Preparation and characterization of complexes of liposomes with gold nanoparticles

Gold nanoparticles (Au NPs), which are extremely useful materials for imaging and photothermal therapy, typically require a drug delivery system to transport them to the affected tissue and into the cells. Since liposomes are approved as drug carriers, complexes of liposomes with Au NPs were considered ideal solutions to deliver Au NPs to the target site in vivo. In this study, we prepared complexes of various liposomes with Au NPs via physical absorption and characterized them. The time dependency of the surface plasmon resonance of this complex, which is a unique property of Au NPs, shows that the liposomes promote the formation of stable dispersions of Au NPs under isotonic conditions, even though intact Au NPs aggregate immediately. From a release assay of calcein from liposomes and transmission electron microscopy analysis, the Au NPs were complexed with liposomes without membrane disruption. These complexes could be formed by using cationic liposomes and polyethylene glycol-modified liposomes, as well as by using phosphatidylcholine liposomes, which are useful for drug and gene delivery. We proposed this kind of complex as a nanomedicine with diagnostic and therapeutic ability.     

Fabrication and characterization of gold/acrylic polymer nanocomposites

We report the method of incorporation of preformed gold nanoparticles (AuNPs) into the acrylic polymer (AP) matrices and optical, TEM characterization of AuNP/AP bulk and film composite. It was shown that incorporation of dodecanethiol-covered AuNP can be enhanced in the presence of SiO₂ nanoparticles, enabling at the same time a wider range of tailoring of composite properties for optical processing.     

An aptamer-based assay for thrombin via structure switch based on gold nanoparticles and magnetic nanoparticles

An aptamer-based assay for thrombin with high specificity and sensitivity was presented. In the protocol, the aptamer for thrombin was immobilized on magnetic nanoparticle, and its complementary oligonucleotide was labeled with gold nanoparticles, then the aptamer was hybridized with the complementary oligonucleotide to form the duplex structure as a probe, this probe could be used for the specific recognition for thrombin. In the presence of thrombin, the aptamer prefer to form the G-quarter structure with thrombin, resulting in the dissociation of the duplex of the probe and the release of the gold labeled oligonucleotide. Upon this, we were able to detect thrombin through the detection of the electrochemical signal of gold nanoparticles. The strategy combines with the high specificity of aptamer and the excellent characteristics of nanoparticles. This assay is simple, rapid, sensitive and highly specific, it does not require labeling of thrombin, and it could be applied to detect thrombin in complex real sample. The method shows great potential in other protein analysis and in disease diagnosis.     

Synthesis and electrochemical applications of gold nanoparticles

This review covers recent advances in synthesis and electrochemical applications of gold nanoparticles (AuNPs). Described approaches include the synthesis of AuNPs via designing and choosing new protecting ligands; and applications in electrochemistry of AuNPs including AuNPs-based bioelectrochemical sensors, such as direct electrochemistry of redox-proteins, genosensors and immunosensors, and AuNPs as enhancing platform for electrocatalysis and electrochemical sensors.     

Self-assembled gold nanoparticles on functionalized gold (111) studied by scanning tunneling microscopy

Nanogold colloidal solutions are prepared by the reduction of HAuClO4 with sodium citrate and sodium borohydride.4-Aminothiophenol (ATP) self-assembled monolayers (SAMs) are formed on gold(111) surface,on which gold nanopartides are immobilized and a sub-monolayer of the particles appears.This sub-monolayer of gold nanopartides is characterized with scanning tunneling microscopy (STM),and a dual energy barrier tunneling model is proposed to explain the imageability of the gold nanopartides by STM.This model can also be used to construct multiple energy barrier structure on solid/ liquid interface and to evaluate the electron transport ability of some organic monolayers with the aid of electrochemical method.     

各向异性金纳米粒子的制备及其在催化中的应用

尽管有关金纳米粒子催化的研究工作很多,但其中大多数都是采用传统的浸渍法将金盐负载到载体上、共沉淀或沉积-沉淀法制得负载的纳米粒子,但这些方法并未吸收最新的纳米技术。最近,金催化剂的研究者开发了在胶态悬浮液中制取金属纳米粒子,然后进行固载,从而使得单金属和双金属催化剂的催化活性和形貌控制取得较大进展。另一方面,最近十年出现了金纳米粒子合成的高级控制技术,得到了许多各向异性的金纳米粒子,且很容易制得新的形貌,可以控制纳米粒子的表面原子配位数和光学特性(可调的等离子体带),这些都与催化密切相关。这些形貌包括纳米棒、纳米星、纳米花、树枝状纳米结构或多面体纳米粒子等。除了高度关注各向异性金纳米粒子的最新开发的制备方法和性质,本综述也清楚地总结了这些纳米粒子独特的催化性能,以及通过提供更高催化性能的金催化剂、控制暴露的活性位,以及热、电和光催化的鲁棒性和可调性,从而给多相催化领域带来令人惊奇的潜在变革。     

Preparation and characterization of PE and PE-g-MAH/montmorillonite nanocomposites

Polyethylene (PE) was chemically modified with grafting maleic anhydride (MAH) monomer on its backbone at first. Then the melt-direct intercalation method was employed to prepare two kinds of nanocomposites, polyethylene (PE)/organic montmorillonite (Org-MMT) and maleic anhydride grafted polyethylene (PE-g-MAH)/Org-MMT nanocomposites. X-ray diffractometery (XRD) was used to investigate the intercalation effect and transmission electron microscopy (TEM) to observe the dispersion of Org-MMT interlayers in matrixes. The results show that an intercalated structure would be acquired on mixing the PE and Org-MMT; and an almost exfoliated system would be obtained by mixing the PE-g-MAH and Org-MMT. Moreover, further measurements via thermogravimetric (TGA) and differential scanning calorimetry (DSC) showed that both of the nanocomposites had a higher thermal decomposition temperature and a higher crystallization temperature when compared to the original matrix. At the same time, the thermal and crystal properties for the PE-g-MAH prepared in this experiment are also discussed.     

Colorimetric detection of potassium ions using aptamer-functionalized gold nanoparticles

Herein, a simple and novel colorimetric method for detection of potassium ions (K⁺) was developed. The colorimetric experiments revealed that upon the addition of K⁺, the conformation of anti-K⁺ aptamer in solution changed from random coil structure to compact rigid G-quadruplex one. This compact rigid G-quadruplex structure could not protect AuNPs against K⁺-induced aggregation, and thus the visible color change from wine-red to blue-purple could be observed by the naked eye. The linear range of the colorimetric aptasensor covered a large variation of K⁺ concentration from 5 nM to 1 μM and the detection limit of 5 nM was obtained. Moreover, this assay was able to detect K⁺ with high selectivity and had great potential applications.     

半乳糖保护的Au纳米颗粒的制备及性能研究

通过一种简易的方法,利用D-半乳糖胺和氯金酸制备出了能够用于肝癌细胞靶向识别的Au纳米颗粒探针.该纳米颗粒形貌和尺寸均一并且生物相容性良好.通过改变反应体系的pH能够对Au纳米颗粒的尺寸进行调控.此外,这种新型的纳米颗粒对RCA120还具有超高的检测灵敏度,实验结果显示其检测限度可以达到2μg·L^-1.     

Preparation and characterization of waterborne polyurethane/attapulgite nanocomposites

In this paper, waterbrone polyurethane (WPU)/attapulgite (AT) nanocomposites have been prepared by direct emulsion blending. The WPU was synthesized from poly(tetramethylene glycol), 4,4-diphenylmethane diisocyanate, dimethylol butanic acid, and neutralized by triethylamine. SEM examination of fractured surfaces showed that AT particles were irregularly dispersed in the WPU matrix. FTIR analysis suggested no major chemical structural changed in the presence of a small amount of AT. DMA results showed that the storage modulus of WPU/AT nanocomposites was increased and the glass transition temperatures of both soft and hard segments shifted to higher temperature compared to the pristine WPU. Thermal resistance of the samples measured by TGA was improved with the addition of AT. The mechanical properties of the nanocomposites, examined by tensile tests, showed higher tensile strength and elongation at break than that of the pristine WPU.     

Functionalized gold nanoparticles for sample preparation: A review

Sample preparation is a crucial step for the reliable and accurate analysis of both small molecule and biopolymers which often involves processes such as isolation, pre‐concentration, removal of interferences (purification), and pre‐processing (e.g., enzymatic digestion) of targets from a complex matrix. Gold nanoparticle (GNP)‐assisted sample preparation and pre‐concentration has been extensively applied in many analytical procedures in recent years due to the favorable and unique properties of GNPs such as size‐controlled synthesis, large surface‐to‐volume ratio, surface inertness, straightforward surface modification, easy separation requiring minimal manipulation of samples. This review article primarily focuses on applications of GNPs in sample preparation, in particular for bioaffinity capture and biocatalysis. In addition, their most common synthesis, surface modification and characterization methods are briefly summarized. Proper surface modification for GNPs designed in accordance to their target application directly influence their functionalities, e.g., extraction efficiencies, and catalytic efficiencies. Characterization of GNPs after synthesis and modification is worthwhile for monitoring and controlling the fabrication process to ensure proper quality and functionality. Parameters such as morphology, colloidal stability, and physical/chemical properties can be assessed by methods such as surface plasmon resonance, dynamic light scattering, ζ‐potential determinations, transmission electron microscopy, Taylor dispersion analysis, and resonant mass measurement, among others. The accurate determination of the surface coverage appears to be also mandatory for the quality control of functionality of the nanoparticles. Some promising applications of (functionalized) GNPs for bioanalysis and sample preparation are described herein.     

Thiolated mucoadhesive and PEGylated nonmucoadhesive organosilica nanoparticles from 3-mercaptopropyltrimethoxysilane

A novel approach has been developed to synthesize thiolated sub-100 nm organosilica nanoparticles from 3-mercaptopropyltrimethoxysilane (MPTS) through its self-condensation in dimethylsulfoxide in contact with atmospheric oxygen. The formation of MPTS nanoparticles proceeds through the condensation of methoxysilane groups and simultaneous disulfide bridging caused by partial oxidation of thiol groups. These nanoparticles showed excellent colloidal stability in dilute aqueous dispersions but underwent further self-assembly into chains and necklaces at higher concentrations. They exhibited very good ability to adhere to ocular mucosal surfaces, which can find applications in drug delivery. The thiolated nanoparticles could also be easily modified through PEGylation resulting in a loss of their mucoadhesive properties.     

Loading of gold nanoparticles inside the DPPC bilayers of liposome and their effects on membrane fluidities

Gold nanoparticles were loaded in the bilayer of dipalmitoylphosphatidylcholine (DPPC) liposomes, named as gold-loaded liposomes. Above the gel to liquid-crystalline phase transition temperature, membrane fluidities of DPPC liposomes were changed by loading the gold nanoparticles. Compared with liposomes without loading the gold nanoparticles, gold-loaded liposomes showed the lower fluorescence anisotropy values. That is, the membrane fluidities of DPPC bilayer were increased by loading the gold nanoparticles. The membrane fluidities were increased as the amount of gold nanoparticles increased. The existence of gold nanoparticles in the DPPC bilayer was observed by transmission electron microscopy. Through the energy dispersive X-ray spectrometer, the particles in DPPC bilayer were confirmed to be gold nanoparticles.     

Enantioselective open-tubular capillary electrochromatography using cyclodextrin-modified gold nanoparticles as stationary phase

Enantioselective open-tubular CEC (OTCEC) with thiolated β-CD modified gold nanoparticles (CD-GNPs) as stationary phase was developed. The enantioselective OT capillary column was fabricated by electrostatic assembly of poly(diallydimethylammonium chloride) (PDDA) followed by self-adsorption of negatively charged CD-GNPs. The enantioselective capillary column has a steady EOF mobility over a wide pH range of 3.0 to 9.2 (RSD 4.8%), and is quite stable over 240 min with very good column to column reproducibility. Efficient enantioseparation of the presented method was demonstrated by analyzing three drug enantiomers. Our results show that the column exhibits good run-to-run repeatability for enantioseparations and can maintain the enantioselectivity for more than 1 month if the column was stored in CD-GNPs solution at 4 °C.     

Physico-chemical characterization and anti-laryngeal cancer effects of the gold nanoparticles

Most recently, gold nanoparticles due to anticancer properties have been considered in medical science. So the aim of the study was green synthesis of gold nanoparticles using Ocimum basilicum extract and its anticancer activity. The prepared Au nanoparticles were characterized by advanced physicochemical techniques like Fourier Transformed Infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX), X-ray Diffraction (XRD) and UV–vis spectroscopy study. It has been established that Au nanoparticles have a spherical shape with a mean diameter from 19 to 44 nm. In the cellular and molecular part of the recent study, the treated cells with Au nanoparticles were assessed by MTT assay for 48 h about the cytotoxicity and anti-human laryngeal cancer properties on normal (HUVEC) and cancer (HEp-2, TU212, KB, UM-SCC-5, UM-SCC-11A and UM-SCC-11B) cell lines. In the antioxidant test, the IC50 of Au nanoparticles and BHT against DPPH free radicals were 228 and 208 µg/mL, respectively. The IC50 of Au nanoparticles were 174, 231, 179, 143, 230, and 216 µg/mL against HEp-2, TU212, KB, UM-SCC-5, UM-SCC-11A and UM-SCC-11B cell lines, respectively. The viability of malignant cell lines reduced dose-dependently in the presence of Au nanoparticles. It appears that the anti-cancer effect of Au nanoparticles e to their antioxidant effects.     

Preparation and characterization of polyelectrolyte-coated gold nanoparticles

Gold nanoparticles of 5 nm diameter, stabilized by 4-(dimethylamino)pyridine (DMAP), were coated with poly(sodium 4-styrene sulfonate) (PSS) via electrostatic self-assembly. The suspension stability, monitored by the gold surface plasmon band (SPB), was studied by varying the pH, the PSS chain length, and PSS concentration. Enhanced stability is obtained at pH 10 (above the pKa of DMAP) when the polymer chain length matches or exceeds the particle circumference. Solid state 13C NMR was used to determine the presence of DMAP and polymers after subsequent deposition of weak and strong polycations: poly(allylamine hydrochloride) (PAH) and poly(diallyldimethylammonium chloride) (PDADMAC). At pH 10, DMAP remains associated with the nanoparticle after the first PSS layer has been formed. When PAH or PDADMAC are subsequently added at pH 4.5, DMAP is expelled, the suspensions remain stable, and zeta potential values indicate complete charge reversal. In the case of PDADMAC, however, the first layer of PSS is not fully retained. When PDADMAC is added at pH 10, DMAP and the first PSS layer are retained but lower zeta potentials and a higher SPB shift indicate a degraded stability. For PAH addition at pH 9.5, both DMAP and PSS are expelled and the suspension becomes unstable. These differences in stability of the multilayer components and the nanoparticle suspension are rationalized in terms of chain flexibility, polymer charge density, and the ability of the polymer functional groups to directly interact with the gold surface.     

Silver nanoparticles blended PEG/PVA nanocomposites synthesis and characterization for food packaging

In this research investigation Silver nanoparticles were synthesised using rapid biological methods using leaf broth of Capparis zeylanica that provides an environmentally friendly, simple and efficient route for synthesis. Anti-microbial study was investigated against different pathogenic bacteria. Synthesized AgNPs were blended with PVA/PEG biopolymer blend and it has been confirmed by FTIR, DSC, Moisture absorption and Anti-microbial analysis that the AgNPs enhances the stability of the polymer PVA/PEG. This thin film composite shows an excellent characteristic in all aspect that able it for food packaging and bio medical applications.     

Preparation, characterization and biodegradation of biopolymer nanocomposites based on fumed silica

PLA and PCL based nanocomposites prepared by adding three different types of fumed silica were obtained by melt blending. Materials were characterized by means of Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Dynamic–Mechanical Thermal Analysis (DMTA).A good distribution of the fumed silica into both polymer matrices was observed. The highest thermo-mechanical improvements were reached by addition of the fumed silica with higher surface area. PLA and its nanocomposites were degraded in compost at 58 °C; at this temperature all samples presented a significant level of polymer degradation, but a certain protection action of silica towards PLA degradation was observed, whereas the addition of fumed silica did not show considerable influence on the degradation trend of PCL. These dissimilarities were attributed to the different degradation mechanism of the two polymers.     

Preparation and characterization of gold nanoparticles and nanowires loaded into rod-shaped silica by a one-step procedure

Rod-shaped mesoporous silica nanoparticles (RMSN) with built-in gold nanoparticles or thin gold nanowires in the pore channels were in situ synthesized via a one-step procedure. The insertion of a hydrophobic gold precursor into the mesopores of RMSN was reached through a micellar solubilization mechanism and gold nanoparticles were achieved through a thermal reduction. The resulting RMSN and Au-RMSN samples were characterized by using X-ray diffraction, transmission and scanning microscopies (TEM and SEM), X-ray photoelectron spectroscopy (XPS), nitrogen physisorption and solid-state Nuclear Magnetic Resonance (NMR). The interaction of Au precursor (a carbene complex) with the thiol group at the silica surface was identified and found to play a crucial role in the dispersion of the uniform metal nanoparticles at the internal surface of RMSN. Moreover, TEM micrographs revealed the absence of large gold particles outside the mesopore network. The shape of Au nanoparticles and their loading amount in the mesoporous silica could be easily tuned by altering the concentration of gold precursor.     

Characterization and biocompatibility of chitosan nanocomposites

Chitosan nanocomposites were prepared from chitosan and gold nanoparticles (AuNPs) or silver nanoparticles (AgNPs) of ～5 nm size. Transmission electron microscopy (TEM) showed the NPs in chitosan did not aggregate until higher concentrations (120-240 ppm). Atomic force microscopy (AFM) demonstrated that the nanocrystalline domains on chitosan surface were more evident upon addition of AuNPs (60 ppm) or AgNPs (120 ppm). Both nanocomposites showed greater elastic modulus, higher glass transition temperature (T(g)) and better cell proliferation than the pristine chitosan. Additionally, chitosan-Ag nanocomposites had antibacterial ability against Staphylococcus aureus. The potential of chitosan-Au nanocomposites as hemostatic wound dressings was evaluated in animal (rat) studies. Chitosan-Au was found to promote the repair of skin wound and hemostasis of severed hepatic portal vein. This study indicated that a small amount of NPs could induce significant changes in the physicochemical properties of chitosan, which may increase its biocompatibility and potential in wound management.