Polyoxometalate-Coated Magnetic Nanospheres for Highly Selective Isolation of Immunoglobulin G

Polyhedral oligomeric silsesquioxane-modulated mesoporous amorphous bimetallic organic frameworks for the efficient isolation of immunoglobulin G

The efficient and accurate separation of immunoglobulin G (IgG) plays a vital role for disease diagnosis and therapy, but it is always hampered by the huge geometric size and complex structure of IgG. In this work, an amorphous Fe/Co bimetallic organic framework (denoted as PMOF-Fe/Co) is fabricated for IgG separation, with octa-carboxyl polyhedral oligomeric silsesquioxane (OCPOSS) as modulator for the first time. Benefiting from the rigid nanostructure and competitive coordination of OCPOSS, the aperture of PMOF-Fe/Co is enlarged to ∼20 nm along with the generation of enormous structural defects, which enables the accommodation of protein species with high molecular weights and large sizes. OCPOSS is also found exerting a positive impact on mediating the specific recognition and adsorption ability of PMOF-Fe/Co towards IgG through metal affinity, hydrophilic and hydrophobic interactions. Consequently, the multimode and multivalent affinity of PMOF-Fe/Co gives rise to an extraordinary adsorption capacity (2691.7 mg g-1) and satisfactory practical application performance. This study is convinced to provide a simple avenue for the efficient separation of specific large-sized proteins, as well as the engineering of abiotic affinity reagents with compositional and architectural complexity.

Enhanced sludge solid-liquid separation based on Fe2+/periodate conditioning coupled with polyoxometalates: Cell destruction and protein adsorption

Dewatering of waste activated sludge is a necessary step for achieving subsequent reduction, stabilization, and resource utilization. In this study, Fe2+/periodate (PI) coupled with polyoxometalates (POMs) conditioning was tested for realizing sludge deep dewatering. After the addition of POMs (0.20 mmol g-1 VSS), Fe2+/PI/POMs conditioning enhanced the efficiency of sludge dewatering by 42.93% compared to Fe2+/PI conditioning. It was found that the electrostatic repulsion posed a significant influence on the interaction between POMs and proteins. The reduction of electrostatic repulsion facilitated the proximity of POMs to the sludge flocs and promoted its reaction. The strong acidity and interaction with cells of POMs could induce the damage or apoptosis in sludge cells, resulting in the release of intracellular substances. The active radicals generated by Fe2+/PI process attacked TB-EPS, causing the dissolution of EPS and the decomposition of hydrophilic substances. With the assistance of Fe2+/PI process, POMs exhibited an enhanced cell-disruptive effect, thereby inducing the liberation of a greater quantity of intracellular substances. Moreover, Fe2+/PI/POMs conditioning effectively lowered the zeta potential of sludge system, facilitating the interaction between negatively charged POMs anions and the positively charged regions of proteins. This interaction tended to favor adsorption and precipitation rather than destruction. The adsorption and sedimentation of proteins by POMs further reduced the hydrophilicity of sludge system, thereby enhancing sludge dewaterability. Furthermore, POMs could enhance the electron transfer capacity of sludge system, which was beneficial for subsequent filtrate denitrification treatment.

Interfacial modification of recombinant protein for immunoglobulin G adsorption with spindle-shaped MOF as nano molecular containers

Development of fresh solid phase extractant is critical for selective separation and purification of special proteins. Herein, we demonstrated a recombinant Staphylococcal Protein G (rSPG) with a His-tag modified the novel single-metal organic framework (rSPG@Ni-MOF-74). The proposed solid-phase extraction material possessed a uniform spindle-shaped structure, large surface area (709.60 m2 g-1) and pore volume (0.08 m3 g-1), high metal content (22.57 wt%), which facilitated the interaction between host and guest. As results, the composite displayed outstanding selective recognition and adsorption of IgG, due to synergistic effect of the binding ability of rSPG with the Fc region of IgG, maintained through hydrogen bonding and electrostatic attraction, as well as hydrophobic interaction. The adsorption performance and mechanism of rSPG@Ni-MOF-74 have been fully investigated. Additionally, the rSPG@Ni-MOF-74 composite could effectively separate IgG from serum obtained from healthy humans, with the purity of the separated IgG verified through SDS-PAGE analysis. Furthermore, LC-MS/MS analysis identified a high content of IgG (55.3 %) in the eluate from rSPG@Ni-MOF-74, suggesting the great potential of rSPG@Ni-MOF-74 in IgG separation and enrichment from complex matrix.

Bilateral efforts to improve SERS detection efficiency of exosomes by Au/Na7PMo11O39 Combined with Phospholipid Epitope Imprinting

Detection of cancer-related exosomes in body fluids has become a revolutionary strategy for early cancer diagnosis and prognosis prediction. We have developed a two-step targeting detection method, termed PS-MIPs-NELISA SERS, for rapid and highly sensitive exosomes detection. In the first step, a phospholipid polar site imprinting strategy was employed using magnetic PS-MIPs (phospholipids-molecularly imprinted polymers) to selectively isolate and enrich all exosomes from urine samples. In the second step, a nanozyme-linked immunosorbent assay (NELISA) technique was utilized. We constructed Au/Na7PMo11O39 nanoparticles (NPs) with both surface-enhanced Raman scattering (SERS) property and peroxidase catalytic activity, followed by the immobilization of CD9 antibodies on the surface of Au/Na7PMo11O39 NPs. The Au/Na7PMo11O39-CD9 antibody complexes were then used to recognize CD9 proteins on the surface of exosomes enriched by magnetic PS-MIPs. Lastly, the high sensitivity detection of exosomes was achieved indirectly via the SERS activity and peroxidase-like activity of Au/Na7PMo11O39 NPs. The quantity of exosomes in urine samples from pancreatic cancer patients obtained by the PS-MIPs-NELISA SERS technique showed a linear relationship with the SERS intensity in the range of 6.21 × 107-2.81 × 108 particles/mL, with a limit of detection (LOD) of 5.82 × 107 particles/mL. The SERS signal intensity of exosomes in urine samples from pancreatic cancer patients was higher than that of healthy volunteers. This bidirectional MIPs-NELISA-SERS approach enables noninvasive, highly sensitive, and rapid detection of cancer, facilitating the monitoring of disease progression during treatment and opening up a new avenue for rapid early cancer screening.

Titanium-based metal-organic framework MIL-125(Ti) for the highly selective isolation and purification of immunoglobulin G from human serum

Titanium-based metal-organic framework MIL-125(Ti) was synthesized by the hydrothermal method of terephthalic acid and tetra butyl titanate in N-N dimethylformamide and methanol. MIL-125(Ti) was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, nitrogen adsorption-desorption, energy-dispersive X-ray spectroscopy, zeta potential, scanning electron microscope and transmission electron microscopy. The results showed MIL-125(Ti) could be used as a potential adsorbent for protein separation and purification due to the high specific surface area, high stability and strong hydrophobicity. As a result, MIL-125(Ti) had adsorption selectivity for immunoglobulin G, which was due to hydrogen bond between MIL-125(Ti) and protein. At pH 8.0, the maximum adsorption efficiency of 0.25 mg MIL-125(Ti) for 300 μL 100 μg mL^-1 immunoglobulin G was 98.3%, and its maximum adsorption capacity was 232.56 mg g^-1 . The elution efficiency of immunoglobulin G was 92.4% by 0.1% SDS. SDS-PAGE result demonstrated the successful isolation of highly purified immunoglobulin G from the human serum. Therefore, a new method of separation and purification of immunoglobulin G in human serum using titanium-based metal-organic framework MIL-125(Ti) as a solid-phase adsorbent was established, which broadened the application scope of metal-organic frameworks. This article is protected by copyright. All rights reserved.

Fabrication of Yolk-Shell Fe3O4@NiSiO3/Ni Microspheres for Efficient Purification of Histidine-Rich Proteins

Magnetic materials perform well in the purification of histidine-rich proteins (His-proteins). In this work, a facile fabrication of yolk-shell magnetic Fe₃O₄@NiSiO₃/Ni microspheres for the efficient purification of His-proteins has been reported. Yolk-shell Fe₃O₄@NiSiO₃ microspheres were prepared via hydrothermal reaction. Then Ni nanoparticles (NPs) were loaded on Fe₃O₄@NiSiO₃ microspheres after the adsorption and in situ reduction of nickel acetylacetonate. The yolk-shell Fe₃O₄@NiSiO₃/Ni microspheres had a hierarchical flower-like structure and large cavities. The size of the cavity depended on the reaction time. This indicated that the microspheres had a large specific surface area for loading of more Ni NPs, which was crucial to the high His-protein adsorption capacity of Fe₃O₄@NiSiO₃/Ni microspheres. Fe₃O₄@NiSiO₃/Ni microspheres had a high adsorption capacity for bovine hemoglobin (BHb, 2822 mg/g), which was better than the values of other His-protein adsorbents. Fe₃O₄@NiSiO₃/Ni microspheres still had a high BHb separation efficiency after seven separation cycles, indicating its good reusability and stability. Therefore, the as-prepared bifunctional yolk-shell Fe₃O₄@NiSiO₃/Ni microspheres exhibited great practical application value for His-protein purification.

Functionalized polyoxometalate microspheres ensure selective adsorption of phosphoproteins and glycoproteins

Lacunary polyoxometalate (POM), [PW₉O₃₄]^9-, grafts with a boronic acid group attached via an organosilane bridge assemble into microspheres, PW₉-Si-APBA. The oxygen-rich and hydrophilic surface of POM facilitates the binding of phosphate groups in phosphoproteins and glycans in glycoproteins. While the metal-oxo in POM provides π-π interactions with the phosphate groups of phosphoproteins, the boronic acid group specifically binds to glycoproteins via the cis-diols of glycans. Therefore, these multi-driving forces ensure the selective adsorption of phosphoproteins and glycoproteins by PW₉-Si-APBA microspheres in biological sample matrixes, even in the presence of very high protein abundance, i.e., BSA, at mass ratio of β-ca/IgG/OVA/BSA = 1 : 1 : 1 : 200.

A label-free immunosensor for the detection of a new lung cancer biomarker, GM2 activator protein, using a phosphomolybdic acid/polyethyleneimine coated gold nanoparticle composite

A novel electrochemical immunosensor for the detection of a new lung cancer biomarker based on a polyoxometalate-adsorbed poly(ethylenimine)-coated gold nanoparticle modified electrode.

Polyoxometalate-functionalized macroporous microspheres for selective separation/enrichment of glycoproteins

Glycoproteins always participate in various biological processes. Selective separation and enrichment of glycoproteins are of great significance for the research of pathogenesis. Herein, macroporous polymer microspheres were fabricated, and further functionalized by polyoxometalate. Thus, a simple, efficient and highly selective approach was constructed for glycoprotein enrichment from a complex matrix. The as-prepared material shows promise as a potential adsorbent in bio-separation and downstream clinical applications.

Electronic Consequences of Ligand Substitution at Heterometal Centers in Polyoxovanadium Clusters: Controlling the Redox Properties through Heterometal Coordination Number

The rational control of the electrochemical properties of polyoxovanadate-alkoxide clusters is dependent on understanding the influence of various synthetic modifications on the overall redox processes of these systems. In this work, the electronic consequences of ligand substitution at the heteroion in a heterometal-functionalized cluster was examined. The redox properties of [V5 O6 (OCH3 )12 FeCl] (1-[V5 FeCl]) and [V5 O6 (OCH3 )12 Fe]X (2-[V5 Fe]X; X=ClO4 , OTf) were compared in order to assess the effects of changing the coordination environment around the iron center on the electrochemical properties of the cluster. Coordination of a chloride anion to iron leads to an anodic shift in redox events. Theoretical modelling of the electronic structure of these heterometal-functionalized clusters reveals that differences in the redox profiles of 1-[V5 FeCl] and 2-[V5 Fe]X arise from changes in the number of ligands surrounding the iron center (e.g., 6-coordinate vs. 5-coordinate). Specifically, binding of the chloride to the sixth coordination site appears to change the orbital interaction between the iron and the delocalized electronic structure of the mixed-valent polyoxovanadate core. Tuning the heterometal coordination environment can therefore be used to modulate the redox properties of the whole cluster.

DMSA-Functionalized Mesoporous Alumina with a High Capacity for Selective Isolation of Immunoglobulin G

A novel dimercaptosuccinic acid-functionalized mesoporous alumina (DMSA-MA) is synthesized by the dicarboxylic acid groups of dimercaptosuccinic acid molecules coordinating to the Al³⁺ ions located in the mesostructure. The as-prepared DMSA-MA composites possess a large surface area of 91.17 m²/g as well as a uniform pore size and a high pore volume of 17.22 nm and 0.23 cm³/g, respectively. DMSA coating of mesostructures significantly enhanced their selectivity for glycoprotein adsorption through a powerful hydrophilic binding force, and the maximum adsorption capacity of immunoglobulin G (IgG) can reach 2298.6 mg g^-1. The captured IgG could be lightly stripped from the DMSA-MA composites with an elution rate of 98.3% by using 0.5 wt % CTAB solution as the elution reagent. DMSA-MA is further employed as a sorbent for the enrichment of IgG heavy chain and light chain from human serum sample. SDS-PAGE assay results showed the obtained IgG with high purity compared to that of the standard solution of IgG.

Two-dimensional titanate-based zwitterionic hydrophilic sorbent for the selective adsorption of glycoproteins

The selective adsorption towards glycoproteins from complex biosamples is of vital importance in life science studies. A new zwitterionic hydrophilic material, i.e., a functionalized titanate nanosheet, is prepared by assembling well-dispersed gold nanoparticles (AuNPs) on the surface of ultrathin titanate nanosheets via an ion-exchange approach, followed through immobilizing l-cysteine (L-Cys) by Au-S bonding. This 2D-titanate-based zwitterionic hydrophilic material is shortly termed as L-Cys/Au/TiNSs and it exhibits transverse several hundred nanometers with an ultrathin nanosheet structure. The zwitterionic hydrophilic titanate nanosheets have strong adsorption affinity to glycoproteins, offering a large binding capacity towards immunoglobulin G (1098.9 mg g^-1), which could be readily stripped into an ammonium hydroxide (NH₄OH) solution (0.5%, m/v) with a recovery of 82.4%. The practical applications of L-Cys/Au/TiNSs are further proved by successful specific adsorption of IgG from human serum.

Boron-titanate monolayer nanosheets for highly selective adsorption of immunoglobulin G

Boron-titanate monolayer nanosheets were prepared through a scalable step by step intercalation approach for anchoring 3-mercaptopropyltriethoxysilane (MPTS) on the surface. MPTS provides clickable sites with 4-vinylphenylboronic acid (VPBA) via a thiol-ene (TE) click reaction to obtain monolayer titanate nanosheets with boronic acid ligands immobilized on the surface. The nanosheets obtained are denoted as VPBA-MPTS-TiNSs, with a lateral dimension of a few dozen nanometers and with a thickness of ca. 3.5 nm. The nanosheets exhibit a superior adsorption capacity of 1669.7 mg g-1 and favorable selectivity for the adsorption of glycoproteins by employing immunoglobulin G (IgG) as the protein model. The adsorbed IgG is thereafter readily collected by using 0.1% (m/v) cetane trimethyl ammonium bromide (CTAB) as the eluent. The practical applications of VPBA-MPTS-TiNSs are further demonstrated by the selective adsorption/purification of IgG from human serum.

Three new Strandberg-type phenylphosphomolybdate supports for immobilizing horseradish peroxidase and their catalytic oxidation performances

Three new Strandberg-type polyoxometalate TM-(PhP)2Mo5 supports for immobilizing HRP showed high adsorption capacity and good catalytic oxidation activity.