Magnetic Silica Microspheres Research Articles

Smart Hydrophilic Modification of Magnetic Mesoporous Silica with Zwitterionic l-Cysteine for Endogenous Glycopeptides Recognition

There are still few reports about endogenous glycosylated peptides although the significance of the study of them has been confirmed since they may provide higher sensitivity and specificity in clinical practice. In this work, magnetic mesoporous silica microspheres were endowed with strong hydrophilicity by a simple and smart modification way to l-cysteine, which was attributed to the bond formation of Fe–S. The microsphere (denoted as l-Cys-Fe3O4@mSiO2) was composed of Fe3O4 core, mesoporous silica layer, and innumerable perpendicularly aligned mesopores, as well as abundant l-cysteine in the mesopores. Thanks to the excellent hydrophilicity of l-cysteine probe, the l-Cys-Fe3O4@mSiO2 microspheres showed strong recognition ability toward glycopeptides. Owing to the superparamagnetic cores well encapsulated in microspheres, the whole process is quite time-saving by magnetic separation. Also, due to the appropriate pore size of the l-Cys-Fe3O4@mSiO2 microspheres, the extraction method exhibited good size-e...

Hydrophilic phytic acid-functionalized magnetic dendritic mesoporous silica nanospheres with immobilized Ti4+: A dual-purpose affinity material for highly efficient enrichment of glycopeptides/phosphopeptides

In this work, magnetic mesoporous silica microspheres (Mag-MSMs) with ordered radial mesochannels were fabricated by a self-assembly synthesis in chlorobenzene-water mixed system. Then, the obtained Mag-MSMs were modified with polyethyleneimine (PEI), phytic acid (PA) and Ti4+ (denoted as Mag-MSMs@PEI-PA-Ti4+) via layer by layer (LbL) assembly. Due to the excellent hydrophilicity of PEI and PA and the large amount of Ti4+, the Mag-MSMs@PEI-PA-Ti4+ possessed combined properties of hydrophilic interaction liquid chromatography (HILIC)- and immobilized metal ion affinity chromatography (IMAC)-based materials, which could be used as a dual-purpose material for N-glycopeptides or phosphopeptides enrichment. The proposed Mag-MSMs@PEI-PA-Ti4+ exhibited an outstanding performance for N-glycopeptides enrichment (selectivity: IgG/BSA = 1:1000; sensitivity: 0.5 fmol/μL IgG) and phosphopeptides enrichment (selectivity: α-casein/BSA=1:5000; sensitivity: 0.2 fmol/μL α-casein). Furthermore, after enrichment with Mag-MSMs@PEI-PA-Ti4+, a total of 276 N-glycopeptides assigned to 132 glycoproteins were identified from 2 μL human serum and 1645 phosphopeptides corresponding to 704 phosphoproteins were identified from 200 μg HeLa cell extracts.

Synthesis of recyclable magnetic mesoporous RH-FSBA photoelectrocatalyst with double cavity structure

In this paper, a series of BiOCl-Ag/AgBr heterojunctions supported by magnetic mesoporous silica microspheres with double cavity structure (RH-FSBAx) were successfully synthesized. For the combination of double cavity structure and orderly mesoporous opening structure of magnetic mesoporous RH-FSBAx photoelectrocatalysts, they exhibited ultra-strong enriching property to targeted pollutants. For the formation of BiOCl-AgBr heterojunctions, superior photosensitization of AgBr and existence of metallic Ag plasmas with surface plasmon resonance (SPR) effect, the photoelectrocatalysts exhibited enhanced visible light photoelectrocatalytic performance. Furthermore, the photoelectrocatalyst can be recycled easily by magnetic separation for its superior magnetic response. Particularly, the magnetic mesoporous RH-FSBA0.03 photoelectrocatalyst exhibited the highest photoelectrocatalytic activity (k = 1.3 × 10−2 min−1) in degradation of acid fuchsin (AF) under visible light irradiation, and it was about 4 times of RH-FSB photoelectrocatalyst. Therefore, this novel photoelectrocatalyst can effectively decompose organic pollutants in water system under visible light irradiation by rapid enrichment and efficient photodegradation.

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.

Magnetic solid–phase extraction of tetracyclines using ferrous oxide coated magnetic silica microspheres from water samples

A novel magnetic solid–phase extraction approach was proposed for extraction of potential residues of tetracyclines (TCs) in tap and river water samples, based on Fe3O4@SiO2@FeO magnetic nanocomposite. Characterized results showed that the received Fe3O4@SiO2@FeO had distinguished magnetism and core–shell structure. Modified FeO nanoparticles with an ∼5 nm size distribution were homogeneously dispersed on the surface of the silica shell. Owing to the strong surface affinity of Fe (II) toward TCs, the magnetic nanocomposite could be applied to efficiently extract three TCs antibiotics, namely, oxytetracycline, tetracycline and chlortetracycline from water samples. Several factors, such as sorbent amount, pH condition, adsorption and desorption time, desorption solvent, selectivity and sample volume, influencing the extraction performance of TCs were investigated and optimized. The developed method showed excellent linearity (R > 0.9992) in the range of 0.133–333 μg L−1, under optimized conditions. The limits of detection were between 0.027 and 0.107 μg L−1 for oxytetracycline, tetracycline and chlortetracycline, respectively. The feasibility of this method was evaluated by analysis of tap and river water samples. The recoveries at the spiked concentration levels ranged from 91.0% to 104.6% with favorable reproducibility (RSD < 4%).

Plasmolysis-Inspired Nanoengineering of Functional Yolk-Shell Microspheres with Magnetic Core and Mesoporous Silica Shell.

Yolk-shell nanomaterials with a rattle-like structure have been considered ideal carriers and nanoreactors. Traditional methods to constructing yolk-shell nanostructures mainly rely on multistep sacrificial template strategy. In this study, a facile and effective plasmolysis-inspired nanoengineering strategy is developed to controllably fabricate yolk-shell magnetic mesoporous silica microspheres via the swelling-shrinkage of resorcinol-formaldehyde (RF) upon soaking in or removal of n-hexane. Using Fe3O4@RF microspheres as seeds, surfactant-silica mesostructured composite is deposited on the swelled seeds through the multicomponent interface coassembly, followed by solvent extraction to remove surfactant and simultaneously induce shrinkage of RF shell. The obtained yolk-shell microspheres (Fe3O4@RF@void@mSiO2) possess a high magnetization of 40.3 emu/g, high surface area (439 m2/g), radially aligned mesopores (5.4 nm) in the outer shell, tunable middle hollow space (472-638 nm in diameter), and a superparamagnetic core. This simple method allows a simultaneous encapsulation of Au nanoparticles into the hollow space during synthesis, and it leads to spherical Fe3O4@RF@void-Au@mSiO2 magnetic nanocatalysts, which show excellent catalysis efficiency for hydrogenation of 4-nitrophenol by NaBH4 with a high conversion rate (98%) and magnetic recycling stability.

Synergetic integration of laccase and versatile peroxidase with magnetic silica microspheres towards remediation of biorefinery wastewater.

In this study, a tailor-made biocatalyst consisting of a co-immobilized lignolytic enzyme cascade on multi-functionalized magnetic silica microspheres (MSMS) was developed. Physical adsorption was the most promising strategy for the synthesis of individual immobilized laccase (IL), immobilized versatile peroxidase (IP), as well as co-immobilized laccase (Lac) and versatile peroxidase (VP) with an enzyme activity recovery of about 79, 93, 27, and 27.5%, respectively. Similarly, the biocatalytic load of 116, 183, 23.6, and 31U/g was obtained for IL, IP, and co-immobilized Lac and VP, respectively. The co-immobilized enzyme system exhibited better pH stability than the free and individual immobilized system by retaining more than 100% residual activity at pH7.0 after a 150-h incubation; whereas, the thermal stability and kinetics of the co-immobilized biocatalyst were not much improved. IL and IP could be recycled for 10cycles after which they retained 31 and 44% of their initial activities. Co-immobilized Lac and VP were reused for ten consecutive cycles at the end of which Lac activity was depleted, and 37% of VP activity was left. Free enzymes, IL, IP, co-immobilized Lac, and VP were applied to biorefinery wastewater (BRW) in a batch study to investigate the transformation of phenolic contaminants over a period of 5days. The major classes of phenolic constituents in terms of their order of removal in a Lac-VP system was phenol >2-chlorophenol > trichlorophenol > dichlorophenol > cresols > dimethylphenol >2 methyl- 4, 6-dinitrophenol > 4-nitrophenol > tetrachlorophenols > pentachlorophenol. The free enzymes and individually immobilized enzymes resulted in 80% dephenolization in 5days. By contrast, the co-immobilized biocatalyst provided rapid dephenolization yielding the same 80% removal within 24h and 96% removal of phenols in 60h after which the system stabilized, which is the major advantage of the co-immobilized biocatalyst. ᅟ Graphical abstract.

Selective adsorption of chiral mandelic acid by molecularly imprinted poly(dimethylaminoethyl methacrylate) on surface of magnetic silica microspheres

ABSTRACTA chiral mandelic acid (MA) molecularly imprinted microsphere with magnetism was designed in this paper. Firstly, a Fe3O4 core was synthesized by a simple and classical solvot hermal method. Then the SiO2 shell was coated to the surface of Fe3O4 by a improved Stober method. Finally, dimethylaminoethyl methacrylate (DMAEMA) was graft-polymerized onto the surfaces of Fe3O4 @SiO2 microspheres, and the molecular imprinting was conducted with S-MA as template molecule. The results of ultraviolet (UV) spectroscopy detection indicated that the magnetic chiral molecular imprinting had good selectivity for S-Mandelic acid and its enantiomer.

Nanoengineering of Core-Shell Magnetic Mesoporous Microspheres with Tunable Surface Roughness.

Functional core-shell mesoporous microspheres with integrated functions, controlled structure, and surface properties and morphologies have received increasing attention due to their excellent physicochemical properties. Herein, core-shell magnetic mesoporous materials with cauliflower-like morphology and tunable surface roughness have been synthesized through a kinetics-controlled interface co-assembly and deposition of mesostructured nanocomposites on Fe3O4@RF microspheres (RF refers to resorcinol formaldehyde resin). The obtained microspheres, synthesized via this interface nanoengineering method, possess well-defined sandwich structure with a tunable rough morphology, uniform size (560-1000 nm), perpendicularly aligned mesopores (∼5.7 nm) in the outer shell, RF-protected magnetic responsive core, high surface area up to 382 m2/g, and large pore volume of 0.66 cm3/g. As a result of the unique surface features and magnetic properties, these microspheres exhibit excellent performance in stabilizing and oxygen-free manipulating aqueous solutions in petroleum ether by a magnetic field. They also exhibit superior cell uptake properties compared with traditional smooth core-shell magnetic mesoporous silica microspheres, opening up the possible applications in fast drug delivery in cancer therapy.

PLA–PEG‐grafted hollow magnetic silica microspheres as the carrier of iodinated contrast media

ABSTRACTIn this work, hollow magnetic silica microspheres (HMS) were synthesized by the template method, polyethylene glycol (PEG) and poly(lactic acid) (PLA)‐grafted hollow magnetic microspheres HMS@PLA–PEG were successfully prepared through ring‐opening polymerization method. Ioversol was loaded into HMS@PLA–PEG by physical coating, and the drug loading content was up to 39.4%. It also exhibited a slower and steady release than HMS and the cumulative release was up to 55.1% at physiological pH, which implied the PLA–PEG could prolong the circulation time. Meanwhile, to improve the efficiency of contrast, we have developed composite microspheres encapsulating superparamagnetic iron oxide (Fe3O4) as magnetic target for increasing the local concentration of the contrast media and expecting to put magnetic resonance imaging (MRI) and computed tomography (CT) technology together to apply in medical applications. Furthermore, the cytotoxicity assay in vitro was also investigated. The results revealed the ioversol‐loaded HMS@PLA–PEG exhibited low toxicity at a higher concentration, even it is up to 400 μg/mL. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44914.

Rational synthesis of hierarchical magnetic mesoporous silica microspheres with tunable mesochannels for enhanced enzyme immobilization.

Hierarchical magnetic mesoporous silica microspheres (MMSMs) with a core-shell structure have been fabricated through an improved water/oil biphase synthesis strategy. We firstly reported that the mesopore size can be readily tuned from 6.1 to 11.4 nm by the synergistic effect of surfactant concentration and an amphiphilic agent, thus holding a bright future in many possible applications.

Synthesis of core–shell structured magnetic mesoporous silica microspheres with accessible carboxyl functionalized surfaces and radially oriented large mesopores as adsorbents for the removal of heavy metal ions

Core–shell structured mesoporous silica with accessible carboxyl functionalized surfaces and radial oriented large mesopores was fabricated as a recyclable adsorbent for the adsorption of Cd(ii), Cu(ii), and Pb(ii).

Adsorption of uranium(VI) from aqueous solution using phosphonic acid-functionalized silica magnetic microspheres

The phosphonic acid-functionalized silica magnetic microspheres (PA-SMM) were successfully synthesized for U(VI) adsorption. The PA-SMM exhibited higher adsorption capacity for U(VI) compared to unmodified silica magnetic microspheres due to the high affinity of phosphonic acid groups with U(VI). The adsorption was dominated by inner sphere surface chelation and kinetically followed the pseudo-second-order equation. The adsorption isotherms fitted well to the Langmuir model, with the maximum adsorption capacity of 76.9 mg/g at 298 K and pH 5.0. Thermodynamic parameters indicated the endothermic and spontaneous nature of U(VI) adsorption. The PA-SMM could be regenerated using 0.2 M EDTA-0.5 M HNO3 as the eluent.

Preparation of core-shell structure Fe3 O4 @SiO2 superparamagnetic microspheres immoblized with iminodiacetic acid as immobilized metal ion affinity adsorbents for His-tag protein purification.

The core-shell structure Fe3 O4 /SiO2 magnetic microspheres were prepared by a sol-gel method, and immobiled with iminodiacetic acid (IDA) as metal ion affinity ligands for protein adsorption. The size, morphology, magnetic properties and surface modification of magnetic silica nanospheres were characterized by various modern analytical instruments. It was shown that the magnetic silica nanospheres exhibited superparamagnetism with saturation magnetization values of up to 58.1 emu/g. Three divalent metal ions, Cu(2+) , Ni(2+) and Zn(2+) , were chelated on the Fe3 O4 @SiO2 -IDA magnetic microspheres to adsorb lysozyme. The results indicated that Ni(2+) -chelating magnetic microspheres had the maximum adsorption capacity for lysozyme of 51.0 mg/g, adsorption equilibrium could be achieved within 60 min and the adsorbed protein could be easily eluted. Furthermore, the synthesized Fe3 O4 @SiO2 -IDA-Ni(2+) magnetic microspheres were successfully applied for selective enrichment lysozyme from egg white and His-tag recombinant Homer 1a from the inclusion extraction expressed in Escherichia coli. The result indicated that the magnetic microspheres showed unique characteristics of high selective separation behavior of protein mixture, low nonspecific adsorption, and easy handling. This demonstrates that the magnetic silica microspheres can be used efficiently in protein separation or purification and show great potential in the pretreatment of the biological sample.

Preparation of phenyl-functionalized magnetic mesoporous silica microspheres for the fast separation and selective enrichment of phenyl-containing peptides.

Peptide enrichment before mass spectrometry analysis is essential for large-scale peptidomic studies, but challenges still remain. Herein, magnetic mesoporous silica microspheres with phenyl group modified interior pore walls were prepared by a facile sol-gel coating strategy, and were successfully applied for selective enrichment of phenyl-containing peptides in complex biological samples. The newly prepared nanomaterials possessed abundant silanol groups in the exterior surface and numerous phenyl groups in the interior pore walls, as well as a large surface area (592.6 m2 /g), large pore volume (0.33 cm3 /g), uniform mesopores (3.8 nm), strong magnetic response (29.3 emu/g), and good dispersibility in aqueous solution. As a result of the unique structural properties and size-exclusion effect, the core-shell phenyl-functionalized magnetic mesoporous silica microspheres exhibited excellent performance in fast separation and selective enrichment of phenyl-containing peptides, and the adsorption capacity for bradykinin reached 22.55 mg/g. In addition, selective enrichment of phenyl-containing peptides from complex samples that are consist of peptides, large proteins, and human serum were achieved by using the as-prepared microspheres, followed by high-performance liquid chromatography withultravioletdetection and electrospray ionization quadrupole time-of-flight mass spectrometry analysis. These results demonstrated the as-prepared microspheres would be a potential candidate for endogenous phenyl-containing peptides enrichment and biomarkers discovery in peptidome analysis.

An Interface Coassembly in Biliquid Phase: Toward Core-Shell Magnetic Mesoporous Silica Microspheres with Tunable Pore Size.

Core-shell magnetic mesoporous silica microspheres (Magn-MSMs) with tunable large mesopores in the shell are highly desired in biocatalysis, magnetic bioseparation, and enrichment. In this study, a shearing assisted interface coassembly in n-hexane/water biliquid systems is developed to synthesize uniform Magn-MSMs with magnetic core and mesoporous silica shell for an efficient size-selective biocatalysis. The synthesis features the rational control over the electrostatic interaction among cationic surfactant molecules, silicate oligomers, and Fe3O4@RF microspheres (RF: resorcinol formaldehyde) in the presence of shearing-regulated solubilization of n-hexane in surfactant micelles. Through this multicomponent interface coassembly, surfactant-silica mesostructured composite has been uniformly deposited on the Fe3O4@RF microspheres, and core-shell Magn-MSMs are obtained after removing the surfactant and n-hexane. The obtained Magn-MSMs possess excellent water dispersibility, uniform diameter (600 nm), large and tunable perpendicular mesopores (5.0-9.0 nm), high surface area (498-623 m(2)/g), large pore volume (0.91-0.98 cm(3)/g), and high magnetization (34.5-37.1 emu/g). By utilization of their large and open mesopores, Magn-MSMs with a pore size of about 9.0 nm have been demonstrated to be able to immobilize a large bioenzyme (trypsin with size of 4.0 nm) with a high loading capacity of ∼97 μg/mg via chemically binding. Magn-MSMs with immobilized trypsin exhibit an excellent convenient and size selective enzymolysis of low molecular proteins in the mixture of proteins of different sizes and a good recycling performance by using the magnetic separability of the microspheres.

Biotemplate-directed fabrication of size-controlled monodisperse magnetic silica microspheres

Biotemplating is an effective strategy to obtain morphology-controllable materials with structural specificity, complexity, and corresponding unique functions. Herein we take advantage of the unique heavy-metal-ion biosorption behavior of cyanobacteria cells to fabricate Fe3O4/cell composites. Meanwhile, cyanobacteria cells served as a biotemplate for fabricating solid and hollow magnetic silica microspheres (MSMs). The obtained MSMs retained the original morphology of the cells, and exhibited excellent monodispersity and uniform spherical shape with narrow size distribution. Furthermore, they demonstrated ferromagnetic behavior at room temperature when measured using a vibrating sample magnetometer.

Hydrophilic gallic acid–imprinted polymers over magnetic mesoporous silica microspheres with excellent molecular recognition ability in aqueous fruit juices

Hydrophilic molecularly imprinted polymers (MIPs) for gallic acid (GA) were prepared with excellent recognition ability in an aqueous solution. The proposed MIPs were designed by self-polymerization of dopamine (DA) on magnetic mesoporous silica (Fe3O4@SiO2@mSiO2, MMS) using GA as template. Resulting Fe3O4@SiO2@mSiO2@MIPs (MMS–MIPs) were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), vibrating sample magnetometer (VSM), and evaluated by adsorption isotherms/kinetics and competitive adsorption. The adsorption behavior between GA and MMS–MIPs followed Langmuir and Sips adsorption isotherms with a maximum adsorption capacity at 88.7mg/g and pseudo-second-order reaction kinetics with fast binding (equilibrium time at 100min). In addition, MMS–MIPs showed rapid magnetic separation (10s) and stability (retained 95.2% after six cycles). Subsequently, MMS–MIPs were applied for the selective extraction and determination of GA from grape, apple, peach and orange juices (4.02, 3.91, 5.97, and 0.67μg/g, respectively). Generally, the described method may pave the way towards rationally designing more advanced hydrophilic MIPs.

Novel molecular imprinted polymers over magnetic mesoporous silica microspheres for selective and efficient determination of protocatechuic acid in Syzygium aromaticum

Improving sites accessibility can increase the binding efficiency of molecular imprinted polymers (MIPs). In this work, we firstly synthesized MIPs over magnetic mesoporous silica microspheres (Fe3O4@mSiO2@MIPs) for the selective recognition of protocatechuic acid (PCA). The resulting Fe3O4@mSiO2@MIPs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR), thermo-gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), and vibration sample magnetometer (VSM), and evaluated by adsorption isotherms/kinetics and competitive adsorption. The maximum adsorption capacity of PCA on Fe3O4@mSiO2@MIPs was 17.2mg/g (2.3 times that on Fe3O4@SiO2@MIPs). In addition, Fe3O4@mSiO2@MIPs showed a short equilibrium time (140min), rapid magnetic separation (5s) and high stability (retained 94.4% after six cycles). Subsequently, Fe3O4@mSiO2@MIPs were successfully applied for the selective and efficient determination of PCA (29.3μg/g) from Syzygium aromaticum. Conclusively, we combined three advantages into Fe3O4@mSiO2@MIPs, namely, Fe3O4 core for quick separation, mSiO2 layer for enough accessible sites, and surface imprinting MIPs for fast binding and excellent selectivity, to extract PCA from complex systems.

Gold nanoparticle modified magnetic fibrous silica microspheres as a highly efficient and recyclable catalyst for the reduction of 4-nitrophenol

Au nanoparticles were immobilized on magnetic fibrous silica microspheres as highly active and recyclable nanocatalysts for the catalytic reduction of 4-nitrophenol to 4-aminophenol.