Synthesis and preparation of nanoparticles composed of amphiphilic poly(γ-glutamic acid) with different hydrophobic side chains and their potential of membrane disruptive activity

In the development of nanoparticle-based vaccine adjuvants, the interaction between nanoparticles (NPs) and the cells is a key factor. To control them, we focused on the relationship between the hydrophobicity of the side chains and the cell membrane. In this study, amphiphilic poly(γ-glutamic acid) (γ-PGA), using various types of hydrophobic side chains, was synthesized and used to prepare NPs for evaluating the membrane disruptive activity. When leucine ethyl ester (Leu), methionine ethyl ester (Met), or tryptophan ethyl ester (Trp) was grafted, each polymer formed monodispersed NPs at physiological conditions. Significantly, NPs composed of Leu and Trp showed a membrane disruptive activity at the endosomal environment (pH 5–6.5), while NPs composed of Met did not show. This might be due to the weak hydrophobicity of Met compared to that of Leu and Trp, which demonstrated that the interaction between NPs and cells could be controlled by designing the polymer compositions.     

Preparation of photo-sensitive poly(γ-glutamic acid) nanoparticles and application for immobilizing hemoglobin on electrode

Poly(γ-glutamic acid) (γ-PGA) has been widely used in many applications due to its excellent biodegradability, biocompatibility, and nontoxic properties. In this study, we synthesized a novel photo-sensitive amphiphilic poly(γ-glutamic acid)-graft-7-amino-4-methylcoumarin (AMC-γ-PGA) copolymer, which can self-assemble into nanoparticles (NPs) via solvent exchange method. The resultant AMC-γ-PGA NPs showed sensitivity to UV irradiation, pH, and ionic strength, owing to the presence of coumarin groups and carboxyl groups on the AMC-γ-PGA copolymer. The AMC-γ-PGA NPs were then used as a matrix to entrap hemoglobin (Hb). The obtained Hb@AMC-γ-PGA nanocomposites were cast on the electrode to form a nanocomposite film, which was then photo-crosslinked by UV irradiation to lock and immobilize Hb. Cyclic voltammetry (CV) experiment showed that the Hb@AMC-γ-PGA-nanocomposite-modified electrode exhibited good electrochemical catalytic activity for H₂O₂, implying that the AMC-γ-PGA NPs provided a favorable microenvironment for Hb and preserved the bioactivity of Hb. In addition, the leakage of Hb was efficiently avoided with the photo-crosslinking of the AMC-γ-PGA NPs. The biocompatible photo-sensitive AMC-γ-PGA NPs provided an excellent platform for immobilization of Hb on electrode.     

A wide range optical pH sensor for living cells using Au@Ag nanoparticles functionalized carbon nanotubes based on SERS signals

p-Aminothiophenol (pATP) functionalized multi-walled carbon nanotubes (MWCNTs) have been demonstrated as an efficient pH sensor for living cells. The proposed sensor employs gold/silver core-shell nanoparticles (Au@Ag NPs) functionalized MWCNTs hybrid structure as the surface-enhanced Raman scattering (SERS) substrate and pATP molecules as the SERS reporters, which possess a pH-dependent SERS performance. By using MWCNTs as the substrate to be in a state of aggregation, the pH sensing range could be extended to pH 3.0～14.0, which is much wider than that using unaggregated Au@Ag NPs without MWCNTs. Furthermore, the pH-sensitive performance was well retained in living cells with a low cytotoxicity. The developed SERS-active MWCNTs-based nanocomposite is expected to be an efficient intracellular pH sensor for bio-applications.     

Facile formation of stimuli-responsive,fluorescent and magnetic nanoparticles based on cellulose stearoyl ester via nanoprecipitation

In comparison to stimuli-responsive, multi-functional nanoparticles (NPs) from synthetic polymers, such NPs based on sustainable, naturally occurring polysaccharides are still scarce. In the present study, stable stimuli-responsive, fluorescent and magnetic NPs were fabricated using cellulose stearoyl esters (CSEs) consisting of cellulose and stearoyl groups. The multifunctional NPs with the average diameters between 80 and 250 nm were obtained after facile nanoprecipitation using CSE solutions containing Fe₃O₄-NPs. Using the aqueous solution of fluorescent rhodamine B as precipitant, NPs with rhodamine B on NP surface were obtained. Rhodamine B could be released depending on the temperature. In comparison, stearoylaminoethyl rhodamine B can be encapsulated in CSE-NPs, which renders obtained NPs reversible fluorescence in response to UV illumination and heat treatment.     

Biosynthesis and Characterization of Pd and Pt Nanoparticles Using Piper betle L. Plant in a Photoreduction Method

An extremely rapid green approach that generates bulk quantities of nanocrystals of noble metals such as palladium (Pd) and platinum (Pt) nanoparticles (NPs) with a small sizes of 3.8 ± 0.2 and 2.1 ± 0.4 nm by using Piper betle L. (Piperaceae) leaf extract is described. The highly stable and monodispersed Pd and Pt NPs were obtained at 10 min of continuous sunlight exposure. The bio-reduced Pd and Pt NPs were further characterized by using UV–Visible spectroscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry measurements. The particles, although discrete, were predominately associated with the P. betle plant proteins, which makes them stable over long time periods. These synthesized biogenic Pd and Pt NPs were evaluated for their acute toxicity studies against aquatic organism, Daphnia magna.     

Production of Pt nanoparticles-supported chelating group-modified graphene for direct methanol fuel cells

In this study, Pt nanoparticles (NPs) were supported on reduced graphene oxide with the aid of disodium ethylenediamine-tetraacetate, where the Pt iona were initially attached to EDTA-functionalized graphene oxide (EDTA-GO) sheets and then the metal ion and the graphene oxide were reduced simultaneously by ethylene glycol. Electrochemical properties of the catalysts were studied by measuring cyclic voltammetries, and functional groups of the synthesized materials were investigated by Fourier transform infrared spectrometry. Average sizes and lattice parameters were measured by scanning electron microscopy, transmission electron microscopy images, and X-ray diffraction. The results showed that Pt NPs were successfully deposited on the EDTA-GO with the crystallite size of about 2.3 nm. The prepared catalysts demonstrated an enhanced tolerance towards CO poisoning, when EDTA-GO was used as supports. This suggests that EDTA plays a crucial role in the dispersion and electrocatalytic activity of the metal nanoparticles.     

Preparation,characterization, catalytic performance and antibacterial activity of Ag photodeposited on monodisperse ZnO submicron spheres

Monodisperse ZnO colloidal spheres were produced by a two-stage sol–gel reaction process. The sub-micrometer sized ZnO/Ag composite spheres were prepared by photodeposition route. The photochemical reduction method needs no other reductant or surfactant and is an effective means to enable the uniform distribution of Ag nanoparticles (NPs) over the ZnO spheres. The size and shape as well as the optical properties of the composites were characterized with transmission electron microscopy and UV–Vis spectroscopy. The results showed that average size of ZnO and Ag NPs among the composites was around 480, 10 nm, respectively. Ag NPs were relatively monodisperse, presented spherical shape, and their deposition over the ZnO surface was uniform. Formation of Ag NPs on the surface of ZnO spheres was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy, and the catalytic performance and antibacterial activity was also investigated. The ZnO/Ag composites possess excellent catalytic performance for catalytic reduction of 4-nitrophenol to 4-aminophenol and can effectively inhibit Escherichia coli and Bacillus subtilis growth at 0.25 mg/mL.     

Solid-phase microextraction/gas chromatography–mass spectrometry method optimization for characterization of surface adsorption forces of nanoparticles

A complete characterization of the different physico-chemical properties of nanoparticles (NPs) is necessary for the evaluation of their impact on health and environment. Among these properties, the surface characterization of the nanomaterial is the least developed and in many cases limited to the measurement of surface composition and zetapotential. The biological surface adsorption index approach (BSAI) for characterization of surface adsorption properties of NPs has recently been introduced (Xia et al. Nat Nanotechnol 5:671–675, 2010; Xia et al. ACS Nano 5(11):9074–9081, 2011). The BSAI approach offers in principle the possibility to characterize the different interaction forces exerted between a NP's surface and an organic—and by extension biological—entity. The present work further develops the BSAI approach and optimizes a solid-phase microextraction gas chromatography–mass spectrometry (SPME/GC-MS) method which, as an outcome, gives a better-defined quantification of the adsorption properties on NPs. We investigated the various aspects of the SPME/GC-MS method, including kinetics of adsorption of probe compounds on SPME fiber, kinetic of adsorption of probe compounds on NP's surface, and optimization of NP's concentration. The optimized conditions were then tested on 33 probe compounds and on Au NPs (15 nm) and SiO₂ NPs (50 nm). The procedure allowed the identification of three compounds adsorbed by silica NPs and nine compounds by Au NPs, with equilibrium times which varied between 30 min and 12 h. Adsorption coefficients of 4.66?±?0.23 and 4.44?±?0.26 were calculated for 1-methylnaphtalene and biphenyl, compared to literature values of 4.89 and 5.18, respectively. The results demonstrated that the detailed optimization of the SPME/GC-MS method under various conditions is a critical factor and a prerequisite to the application of the BSAI approach as a tool to characterize surface adsorption properties of NPs and therefore to draw any further conclusions on their potential impact on health. Graphical Abstract

The basic principle of SPME/GC-MS method for characterization of nanoparticles surface adsorption forces     

Effects of Cu addition on the structure and magnetic properties of L10-FePt nanoparticles prepared by sol–gel method

(FePt)₁₀₀Cu₀, (FePt)₉₅Cu₅ and (FePt)₉₀Cu₁₀ nanoparticles (NPs) were successfully synthesized by the sol–gel method. The relationship between Cu doping and structure and magnetic properties of L1₀-FePt NPs was studied. The results indicated that all three samples originated a L1₀-FePt structure and Cu doping did not destroy the ordered structure of L1₀-FePt. By increasing the Cu content, c/a ratio of the FePtCu NPs linearly decreased. Pawley refinement showed symmetry of (FePt)₉₅Cu₅ NPs was still tetragonal. When the Cu concentration increased from 0 to 10 %, coercivity increased from 7,050 to 11,250 Oe. This result confirms that the prepared alloys can be promising candidates for magnetic storage applications.     

Gel-assisted synthesis of anatase TiO2 nanoparticles and application for electrochemical determination of L-tryptophan

Anatase titanium dioxide nanoparticles (TiO₂-NPs) were synthesized with and without gelatin via the sol-gel method. The TiO₂-NPs were characterized by a number of techniques, such as thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR) and ultraviolet visible spectroscopy (UV-Vis). The particle sizes of the TiO₂-NPs prepared with and without gelatin were ～13 and ～17 nm, respectively. The main advantage of using gelatin as a stabilizing agent is that it provides long-term stability for nanoparticles by preventing particles agglomeration. The results indicated that gelatin was a reliable green stabilizer, which can be used as a polymerization agent in the sol-gel method for synthesis of tiny size TiO₂-NPs. Moreover, the composite film was prepared by synthesized TiO₂-NPs nanoparticles and multi wall carbon nanotube (MWNT) on glassy carbon electrode (TiO₂-MWNT/GCE). The TiO₂-MWNT/GCE responded linearly to L-tryptophan (L-Trp) in the concentration of 1.0 × 10^?6 to 1.5 × 10^?4 M with detection limit of 5.2 × 10^?7 M at 3 using amperometry. The studied sensor exhibited good reproducibility and long-term stability.     

Direct electrochemistry and electrocatalysis of hemoglobin on a glassy carbon electrode modified with poly(ethylene glycol diglycidyl ether) and gold nanoparticles on a quaternized cellulose support. A sensor for hydrogen peroxide and nitric oxide

A glassy carbon electrode was modified with gold nanoparticles (Au-NPs) on a quaternized cellulose support in a film composed of poly(ethylene glycol diglycidyl ether) (PEGDGE), and Hb was immobilized on the Au-NPs. The sensor film was characterized by UV–vis spectra, scanning electron microscopy, and electrochemical impedance spectroscopy. Cyclic voltammetry of the Hb in the Au@Qc/PEGDGE film revealed a pair of well-defined and quasi reversible peaks for the protein heme Fe(III)/Fe(II) redox couple at about ?0.333 V (vs. SCE). The sensor film also exhibited good electrocatalytic activity for the reduction of nitric oxide and hydrogen peroxide. The amperometric response of the biosensor depends linearly on the concentration of nitric oxide in the 0.9 to 160 μM range, and the detection limit is as low as 12 nM (at 3σ). The response to hydrogen peroxide is linear in the 59 nM to 4.6 μM concentration range, and the detection limit is 16 nM (at 3σ). This biosensor is sensitive, reproducible, and long-term stable. Figure

An electrochemical biosensor based on the immobilization of hemoglobin in Au@Qc NPs /Poly ethylene glycol diglycidyl ether composite film is developed.     

Preparation and reflow soldering characteristics of solder paste containing submicron Sn powders synthesised via chemical reduction

Sn nanoparticles (NPs) were synthesised via chemical reduction. Trisodium citrate dihydrate and mixtures of trisodium citrate dihydrate and 1,10-phenanthroline monohydrate were used as capping agents for the synthesis. When a specific amount of trisodium citrate dihydrate (3.4 × 10^?1 mM) was solely added, very fine particle sizes and excellent suppression of aggregation were achieved in the dried samples. When 5 mM of 1,10-phenanthroline monohydrate was used in combination with trisodium citrate dihydrate (at the optimum concentration of 3.4 × 10^?2 mM), the particle refining and the suppression of aggregation were further improved. The nano-solder paste prepared by mixing the synthesised Sn NPs with a commercial flux exhibited stable reflow soldering characteristics. The formation of an intermetallic layer, similar to that observed when commercial solder pastes containing micron-sized powders were used, was seen when soldering was carried out with the solder paste containing the synthesised Sn NPs.     

Thermally stimulated discharge current (TSDC) characteristics in β-phase PVDF–BaTiO3 nanocomposites

β-phase polyvinylidene fluoride (PVDF)–BaTiO₃ nanocomposite samples have been prepared by solution mixing method. XRD data represent that the crystallinity of PVDF decreases with increase in loading level of BaTiO₃ nanoparticles. DSC curve represents that the melting point of PVDF is lightly affected by loading concentration of BaTiO₃. The morphology and microstructure of PVDF and PVDF embedded by BaTiO₃ nanofillers were investigated by using inverted contrast microscopy (ICM) and scanning electron microscopy (SEM). FTIR interferrometry is proven that PVDF and BaTiO₃ are not chemically interacting; therefore, interaction of BaTiO₃ is van der Waals type of interaction. The thermally stimulated discharge current (TSDC) of PVDF and PVDF–BaTiO₃ nanocomposites sample was characterized by single peak. The observed TSDC peak is discussed on the basis of dipolar and interfacial polarization.     

Optical,mechanical, and thermal behavior of poly(vinyl alcohol) composite films embedded with biosafe and optically active poly(amide–imide)-ZnO quantum dot nanocomposite as a novel reinforcement

Poly(vinyl alcohol) (PVA), a polyhydroxy polymer, is the synthetic resin produced in the world due to the physical properties and complete biodegradability. This work tries to introduce novel reinforcement for PVA to improve properties without effect on its biocompatibility. The present investigation deals with the fabrication of new PVA/poly(amide–imide)-zinc oxide nanocomposites (PVA/PAI–ZnO NCs) with different PAI–ZnO loading by using ultrasound irradiation. At first, the surface of ZnO nanoparticles (NPs) was modified by biosafe diacid for the better dispersion of NPs and increasing possible interactions between NPs and PAI. Then, PAI–ZnO was used as filler in the PVA matrix. Surface morphology results were amazing. The TEM images and related histograms show a noticeable size decreasing of ZnO NPs from about 31 to 3 nm after preparation of NCs. Other analyses showed that the reinforcement of PAI–ZnO NC into the PVA matrix enhances mechanical and thermal properties of the PVA composites.     

The Prognostic Value of Histidine-Rich Glycoprotein RNA in Breast Tissue Using Unmodified Gold Nanoparticles Assay

The aim of is this study is to explore the role of tissue histidine-rich glycoprotein (HRG) RNA as a promising clinically useful biomarker for breast cancer patients prognosis using nanogold assay. Expression of the HRG RNA was assessed by gold nanoparticles and conventional RT-PCR after purification by magnetic nanoparticles in breast tissue samples. The study included 120 patients, 60 of which were histologically proven breast carcinoma cases, 30 had benign breast lesions and 30 were healthy individuals who had undergone reductive plastic surgery. ER, PR and HER2 status were also investigated. The prognostic significance of tissue HRG RNA expression in breast cancer was explored. The magnetic nanoparticles coated with specific thiol modified oligonucleotide probe were used successfully in purification of HRG RNA from breast tissue total RNAs with satisfactory yield. The developed HRG AuNPs assay had a sensitivity and a specificity of 90 %, and a detection limit of 1.5 nmol/l. The concordance rate between the HRG AuNPs assay with RT-PCR after RNA purification using magnetic nanoparticles was 93.3 %. The median follow-up period was 60 months. Among traditional prognostic biomarkers, HRG was a significant independent prognostic marker in relapse-free survival (RFS). HRG RNA is an independent prognostic marker for breast cancer and can be detected using gold NPs assay, which is rapid, sensitive, specific, inexpensive to extend the value for breast cancer prognosis.     

Synthesis,Colloidal Properties and Cytotoxicity of Biopolymer Nanoparticles

To characterize the physicochemical and biological stability of nanodevices suitable for biomedical applications, polylactic acid (PLA) nanoparticles (NPs) of 112?±?6 nm and polyhydroxy butyrate (PHB) of 15?±?5 nm size were prepared by standardizing the suitable method for each. Morphology of NPs was studied by scanning and transmission electron microscopy and temperature stability by thermogravimetric analysis. Their stability in biological fluids (simulated gastrointestinal and saliva) and tolerance against 0.5 mM NaCl were analyzed. PHB NPs remained stable in all fluids, while after 24 h treatment, the PLA NPs showed the beginning of disintegration with intestinal fluid mimic. In addition to the preparation of polyethylene glycol (PEG) surface-coated NPs, PLA–PEG–PLA triblock copolymer (MW?～?7,366 Da) was also chemically synthesized and characterized. Cytotoxicity of all forms of nanoparticles was tested by MTT assay and by annexin pi staining.     

Melt miscibility of HDPE/UHMWPE,LDPE/UHMWPE,and LLDPE/UHMWPE blends detected by dynamic rheometer

The dynamic rheological behavior of high density polyethylene (HDPE)/ultrahigh molecular weight polyethylene (UHMWPE) blends, low density polyethylene (LDPE)/UHMWPE blends and linear low density polyethylene (LLDPE)/ UHMWPE blends was measured in parallel plate rheometer at 200°C. The analysis of log-additivity rule, Cole-Cole plots and Han curves of the three series blends indicated that the LDPE/UHMWPE blends were miscible in the melt, while the HDPE/UHMWPE blends and LLDPE/UHMWPE blends showed phase separation. The DSC results of LLDPE/UHMWPE blends and HDPE/UHMWPE blends were consistent with the rheological properties, while for the thermal properties of LDPE/UHMWPE blends, results revealed three endothermic peaks, which indicated a liquid-solid phase separation in LDPE/UHMWPE blends.     

Spin-trapped Radicals: Determination by LC-TSP-MS and LC-ESI-MS

The 4-POBN[α-(4-pyridyl-l-oxide)-N-tert-butyl-nitrone] radical adducts of ethyl and pentyl radicals were determined by a combination of high performance liquid chromatography (HPLC) combined with electron paramagnetic resonance (EPR) with HPLC-electrospray (ESI)-mass spectrometry and HPLC-thermospray (TSP)-MS. The identifIcation of the peak corresponding to the spin-trapped radical was done by performing HPLC-EPR under the same chromatographic conditions as the HPLC-MS. The radical adducts could be determined by both techniques, even though for ESI only 12 μL/min of the total 1 mL/min HPLC flow rate could be directed into the ion source.