•A pH-responsive dendrimer C18N5 was developed for the separation of nanoparticles.•Gold nanoplates with purity of 97% were achieved by using the dendrimer C18N5.•The mechanism for shape-selective separation of gold nanoplates was discussed.We present a novel method for shape-selective separation of nanoparticles in aqueous media utilizing an amphiphilic cationic dendrimer (C18N5) through regulation of the pH of the dispersion medium. This amphiphilic dendrimer (C18N5) bears a poly(amidoamine) dendron with four terminal amine groups and one hydrophobic long alkyl chain, and it can strongly adsorb to the surface of gold nanoparticles at low pH and promote their aggregation at high pH. During aggregation, isotropic NPs with smaller inter-particle contact area have much better solution stability than anisotropic NPs. Therefore, isotropic NPs remain stable in the supernatant, while anisotropic NPs are subject to aggregation and subsequent precipitation. As a result of this simple separation strategy, gold nanoplates with a purity level of 97% (in number density) can be rapidly and conveniently achieved.

Recently gold nanomaterials have been widely applied in the biomedical field, but their biosafety is still controversial. We immobilized small gold nanoparticles (AuNPs) on a large silica substrate to form silica–gold core–shell materials (SiO2@AuNPs) via classical seed-mediated growth. In vitro, 500 nm-SiO2@AuNPs could promote the proliferation of mouse embryonic fibroblast cells (NIH/3T3). The results of transmission electron microscope (TEM) showed that the vast majority of particles did not enter cells and that the morphology of microtubules experienced no change as observed in the confocal microscope images. The mechanism may be that the large silica substrate kept AuNPs outside the cells and the nano-size concavo-convex gold shell facilitated to cell adhesion, resulting in the proliferation. In vivo, a cutaneous full-thickness excisional wound rat model was applied to assess the healing efficiency of 500 nm-SiO2@AuNPs. The results indicated that SiO2@AuNPs could promote wound healing, which was potentially related to the anti-inflammatory and antioxidation of AuNPs. The pathological finding showed that the healing levels of SiO2@AuNPs were significantly better than those of the control groups. Our study may provide insight into the application of silica–gold core–shell materials in the treatment of cutaneous wounds.

We report a sensitive, selective and low-cost method for the naked-eye detection of Hg2+. The principle is based on rapid interaction between functionalized PDA vesicles and Hg2+, which leads to obvious aggregation of vesicles. Furthermore, using only a simple filtration process, without using any other color indicator or specialized equipment, a higher detection sensitivity for Hg2+ (0.1 μM) than chromophoric colorimetric sensors (approximately 1–100 μM) was obtained.

•We prepare SiO2@AuNPs core-shell materials by seed-mediated method.•SiO2@AuNPs can promote the growth of HeLa cells, while 4 nm AuNPs lead to cell death.•The silica substrates hold their attached AuNPs outside the cells.•The concavo-convex surface of SiO2@AuNPs is facilitated to cell adhesion, probably resulting in the proliferation of HeLa cells.Recently, the biosafety of gold nanomaterials has attracted more attention. Some consider them as an adverse factor for cell growth, whereas others regard them as biocompatible. In this work, we reported a type of silica-gold core-shell structure (SiO2@AuNPs) with the diameter more than 70 nm that could promote cell growth. The synthesis of SiO2@AuNPs adopted a step-by-step protocol involving the fabrication of silica substrate followed by their amination, the attachment of fine (about 4 nm) gold seeds, and the formation of a gold shell by reducing HAuCl4 on seeds. The cell viability experiment indicated that AuNPs attached to silica substrate could promote the growth of HeLa cell. With increasing concentration of SiO2@AuNPs or the content of gold shell, the viability of co-cultured HeLa cells also increased; on the contrary, acute cytotoxicity was observed when pure 4 nm AuNPs were added. Moreover, we found that the proliferative effect could be enhanced by enlarging the size of silica substrate. Due to large SiO2@AuNPs not entering the cell, their nano-size concavo-convex surface was facilitated to cell adhesion, probably leading to the proliferation of HeLa cells. However, detailed mechanism responsible for cell growth is still unclear and it requires more studies. Although the mechanism remains enigmatic, the findings may have practical significance for cell proliferation, which is in great demand in numerous fields such as tissue engineering. In addition, the core-shell materials were characterized by scanning electron microscope (SEM) and energy-dispersive X-ray spectrum (EDX), and the cell viability was measured by Cell Counting Kit-8 (CCK-8).

Gold nanodendrites with a long and densely branched morphology were fabricated by a seed-mediated method in a solution containing gold nanoparticles (AuNPs), bis(amidoethyl-carbamoylethyl)octadecylamine (C18N3), HAuCl4, and the reducing agent ascorbic acid (AA). The length and density of the branches could be mediated by changing the AuNP seed and AA concentrations. The amphiphilic C18N3 molecules function as a template and induce the unique morphology of the AuNPs/C18N3 structures. The localized surface plasmon resonance (LSPR) peaks of the gold nanodendrites can be modulated from the visible (∼530 nm) to the near-infrared region (∼1100 nm) of the electromagnetic spectrum. Surface-enhanced Raman scattering (SERS) signals using rhodamine can also be mediated by changing the seed and AA concentrations. These unique highly branched gold nanodendrites with a narrow size distribution and tunable NIR and SERS spectra should have great potential in sensing applications.Keywords: gold nanodendrites; multiamine surfactant; NIR; SERS;

A relatively new and efficient method is reported here for the purification and arrangement of high-aspect-ratio gold nanorods (AuNRs) using a multiamine surfactant, bis[[(amidoethyl)carbamoyl]ethyl]octadecylamine (C18N3), which strongly adsorbs to the surface of AuNRs. The adsorbed layers of the multiamine surfactant on AuNRs exhibit the ability to deaggregate gold nanoparticles at low pH in an aqueous medium and to promote their aggregation at high pH. Through regulation of the pH of the dispersion medium, a well-ordered arrangement of 99% monodisperse AuNRs was obtained, having dimensions of approximately 18 nm diameter and 353 nm length and an area of several dozens of square micrometers, which is much larger than what has been reported in the literature. A very strong optical absorption in the near-infrared region of as-prepared AuNRs was shown. This strategy of using pH-responsive multiamine surfactant to mediate both the homogenization in shape and the arrangement of nanoparticles provides a new methodology for the formation of nanoparticle assemblies.Keywords: arrangement; homogenization; multiamine surfactant; nanorod; purifying;

The effect of gold nanoparticles (Au NPs) on cells remains open for investigation. Here we show that small Au NPs can be endocytosed by cells and form aggregates inside the cell, resulting in cytotoxicity. When the aggregates become too large to enter the cell and instead adhere onto the cell surface, however, the growth rate of HeLa cells increases. Printed patterns of Au NPs fabricated through inkjet printing technology were used to study the effects of Au NP aggregation on human cervical carcinoma (HeLa) cell activity. The growth of the HeLa cells was inhibited on the polymer-coated Au NPs but increased on the silicon substrate. On the uncoated Au NP surface, however, the HeLa cell growth rate was higher than that on the silicon substrate. Experiments with Escherichia coli cells showed a similar effect of the Au NPs. This phenomenon provides a new perspective for research on toxicity in nanoparticle biology.From the Clinical EditorPrinted patterns of Au NPs fabricated through inkjet printing technology were used to study the effects of Au NP aggregation on human cervical carcinoma (HeLa) cell activity. Small Au NPs can be endocytosed by cells resulting in cytotoxicity; in contrast, large aggregates adhere onto the cell surface and increase the growth rate of HeLa cells.When co-culturing with cells, the aggregates or large size of gold nanoparticles remained outside the cells, and contrary to expectations, the growth rate of the cells increased. In contrast, smaller particles appeared to be toxic due to their ability to enter the cell.

A novel kind of rattle-type magnetic mesoporous sphere with a hollow magnetite core and perpendicularly aligned mesoporous carbon shell (RTMMCS) has been successfully fabricated. In addition, the RTMMCS demonstrates strong surface affinity toward contaminants, which contributes to the convenient, efficient, and fast removal of microcystins in water.

Unique, narrow polydispersity, hierarchical gold nanoflowers were synthesized by a two-step method using a tree-type multi-amine surfactant (C18N3) as the template and ascorbic acid (AA) as the reductant. Upon the addition of a stronger reductant AA, the C18N3–HAuCl4 composite changed to a black color, due to the gold nanoflower formation. Under a specific concentration ratio of C18N3, HAuCl4, and AA, narrow polydispersity flower-like gold structures were obtained. These nanoflowers were stable as an aqueous solution for months, with no deformation to particle size and no obvious change in the surface morphology. The experimental results demonstrated that the complexation between C18N3 and HAuCl4 is essential for the formation of gold nanoflowers with a narrow size distribution. The morphology and size of the composites can be easily adjusted by changing the concentration of C18N3, HAuCl4, and AA. The growth of nanoflowers is discussed in terms of two steps: the formation of complexes between C18N3 and HAuCl4, which determines the core size of the nanoflowers, and the surface nanocrystal growth, due to the reduction of HAuCl4 by AA, which determines the thickness and morphology of nanoflower surface layers. In the measurement of surface-enhanced Raman scattering (SERS) using rhodamine 6G, the gold nanoflowers exhibited a significant enhancement factor, indicating their potential in biosensing and nanodevice applications.

In this paper, the morphology of copper hydroxide nano/microcrystals is finely controlled by adjusting the concentration of surfactant and NH4Cl as well as the reaction temperature, to provide plates, belts, wires, rods and urchin-like spheres, among others. A tree-type multiple head surfactant, bis (amidoethyl-carbamoylethyl) octadecylamine (C18N3), was used to prepare the copper hydroxide nano/microcrystals and it acted as a face-selective additive in the reaction system. The morphology of the Cu(OH)2 microcrystals could be transformed from elliptical plates into truncated square plates as the NH4Cl concentration was increased. The results showed that the Cu(OH)2 crystals were better than the amorphous type of Cu(OH)2 in catalyzing the oxidation of resorcinol with H2O2. Additionally, an investigation of the formation process of the nano/microcrystals was performed, which we believe is valuable for a precise understanding of the formation and fabrication of other metal hydroxides and metal oxides.Graphical abstractSchematic illustration of the overall formation and shape evolution of Cu(OH)2 nano/microcrystals.Research highlights► In this manuscript a simple and useful method had been introduced to fabricate various copper hydroxide nano/microcrystals by just adjusting the concentration of surfactant and NH4Cl as well as reaction temperature, to provide plates, belts, wires, rods and urchin-like spheres among others. ► An application was developed to test the catalysis characteristics of the Cu(OH)2 crystals. Our results showed that the obtained Cu(OH)2 crystals were better than the amorphous type of Cu(OH)2 for catalyzing the oxidation of resorcinol with H2O2, which means that our products may contribute to eliminating pollution caused by phenolic compounds. ► Additionally, an investigation of the formation process of the Cu(OH)2 nano/microcrystals was performed, which we believe is valuable for a precise understanding of the formation and fabrication of other metal hydroxides and metal oxides.

An immunoassay based on the enrichment of antibodies by magnetic beads (MB) and their subsequent detection of antigens in a microfluidic chip (MFC)–quartz crystal microbalance (QCM) was developed and investigated. The MB conjugated to goat anti-human-immunoglobulin G (MB-anti-h-IgG) were concentrated within microchannels by the application of a magnetic field, which also functioned as a separation switch outside the MFC. The conjugation of the MB and the anti-h-IgG antibody in the MFC was completed in 1 min. Removal of the magnetic field allowed the resulting tributary buffer solution to flush the MB-anti-h-IgG out of the MFC and onto a QCM chip. The combination of the MB-anti-h-IgG and the QCM chip amplified the detection sensitivity of antigen(s) to 10−1 ng/ml. By controlling the enrichment velocity and sample injection mode in the MFC, a linear response ranging from 10−1 to 103 ng/ml was obtained. This technique establishes a simple, rapid MFC method for the amplification of a QCM-based immunoassay.

A highly sensitive, portable method of detecting the hepatotoxin microcystin-LR (MC-LR) has been developed by a surface modification and gold nanoparticle (AuNP) technology. By using this technology a detection sensitivity of 0.1 pg μL−1 MC-LR can be reached which meets the standard of World Health Organization (WHO) requirements for the drinking water (1 μg μL−1 MC-LR) and compatible with those of conventional techniques, such as high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA). Our method includes an inexpensive sensor, composed of a quartz crystal microbalance (QCM) along with gold nanoparticles (AuNPs), and a sandwiched immunoassay for rapid and in situ detection of MC-LR. The volume of analyte for once detection was generally less than 50 μL. The method specifically involves self-assembled monolayer formation on the QCM gold electrodes, immobilisation of MC-LR antibodies and AuNP signal amplification. It has been found that 30 nm is the optimal size for AuNPs which could effectively amplify the signals of MC. All the process was easily and promptly operated. Thus, a fast and convenient sandwiched immunoassay sensor has been established.Schematic diagram of the step-by-step fabrication of the QCM immunosensor chip. MPA at 2% was first absorbed on the QCM via a specific thiol–gold interaction, followed by mAb (10 μL of 150 pg μL−1) immobilisation by replacing the NHS ester of a chemically modified gold electrode of the QCM. The unreacted NHS esters were then blocked using 10 μL of a 3% BSA solution. Next, 10 μL of a MC-LR solution was applied to the gold electrode. Finally, an amplifying AuNP–mAb solution was applied to the QCM to augment the immunoassay response.

Enhanced sensitivity for the hepatotoxin microcystin-LR (MC-LR) was achieved in a quartz crystal microbalance (QCM) system via double amplification. For primary amplification, an innovative interface on the QCM was obtained as a matrix by the vesicle layer formed by our synthetic dendritic surfactant, bis (amidoethyl-carbamoylethyl) octadecylamine (C18N3). The vesicle matrix was then functionalised by an optimised concentration of monoclonal antibodies against MC-LR (anti-MC-LR) to detect the analyte. The results showed that a detection limit of 100 ng/mL was achieved by primary amplification. To achieve higher sensitivity, secondary amplification was implemented with anti-MC-LR gold nanoparticle (AuNPs) conjugates as probes, which lowered the detection limit for MC-LR to 1 ng/mL (the maximum concentration recommended by the World Health Organization [WHO] in drinking water for humans). The QCM immunosensor reported here has advantages such as high sensitivity, portability, simplicity, and cost-effectiveness for MC-LR detection. It would be uniquely superior compared with current MC-LR detection techniques for on-the-spot water detection. Furthermore, the methodology described here is also potentially significant in many fields for the routine monitoring of environmental and food safety.Graphical abstractHighlights► We fabricated a QCM immunosensor for microcystin-LR harmful to the health of humans. ► It combines the good simplicity, portability and sensitivity. ► Comparatively, an enhanced sensitivity was successfully achieved by doubly amplification dependent on new dendritic surfactant and gold nanoparticles.

A simple and sensitive method was developed for the detection of mercury ions with quartz crystal microbalance (QCM), based on the specific thymine–Hg2+–thymine (T–Hg2+–T) interaction and gold nanoparticle-mediated signal amplification. To enhance the sensitivity of detection a sandwich hybridization approach was adopted in this work. The QCM gold surface was modified with the probe SH-oligonucleotides (Oligo-1) and 6-Mercapto-1-hexanol to form an active surface for the hybridization of a longer ss-DNA (Oligo-2), and then Oligo-3 hybridazated with an excess and matching part of Oligo-2. In all oligonucleotides, there existed T bases. In the presence of Hg2+ ions, special T–Hg2+–T reaction greatly enhanced the hybridization of oligonucleotides and detection sensitivity. The gold nanoparticle (Au NPs) amplifier method further increased the sensitivity of detection. A detection sensitivity of 5 nM Hg2+ was obtained in the QCM system, whereas other coexisting metal ions (such as Ni2+, Mg2+, Co2+, Cr3+, Pb2+, Cd2+, Mn2+, Ba2+) had no significant interference. This method reveals a new approach for the manufacture of a kind of simple and low cost sensors for the Hg2+ detection.Graphical abstractA high sensitive and selective method for detection of Hg2+ based on the specific thymine–Hg2+–thymine interaction in the DNA hybridization on the surface of quartz crystal microbalance.Highlights► A quartz crystal microbalance (QCM) sensor is designed to detect Hg2+. ► Thymine rich oligonucleotide probes were used to capture Hg2+ and oligonulcleotide modified gold nanoparticles (Au NPs) was used as a weight amplifier. ► The detection limit is 5 nM and coexisting metal ions (such as Ni2+, Mg2+, Co2+, Cr3+, Pb2+, Cd2+, Mn2+, Ba2+) have no significant interference.

In this paper, a single tree-type multiple-head surfactant, bis (amidoethyl-carbamoylethyl) octadecylamine (C18N3), which functions as both the reducing and capping agent in the reaction system, has been used to fabricate gold nano- and microplates. The triangle and hexagonal plate, polyhedron, and sphere morphology of the gold nanoparticles could be easily controlled simply by changing the molar ratio of C18N3/HAuCl4. Other influences on the morphology of the gold particles, such as Cl− concentration, temperature and time, were also studied. At standard conditions, 80 °C, and a molar ratio C18N3/HAuCl4 of 6.9 in a 0.5 M KCl aqueous solution, the size of the plates could be manipulated from several tens of nanometers to several micrometers just by changing the C18N3 concentration. A crystalline growth process for the nanoplate formation has been observed in this system. At the initiation of the crystalline formation, the predominant morphology was triangular, followed by a mixture of triangular, hexagonal, and truncated triangular structures as the particle grew larger. Ultimately, the structures became primarily hexagonal. As-prepared gold nano- and microplates greatly enhanced the surface enhanced Raman scattering (SERS) of ascorbic acid molecules compared to that of other gold nanoparticle morphologies.

In this paper we presented a novel water-based nanoparticle printing ink which can easily be used in producing electric-conductive patterns for the microfabrication and microelectronic devices by commercial printers. The well-dispersed nanoparticle ink was composed of metallic colloids which had a gold core less than 5 nm in diameter and were protected by two overlapped layers of polymers, poly(N-vinylpyrrolidone) (PVP) and acrylic resin (AR). The double layer protected gold nanoparticle (AuNP) ink was stable against aggregation for more than 1 year even at gold concentration higher than 20%. Viscosity of as-prepared ink was similar to the commercial inks which could be used in producing continuous and smooth lines 10 μm in width and could be printed on various substrates. It has been found that the obtained gold patterns after sintered at 500 °C for 3 h would convert to electrical conductive ones. The density of metallic particles as well as the conductivity of patterns can be controlled by mediating the number of printing layers and the conditions of sintering process. A 50-layer printed line obtained in our experiment showed apparent conductivity of 8.0 × 104 S cm−1 which was near to the conductivity value of the bulk gold metal.

This paper describes a quantitative investigation of the influence of gold nanoparticles (AuNPs) on DNA hybridization using a programmed multi-channel quartz crystal microbalance (QCM) device. This system has the benefit of continuous deposition, adsorption, washing, and drying of samples automatically, which saves time and enhances the accuracy of QCM measurements. A demonstration of the hybridization study has been carried out using a DNA fragment of the P53 gene near codon 248. The results demonstrated that the reliability and hybridization sensitivity of the QCM could be significantly improved by introducing AuNPs. The study revealed a significant increase in the apparent hybridization constant (KD−1 of 5.29 × 1010 M−1) with the addition of AuNPs, compared to those obtained without addition of AuNPs (about 107 M−1); this effect has not been reported before. The results of the experiment indicate the advantage of the multi-channel QCM chip in studying complicated DNA fixation and hybridization, the conjugating interaction between biomolecules and nanoparticles, and the hybridization dynamics.

A highly sensitive and simple approach for detecting hepatotoxin microcystin-LR (MC-LR) was developed based on color-changeable polydiacetylene (PDA) vesicles. By an EDC/NHS reaction, we successfully embedded a monoclonal antibody (mAb) of MC-LR (anti-MC-LR) onto the PDA vesicle surfaces, and a MC-LR recognition vesicle (PDA-anti-MC-LR) was formed. The optimal concentration for anti-MC-LR was determined that would guarantee the PDA immunosensor to exert its highest recognition effect. Upon application of MC-LR, a specific immunoreaction took place, which altered the PDA conformation and led to a color change. The lowest detection limit could be 1 ng/mL—the maximum concentration recommended by WHO in drinking water for humans. Although immunoassays have found applications in medical diagnostics and therapy, the procedures commonly used nowadays are too complicated. This chromatic immunosensor based on PDA reported in this paper has the advantage of high sensitivity, rapidity, cost-effectiveness, and convenience for MC-LR detection. Not only it is more adaptable for on-the-spot water detection, compared with current MC-LR detecting techniques, but the methodology here ensured optimal embedding of antibody to the PDA vesicles of great significance for fabrication of other nanosensors. This technology, based on antibody–antigen interaction, and its broadened use in PDA biosensors, has potential application in many fields.

Fast and sensitive detection of epidemic virus is of the utmost importance for human being in nowadays. Various biosensors have been designed for this goal based on conjugation event between host cell glycolipids and invading virus. However, multihead glycolipids analogous to native receptors on cell surface are known to be very difficult to mimic because of the complexity of chemical synthesis. Here, we developed a new approach where two types of monohead glycolipids, active sialic acid-β-glucoside (G1) and inactive lactose- β-glucoside (G2), are embedded onto the surface of a polydiacetylene (PDA) vesicle to mimic native glycolipids on the cell surface. Vesicles prepared in this manner show good selectivity with a 10 ng/mL detection limit and 5 min response time to Hemagglutinin (HA1), which is more sensitive than any HA1 biosensors ever known. Moreover, in the formation of color-changeable vesicles, a very strong synergistic effect between G1 and G2 has been found, offering a novel strategy to construct effective biosensor receptors, as well as a new way to study the surface combination effect that is potentially important to the immunology study of epidemic disease.

A chitosan-based electrode filled with silver nanoparticles (AgNPs) and glucose oxidase (GOD) was used as an enzyme electrode to investigate the effect of aging process of AgNPs on the GOD activity. Freshly prepared AgNPs inhibit the GOD activity, however, the inhibitory effect decreased with the increase of aging time. After aged for a period of time, AgNPs showed enhancement effect on the GOD activity. The effect of aging was studied by the measurements of Ag+ ions concentration, zeta (ζ) potential and X-ray photoelectron spectroscopy (XPS). And the results indicated that the concentration of Ag+ ions in the silver sol decreased during the aging period (i.e. Ag+ ions converted to more inert silver metal Ag0). The effect of AgNPs on the GOD activity can be changed by controlling the aging time of AgNPs. This research provides a new and simple approach to mediate AgNPs property, which is of great value in potential application of AgNPs in biosensors and nanoscale devices.

A simple “chimney” method was used to eliminate the voids in an arrangement of quantum dots sized 2 nm on a solid substrate, which resulted in a large well ordered superlattice of area in the order more than 1 μm2. Based on the principle of speeding up the interparticle interaction of nanoparticles to overcome the particle–substrate one, a lateral centripetal force originated from a glass tube acting as a chimney in a simple evaporation device is imposed. This method allows the packing process to be controlled in a mechanical force field, that is, with the same nanogold dispersion different patterns on a substrate—from separate dots to an ordered compact monolayer or even a multilayer structure—could be easily obtained.

A supramolecular assembly of phospholipid-polymerized diacetylene vesicles functionalized with glycolipid can provide a molecular recognition function. The Escherichia coli–glycolipid binding event leads to a visible color change from blue to red, readily seen with the naked eye and quantified by absorption spectroscopy. The biosensor signal is amplified through a suitable increase of phospholipid content in the mixed lipid vesicles and pH of aqueous solutions.

A novel kind of rattle-type magnetic mesoporous sphere with a hollow magnetite core and perpendicularly aligned mesoporous carbon shell (RTMMCS) has been successfully fabricated. In addition, the RTMMCS demonstrates strong surface affinity toward contaminants, which contributes to the convenient, efficient, and fast removal of microcystins in water.