials for high energy storage applications.     

Influence of Gold Nanoparticles of Varying Size in Improving the Lipase Activity within Cationic Reverse Micelles

Herein, we report the effect of gold nanoparticles (GNPs) in enhancing lipase activity in reverse micelles of cetyltrimethylammonium bromide (CTAB)/water/isooctane/n‐hexanol. The size and concentration of the nanoparticles were varied and their specific roles were assessed in detail. An overall enhancement of activity was observed in the GNP‐doped CTAB reverse micelles. The improvement in activity becomes more prominent with increasing concentration and size of the GNPs (0–52 μM and ca. 3–30 nm, respectively). The observed highest lipase activity (k₂=1070±12 cm³ g^?1 s^?1) in GNP‐doped CTAB reverse micelles ([GNP]: 52 μm, ca. 20 nm) is 2.5‐fold higher than in CTAB reverse micelles without GNPs. Improvement in the lipase activity is only specific to the GNP‐doped reverse micellar media, whereas GNP deactivates and structurally deforms the enzyme in aqueous media. The reason for this activation is probably due to the formation of larger‐sized reverse micelles in which the GNP acts as a polar core and the surfactants aggregate around the nanoparticle (‘GNP pool’) instead of only water. Lipase at the augmented interface of the GNP‐doped reverse micelle showed improved activity because of enhancement in both the substrate and enzyme concentrations and increased flexibility in the lipase conformation. The extent of the activation is greater in the case of the larger‐sized GNPs. A correlation has been established between the activity of lipase and its secondary structure by using circular dichroism and FTIR spectroscopic analysis. The generalized influence of GNP is verified in the reverse micelles of another surfactant, namely, cetyltripropylammonium bromide (CTPAB). TEM, dynamic light scattering (DLS), and UV/Vis spectroscopic analysis were utilized to characterize the GNPs and the organized aggregates. For the first time, CTAB‐based reverse micelles have been found to be an excellent host for lipase simply by doping with appropriately sized GNPs.     

Nucleosides rich extract from Cordyceps cicadae alleviated cisplatin-induced neurotoxicity in rats: A behavioral,biochemical and histopathological study

This work explored the protective effects of nucleosides rich extract from C. cicadae (CCNE) against cisplatin-induced neurotoxicity. The rats were divided into four groups: normal control (NCA), cisplatin control (CCA), CCNE-L + cisplatin (CCNE-L) and CCNE-H + cisplatin (CCNE-H). The rats in CCNE-L and CCNE-H were orally administered with 100 and 400 mg/kg of CCNE, respectively for five weeks, while the rats in CCA, CCNE-L and CCNE-H groups received intraperitoneal injection of 2.5 mg/kg cisplatin once a week for four weeks starting from the second week of CCNE treatment. After the final treatment, the rats were subjected to behavioural task including Morris water maze test (MWMT), Y maze test, forced swimming (FST), open field test (OFT), rotarod test as well as heat and mechanical hyperalgesia test. Thereafter, the animals were sacrificed and oxidative stress biomarkers, inflammatory mediators and acetylcholinesterase activities were measured in the brain. The histopathological assessment of the brain issues was also performed using H&E staining. The results indicated that CCNE significantly ameliorative cisplatin induced learning and memory impairment (MWMT and Y maze test), depressive behaviours (FST and OFT), motor coordination as well as thermal (hot plate and tail withdrawal test) and mechanical hyperalgesia (von Frey filament test). Furthermore, CCNE decreased acetylcholinesterase level, proinflammatory cytokines levels and lipid peroxidation, with concomitant increase in antioxidant enzymes profiles in the brain tissues of cisplatin treated rats. Additionally, CCNE treatment alleviated histopathological alterations in the brain tissues caused by cisplatin treatment. These results suggested that CCNE ameliorated memory impairment deficits, neuropathy, increased oxidative stress, inflammation in cisplatin treated rats through the inhibition of oxidative stress and inflammation.     

Effect of gambogenic acid in attenuating diethylnitrosamine (DEN)-induced hepatocellular carcinoma in rat model

Liver cancer, specifically hepatocellular carcinoma has been a widespread problem among general population. This study aims to investigate the modulating mechanism of gambogenic acid, a phenolic xanthonoid, in diethylnitrosamine (DEN)-induced liver cancer in rats. Male Wistar albino rats were clustered into four groups (n = 6). Group I served as control treated with normal saline. Hepatocellular carcinogenesis was induced in rats by single intraperitoneal (i.p.) administration of DEN in saline (200 mg/kg b.w.) for groups II and III. Group III received oral administration of gambogenic acid (20 mg/kg b.w.) one hour post DEN administration, whereas group IV received oral administration of gambogenic acid (20 mg/kg b.w.) alone. Rats were sacrificed after 16 weeks to determine the levels of hepatic biomarkers, oxidative stress markers, hematological profile and histopathological changes. Gambogenic acid significantly ameliorated the expressions of oxidative stress markers TBARS, GSH (P < 0.05), enzymatic antioxidants GPx, CAT, SOD, GST (P < 0.05), apoptosis mediators (P < 0.05), and serum biomarkers for liver damage and tumor formation (P < 0.05) compared with DEN-induced model group. Hepatocellular levels of 8-OHdG were significantly diminished (P < 0.05) by gambogenic acid against the damage incurred by DEN. Liver histopathological derangements caused by DEN were reversed by gambogenic acid. The results clearly impacted the effect of gambogenic acid in attenuating DEN-induced hepatocellular carcinoma in rats mediated through NF-kβ pathway and hepatocellular oxidative damage.     

Redox-active ionic-liquid-assisted one-step general method for preparing gold nanoparticle thin films: applications in refractive index sensing and catalysis

We describe a general one-step facile method for depositing gold nanoparticle (GNP) thin films onto any type of substrates by the in situ reduction of AuCl(3) using a newly designed redox-active ionic liquid (IL), tetrabutylphosphonium citrate ([TBP][Ci]). Various substrates such as positively charged glass, negatively charged glass/quartz, neutral hydrophobic glass, polypropylene, polystyrene, plain paper, and cellophane paper are successfully coated with a thin film of GNPs. This IL ([TBP][Ci]) is prepared by the simple neutralization of tetrabutylphosphonium hydroxide with citric acid. We also demonstrate that the [TBP][Ci] ionic liquid can be successfully used to generate GNPs in an aqueous colloidal suspension in situ. The deposited GNP thin films on various surfaces are made up of mostly discrete spherical GNPs that are well distributed throughout the film, as confirmed by field-emission scanning electron microscopy. However, it seems that some GNPs are arranged to form arrays depending on the nature of surface. We also characterize these GNP thin films via UV-vis spectroscopy and X-ray diffractometry. The as-formed GNP thin films show excellent stability toward solvent washing. We demonstrate that the thin film of GNPs on a glass/quartz surface can be successfully used as a refractive index (RI) sensor for different polar and nonpolar organic solvents. The as-formed GNP thin films on different surfaces show excellent catalytic activity in the borohydride reduction of p-nitrophenol.     

Disclosure of the imidazolium cation coordination and stabilization mode in ionic liquid stabilized gold(0) nanoparticles

A surface-enhanced Raman spectroscopy (SERS) study of imidazolium ionic liquid stabilized gold(0) nanoparticles (GNPs) furnished previously unknown knowledge about the coordination and stabilization mode of the imidazolium cation. GNPs were prepared by hydrazine reduction of a chloroauric acid solution in 1-triethylene glycol monomethyl ether-3-methylimidazolium methanesulfonate 2 as ether-functionalized room-temperature ionic liquid (RTIL). UV-vis spectroscopy showed the presence of GNP aggregates as absorptions extended to the NIR region. A parallel coordination mode for the imidazolium cation of RTIL 2 on the GNP surface was observed by SERS, which occurred without the simultaneous coordination of the 1-triethylene glycol monomethyl ether-functionality. Instead of this, the ether-functionality was directed away from the GNP surface and acted as steric barrier between the GNPs/GNP aggregates, thus preventing further aggregation. These new insights suggest that the imidazolium cation is responsible for electrosteric stabilization.     

The nanomechanical behavior of a graphite nanoplatelet/polycarbonate nanocomposite

Quasi-static nanoindentation has been used to characterize the mechanical properties of polycarbonate reinforced with graphite nanoplatelets (GNPs). Poor dispersion or low quality interfacial interactions of GNPs in a polymer matrix can significantly decrease the relative improvement in the material's mechanical strength and stiffness. In this study, the surfaces of GNPs were modified to achieve better dispersion and interfacial interaction between fillers and matrix. The GNP/PC nanocomposite has a heterogeneous microstructure, and the original mechanical properties between filler and matrix have large differences. Using a spatially sensitive probe method leads to measured values of modulus and hardness that correlate with the indentation sampled volume. A grid indentation procedure was performed with variable sampling volumes to provide a statistical measurement of modulus and hardness for the nanocomposite materials. The surface treatment leads to a significant increase in both stiffness and hardness for GNP reinforced composites.     

Quercetin attenuates cisplatin-induced ovarian toxicity in rats: Emphasis on anti-oxidant,anti-inflammatory and anti-apoptotic activities

Ovarian toxicity is a devastating adverse effect of cisplatin therapy. The objective of the current study was to address whether or not quercetin could protect against cisplatin-induced ovarian toxicity in rats as well as the possible underlying mechanisms. Rats were allocated into five groups. Group 1 represented the control, group 2 was administered quercetin (10 mg/kg), group 3 received cisplatin (6 mg/kg single i.p. dose) on days 7 and 14, the forth group was given cisplatin + quercetin (5 mg/kg) and the fifth group was administered cisplatin + quercetin (10 mg/kg). Quercetin ameliorated cisplatin-induced histopathological changes in ovarian tissues and significantly prevented the decline in the percentage of healthy follicles and serum anti-Mullerian hormone (AMH). Quercetin exhibited significant anti-oxidant effects evidenced by preventing MDA accumulation, glutathione depletion and superoxide and glutathione peroxidase exhaustion in the ovary. Also, quercetin displayed activities against cisplatin-induced inflammatory responses in the ovary. Quercetin significantly inhibited expression of NFκb, Cox-2 and IL-6 and elevated ovarian content of TNF-α. Further, quercetin showed anti-apoptotic activity as demonstrated by decreased caspase-3 content and modulation of Bax and Bcl2 expression in the ovary. Conclusively, quercetin protects against cisplatin-induced ovarian toxicity in rats. This is mediated, at least partly, by its anti-oxidant, anti-inflammatory and anti-apoptotic activities.     

One-Step Synthesis of Stable Colloidal Gold Nanoparticles Through Bioconjugation with Bovine Serum Albumin in Harsh Environments

In saline solutions with NaCl concentrations less than that typical of blood plasma and bodily fluids, gold nanoparticles (GNPs) aggregate and precipitate because of GNP cation complexation with the Cl^? anions in the solution. It is difficult to retain stable colloidal GNPs within any saline solution for a relatively long time without aggregation and precipitation. In this study, we developed a method to synthesize stable GNPs in harsh anion-containing environments. GNPs were formed by laser ablation in a saline solution, and their stabilization was achieved by adding bovine serum albumin (BSA) to the NaCl solution; this has been shown to be a quick, efficient approach to producing stable colloidal GNPs. GNP nanoclusters in saline solutions with and without BSA were observed via high-resolution transmission electron microscopy and selected area electron diffraction. The results reveal that our methodology yields colloidal GNPs with long-term stability in a BSA-containing saline solution.     

Determination of 3-chloro-1,2-propanediol in biological samples by quick-easy-cheap-effective-rugged-and-safe extraction coupled with gas chromatography-mass spectrometry and its biodistribution in rats

3-Chloro-1,2-propanediol is a common food contaminant, but reports on its determination in biological tissues are lacking. In the present study, a method was developed to detect 3-chloro-1,2-propanediol contents in rat tissues by quick-easy-cheap-effective-rugged-and-safe extraction and gas chromatography-mass spectrometry analysis. Biological samples were extracted with ethyl acetate and purified with adsorbents. The optimized adsorbent for each sample was selected from 4–5 combinations of N-propylethylenediamine, octadecylsilane, graphitized carbon black, strong anion exchange, and florisil. Extracted 3-chloro-1,2-propanediol was derivatized with heptafluorobutyric anhydride and subjected to gas chromatography-mass spectrometry. This method had good linearity (correlation coefficients >0.99) in the range of 2–2000 ng/g for blood, kidney, liver, testis, and brain samples. The limits of detection were under 0.8 ng/g; the limits of quantification were 2 ng/g; the recovery rates were 85%–102%; and the matrix effects were 1.98%–7.67%. This method also had good precision. The dynamic changes in 3-chloro-1,2-propanediol in rats gavaged with 20 mg/kg b.w. for 24 h were detected using this method. The 3-chloro-1,2-propanediol content in each tissue sharply increased to a peak, rapidly decreased within 2 h, and stabilized at 12 h. 3-Chloro-1,2-propanediol persisted in the kidney, testis, and liver 24 h after gavage.     

Sonochemical Synthesis of Gold Nanoparticles by Using High Intensity Focused Ultrasound

The sonochemical synthesis of gold nanoparticles (GNPs) with different shapes and size distributions by using high‐intensity focused ultrasound (HIFU) operating at 463 kHz is reported. GNP formation proceeds through the reduction of Au³⁺ to Au⁰ by radicals generated by acoustic cavitation. TEM images reveal that GNPs show irregular shapes at 30 W, are primarily icosahedral at 50 W and form a significant amount of nanorods at 70 W. The size of GNPs decreases with increasing acoustic power with a narrower size distribution. Sonochemiluminescence images help in the understanding of the effect of HIFU in controlling the size and shapes of GNPs. The number of radicals that form and the mechanical forces that are generated control the shape and size of the GNPs. UV/Vis spectra and TEM images are used to propose a possible mechanism for the observed effects. The results presented demonstrate, for the first time, that the HIFU system can be used to synthesise size‐ and shape‐controlled metal nanoparticles.     

Cellular Uptake of Gold Nanoparticles and Their Movement in 3D Multicellular Tumor Spheroids: Effect of Molecular Weight and Grafting Density of Poly(2‐hydroxyl ethyl acrylate)

It is known that the size of gold nanoparticles (GNPs) is not the only determining factor in the uptake by cells such as cancer cells. The surface functionalization plays a crucial role, in particular the nature of the ligand as well as the molecular weight and the grafting density. Here, poly(2‐hydroxy ethyl) acrylate (pHEA) with molecular weights ranging from 10, 20 to 39 g mol^?1 via reversible addition–fragmentation chain transfer polymerization is synthesized. These polymers are used directly to coat GNPs with sizes of 20, 40, and 70 nm as the trithiocarbonate functionality can strongly bind to the gold surface. The library of nine GNP is found to be nontoxic against lung carcinoma cells A549 and has negligible albumin protein absorption as determined by quartz crystal microbalance. Laser scanning confocal microscopy and flow cytometry reveal that GNP coated with medium length pHEA displays the highest cellular uptake while the effect of the size is not statistically significant. In contrast, multicellular tumor spheroids, which is a 3D model that simulates the tissue, enable the penetration of GNP coated with the longest pHEA chain while it also appears that smaller GNPs have now a clear advantage.     

Filler network structure in graphene nanoplatelet (GNP)-filled polymethyl methacrylate (PMMA) composites: From thermorheology to electrically and thermally conductive properties

In this work, graphene nanoplatelet (GNP) filled polymethyl methacrylate (PMMA) composites were prepared using solution method via a specially designed route and relatively high thermal conductivities of the composites were achieved at a low GNP loading. The effect of GNP content on rheological behavior, thermal and electrical conductivity of the composites was intensively investigated. Thermorheological complexity was displayed at elevated GNP loading, and the rheological percolation threshold of GNP in PMMA decreased from 7.96 wt% at 220 °C to 4.02 wt% at 260 °C according to Winter-Chambon method, suggesting that GNP was more likely to form a seepage network at higher temperature. The DMTA results showed that the increase in moduli of the composites should be ascribed to the formation of the GNP-GNP network structure. The electrical conductivity of the composites underwent a sudden jump by seven orders of magnitude, which also indicated the formation of a GNP conductive pathway in the matrix with an electrical percolation threshold of 2–4 wt%. The results of transient temperature measurement were in good consistent with the thermal conductivity versus GNP loading, which was compared with various thermal conduction models with a modified Agari model presenting an acceptable evaluation of the dispersion status of GNP in the matrix. The experimental electrical and thermal conductivities as a function of GNP content could well be interpreted by the filler network structure as observed in morphological studies.