Core-shell Magnetic Mesoporous Silica Research Articles

Synthesis of core-shell magnetic mesoporous silica nanoparticles to disperse amine functionalities for post-combustion carbon dioxide capture

BackgroundPost-combustion capture technology appears a suitable approach to reduce the emission of CO2 by power plants. The use of solid sorbents would permit to overcome the limitations of the well-established liquid amine-based absorption process. In particular, mesoporous silica materials have been proposed as suitable sorbents especially if functionalized with amines. MethodsThe properties of as-synthesized (by using dodecylamine as synthesis amine) and calcined hexagonal mesoporous silica (HMS), impregnated or not with tetraethylenepentamine (TEPA), were studied. Magnetite (Fe3O4) nanoparticles were specifically used to obtain HMS core-shell nanoparticles in order to investigate the effect of the magnetite core on CO2 uptake capability. CO2 uptake measurements were carried out on all HMS and core-shell particles. Furthermore, Transmission Electron Microscopy (TEM) images, Fourier Transform Infrared (FTIR) spectra and N2 adsorption/desorption measurements allowed analyzing some important properties of the sorbent particles, such as particle aggregation, incorporation and dispersion of amines, surface area, pore volume and pore size distribution. Significant FindingsThe best performance in terms of chemical CO2 uptake was obtained on core-shell material, calcined and impregnated with TEPA (about 89 mg/g), but also the as prepared core-shell sample impregnated with TEPA seems promising since the synthesis dodecylamine sites can be activated during the impregnation process.

Immobilization of laccase on magnetic mesoporous silica as a recoverable biocatalyst for the efficient degradation of benzo[a]pyrene

Laccase is an efficient green biocatalyst, widely used for the degradation of various organic pollutants. However, free laccase is unstable and difficult to recover, which limits its practical application. In this study, a multilayer core-shell magnetic mesoporous silica (Fe3O4@d-SiO2@p-SiO2) microsphere with high specific surface area (275 m2 g−1) was fabricated for immobilization of laccase. The unique structure of Fe3O4@d-SiO2@p-SiO2 enabled the successful immobilization of laccase. Under the optimal immobilization conditions of laccase concentration of 1.5 mg mL−1, immobilization time of 6 h, immobilization pH of 6, the loading capacity of laccase was up to 567 mg g−1. Compared with free laccase, immobilized laccase exhibited remarkable pH stability, thermal stability and storage stability. Moreover, the immobilized laccase was easy to achieve magnetic recovery and possessed excellent reusability, with its activity remaining 58.2% after 10 consecutive reuses. More importantly, immobilized laccase had good degradation performance for benzo[a]pyrene (BaP), which can achieve rapid and efficient degradation of low concentration BaP over a wide range of pH and temperature. The removal efficiency of BaP was up to 99.0% within 1 h, and still exceeded 35.0% after 5 cycles. The removal of BaP by immobilized laccase was achieved through both adsorption and degradation. The degradation products and possible degradation pathways were determined by GC-MS analysis. This study indicated that Fe3O4@d-SiO2@p-SiO2 could effectively enhance the stability and biocatalytic activity of laccase, which is expected to provide a new clean biotechnology for the remediation of BaP contaminated sites.

A Novel pH-Responsive Iron Oxide Core-Shell Magnetic Mesoporous Silica Nanoparticle (M-MSN) System Encapsulating Doxorubicin (DOX) and Glucose Oxidase (Gox) for Pancreatic Cancer Treatment.

This study developed a pancreatic cancer targeted drug delivery system that responds to changes in acidity. The system was based on iron oxide core-shell magnetic mesoporous silica nanoparticles (M-MSNs) to treat pancreatic cancer through combined chemotherapy and starvation therapy. Glucose oxidase (Gox) was coupled to the cancer cell surface to reduce glucose availability for cancer cells, exacerbating the heterogeneity of the tumor microenvironment. Reduced pH accelerated the depolymerization of pH-sensitive polydopamine (PDA), thereby controlling the spatial distribution of Gox and release of doxorubicin (DOX) within tumor cells. Characterization results showed the successful synthesis of DG@M-MSN-PDA-PEG-FA (DG@NPs) with a diameter of 66.02 ± 3.6 nm. In vitro data indicated DG@NPs were highly effective and stable with good cellular uptake shown by confocal laser scanning microscopy (CLSM). DG@NPs exhibited high cytotoxicity and induced apoptosis. Additionally, in vivo experiments confirmed DG@NPs effectively inhibited tumor growth in nude mice with good biosafety. The combination of starvation therapy and chemotherapy facilitated drug release, suggesting DG@NPs as a novel drug delivery system for pancreatic cancer treatment. This study successfully constructed a doxorubicin release system responsive to acidity changes for targeted delivery in pancreatic cancer, providing a new strategy for combination therapy.

Iron tailings derived core-shell magnetic mesoporous silica microspheres for effective Congo red removal

Iron tailings derived core-shell magnetic mesoporous silica microspheres for effective Congo red removal

Introducing a green nanocatalytic process toward the synthesis of benzo[a]pyrano-[2,3-c]phenazines utilizing copper oxide quantum dot-modified core-shell magnetic mesoporous silica nanoparticles as high throughput and reusable nanocatalysts.

In this contribution, a green, simple, efficient, and straightforward nanocatalytic process was developed for the synthesis of benzo[a]pyrano[2,3-c]phenazine derivatives under mild thermal conditions. In this regard, the copper oxide quantum dot-modified magnetic silica mesoporous nanoparticles (M-MSNs/CuO(QDs)) were synthesized by surface modification of M-MSNs with CuO QDs to prepare a highly powerful magnetic core–shell nanocatalyst. The prepared nanocatalyst was then characterized for its functionality, size, morphology, elemental composition, surface area, crystallinity, and magnetic properties. Afterwards, it was applied for the synthesis of benzo[a]pyrano[2,3-c]phenazine derivatives under green reaction conditions. The factors affecting the reaction yield were optimized by the one-factor-at-a-time optimization method. Under obtained optimal conditions, the developed method showed a reaction yield range as high as 86–95% for different derivatives. The reusability studies were performed for indexing the cycling stability of the prepared magnetic nanocatalyst. The results exhibited that the catalytic efficiency of the nanocatalyst was saved for at least 5 operational times, showing high cycling stability of M-MSNs/CuO(QDs). Finally, the catalytic performances of the nanocatalyst was compared with the reported ones, revealing that the M-MSNs/CuO(QDs) presents very better performances toward the synthesis of benzo[a]pyrano[2,3-c]phenazine derivatives than the reported ones.

Preparation of polydopamine-functionalized mesoporous silica-coated core/shell magnetic nanocomposite for efficiently extracting five amphetamine-type stimulants from wastewater followed by UPLC-MS/MS determination

Wastewater-based epidemiology (WBE) was a near-real-time monitoring strategy for illegal drugs. However, solid-phase extraction (SPE) widely used in WBE was time-consuming and labor-intensive to extract ultra-trace target compounds from wastewater. In this study, a convenient magnetic solid-phase extraction (MSPE) approach based on newly designed and synthesized polydopamine functionalized core-shell magnetic mesoporous silica (Fe3O4@nSiO2@mSiO2@PDA) nanocomposite was synthesized and firstly utilized for simultaneously extracting five amphetamine-type stimulants (ATSs) from wastewater samples. Subsequently, ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method coupled with optimal MSPE was developed for determination of ultra-trace ATSs in wastewater. The validation results indicated a favorable linearity ranging from 1 to 200 ng L−1, low limit of detection (0.5–2.5 ng L−1), and qualified recovery (95.1–106.6%) and repeatability (0.6–6.2%). In addition, the Fe3O4@nSiO2@mSiO2@PDA nanoparticles could be reused for at least ten times without significant loss of the adsorption efficiencies of ATSs. Finally, the MSPE-UPLC-MS/MS method was successfully applied to real wastewater samples with the results that the preparation procedure was shrunk from 2 h to 30 min without obvious decline of extraction efficiency compared with the SPE. Hence, based on merits of the novel Fe3O4@nSiO2@mSiO2@PDA nanocomposite, the proposed method is convenient and reliable for determination of ATSs in wastewater.

Orienting the Pore Morphology of Core-Shell Magnetic Mesoporous Silica with the Sol-Gel Temperature. Influence on MRI and Magnetic Hyperthermia Properties.

The controlled design of robust, well reproducible, and functional nanomaterials made according to simple processes is of key importance to envision future applications. In the field of porous materials, tuning nanoparticle features such as specific area, pore size and morphology by adjusting simple parameters such as pH, temperature or solvent is highly needed. In this work, we address the tunable control of the pore morphology of mesoporous silica (MS) nanoparticles (NPs) with the sol-gel reaction temperature (Tsg). We show that the pore morphology of MS NPs alone or of MS shell covering iron oxide nanoparticles (IO NPs) can be easily tailored with Tsg orienting either towards stellar (ST) morphology (large radial pore of around 10 nm) below 80 °C or towards a worm-like (WL) morphology (small randomly oriented pores channel network, of 3–4 nm pore size) above 80 °C. The relaxometric and magnetothermal features of IO@STMS or IO@WLMS core shell NPs having respectively stellar or worm-like morphologies are compared and discussed to understand the role of the pore structure for MRI and magnetic hyperthermia applications.

A novel electrochemical lung cancer biomarker cytokeratin 19 fragment antigen 21-1 immunosensor based on Si3N4/MoS2 incorporated MWCNTs and core-shell type magnetic nanoparticles.

Lung cancer isone ofdeadliest and most life threateningcancer types. Cytokeratin 19 fragment antigen 21-1 (CYFRA 21-1) is a significant biomarker for the diagnosis of non-small cell lung cancer (NSCLC). Due to these reasons, a novel electrochemical immunosensor based on a silicon nitride (Si3N4)-molybdenum disulfide (MoS2) composite on multi-walled carbon nanotubes (Si3N4/MoS2-MWCNTs) as an electrochemical sensor platform and core-shell type magnetic mesoporous silica nanoparticles@gold nanoparticles (MMSNs@AuNPs) as a signal amplifier was presented for CYFRA21-1 detection in this study. Capture antibody (Ab1) immobilization on a Si3N4/MoS2-MWCNT modified glassy carbon electrode (Si3N4/MoS2-MWCNTs/GCE) was firstly successfully performed by stable electrostatic/ionic interactions between the -NH2 groups of the capture antibody and the polar groups of Si3N4/MoS2. Then, specific antibody-antigen interactions between the electrochemical sensor platform and the signal amplifier formed a novel voltammetric CYFRA21-1 immunosensor. The prepared composite materials and electrochemical sensor surfaces were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A linearity range of 0.01-1.0 pg mL-1 and a low detection limit (LOD) of 2.00 fg mL-1 were also obtained for analytical applications. Thus, the proposed immunosensor based on Si3N4/MoS2-MWCNTs and MMSNs@AuNPs has great potential for medical diagnosis of lung cancer.

Advances in the Interfacial Assembly of Mesoporous Silica on Magnetite Particles

AbstractInterfacing magnetic particles with ordered mesoporous materials is an effective direction for the development of functional porous composite materials with rationally designed core–shell structures. Owing to the combined properties of magnetic nanoparticles and mesoporous silica (high surface area, large pore volume, porosity, and biocompatibility), core–shell magnetic mesoporous silica materials have generated tremendous interest in various disciplines, including chemistry, materials, bioengineering, and biomedicine. Interfacial assembly strategies enable the rational construction of magnetic mesoporous silica materials with well‐defined core–shell structure, morphology, pore parameters, and surface wettability, which can decisively influence their physical and chemical properties and thus improve their application performance. This Minireview summarizes recent progress in the synthesis of core–shell magnetic mesoporous silica and the adjustment of key parameters, including pore size, morphology, and pore orientation.

Advances in the Interfacial Assembly of Mesoporous Silica on Magnetite Particles.

Interfacing magnetic particles with ordered mesoporous materials is an effective direction for the development of functional porous composite materials with rationally designed core-shell structures. Owing to the combined properties of magnetic nanoparticles and mesoporous silica (high surface area, large pore volume, porosity, and biocompatibility), core-shell magnetic mesoporous silica materials have generated tremendous interest in various disciplines, including chemistry, materials, bioengineering, and biomedicine. Interfacial assembly strategies enable the rational construction of magnetic mesoporous silica materials with well-defined core-shell structure, morphology, pore parameters, and surface wettability, which can decisively influence their physical and chemical properties and thus improve their application performance. This Minireview summarizes recent progress in the synthesis of core-shell magnetic mesoporous silica and the adjustment of key parameters, including pore size, morphology, and pore orientation.

Recent Advances in the Synthesis, Surface Modifications and Applications of Core‐Shell Magnetic Mesoporous Silica Nanospheres

The hierarchically structured core-shell magnetic mesoporous silica nanospheres (Mag-MSNs) have attracted extensive attention, particularly in studies involving reliable preparations and diverse applications of the multifunctional nanomaterials in multi-disciplinary fields. Intriguingly, Mag-MSNs have been prepared with well-designed synthesis strategies and used as adsorbent materials, biomedicines, and in proteomics and catalysis due to their excellent magnetic responsiveness, enormous specific surface area and readiness for surface modifications. Through a carefully designed surface modification of Mag-MSNs, the performance and application prospects of the material are greatly improved. Typically, the introduction of various molecular matrices into the shell of Mag-MSNs facilitates the combination of surface modifications and magnetic separation technology. So far, as sustainable chemistry is concerned, it is important to recover the functionalized core-shell Mag-MSNs after the reaction and reuse them without losing activity. In this review, the design conceptions and the construction of core-shell Mag-MSNs are discussed. Furthermore, various surface modification approaches of core-shell Mag-MSNs are summarized, and recent applications of these functionalized nanomaterials in the fields of biomedicine, catalysis, proteomics and wastewater treatment are exemplified.

Synthesis of sulphonic acid functionalized magnetic mesoporous silica for Cu(II) and Co(II) adsorption

Sulphonic acid functionalized core-shell magnetic mesoporous silica nanoparticles have been synthesized and used for preconcentration and enrichment of Cu(II) and Co(II). Mercapto groups were introduced via co-condensation which were then oxidized by H2O2 to incorporate the sulphonic acid functionality on the silica shell. The higher surface area of the sorbent and magnetic core simplified the extraction process. The adsorption of Cu(II) and Co(II) was achieved in less than 30 min at pH 7. The data showed that the adsorption mechanism followed pseudo-second order rate. The experimental data fits well in Langmuir, Freundlich and Temkin adsorption models. The maximum adsorption capacities for Cu(II) and Co(II) were 132 mg/g and 99.1 mg/g respectively. The newly synthesized material was successfully employed to develop an efficient preconcentarion method prior to the analysis of Cu(II) and Co(II) by graphite furnace atomic absorption spectrometer (GFAAS). The factors affecting the analysis were optimized and interferences from co-existing ions were also investigated. The detection limits for Cu(II) and Co(II) were 20 ng/L and 27 ng/L respectively. The results indicate that the new sorbent can be used for efficient preconcentration of Cu(II) and Co(II) from complex environmental samples.

A facile design of smart silica nanocarriers via surface-initiated RAFT polymerization as a dual-stimuli drug release platform

The rational design of hybrid nanostructures with an active core and a modified shell can promote several biological applications. Herein, a coating platform has been developed to obtain monodispersed core-shell magnetic mesoporous silica nanocarriers. The surface of silica shells has been successfully modified by disulfide bonds and the photoresponsive polymer, poly(2-nitrobenzyl acrylate) (PNBA), via RAFT polymerization using azobisisobutyronitrile (AIBN) as a thermal initiator. The results showed that these nanocarriers have nanospherical morphologies with high porosity, large surface areas, and suitable pore volumes. Furthermore, ibuprofen (IBU) as a model drug has been loaded easily into the polymeric nanocontainers with a high loading content, followed by coating with β-Cyclodextrin (β-CD) as effective gatekeeper molecules. Treating these nanocarriers with ultraviolet light causes the photocleavage of o-nitrobenzyl ester moieties contained in the growing polymer chains. The controlled release of the loaded IBU cargo can be achieved by ultraviolet light, or reduction cleavable of the disulfide bond, or both together. Interestingly, the magnetic core can enhance the release process through magnetic guiding and pushing the nanocarriers to the targeted sites by using an external magnet or a directed magnetic field. The prepared photodegradable polymer nanocarriers can be widely applied in the fields of controlled drug delivery systems (DDS) and pharmacologically active polymers.

Synthesis and in vitro testing of thermoresponsive polymer-grafted core-shell magnetic mesoporous silica nanoparticles for efficient controlled and targeted drug delivery

In this work, thermoresponsive polymer grafted magnetic mesoporous silica nanoparticles were prepared, fully characterized and tested as controlled drug delivery systems. For this purpose, iron oxide nanoparticles coated with mesoporous silica shell were grafted with poly(N-isopropylacrylamide-co-3-(methacryloxypropyl)trimethoxysilane) (PNIPAM-co-MPS). The grafting and polymerization on the as-prepared nanoparticles were performed in one-step procedure. Using this methodology, the polymer was successfully grafted mainly onto the silica surface, leaving the mesopores empty for the drug loading. The prepared hybrid nanoparticles (MMSNP-PNIPAM-co-MPS) showed high magnetization saturation (19.5 emu g−1) and high specific surface area (505 m2 g−1) and pore volume (0.29 cm3 g−1). Ibuprofen was used as a model drug to test the performance of the hybrid particles as thermosensitive drug delivery systems. For this, in vitro drug delivery tests were conducted below (25 °C) and above (40 °C) the lower critical solution temperature (LCST) of the polymer (PNIPAM-co-MPS). Considerable difference (80%) in the ibuprofen release at these two temperatures and a fast and complete release of the drug at 40 °C was observed. These results suggest that the thermoresponsive copolymer acts as a gatekeeper for the temperature-controlled release of the drug loaded inside the mesopores. Therefore, MMSNP-PNIPAM-co-MPS are promising magnetic and thermoresponsive nanocarriers for targeted delivery of therapeutic substances.

Core–Shell Magnetic Mesoporous Silica Microspheres with Large Mesopores for Enzyme Immobilization in Biocatalysis

Magnetic mesoporous silica microspheres with core-shell structure and large pores are highly desired in macromolecules delivery and biocatalysis, biospeparation, and adsorption. In this work, a controllable solvent evaporation induced solution-phase interface co-assembly approach was developed to synthesize core-shell structural magnetic mesoporous silica microspheres with ultralarge mesopore size (denoted as LP-MMS). The synthesis was achieved by employing large-molecular-weight amphiphilic block copolymers poly(ethylene oxide)- block-poly(methyl methacrylate) (PEO- b-PMMA) and small surfactant cetyltrimethylammonium bromide as co-templates, which can co-assemble with silica source in tetrahydrofuran/water solutions. The obtained LP-MMS microspheres possess uniform rasberry-like morphology with a diameter of 600 nm, large primary spherical mesopores (ca. 36 nm), large specific surface area (348 m2/g), high specific pore volume (0.59 cm3/g), and fast magnetic responsivity with high magnetization (15.9 emu/g). The mesopore morphology can be transformed from spherical to cylindrical through introducing a shearing force during the interfacial co-assembly in the synthesis system. The designed LP-MMS microspheres turn out to be good carriers for enzyme (trypsin) immobilization with a high loading capacity of 80 μg/mg and demonstrate excellent biocatalysis efficiency up to 99.1% for protein digestion within 30 min and good recycling stability with negligible decay in digestion efficiency after reuse for five times.

Amphiphilic Block Copolymers Directed Interface Coassembly to Construct Multifunctional Microspheres with Magnetic Core and Monolayer Mesoporous Aluminosilicate Shell.

Core-shell magnetic porous microspheres have wide applications in drug delivery, catalysis and bioseparation, and so on. However, it is great challenge to controllably synthesize magnetic porous microspheres with uniform well-aligned accessible large mesopores (>10 nm) which are highly desired for applications involving immobilization or adsorption of large guest molecules or nanoobjects. In this study, a facile and general amphiphilic block copolymer directed interfacial coassembly strategy is developed to synthesize core-shell magnetic mesoporous microspheres with a monolayer of mesoporous shell of different composition (FDUcs-17D), such as core-shell magnetic mesoporous aluminosilicate (CS-MMAS), silica (CS-MMS), and zirconia-silica (CS-MMZS), open and large pores by employing polystyrene-block-poly (4-vinylpyridine) (PS-b-P4VP) as an interface structure directing agent and aluminum acetylacetonate (Al(acac)3 ), zirconium acetylacetonate, and tetraethyl orthosilicate as shell precursors. The obtained CS-MMAS microspheres possess magnetic core, perpendicular mesopores (20-32 nm) in the shell, high surface area (244.7 m2 g-1 ), and abundant acid sites (0.44 mmol g-1 ), and as a result, they exhibit superior performance in removal of organophosphorus pesticides (fenthion) with a fast adsorption dynamics and high adsorption capacity. CS-MMAS microspheres loaded with Au nanoparticles (≈3.5 nm) behavior as a highly active heterogeneous nanocatalyst for N-alkylation reaction for producing N-phenylbenzylamine with a selectivity and yields of over 90% and good magnetic recyclability.

A systematic investigation of the bio-toxicity of core-shell magnetic mesoporous silica microspheres using zebrafish model

In this work, shearing interface coassembly in biliquid phase systems is employed to synthesize biocompatible core-shell magnetic mesoporous silica microspheres with uniform size of about 600 nm, perpendicular mesopores of 6.0 nm and large pore volume of 0.77 cm3/g. The toxicology assays based on the zebrafish model was conducted to test under a high-throughput manner for the biosafety of Fe3O4@RF@mSiO2 microspheres. The highest no observed toxic effect concentration (NOEC) estimated by the acute toxicity assay for the microspheres was 1.6 mg/mL. The estimated number (measured by ICP-MS) of the penetrated microspheres at this concentration was 2 × 106 per embryo. The results of three different performed toxicity assays show no overall acute toxicity, teratogenicity, or neurotoxicity of the microspheres on zebrafish embryos at any of the tested concentrations (from 0.1 to 1.6 mg/mL) via its multifunctional microstructure. Here, gemcitabine (GEM) as a model of anti-cancer drug was loaded into the mesopores of Fe3O4@RF@mSiO2 microspheres to study their drug release behavior. The microspheres were found to exhibit pH responsive property, which benefits for the GEM release under cancer therapy. Overall, this study offers promising avenue for effective evaluation of magnetic core-shell microspheres for drug delivery and cancer therapy applications.

Dual-target recognition sandwich assay based on core-shell magnetic mesoporous silica nanoparticles for sensitive detection of breast cancer cells

A novel dual-target recognition sandwich strategy for selective capture and detection of MCF-7 breast cancer cells based on core-shell magnetic mesoporous silica (Fe3O4@nSiO2@mSiO2@apt) nanoparticles was developed. Fe3O4@nSiO2@mSiO2@apt nanoparticles, which were prepared by a layer-by-layer method and were used for the first time to capture cancer cells, have large surface areas, particularly accessible mesochannels, and good biocompatibility, enabling aptamers to be compactly anchored onto the surface of the core-shell magnetic nanoparticles. A mucin 1 protein (MUC1)-targeted Fe3O4@nSiO2@mSiO2@apt nanoparticle was used as an affinity magnetic isolate material to capture target MCF-7 cells selectively and to reduce interference through affinity interaction between the anti-MUC1 aptamer and the MUC1 protein over-expressed on the surface of the MCF-7 cells. Meanwhile, a folate receptor (FR)-targeted affinity fluorescent probe (FA-BSA-FITC) was developed by coupling folic acid and FITC to the surface of BSA, enabling high sensitivity, selective fluorescent labeling of FR over-expressed MCF-7 cells. A dual-target recognition sandwich assay was developed based on the MUC1-targeted magnetic nanoparticles and the FR-targeted fluorescent probes. Under optimum conditions, a quantitative assay of MCF-7 cells was achieved with a dynamic range of 102–105 cells/mL (R2 = 0.9991). This assay showed high specificity and sensitivity to the target MCF-7 cells. Finally, the proposed strategy could be extended to detect MCF-7 cells in human plasma and whole blood with a recovery range of 86.1–104.0% and a RSD range of 1.2–8.4%, respectively. This indicates that the dual-target recognition method developed in this research exhibits good selectivity, anti-interference capability, and reliability even in plasma and whole blood samples and is more suitable for complex samples than previous targeted assays. Therefore, the approach proposed here may have great potential for early breast cancer diagnosis.

Biological Fate of Fe₃O₄ Core-Shell Mesoporous Silica Nanoparticles Depending on Particle Surface Chemistry.

The biological fate of nanoparticles (NPs) for biomedical applications is highly dependent of their size and charge, their aggregation state and their surface chemistry. The chemical composition of the NPs surface influences their stability in biological fluids, their interaction with proteins, and their attraction to the cell membranes. In this work, core-shell magnetic mesoporous silica nanoparticles (Fe3O4@MSN), that are considered as potential theranostic candidates, are coated with polyethylene glycol (PEG) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayer. Their biological fate is studied in comparison to the native NPs. The physicochemical properties of these three types of NPs and their suspension behavior in different media are investigated. The attraction to a membrane model is also evaluated using a supported lipid bilayer. The surface composition of NPs strongly influences their dispersion in biological fluids mimics, protein binding and their interaction with cell membrane. While none of these types of NPs is found to be toxic on mice four days after intravenous injection of a dose of 40 mg kg−1 of NPs, their surface coating nature influences the in vivo biodistribution. Importantly, NP coated with DMPC exhibit a strong accumulation in liver and a very low accumulation in lung in comparison with nude or PEG ones.

Nitrogen rich core–shell magnetic mesoporous silica as an effective adsorbent for removal of silver nanoparticles from water

The production and increasing use of silver nanoparticles (AgNPs) obviously results in their release into the environment, leading to a risk to the environment due to their toxic effects. Thus, the removal of AgNPs from water is highly needed. Here, we demonstrate that nitrogen rich (∼10% nitrogen content) core–shell magnetic mesoporous silica is a promising adsorbent for the removal of AgNPs. For this, the poly(ethylenimine) functionalized core–shell magnetic mesoporous silica composites (Fe3O4@SiO2-PEI) were prepared, and characterized by TEM, FT-IR, XRD, TG and N2 adsorption–desorption. The removal of AgNPs by Fe3O4@SiO2-PEI as a function of contact time, concentration of AgNPs, solution pH and ionic strength were studied. The adsorption kinetic data could be described by the pseudo-second-order rate model. Both Langmuir and Freundlich models fitted the adsorption data well. The adsorption capacity for AgNPs is 909.1mg/g, which is 5–181 times higher than that of the previously reported adsorbents for AgNPs. Interestingly, the silver adsorbed onto Fe3O4@SiO2-PEI exhibits highly catalytic activity for 4-nitropheol (4-NP) reduction with a rate constant of 0.072min−1, which is much higher than those by other AgNPs reported before. The silver-loaded Fe3O4@SiO2-PEI promises good recyclability for at least five cycles, showing great potential in practical applications.