Superparamagnetic sub-5 nm Fe@C nanoparticles: isolation, structure, magnetic properties, and directed assembly

A method for isolating single crystalline sub-5 nm carbon coated iron nanoparticles (Fe@C NPs) from a carbon nanotube matrix has been developed. The isolation of such particles allows for their characterization by high resolution electron microscopy methods and SQUID magnetometry. While the NPs are superparamagnetic at room temperature, at 10 K they exhibit a coercivity nearly 30 times greater than that of commercial Fe3O4 NPs of comparable size. A novel nanotemplate directed assembly method for manipulating the particles at the individual particle level is also reported.     

Amorphous Silica Nanoparticles Promote Monocyte Adhesion to Human Endothelial Cells: Size‐Dependent Effect

There is evidence that nanoparticles can induce endothelial dysfunction. Here, the effect of monodisperse amorphous silica nanoparticles (SiO₂‐NPs) of different diameters on endothelial cells function is examined. Human endothelial cell line (EA.hy926) or primary human pulmonary artery endothelial cells (hPAEC) are seeded in inserts introduced or not above triple cell co‐cultures (pneumocytes, macrophages, and mast cells). Endothelial cells are incubated with SiO₂‐NPs at non‐cytotoxic concentrations for 12 h. A significant increase (up to 2‐fold) in human monocytes adhesion to endothelial cells is observed for 18 and 54 nm particles. Exposure to SiO₂‐NPs induces protein expression of adhesion molecules (ICAM‐1 and VCAM‐1) as well as significant up‐regulation in mRNA expression of ICAM‐1 in both endothelial cell types. Experiments performed with fluorescent‐labelled monodisperse amorphous SiO₂‐NPs of similar size evidence nanoparticle uptake into the cytoplasm of endothelial cells. It is concluded that exposure of human endothelial cells to amorphous silica nanoparticles enhances their adhesive properties. This process is modified by the size of the nanoparticle and the presence of other co‐cultured cells.     

Quantitative Evaluation of Cellular Uptake and Trafficking of Plain and Polyethylene Glycol‐Coated Gold Nanoparticles

This study addresses the cellular uptake and intracellular trafficking of 15‐nm gold nanoparticles (NPs), either plain (i.e., stabilized with citrate) or coated with polyethylene glycol (PEG), exposed to human alveolar epithelial cells (A549) at the air–liquid interface for 1, 4, and 24 h. Quantitative analysis by stereology on transmission electron microscopy images reveals a significant, nonrandom intracellular distribution for both NP types. No particles are observed in the nucleus, mitochondria, endoplasmic reticulum, or golgi. The cytosol is not a preferred cellular compartment for both NP types, although significantly more PEG‐coated than citrate‐stabilized NPs are present there. The preferred particle localizations are vesicles of different sizes (<150, 150–1000, >1000 nm). This is observed for both NP types and indicates a predominant uptake by endocytosis. Subsequent inhibition of caveolin‐ and clathrin‐mediated endocytosis by methyl‐β‐cyclodextrin (MβCD) results in a significant reduction of intracellular NPs. The inhibition, however, is more pronounced for PEG‐coated than citrate‐stabilized NPs. The latter are mostly found in larger vesicles; therefore, they are potentially taken up by macropinocytosis, which is not inhibited by MβCD. With prolonged exposure times, both NPs are preferentially localized in larger‐sized intracellular vesicles such as lysosomes, thus indicating intracellular particle trafficking. This quantitative evaluation reveals that NP surface coatings modulate endocytotic uptake pathways and cellular NP trafficking. Other nonendocytotic entry mechanisms are found to be involved as well, as indicated by localization of a minority of PEG‐coated NPs in the cytosol.     

Mammalian Cells Exhibit a Range of Sensitivities to Silver Nanoparticles that are Partially Explicable by Variations in Antioxidant Defense and Metallothionein Expression

While it is well known that there are interspecies differences in Ag sensitivity, differences in the cytotoxic responses of mammalian cells to silver nanoparticles (Ag NPs) are also observed. In order to explore these response outcomes, six cell lines, including epithelial cells (Caco‐2, NHBE, RLE‐6TN, and BEAS‐2B) and macrophages (RAW 264.7 and THP‐1) of human and rodent origin, are exposed to 20 nm citrate‐ and PVP‐coated Ag NPs with Au cores, as well as 20 nm citrate‐coated particles without cores. An MTS assay shows that while Caco‐2 and NHBE cells are resistant to particles over a 0.1–50 μg mL^?1 dose range, RAW 264.7, THP‐1, RLE‐6TN, and BEAS‐2B cells are more susceptible. While there are small differences in dissolution rates, there are no major differences in the cytotoxic potential of the different particles. However, differences in anti‐oxidant defense and metallothionein expression among different cell types are observed, which can partially explain differential Ag NP sensitivity. So, it is important to consider these differences in understanding the potential heterogeneous effects of nano Ag on mammalian biological systems.     

Silver Nanoparticles with Controlled Dispersity and Their Assembly into Superstructures

In this paper we report on the influence of particle size distribution, particle substrate interaction, and drying behavior on the self‐assembly process using ligand stabilized silver particles. Two‐dimensional particle arrays were characterized using transmission electron microscopy and extensive image analysis. The formation of such structures was observed in situ using an environmental scanning electron microscope in WET‐STEM mode. The results confirm that a small particle size distribution is crucial for the formation of regular particle patterns with long range order, but also the particle substrate interaction and the particle density have an influence on the degree of ordering. Additionally, we find that separated binary particle assemblies keep the orientation of their two‐dimensional hexagonal lattices over alternating domains of small and big particles. This is probably enabled due to the formation of dislocations and a small change of the course of the lattice lines within the respective boundary.     

Influence of Silicification on the Structural and Biological Properties of Buffer‐Mediated Collagen Hydrogels

A buffer‐mediated gelation route for collagen hydrogels that allows the formation of homogeneous composite and hybrid materials with various silica sources (i.e., colloidal silica and soluble silicates) at high concentration (up to 25 × 10^?3 M ) is described. Most significant improvement in rheological properties and proliferation of primary adult human dermal fibroblasts was obtained for the silicate‐based hybrid materials. A similar trend was observed in composite materials incorporating 14 nm SiO₂ nanoparticles, although to a much lesser extent, whereas larger colloids (80 and 390 nm) did not significantly impact mechanical stability and cell behavior. Modification of 80 nm particles surface with amine groups weakens the collagen‐mineral interface, resulting in the decrease of material stability and leading to particle aggregation during the course of cell proliferation experiments.     

Modeling the optical properties of mineral particles suspended in seawater and their influence on ocean reflectance and chlorophyll estimation from remote sensing algorithms

The optical properties of mineral particles suspended in seawater were calculated from the Mie scattering theory for different size distributions and complex refractive indices of the particles. The ratio of the spectral backscattering coefficient to the sum of the spectral absorption and backscattering coefficients of seawater, b(b)(lambda)/[a(lambda) + b(b)(lambda)], was analyzed as a proxy for ocean reflectance for varying properties and concentrations of mineral particles. Given the plausible range of variability in the particle size distribution and the refractive index, the general parameterizations of the absorption and scattering properties of mineral particles and their effects on ocean reflectance in terms of particle mass concentration alone are inadequate. The variations in the particle size distribution and the refractive index must be taken into account. The errors in chlorophyll estimation obtained from the remote sensing algorithms that are due to the presence of mineral particles can be very large. For example, when the mineral concentration is 1 g m(-3) and the chlorophyll a concentration is low (0.05 mg m(-3)), current global algorithms based on a blue-to-green reflectance ratio can produce a chlorophyll overestimation ranging from approximately 50% to as much as 20-fold.     

Biohybrid Nanoparticles to Negotiate with Biological Barriers

Incapability of effective cross‐talk with biological environments has partly impaired the in vivo functionality of nanoparticles (NPs). Homing, biodistribution, and function of NPs could be engineered through regulating their interactions with in vivo niches. Inspired by communications in biological systems, endowing a “biological identity” to synthetic NPs is one approach to control their biodistribution, and immunonegotiation profiles. This synthetic‐biological combination is referred to as biohybrid NPs, which comprise both i) engineerable, readily producible, and trackable synthetic NPs as well as ii) biological moieties with the capability to cross‐talk with immunological barriers. Here, the latest understanding on the in vivo interactions of NPs, biological barriers they face, and emerging methods for quantitative measurements of NPs' biodistribution are reviewed. Some key biomolecules that have emerged as negotiators with the immune system in the context of cancer and autoimmunity, and their inspirations on biohybrid NPs are introduced. Critical design considerations for efficient cross‐talk between NPs and innate and adaptive immunity followed by hybridization methods are also discussed. Finally, clinical translation challenges and future perspectives regarding biohybrid NPs are discussed.     

All Roads Lead to the Liver: Metal Nanoparticles and Their Implications for Liver Health

Metal nanoparticles (NPs) are frequently encountered in daily life, and concerns have been raised about their toxicity and safety. Among which, they naturally accumulate in the liver after introduction into the body, independent of the route of administration. Some NPs exhibit intrinsic pharmaceutical effects that are related to their physical parameters, and their inadvertent accumulation in the liver can exert strong effects on liver function and structure. Even as such physiological consequences are often categorically dismissed as toxic and deleterious, there are cell type‐specific and NP‐specific biological responses that elicit distinctive pharmacological consequences that can be harnessed for good. By limiting the scope of discussion to metallic NPs, this work attempts to provide a balanced perspective on their safety in the liver, and discusses both possible therapeutic benefits and potential accidental liver damage arising from their interaction with specific parenchymal and nonparenchymal cell types in the liver.     

Surfactants-aided syntheses of different sizes and triangular shape of gold nanoparticles using trisodium citrate in environmentally friendly and photoinduced methods

We prepared gold nanoparticles (Au NPs) by only using trisodium citrate as the stabilizer. The detailed reaction mechanisms of S(N)1 and E1 reactions are examined and evidenced in this study by FTIR data. Citric acid is a kind of tertiary substrate. In aqueous solution, the substitution nucleophile path 1 (S(N)1) reaction and Elimination path 1 (E1) reaction usually occur simultaneously. Chloride ions, the substitution nucleophile, play a very important role to launch the mechanisms of S(N)1 and E1 reactions. Controlling the concentration of the chloride ions with the addition of HCl(aq) according to Le Chatelier theory, the average particle size of Au NPs (5.5 nm) was achieved to overcome the minimum limited size (approximately 10 nm). Two stages of the photoinduced method, aggregation into triangular conglomerates and growth into triangular particles, were determined form TEM observations. This preparation of Au NPs has potential in tuning the size, shape, and mechanism of Au NP formation by using only environmentally friendly trisodium citrate and the photoinduced method.     

Nanoparticles: biosynthesis,translocation and role in plant metabolism

Nanotechnology is an emerging field of science that applies particles between 1 and 100 nm in size for a range of practical uses. Nano‐technological discoveries have opened novel applications in biotechnology and agriculture. Many reactions involving nanoparticles (NPs) are more efficient compared to those of their respective bulk materials. NPs obtained from plant material, denoted as biogenic or phytosynthesised NPs, are preferred over chemically synthesised NPs due to their low toxicity, rapid reactions and cost‐effective production. NPs impart both positive and negative impacts on plant growth and development. NPs exhibit their unique actions as a function of their size, reactivity, surface area and concentration. An insight into NP biosynthesis and translocation within the plant system will shed some light on the roles and mechanisms of NP‐mediated regulation of plant metabolism. This review is a step towards that goal.Inspec keywords: nanofabrication, nanoparticles, nanobiotechnology, particle size, reviews, botany, biochemistryOther keywords: chemically synthesised NPs, low toxicity, rapid reactions, cost‐effective production, positive impacts, plant growth, translocation, plant system, plant metabolism, nanotechnological discoveries, biotechnology, agriculture, plant material, biogenic NPs, phytosynthesised NPs, bulk materials, nanoparticles, biosynthesis, surface area, review, size 1.0 nm to 100.0 nm     

Fluorescence‐Encoded Gold Nanoparticles: Library Design and Modulation of Cellular Uptake into Dendritic Cells

In order to harness the unique properties of nanoparticles for novel clinical applications and to modulate their uptake into specific immune cells we designed a new library of homo‐ and hetero‐functional fluorescence‐encoded gold nanoparticles (Au‐NPs) using different poly(vinyl alcohol) and poly(ethylene glycol)‐based polymers for particle coating and stabilization. The encoded particles were fully characterized by UV‐Vis and fluorescence spectroscopy, zeta potential and dynamic light scattering. The uptake by human monocyte derived dendritic cells in vitro was studied by confocal laser scanning microscopy and quantified by fluorescence‐activated cell sorting and inductively coupled plasma atomic emission spectroscopy. We show how the chemical modification of particle surfaces, for instance by attaching fluorescent dyes, can conceal fundamental particle properties and modulate cellular uptake. In order to mask the influence of fluorescent dyes on cellular uptake while still exploiting its fluorescence for detection, we have created hetero‐functionalized Au‐NPs, which again show typical particle dependent cellular interactions. Our study clearly prove that the thorough characterization of nanoparticles at each modification step in the engineering process is absolutely essential and that it can be necessary to make substantial adjustments of the particles in order to obtain reliable cellular uptake data, which truly reflects particle properties.     

Ultrafine Silver Nanoparticles Embedded in Cyclodextrin Metal‐Organic Frameworks with GRGDS Functionalization to Promote Antibacterial and Wound Healing Application

The challenge of bacterial infection increases the risk of mortality and morbidity in acute and chronic wound healing. Silver nanoparticles (Ag NPs) are a promising new version of conventional antibacterial nanosystem to fight against the bacterial resistance in concern of the drug discovery void. However, there are several challenges in controlling the size and colloidal stability of Ag NPs, which readily aggregate or coalesce in both solid and aqueous state. In this study, a template‐guided synthesis of ultrafine Ag NPs of around 2 nm using water‐soluble and biocompatible γ‐cyclodextrin metal‐organic frameworks (CD‐MOFs) is reported. The CD‐MOF based synthetic strategy integrates AgNO₃ reduction and Ag NPs immobilization in one pot achieving dual functions of reduced particle size and enhanced stability. Meanwhile, the synthesized Ag NPs are easily dispersible in aqueous media and exhibit effective bacterial inhibition. The surface modification of cross‐linked CD‐MOF particles with GRGDS peptide boosts the hemostatic effect that further enhances wound healing in synergy with the antibacterial effect. Hence, the strategy of ultrafine Ag NPs synthesis and immobilization in CD‐MOFs together with GRGDS modification holds promising potential for the rational design of effective wound healing devices.     

Uptake Kinetics and Nanotoxicity of Silica Nanoparticles Are Cell Type Dependent

In this study, it is shown that the cytotoxic response of cells as well as the uptake kinetics of nanoparticles (NPs) is cell type dependent. We use silica NPs with a diameter of 310 nm labeled with perylene dye and 304 nm unlabeled particles to evaluate cell type‐dependent uptake and cytotoxicity on human vascular endothelial cells (HUVEC) and cancer cells derived from the cervix carcinoma (HeLa). Besides their size, the particles are characterized concerning homogeneity of the labeling and their zeta potential. The cellular uptake of the labeled NPs is quantified by imaging the cells via confocal microscopy in a time‐dependent manner, with subsequent image analysis via a custom‐made and freely available digital method, Particle_in_Cell‐3D. We find that within the first 4 h of interaction, the uptake of silica NPs into the cytoplasm is up to 10 times more efficient in HUVEC than in HeLa cells. Interestingly, after 10 or 24 h of interaction, the number of intracellular particles for HeLa cells by far surpasses the one for HUVEC. Inhibitor studies show that these endothelial cells internalize 310 nm SiO₂ NPs via the clathrin‐dependent pathway. Remarkably, the differences in the amount of taken up NPs are not directly reflected by the metabolic activity and membrane integrity of the individual cell types. Interaction with NPs leads to a concentration‐dependent decrease in mitochondrial activity and an increase in membrane leakage for HUVEC, whereas HeLa cells show only a reduced mitochondrial activity and no membrane leakage. In addition, silica NPs lead to HUVEC cell death while HeLa cells survive. These findings indicate that HUVEC are more sensitive than HeLa cells upon silica NP exposure.     

Receptor‐Mediated Cellular Uptake of Folate‐Conjugated Fluorescent Nanodiamonds: A Combined Ensemble and Single‐Particle Study

Fluorescent nanodiamonds (FNDs) are nontoxic and photostable nanomaterials, ideal for long‐term in vivo imaging applications. This paper reports that FNDs with a size of ≈140 nm can be covalently conjugated with folic acid (FA) for receptor‐mediated targeting of cancer cells at the single‐particle level. The conjugation is made by using biocompatible polymers, such as polyethylene glycol, as crosslinked buffer layers. Ensemble‐averaged measurements with flow cytometry indicate that more than 50% of the FA‐conjugated FND particles can be internalized by the cells (such as HeLa cells) through receptor‐mediated endocytosis, as confirmed by competitive inhibition assays. Confocal fluorescence microscopy reveals that these FND particles accumulate in the perinuclear region. The absolute number of FNDs internalized by HeLa cells after 3 h of incubation at a particle concentration of 10 µg mL^?1 is in the range of 100 particles per cell. The receptor‐mediated uptake process is further elucidated by single‐particle tracking of 35‐nm FNDs in three dimensions and real time during the endocytosis.     

Synthesis and optical characterization of copper nanoparticles prepared by laser ablation

The remarkable size-tunable properties of nanoparticles (NPs) make them a hot research topic with applications in a wide range of fields. Hence, copper (Cu) colloidal NPs were prepared using laser ablation (Nd:YAG, 1064 nm, 7 ns, 10 Hz, 6000 pulses) of a copper metal plate at different laser fluences (LFs) in the range of 1–2.5 J cm^?2 in ethylene glycol (EG), at room temperature. Analysis of NPs was carried using different independent techniques such as ultraviolet–visible (UV–vis) spectroscopy; transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. TEM analysis showed that the NPs were spherical with a bimodal distribution and an average particle size of 5 and 16 nm influence of 1.2 J cms^?2, and 9 and 22 nm at 2 J cm^?2. The UV–vis spectra of colloidal NPs revealed the maximum absorbance at around 584 nm, indicating the formation of Cu NPs, which supported using FTIR spectra. Furthermore, the absorption spectra confirmed the metallic nature of Cu NPs. FTIR spectroscopy was utilized to verify information about the NPs surface state and chemical bonds constructed in the atom groups apparent on their surface.     

Fluorescent Polymer Nanoparticles Based on Dyes: Seeking Brighter Tools for Bioimaging

Speed, resolution and sensitivity of today's fluorescence bioimaging can be drastically improved by fluorescent nanoparticles (NPs) that are many‐fold brighter than organic dyes and fluorescent proteins. While the field is currently dominated by inorganic NPs, notably quantum dots (QDs), fluorescent polymer NPs encapsulating large quantities of dyes (dye‐loaded NPs) have emerged recently as an attractive alternative. These new nanomaterials, inspired from the fields of polymeric drug delivery vehicles and advanced fluorophores, can combine superior brightness with biodegradability and low toxicity. Here, we describe the strategies for synthesis of dye‐loaded polymer NPs by emulsion polymerization and assembly of pre‐formed polymers. Superior brightness requires strong dye loading without aggregation‐caused quenching (ACQ). Only recently several strategies of dye design were proposed to overcome ACQ in polymer NPs: aggregation induced emission (AIE), dye modification with bulky side groups and use of bulky hydrophobic counterions. The resulting NPs now surpass the brightness of QDs by ≈10‐fold for a comparable size, and have started reaching the level of the brightest conjugated polymer NPs. Other properties, notably photostability, color, blinking, as well as particle size and surface chemistry are also systematically analyzed. Finally, major and emerging applications of dye‐loaded NPs for in vitro and in vivo imaging are reviewed.     

Transformation of Amorphous Polyphosphate Nanoparticles into Coacervate Complexes: An Approach for the Encapsulation of Mesenchymal Stem Cells

Inorganic polyphosphate [polyP] has proven to be a promising physiological biopolymer for potential use in regenerative medicine because of its morphogenetic activity and function as an extracellular energy‐donating system. Amorphous Ca²⁺–polyP nanoparticles [Ca–polyP‐NPs] are characterized by a high zeta potential with −34 mV (at pH 7.4). This should contribute to the stability of suspensions of the spherical nanoparticles (radius 94 nm), but make them less biocompatible. The zeta potential decreases to near zero after exposure of the Ca–polyP‐NPs to protein/peptide‐containing serum or medium plus serum. Electron microscopy analysis reveals that the particles rapidly change into a coacervate phase. Those mats are amorphous, but less stable than the likewise amorphous Ca–polyP‐NPs and are morphogenetically active. Mesenchymal stem cells grown onto the polyP coacervate show enhanced growth/proliferation and become embedded in the coacervate. These results suggest that the Ca–polyP coacervate, formed from Ca–polyP‐NPs in the presence of protein, can act as an adaptable framework that mimics a niche and provides metabolic energy in bone/cartilage engineering.     

Comparative Study of Antioxidant and Catalytic Activity of Silver and Gold Nanoparticles Synthesized From Costus pictus Leaf Extract

Biological synthesis of silver and gold nanoparticles using Costus pictus leaf extract(CPLE) and their potential in vitro antioxidant and catalytic activities were reported here. Formation of Costus pictus silver(CPAgN Ps) and gold(CPAuN Ps) nanoparticles was confirmed by UV-visible spectroscopy and their spherical shape by scanning electron microscopy. The synthesized nanoparticles gave strong signals for silver and gold in energy dispersive X-ray spectroscopy. The CPAgN Ps and CPAuN Ps had an average size of 46.7and 37.2 nm, respectively, as determined by dynamic light scattering particle size analyzer. Fourier transform infrared spectroscopy(FTIR) analysis indicated involvement of amine and carbonyl groups in the formation of CPAg NPs and CPAu NPs. Thermal stability of synthesized nanoparticles was assessed by thermogravimetric analysis-differential scanning calorimetry. CPAgN Ps, CPAuN Ps and CPLE exhibited tremendous antioxidant activity when being assessed by various in vitro assays, and their activity was comparable to standard antioxidants. CPAg NPs, CPAu NPs and CPLE also caused degradation of dyes like methylene blue and methyl red. While CPAgN Ps, CPAuN Ps and CPLE caused respective 85%, 42% and 30%degradation of methylene blue, they showed less activity against methyl red. These observations signify that such green methods open up new avenues in nanobiotechnology for the synthesis of nanoparticles with extensive industrial and biomedical applications.     

Engineered Multifunctional Albumin‐Decorated Porous Silicon Nanoparticles for FcRn Translocation of Insulin

The last decade has seen remarkable advances in the development of drug delivery systems as alternative to parenteral injection‐based delivery of insulin. Neonatal Fc receptor (FcRn)‐mediated transcytosis has been recently proposed as a strategy to increase the transport of drugs across the intestinal epithelium. FcRn‐targeted nanoparticles (NPs) could hijack the FcRn transcytotic pathway and cross the epithelial cell layer. In this study, a novel nanoparticulate system for insulin delivery based on porous silicon NPs is proposed. After surface conjugation with albumin and loading with insulin, the NPs are encapsulated into a pH‐responsive polymeric particle by nanoprecipitation. The developed NP formulation shows controlled size and homogeneous size distribution. Transmission electron microscopy (TEM) images show successful encapsulation of the NPs into pH‐sensitive polymeric particles. No insulin release is detected at acidic conditions, but a controlled release profile is observed at intestinal pH. Toxicity studies show high compatibility of the NPs with intestinal cells. In vitro insulin permeation across the intestinal epithelium shows approximately fivefold increase when insulin is loaded into FcRn‐targeted NPs. Overall, these FcRn‐targeted NPs offer a toolbox in the development of targeted therapies for oral delivery of insulin.