Hydrophilic dual-responsive magnetite/PMAA core/shell microspheres with high magnetic susceptibility and ph sensitivity via distillation-precipitation polymerization

Geldanaycin-encapsulated magnetic nanoparticle for isolation of myosin in proteomics

The grafting of a drug molecule, i.e., geldanamycin (GA) onto polyethyleneimine (PEI)-coated magnetic nanoparticle produces a novel composite, GA@Fe3O4-NH2. The composite is confirmed by characterizations with FT-IR, Raman, SEM, EDS, VSM and TEM. Due to the high binding-affinity of GA with myosin heavy chain (MYH), GA@Fe3O4-NH2 exhibits excellent adsorption performance towards myosin. Consequently, a solid-phase extraction procedure is established for highly efficient and selective separation of myosin from pig heart extract. At pH 6.0, an adsorption efficiency of 97.1 % is achieved for treating 100 μg mL-1 myosin (0.1 mL) with 0.1 mg GA@Fe3O4-NH2 as adsorbent. The adsorption behavior of myosin onto GA@Fe3O4-NH2 fits Langmuir model, corresponding to a theoretical adsorption capacity of 518.1 mg g-1. The adsorbed myosin can be readily recycled by the SDS solution (1 %, m/m) with an elution efficiency of 91.8 %. According to circular dichroism spectroscopy, the conformational changes of myosin during adsorption and elution are reversible. For practical application, myosin is successfully isolated from the pig left ventricular protein extract with GA@Fe3O4-NH2, and SDS-PAGE and LC-MS/MS showed that myosin had high purity and a total of 716 proteins could be identified. Significantly, Geldamycin-encapsulated magnetic nanoparticle for the separation of myosin well exploits the potential of the nanomaterials modified by drug molecules in the separation and purification of target proteins.

Magnetic Assembly of Eu-Doped NaYF4 Nanorods for Field-Responsive Linearly and Circularly Polarized Luminescence

Colloidal assembly has emerged as an effective avenue for achieving polarized light emission. Here, we showcase the efficacy and versatility of the magnetic colloidal assembly in enabling both linearly and circularly polarized luminescence. Colloidal europium-doped NaYF4 nanorods with surface-bound Fe3O4 nanoparticles are magnetically assembled into linear or chiral superstructures using corresponding fields created in permanent magnets. In a uniform magnetic field generated by opposing poles, the assemblies exhibit photoluminescence with intensity tunable in response to the magnetic field direction, which is higher when the nanorods are perpendicular to light propagation than when they are parallel. The obtained superstructures display strong linearly polarized luminescence when the nanorods are aligned vertically, exhibiting a high degree of polarization up to 0.61. In a quadrupole chiral field generated by permanent magnets, the assemblies emit left-handed or right-handed polarized light depending on the position of the sample placement, attaining a g-factor of 0.04. Furthermore, the superstructures immobilized in a hydrogel film are found to retain their chirality, exhibiting opposite chiroptical responses depending on the sample orientation. The magnetic colloidal assembly approach facilitates the convenient and efficient generation of polarized light emissions from nonmagnetic luminescent materials, thus creating opportunities for tailoring light behavior in developing innovative optoelectronic devices.

Magnetic nanoclusters mediated photothermal effect and macrophage modulation for synergistically photothermal immunotherapy of cancer

In tumor microenvironment, macrophages predominately exhibit M2-type functionalities which promote malignant progression and cancer metastasis, thus bring big hurdle to current anticancer strategies. Different approaches had been exploited to reverse...

β-Amyloid Peptide 1-42-Conjugated Magnetic Nanoparticles for the Isolation and Purification of Glycoproteins in Egg White

Aβ_1-42-conjugated magnetic nanoparticles, Aβ_1-42@MNP, were prepared by covalently coupling Aβ_1-42 to hyperbranched polyethyleneimine (PEI)-modified magnetic nanoparticles via N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC). Aβ_1-42's high binding capacity to glycosyl groups facilitates Aβ_1-42@MNP composite to be a promising selective adsorbent for glycoproteins in egg whites. In our study, under conditions of pH 4.0, the adsorption efficiency of Aβ_1-42@MNP composite for ovalbumin (100 μg mL^-1) was 98.4% and its maximum adsorption capacity was 344.8 mg g ^-1; under the condition of pH 4.0 and 200 mmol L^-1 NaCl, its adsorption efficiencies for ovalbumin and ovotransferrin were 96.9% and 60.0%, respectively. According to these primary data, in practice, ovalbumin was removed from egg white by Aβ_1-42@MNP composite at pH 4.0 (step I), and then after adding NaCl until the final salt concentration reached 200 mmol L^-1 (pretreated egg white), we utilized the same adsorbent to further isolate/purify glycoproteins (step II). SDS-PAGE results showed that Aβ_1-42@MNP composite could largely remove ovalbumin in step I and could isolate/purify the remaining ovalbumin and ovotransferrin in step II. LC-MS/MS analysis results showed that the removal of ovalbumin reduced its percentage in egg white samples from 32.93% to 11.05% in step I and the remaining ovalbumin and ovotransferrin were enriched in step II, where the final percentage reached 11.6% and 12.6%, respectively. In summary, 81 protein species were identified after two-step extraction with Aβ_1-42@MNP on egg white, while only 46 protein species were identified directly from raw egg white without any pretreatment. This work well illustrates the excellent adsorption performance of Aβ_1-42@MNP composite to glycoproteins and its potential in the application of proteomic studies on low-abundance proteins in egg white.

Redox-Activated Near-Infrared-Responsive Polyoxometalates Used for Photothermal Treatment of Alzheimer's Disease

Adjustable structure, excellent physiochemical properties, and good biocompatibility render polyoxometalates (POMs) as a suitable drug agent for the treatment of Alzheimer's disease (AD). However, previous works using POMs against AD just focus on the inhibition of amyloid-β (Aβ) monomer aggregation. In consideration that both Aβ fibrils and reactive oxygen species (ROS) are closely associated with clinical development of AD symptoms, it would be more effective if POMs can disaggregate Aβ fibrils and eliminate ROS as well. Herein, a redox-activated near-infrared (NIR) responsive POMs-based nanoplaform (rPOMs@MSNs@copolymer) is developed with high photothermal effect and antioxidant activity. The rPOMs@MSNs@copolymer can generate local hyperthermia to disaggregate Aβ fibrils under NIR laser irradiation because of POMs (rPOMs) with strong NIR absorption. Furthermore, Aβ-induced ROS can be scavenged by the antioxidant activity of rPOMs. To the authors' knowledge, there is no report of using rPOMs for NIR photothermal treatment of AD. This work may promote the development of multifunctional inorganic agents for biomedical applications.

Development of hierarchical Fe3O4 magnetic microspheres as solid substrates for high sensitive immunoassays

Improving the detection sensitivity of enzyme linked immunosorbent assay (ELISA) is of the utmost importance for meeting the demand of early disease diagnosis. In this work, a sensitive solid substrate for ELISA, i.e., hierarchical iron oxide magnetic microspheres, Fe₃O₄@mSiO₂@poly[poly(ethylene glycol) methacrylate-co-glycidyl methacrylate], was developed via a novel surface-initiated photoiniferter-mediated polymerization (SI-PIMP) strategy. The magnetic microspheres consist of a magnetic Fe₃O₄ core that gives a high magnetic response, a 3D backbone, a mesoporous SiO₂ middle layer, that facilitates microsphere stability and provides anchoring sites, and polymer brushes, that serve as an antifouling and oriented antibody immobilization layer. As a result, the as-prepared microspheres possess a high antibody loading capacity, an enhanced detection signal and a dramatically improved sensitivity, resulting in a 25-fold improvement over conventional ELISA solid substrates.

A Near-Infrared Responsive Drug Sequential Release System for Better Eradicating Amyloid Aggregates

Polyphenol compounds, such as curcumin, rutin, rifampicin, can inhibit Aβ aggregation and decrease reactive oxygen species (ROS), and have received much attention in recent years for Alzheimer's disease (AD) treatment. However, the excess metal ions in amyloid plaque can chelate to polyphenol compounds. It significantly declines the efficacy of polyphenol compounds when used in the clinic. In this report, a near-infrared (NIR)-caged upconversion responsive system UCNP@SiO₂ @Cur/CQ is designed and synthesized to control drug sequential release by regulating NIR laser. When the system is irradiated at low intensity of the NIR laser, the caged metal chelator, clioquinol (CQ), is first released for removing free metal ions, which affects the efficacy of curcumin. Subsequently, the strongly caged curcumin is released with increasing the intensity of NIR light. In this way, the treatment efficacy of curcumin is improved. This NIR-caged drug release system can not only remove Cu²⁺ but also clean superfluous ROS. Therefore, developing controllable sequential drug releasing may provide clinical benefits of combination treatment of AD. To the best of our knowledge, this work reports for the first time that a sequentially controlled system can overcome the interference of metal ions on polyphenol compounds for AD treatment.

Biosensing Using Magnetic Particle Detection Techniques

Magnetic particles are widely used as signal labels in a variety of biological sensing applications, such as molecular detection and related strategies that rely on ligand-receptor binding. In this review, we explore the fundamental concepts involved in designing magnetic particles for biosensing applications and the techniques used to detect them. First, we briefly describe the magnetic properties that are important for bio-sensing applications and highlight the associated key parameters (such as the starting materials, size, functionalization methods, and bio-conjugation strategies). Subsequently, we focus on magnetic sensing applications that utilize several types of magnetic detection techniques: spintronic sensors, nuclear magnetic resonance (NMR) sensors, superconducting quantum interference devices (SQUIDs), sensors based on the atomic magnetometer (AM), and others. From the studies reported, we note that the size of the MPs is one of the most important factors in choosing a sensing technique.

A magnetite/PMAA nanospheres-targeting SERS aptasensor for tetracycline sensing using mercapto molecules embedded core/shell nanoparticles for signal amplification

Surface-enhanced Raman scattering (SERS) biosensors have promising potential in the field of antibiotics detection because of their ultrahigh detection sensitivity. This paper reports a rapid and sensitive SERS-based magnetic nanospheres-targeting strategy for sensing tetracycline (TTC) using aptamer-conjugated magnetite colloid nanocrystal clusters (MCNCs)-polymethacrylic acid (PMAA) magnetic nanospheres (MNs) as the recognition and the Au/PATP/SiO₂ (APS) as the labels. Initially, MNs were fabricated and conjugated with the aptamers through condensation reaction. MNs possessed high saturation magnetization (Ms) value of 71.5emu/g and excellent biocompatibility, which facilitated the rapid and easy magnetic separation. Then, complementary DNA (cDNA) were loaded on the APS nanocarrier to produce a large amplification factor of Raman signals. The MNs-targeting aptasensor was thus fabricated by immobilizing the APS to the MNs' surfaces via the hybrid reaction between cDNA and aptamers. Sequel, TTC bound successfully to the aptamer upon its addition with the subsequent release of some cDNA-APS into the bulk solution. Under magnet attraction, the nanospheres were deposited together. Consequently, a display of strong SERS signals by supernatants of the resulting mixtures with increasing TTC concentrations was observed. The proposed aptasensor showed excellent performances for TTC detection along with wide linear range of 0.001-100ng/mL, low detection limit 0.001ng/mL, high sensitivity, and good selectivity to the general coexisted interferences.

pH-Responsive polymers

This review summarizes pH-responsive monomers, polymers and their derivative nano- and micro-structures including micelles, cross-linked micelles, microgels and hydrogels.

Enzymatic Activities of Polycatalytic Complexes with Nonprocessive Cellulases Immobilized on the Surface of Magnetic Nanoparticles

Polycatalytic enzyme complexes made by immobilization of industrial enzymes on polymer- or nanoparticle-based scaffolds are technologically attractive due to their recyclability and their improved substrate binding and catalytic activities. Herein, we report the synthesis of polycatalytic complexes by the immobilization of nonprocessive cellulases on the surface of colloidal polymers with a magnetic nanoparticle core and the study of their binding and catalytic activities. These polycatalytic cellulase complexes have increased binding affinity for the substrate. But due to their larger size, these complexes were unable to access to the internal surfaces of cellulose and have significantly lower binding capacity when compared to those of the corresponding free enzymes. Analysis of released soluble sugars indicated that the formation of complexes may promote the prospect of having consistent, multiple attacks on cellulose substrate. Once bound to the substrate, polycatalytic complexes tend to remain on the surface with very limited mobility due to their strong, multivalent binding to cellulose. Hence, the overall performance of polycatalytic complexes is limited by its substrate accessibility as well as mobility on the substrate surface.

Red blood cell membrane camouflaged magnetic nanoclusters for imaging-guided photothermal therapy

Along with intrinsic magnetic resonance imaging (MRI) advantages, iron oxide nanomaterials capable of photothermal conversion have been reported very recently and have again raised great interest in their designs among biomedical researchers. However, like other inorganic nanomaterials, high macrophage uptake, short blood retention time and unfavorable biodistributions have strongly hampered their applications in vivo. To solve these problems, a rational design of red blood cell (RBC) membrane camouflaged iron oxide magnetic clusters (MNC@RBCs) is presented in this paper. Our data show that by simply introducing an "ultra-stealth" biomimetic coating to iron oxide magnetic nanoclusters (MNCs), MNC@RBCs maintain the imaging and photothermal functionalities inherited from MNCs cores while achieving much lower nonspecific macrophage uptake and dramatically altered fate in vivo. MNC@RBCs with superior prolonged blood retention time, preferred high tumor accumulation and relatively lowered liver biodistribution are demonstrated when injected intravenously in mice, leading to greatly enhanced photothermal therapeutic efficacy by a single treatment without further magnetic force manipulation. Our study illustrates a well prepared integration of MNCs and RBCs, exploiting advantages of both functionalities within a single unit and suggests a promising future for iron-based nanomaterials application in vivo.

Synthesis of Superparamagnetic Core-Shell Structure Supported Pd Nanocatalysts for Catalytic Nitrite Reduction with Enhanced Activity, No Detection of Undesirable Product of Ammonium, and Easy Magnetic Separation Capability

Superparamagnetic nanocatalysts could minimize both the external and internal mass transport limitations and neutralize OH(-) produced in the reaction more effectively to enhance the catalytic nitrite reduction efficiency with the depressed product selectivity to undesirable ammonium, while possess an easy magnetic separation capability. However, commonly used qusi-monodispersed superparamagnetic Fe3O4 nanosphere is not suitable as catalyst support for nitrite reduction because it could reduce the catalytic reaction efficiency and the product selectivity to N2, and the iron leakage could bring secondary contamination to the treated water. In this study, protective shells of SiO2, polymethylacrylic acid, and carbon were introduced to synthesize Fe3O4@SiO2/Pd, Fe3O4@PMAA/Pd, and Fe3O4@C/Pd catalysts for catalytic nitrite reduction. It was found that SiO2 shell could provide the complete protection to Fe3O4 nanosphere core among these shells. Because of its good dispersion, dense structure, and complete protection to Fe3O4, the Fe3O4@SiO2/Pd catalyst demonstrated the highest catalytic nitrite reduction activity without the detection of NH4(+) produced. Due to this unique structure, the activity of Fe3O4@SiO2/Pd catalysts for nitrite reduction was found to be independent of the Pd nanoparticle size or shape, and their product selectivity was independent of the Pd nanoparticle size, shape, and content. Furthermore, their superparamagnetic nature and high saturation magnetization allowed their easy magnetic separation from treated water, and they also demonstrated a good stability during the subsequent recycling experiment.

Preparation of light core/shell magnetic composite microspheres and their application for lipase immobilization

Fe₃O₄@P(GMA-DVB-MAA) magnetic composite microspheres were prepared by facile one-pot distillation–precipitation polymerization and were modified with amino groups for the immobilization of lipase.

Polydopamine-Coated Magnetic Composite Particles with an Enhanced Photothermal Effect

Recently, photothermal therapy (PTT) that utilizes photothermal conversion (PTC) agents to ablate cancer under near-infrared (NIR) irradiation has attracted a growing amount of attention because of its excellent therapeutic efficacy and improved target selectivity. Therefore, exploring novel PTC agents with an outstanding photothermal effect is a current research focus. Herein, we reported a polydopamine-coated magnetic composite particle with an enhanced PTC effect, which was synthesized simply through coating polydopamine (PDA) on the surface of magnetic Fe3O4 particles. Compared with magnetic Fe3O4 particles and PDA nanospheres, the core-shell nanomaterials exhibited an increased NIR absorption, and thus, an enhanced photothermal effect was obtained. We demonstrated the in vitro and in vivo effects of the photothermal therapy using our composite particles and their ability as a contrast agent in the T2-weighted magnetic resonance imaging. These results indicated that the multifunctional composite particles with enhanced photothermal effect are superior to magnetic Fe3O4 particles and PDA nanospheres alone.

Preparation of biodegradable PEGylated pH/reduction dual-stimuli responsive nanohydrogels for controlled release of an anti-cancer drug

A facile and efficient method was developed to prepare the monodisperse biodegradable PEGylated pH and reduction dual-stimuli sensitive poly[methacrylic acid-co-poly(ethylene glycol) methyl ether methacrylate-co-N,N-bis(acryloyl)cystamine] (PMPB) nanohydrogels with dried particle size below 200 nm via one-step distillation precipitation polymerization as a drug delivery system (DDS) for the controlled release of a wide-spectrum anti-cancer drug, doxorubicin hydrochloride (DOX). Under normal physiological media, the nanohydrogels possessed high drug encapsulation efficiency (more than 96%) within 48 h and exhibited good stability with a trifle premature drug release. However, rapid DOX release was achieved at lower pH or in the presence of reductive reagent glutathione (GSH) with a cumulative release of more than 85% within 30 h. Furthermore, the nanohydrogels manifested nontoxicity on HepG2 cells at a concentration of 10 μg mL(-1) or lower. Based on the excellent characteristics of the nanohydrogels, such as low toxicity, impressive biodegradability, sharp dual responsiveness, adequate drug loading capacity and a high drug encapsulation efficiency, they were supposed to have potential application in the area of cancer therapy.

Tumor-Targeting Multifunctional Rattle-Type Theranostic Nanoparticles for MRI/NIRF Bimodal Imaging and Delivery of Hydrophobic Drugs

The development of theranostic systems capable of diagnosis, therapy, and target specificity is considerably significant for accomplishing personalized medicine. Here, a multifunctional rattle-type nanoparticle (MRTN) as an effective biological bimodal imaging and tumor-targeting delivery system is fabricated, and an enhanced loading ability of hydrophobic anticancer drug (paclitaxel) is also realized. The rattle structure with hydrophobic Fe3 O4 as the inner core and mesoporous silica as the shell is obtained by one-step templates removal process, and the size of interstitial hollow space can be easily adjusted. The Fe3 O4 core with hydrophobic poly(tert-butyl acrylate) (PTBA) chains on the surface is not only used as a magnetic resonance imaging (MRI) agent, but contributes to improving hydrophobic drug loading amount. Transferrin (Tf) and a near-infrared fluorescent dye (Cy 7) are successfully modified on the surface of the nanorattle to increase the ability of near-infrared fluorescence (NIRF) imaging and tumor-targeting specificity. In vivo studies show the selective accumulation of MRTN in tumor tissues by Tf-receptor-mediated endocytosis. More importantly, paclitaxel-loaded MRTN shows sustained release character and higher cytotoxicity than the free paclitaxel. This theranostic nanoparticle as an effective MRI/NIRF bimodal imaging probe and drug delivery system shows great potential in cancer diagnosis and therapy.

A generic magnetic microsphere platform with "clickable" ligands for purification and immobilization of targeted proteins

While much effort has been made to prepare magnetic microspheres (MMs) with surface moieties that bind to affinity tags or fusion partners of interest in the recombinant proteins, it remains a challenge to develop a generic platform that is capable of incorporating a variety of capture ligands by a simple chemistry. Herein, we developed core-shell structured magnetic microspheres with a high magnetic susceptibility and a low nonspecific protein adsorption. Surface functionalization of these MMs with azide groups facilitates covalent attachment of alkynylated ligands on their surfaces by "click" chemistry and creates a versatile platform for selective purification and immobilization of recombinant proteins carrying corresponding affinity tags. The general applicability of the approach was demonstrated in incorporating four widely used affinity ligands with different reactive groups (-CHO, -SH, -COOH, and -NH2) onto the MMs platform for purification and immobilization of targeted proteins. The azide-functionalized MMs would be applicable for a variety of ligands and substrates that are amenable to alkynylation modification.

Biodegradable micelles capable of mannose-mediated targeted drug delivery to cancer cells

A targeted micellar drug delivery system is developed from a biocompatible and biodegradable amphiphilic polyester, poly(Lac-OCA)-b-(poly(Tyr(alkynyl)-OCA)-g-mannose) (PLA-b-(PTA-g-mannose), that is synthesized via controlled ring-opening polymerization of O-carboxyanhydride (OCA) and highly efficient "Click" chemistry. Doxorubicin (DOX), a model lipophilic anticancer drug, can be effectively encapsulated into the micelles, and the mannose moiety allows active targeting of the micelles to cancer cells that specifically express mannose receptors, which thereafter enhances the anticancer efficiency of the drug. Comprised entirely of biodegradable and biocompatible polyesters, this micellar system demonstrates promising potentials for targeted drug delivery and cancer therapy.

Magnetic nanoparticle clusters for photothermal therapy with near-infrared irradiation

In this study, the photothermal effect of magnetic nanoparticle clusters was firstly reported for the photothermal ablation of tumors both in vitro in cellular systems but also in vivo study. Compared with individual magnetic Fe3O4 nanoparticles (NPs), clustered Fe3O4 NPs can result in a significant increase in the near-infrared (NIR) absorption. Upon NIR irradiation at 808 nm, clustered Fe3O4 NPs inducing higher temperature were more cytotoxic against A549 cells than individual Fe3O4 NPs. We then performed in vivo photothermal therapy (PTT) studies and observed a promising tumor treatment. Compared with PBS and individual magnetic Fe3O4 NPs by NIR irradiation, the clustered Fe3O4 NPs treatment showed a higher therapeutic efficacy. The treatment effects of clustered Fe3O4 NPs with different time of NIR illumination were also evaluated. The result indicated that a sustained high temperature generated by NIR laser with long irradiation time was more effective in killing tumor cells. Furthermore, histological analysis of H&E staining and TUNEL immunohistological assay were further employed for antitumor efficacy assessment of PTT against A549 tumors.

Core-shell-corona-structured polyelectrolyte brushes-grafting magnetic nanoparticles for water harvesting

A novel superhydrophilic material, charged polymer brushes-grafted magnetic core-shell-corona composite nanoparticles (Fe3O4@SiO2@PSPMA), was developed to harvest water through the hydration effect. Because of both the strong hydration capability and the good swelling performance, the negatively charged polymer brushes, PSPMA brushes, endow the composite nanoparticles with superhydrophilicity and a good water-absorbing performance like a sponge, while the magnetic Fe3O4 cores allow easy separation of Fe3O4@SiO2@PSPMA nanoparticles with absorbed water from oil/water mixture under an external magnetic field. The functional particles have the capability of harvesting water droplets whether floating on an oil surface or in the oil. This water-absorbing material uses selective wettability to harvest water and achieve oil-water separation and may be useful in finding novel approaches for recycling water from sewage and removing water in the petroleum industry.

The synthesis and characterization of monodispersed chitosan-coated Fe3O4 nanoparticles via a facile one-step solvothermal process for adsorption of bovine serum albumin

Preparation of magnetic nanoparticles coated with chitosan (CS-coated Fe3O4 NPs) in one step by the solvothermal method in the presence of different amounts of added chitosan is reported here. The magnetic property of the obtained magnetic composite nanoparticles was confirmed by X-ray diffraction (XRD) and magnetic measurements (VSM). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) allowed the identification of spherical nanoparticles with about 150 nm in average diameter. Characterization of the products by Fourier transform infrared spectroscopy (FTIR) demonstrated that CS-coated Fe3O4 NPs were obtained. Chitosan content in the obtained nanocomposites was estimated by thermogravimetric analysis (TGA). The adsorption properties of the CS-coated Fe3O4 NPs for bovine serum albumin (BSA) were investigated under different concentrations of BSA. Compared with naked Fe3O4 nanoparticles, the CS-coated Fe3O4 NPs showed a higher BSA adsorption capacity (96.5 mg/g) and a fast adsorption rate (45 min) in aqueous solutions. This work demonstrates that the prepared magnetic nanoparticles have promising applications in enzyme and protein immobilization.

Magnetic MSP@ZrO₂ microspheres with yolk-shell structure: designed synthesis and application in highly selective enrichment of phosphopeptides

Magnetic yolk-shell MSP@ZrO2 microspheres consisting of a movable magnetic supraparticle (MSP) core and a crystalline ZrO2 shell were synthesized via a two-step controlled "sol-gel" approach for the first time. First, a large amount of the generated hydrolyzate Zr(OH)4 was firmly fixed onto the surface of the cross-linked polymethylacrylic acid matrix via a strong hydrogen-bonding interaction between Zr(OH)4 and the carboxyl groups. Then a calcination process was adopted to convert the Zr(OH)4 into a continuous ZrO2 shell and simultaneously make the ZrO2 shell crystallized. At the same time, the polymer matrix could be selectively removed to form a yolk-shell structure, which has better dispersibility and higher adsorbing efficiency of phosphopeptides than its solid counterpart. The formation mechanism of such yolk-shell microspheres could be reasonably proved by the results of TEM, TGA, VSM, XRD, and FT-IR characterization. By taking advantage of the unique properties, the yolk-shell MSP@ZrO2 exhibited high specificity and great capability in selective enrichment of phosphopeptides, and a total of 33 unique phosphopeptides mapped to 33 different phosphoproteins had been identified from 1 mL of human saliva. This result clearly demonstrated that the yolk-shell MSP@ZrO2 has great performance in purifying and identifying the low-abundant phosphopeptides from real complex biological samples. Moreover, the synthetic method can be used to produce hybrid yolk-shell MSP@ZrO2-TiO2.

Hydrazide functionalized core-shell magnetic nanocomposites for highly specific enrichment of N-glycopeptides

In view of the biological significance of glycosylation for human health, profiling of glycoproteome from complex biological samples is highly inclined toward the discovery of disease biomarkers and clinical diagnosis. Nevertheless, because of the existence of glycopeptides at relatively low abundances compared with nonglycosylated peptides and glycan microheterogeneity, glycopeptides need to be highly selectively enriched from complex biological samples for mass spectrometry analysis. Herein, a new type of hydrazide functionalized core-shell magnetic nanocomposite has been synthesized for highly specific enrichment of N-glycopeptides. The nanocomposites with both the magnetic core and the polymer shell hanging high density of hydrazide groups were prepared by first functionalization of the magnetic core with polymethacrylic acid by reflux precipitation polymerization to obtain the Fe3O4@poly(methacrylic acid) (Fe3O4@PMAA) and then modification of the surface of Fe3O4@PMAA with adipic acid dihydrazide (ADH) to obtain Fe3O4@poly(methacrylic hydrazide) (Fe3O4@PMAH). The abundant hydrazide groups toward highly specific enrichment of glycopeptides and the magnetic core make it suitable for large-scale, high-throughput, and automated sample processing. In addition, the hydrophilic polymer surface can provide low nonspecific adsorption of other peptides. Compared to commercially available hydrazide resin, Fe3O4@PMAH improved more than 5 times the signal-to-noise ratio of standard glycopeptides. Finally, this nanocomposite was applied in the profiling of N-glycoproteome from the colorectal cancer patient serum. In total, 175 unique glycopeptides and 181 glycosylation sites corresponding to 63 unique glycoproteins were identified in three repeated experiments, with the specificities of the enriched glycopeptides and corresponding glycoproteins of 69.6% and 80.9%, respectively. Because of all these attractive features, we believe that this novel hydrazide functionalized core-shell magnetic nanocomposite will shed new light on the profiling of N-glycoproteome from complex biological samples in high throughput.

Folic acid-conjugated pH/temperature/redox multi-stimuli responsive polymer microspheres for delivery of anti-cancer drug

The folic acid (FA)-conjugated pH/temperature/redox multi-stimuli responsive poly(methacrylic acid-co-N,N-bis(acryloyl)cystamine/poly(N-isopropylacrylamide-co-glycidyl methacrylate-co-N,N-bis(acryloyl)cystamine) microspheres were prepared by a two-stage distillation-precipitation polymerization with subsequent surface modification with FA. The microspheres were characterized by transmission electron microscopy, dynamical light scattering, Fourier-transform infrared spectra, UV-vis spectra and elemental analysis. The degradation of the functional microspheres could be triggered by a reductive reagent, such as glutathione, due to presence of BAC crosslinker. The drug-loaded microspheres exhibited a pH/temperature/redox multi-stimuli responsive drug release character for doxorubicin hydrochloride as a model anti-cancer drug, which was efficiently loaded into the microspheres with a high loading capacity of 208.0% and an encapsulation efficiency of 85.4%. In vitro drug delivery study indicated that the FA-conjugated microspheres could deliver Dox into MCF-7 cells more efficiently than the microspheres without functionalization of FA. Furthermore, WST-1 assay showed that the microspheres had no obvious toxicity to MCF-7 cells even at a high concentration of 2000 μg mL(-1). The resultant microsphere may be a promising vector for delivery of anti-cancer drugs as it exhibits a low cytotoxicity and degradability, precise molecular targeting property and multi-stimuli responsively controlled drug release.

Titania composite microspheres endowed with a size-exclusive effect toward the highly specific revelation of phosphopeptidome

The efficient isolation of low-abundance phosphopeptides from complicated biological samples containing a significant quantity of nonphosphopeptides and proteins is essential for phosphopeptidome research but remains a great challenge. In this Article, magnetic composite microspheres comprising a magnetic colloidal nanocrystal cluster core and a mesoporous titania shell with an average pore diameter of 3.4 nm were modified by directly coating an amorphous titania shell onto the magnetite core, followed by converting the amorphous titania shell into a crystalline structure via a hydrothermal process at 80 °C. The as-prepared magnetic mesoporous titania microspheres possess a remarkable specific surface area that is as high as 603.5 m2/g, which is an appropriate pore size with a narrow size distribution and a high magnetic responsiveness. These outstanding features imply that the composite microspheres exhibit extraordinary performance in phosphopeptidome research, including high specificity toward phosphopeptides, an excellent size-exclusion effect against phosphoproteins, exceptional enrichment capacity, and efficient separation from mixtures. Encouraged by the experimental results, we employed this method to investigate the phosphopeptidome of snake venom for the first time. A total of 35 phosphopeptides was identified from the snake venom from the family Viperidae, accounting for 75% of the total identified peptides. This result represents the largest data set of the phosphopeptidome in snake venom from the family Viperidae.

Benzoboroxole-functionalized magnetic core/shell microspheres for highly specific enrichment of glycoproteins under physiological conditions

Efficient enrichment of specific glycoproteins from complex biological samples is of great importance towards the discovery of disease biomarkers in biological systems. Recently, phenylboronic acid-based functional materials have been widely used for enrichment of glycoproteins. However, such enrichment was mainly carried out under alkaline conditions, which is different to the status of glycoproteins in neutral physiological conditions and may cause some unpredictable degradation. In this study, on-demand neutral enrichment of glycoproteins from crude biological samples is accomplished by utilizing the reversible interaction between the cis-diols of glycoproteins and benzoboroxole-functionalized magnetic composite microspheres (Fe3O4/PAA-AOPB). The Fe3O4/PAA-AOPB composite microspheres are deliberately designed and constructed with a high-magnetic-response magnetic supraparticle (MSP) core and a crosslinked poly(acrylic acid) (PAA) shell anchoring abundant benzoboroxole functional groups on the surface. These nanocomposites possessed many merits, such as large enrichment capacity (93.9 mg/g, protein/beads), low non-specific adsorption, quick enrichment process (10 min) and magnetic separation speed (20 s), and high recovery efficiency. Furthermore, the as-prepared Fe3O4/PAA-AOPB microspheres display high selectivity to glycoproteins even in the E. coli lysate or fetal bovine serum, showing great potential in the identify of low-abundance glycoproteins as biomarkers in real complex biological systems for clinical diagnoses.

Novel smart yolk/shell polymer microspheres as a multiply responsive cargo delivery system

An effective strategy was developed to fabricate the novel dually thermo- and pH-responsive yolk/shell polymer microspheres as a drug delivery system (DDS) for the controlled release of anticancer drugs via two-stage distillation precipitation polymerization and seed precipitation polymerization. Their pH-induced thermally responsive polymer shells act as a smart "valve" to adjust the diffusion of the loaded drugs in/out of the polymer containers according to the body environments, while the movable P(MAA-co-EGDMA) cores enhance the drug loading capacity for the anticancer drug doxorubicin hydrochloride (DOX). The yolk/shell polymer microspheres show a low leakage at high pH values but significantly enhanced release at lower pH values equivalent to the tumor body fluid environments at human body temperature, exhibiting the apparent tumor-environment-responsive controlled "on-off" drug release characteristics. Meanwhile, the yolk/shell microspheres expressed very low in vitro cytotoxicity on HepG2 cells. Consequently, their precise tumor-environment-responsive drug delivery performance and high drug loading capacity offer promise for tumor therapy.

Maltodextrin-modified magnetic microspheres for selective enrichment of maltose binding proteins

In this work, maltodextrin-modified magnetic microspheres Fe3O4@SiO2-Maltodextrin (Fe3O4@SiO2-MD) with uniform size and fine morphology were synthesized through a facile and low-cost method. As the maltodextrins on the surface of microspheres were combined with maltose binding proteins (MBP), the magnetic microspheres could be applied to enriching standard MBP fused proteins. Then, the application of Fe3O4@SiO2-MD in one-step purification and immobilization of MBP fused proteins was demonstrated. For the model protein we examined, Fe3O4@SiO2-MD showed excellent binding selectivity and capacity against other Escherichia coli proteins in the crude cell lysate. Additionally, the maltodextrin-modified magnetic microspheres can be recycled for several times without significant loss of binding capacity.

Preparation, characterization and application of NaHCO3 leached bulk U(VI) imprinted polymers endowed with γ-MPS coated magnetite in contaminated water

A new type of ion imprinted polymer (IIP) embedded with γ-methacryloxypropyltrimethoxysilane (γ-MPS) coated magnetic particles for selective extraction of uranyl ions was synthesized by bulk polymerization. The performance of the magnetic sorbent on the extraction of U(VI) was evaluated by various parameters which included the influence of pH, amount of the magnetic polymers, contact time and initial U(VI) concentration. The adsorption capacity of the magnetic polymers was found to be 1.1 and 0.95mgg(-1) for the IIP and its control ion non-imprinted polymer (NIP), respectively. The optimum amount of the sorbent was 50mg for an initial concentration of 2.5mgL(-1). The prepared magnetic imprinted sorbent displayed an uptake with a time of 45min considered optimum. The magnetic polymer displayed good selectivity and exhibited good reusability. Studies from binary mixtures of metal ions in aqueous solutions showed that the magnetic adsorbent selectivity following the order: U(VI)>Ni(II)>Pb(II). Experimental results illustrated the potential application of magnetic ion imprinted polymer sorbents for selective removal of U(VI) from contaminated water.

Cross-linked poly(dimethylaminoethyl acrylamide) coated magnetic nanoparticles: a high loaded, retrievable, and stable basic catalyst for the synthesis of benzopyranes in water

A high loaded basic magnetic catalyst was synthesized using a distillation–precipitation–polymerization method. The catalyst shows high activity in water for the synthesis of 4H-benzopyrans.