Dextran-coated magnetic supports modified with a biomimetic ligand for IgG purification

Surface Modification of Polystyrene with Boronic Acid for Immunoaffinity-Based Cell Enrichment

Obtaining an enriched and phenotypically pure cell population from heterogeneous cell mixtures is important for diagnostics and biosensing. Existing techniques such as fluorescent-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS) require preincubation with antibodies (Ab) and specialized equipment. Cell immunopanning removes the need for preincubation and can be done with no specialized equipment. The majority of the available antibody-mediated analyte capture techniques require a modification to the Abs for binding. In this work, no antibody modification is used because we take advantage of the carbohydrate chain in the Fc region of Ab. We use boronic acid as a cross-linker to bind the Ab to a modified surface. The process allows for functional orientation and cleavable binding of the Ab. In this study, we created an immunoaffinity matrix on polystyrene (PS), an inexpensive and ubiquitous plastic. We observed a 37% increase in Ab binding compared with that of a passive adsorption approach. The method also displayed a more consistent antibody binding with 17 times less variation in Ab loading among replicates than did the passive adsorption approach. Surface topography analysis revealed that a dextran coating reduced nonspecific antibody binding. Elemental analysis (XPS) was used to characterize the surface at different stages and showed that APBA molecules can bind upside-down on the surface. While upside-down antibodies likely remain functional, their elution behavior might differ from those bound in the desired way. Cell capture experiments show that the new surface has 43% better selectivity and 2.4-fold higher capture efficiency compared to a control surface of passively adsorbed Abs. This specific surface chemistry modification will allow the targeted capture of cells or analytes with the option of chemical detachment for further research and characterization.

Biomimetic Nanomaterials: Diversity, Technology, and Biomedical Applications

Biomimetic nanomaterials (BNMs) are functional materials containing nanoscale components and having structural and technological similarities to natural (biogenic) prototypes. Despite the fact that biomimetic approaches in materials technology have been used since the second half of the 20th century, BNMs are still at the forefront of materials science. This review considered a general classification of such nanomaterials according to the characteristic features of natural analogues that are reproduced in the preparation of BNMs, including biomimetic structure, biomimetic synthesis, and the inclusion of biogenic components. BNMs containing magnetic, metal, or metal oxide organic and ceramic structural elements (including their various combinations) were considered separately. The BNMs under consideration were analyzed according to the declared areas of application, which included tooth and bone reconstruction, magnetic and infrared hyperthermia, chemo- and immunotherapy, the development of new drugs for targeted therapy, antibacterial and anti-inflammatory therapy, and bioimaging. In conclusion, the authors' point of view is given about the prospects for the development of this scientific area associated with the use of native, genetically modified, or completely artificial phospholipid membranes, which allow combining the physicochemical and biological properties of biogenic prototypes with high biocompatibility, economic availability, and scalability of fully synthetic nanomaterials.

Multi-Bit Biomemristic Behavior for Neutral Polysaccharide Dextran Blended with Chitosan

Natural biomaterials applicable for biomemristors have drawn prominent attention and are of benefit to sustainability, biodegradability, biocompatibility, and metabolism. In this work, multi-bit biomemristors based on the neutral polysaccharide dextran were built using the spin-casting method, which was also employed to explore the effect of dextran on the ternary biomemristic behaviors of dextran–chitosan nanocomposites. The doping of 50 wt% dextran onto the bio-nanocomposite optimized the ratio of biomemristance in high-, intermediate-, and low-resistance states (10⁵:10⁴:1). The interaction between dextran and chitosan (hydrogen-bond network) was verified by Fourier transform infrared (FTIR) and Raman spectroscopy analysis; through this interaction, protons derived from the self-dissociation of water may migrate under the electric field, and so proton conduction may be the reason for the ternary biomemristic behaviors. Observations from X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) analysis displayed that the 50 wt% dextran/50 wt% chitosan nanocomposite had the greatest amorphous ratio as well as the highest decomposition and peak transition temperatures in comparison with the other three dextran–chitosan nanocomposites. This work lays the foundation for neutral biomaterials applied to green ultra-high-density data-storage systems.

Advances in magnetic resonance imaging contrast agents for glioblastoma-targeting theranostics

Glioblastoma (GBM) is the most aggressive malignant brain tumour, with a median survival of 3 months without treatment and 15 months with treatment. Early GBM diagnosis can significantly improve patient survival due to early treatment and management procedures. Magnetic resonance imaging (MRI) using contrast agents is the preferred method for the preoperative detection of GBM tumours. However, commercially available clinical contrast agents do not accurately distinguish between GBM, surrounding normal tissue and other cancer types due to their limited ability to cross the blood–brain barrier, their low relaxivity and their potential toxicity. New GBM-specific contrast agents are urgently needed to overcome the limitations of current contrast agents. Recent advances in nanotechnology have produced alternative GBM-targeting contrast agents. The surfaces of nanoparticles (NPs) can be modified with multimodal contrast imaging agents and ligands that can specifically enhance the accumulation of NPs at GBM sites. Using advanced imaging technology, multimodal NP-based contrast agents have been used to obtain accurate GBM diagnoses in addition to an increased amount of clinical diagnostic information. NPs can also serve as drug delivery systems for GBM treatments. This review focuses on the research progress for GBM-targeting MRI contrast agents as well as MRI-guided GBM therapy.

Magnetic particles used in a new approach for designed protein crystallization

Designed protein crystallization using magnetic particles as additives in the crystallization of model case studies.

Seeking Innovative Affinity Approaches: A Performance Comparison between Magnetic Nanoparticle Agglomerates and Chromatography Resins for Antibody Recovery

Monoclonal antibodies are key molecules in medicine and pharmaceuticals. A potentially crucial drawback for faster advances in research here is their high price due to the extremely expensive antibody purification process, particularly the affinity capture step. Affinity chromatography materials have to demonstrate the high binding capacity and recovery efficiency as well as superior chemical and mechanical stability. Low-cost materials and robust, faster processes would reduce costs and enhance industrial immunoglobulin purification. Therefore, exploring the use of alternative materials is necessary. In this context, we conduct the first comparison of the performance of magnetic nanoparticles with commercially available chromatography resins and magnetic microparticles with regard to immobilizing Protein G ligands and recovering immunoglobulin G (IgG). Simultaneously, we demonstrate the suitability of bare as well as silica-coated and epoxy-functionalized magnetite nanoparticles for this purpose. All materials applied have a similar specific surface area but differ in the nature of their matrix and surface accessibility. The nanoparticles are present as micrometer agglomerates in solution. The highest Protein G density can be observed on the nanoparticles. IgG adsorbs as a multilayer on all materials investigated. However, the recovery of IgG after washing indicates a remaining monolayer, which points to the specificity of the IgG binding to the immobilized Protein G. One important finding is the impact of the ligand-binding stoichiometry (Protein G surface coverage) on IgG recovery, reusability, and the ability to withstand long-term sanitization. Differences in the materials' performances are attributed to mass transfer limitations and steric hindrance. These results demonstrate that nanoparticles represent a promising material for the economical and efficient immobilization of proteins and the affinity purification of antibodies, promoting innovation in downstream processing.

Magnetic Precipitation: A New Platform for Protein Purification

One of the trends in downstream processing comprises the use of "anything-but-chromatography" methods to overcome the current downfalls of standard packed-bed chromatography. Precipitation and magnetic separation are two techniques already proven to accomplish protein purification from complex media, yet never used in synergy. With the aim to capture antibodies directly from crude extracts, a new approach combining precipitation and magnetic separation is developed and named as affinity magnetic precipitation. A precipitation screening, based on the Hofmeister series, and a commercial precipitation kit are tested with affinity magnetic particles to assess the best condition for antibody capture from human serum plasma and clarified cell supernatant. The best conditions are obtained when using PEG3350 as precipitant at 4 °C for 1 h, reaching 80% purity and 50% recovery of polyclonal antibodies from plasma, and 99% purity with 97% recovery yield of anti-TNFα mAb from cell supernatants. These results show that the synergetic use of precipitation and magnetic separation can represent an alternative for the efficient capture of antibodies.

Enhancement in Oral Absorption of Ceftriaxone by Highly Functionalized Magnetic Iron Oxide Nanoparticles

The present study aims at the development, characterization, biocompatibility investigation and oral bioavailability evaluation of ceftriaxone (CFT)-loaded N′-methacryloylisonicotinohydrazide (MIH)-functionalized magnetic nanoparticles (CFT-MIH-MNPs). Atomic force microscopy (AFM) and dynamic light scattering (DLS) showed that the developed CFT loaded MIH-MNPs are spherical, with a measured hydrodynamic size of 184.0 ± 2.7 nm and negative zeta potential values (–20.2 ± 0.4 mV). Fourier transformed infrared spectroscopic (FTIR) analysis revealed interactions between the nanocarrier and the drug. Nanoparticles showed high drug entrapment efficiency (EE) of 79.4% ±1.5%, and the drug was released gradually in vitro and showed prolonged in vitro stability using simulated gastrointestinal tract (GIT) fluids. The formulations were found to be highly biocompatible (up to 100 µg/mL) and hemocompatible (up to 1.0 mg/mL). Using an albino rabbit model, the formulation showed a significant enhancement in drug plasma concentration up to 14.4 ± 1.8 µg/mL in comparison with its control (2.0 ± 0.6 µg/mL). Overall, the developed CFT-MIH-MNPs formulation was promising for provision of high drug entrapment, gradual drug release and suitability for enhancing the oral delivery of CFT.

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.

Emerging biomaterials for downstream manufacturing of therapeutic proteins

Downstream processing is considered one of the most challenging phases of industrial manufacturing of therapeutic proteins, accounting for a large portion of the total production costs. The growing demand for therapeutic proteins in the biopharmaceutical market in addition to a significant rise in upstream titers have placed an increasing burden on the downstream purification process, which is often limited by high cost and insufficient capacities. To achieve efficient production and reduced costs, a variety of biomaterials have been exploited to improve the current techniques and also to develop superior alternatives. In this work, we discuss the significance of utilizing traditional biomaterials in downstream processing and review the recent progress in the development of new biomaterials for use in protein separation and purification. Several representative methods will be highlighted and discussed in detail, including affinity chromatography, non-affinity chromatography, membrane separations, magnetic separations, and precipitation/phase separations. STATEMENT OF SIGNIFICANCE: Nowadays, downstream processing of therapeutic proteins is facing great challenges created by the rapid increase of the market size and upstream titers, starving for significant improvements or innovations in current downstream unit operations. Biomaterials have been widely used in downstream manufacturing of proteins and efforts have been continuously devoted to developing more advanced biomaterials for the implementation of more efficient and economical purification methods. This review covers recent advances in the development and application of biomaterials specifically exploited for various chromatographic and non-chromatographic techniques, highlighting several promising alternative strategies.

pSBMA-Conjugated Magnetic Nanoparticles for Selective IgG Separation

Two types of zwitterionic polymer-modified magnetic nanoparticles (NPs) are fabricated by conjugating pSBMA onto PEI-precoated NPs via either a one-step method (1S NPs) or two-step method (2S NPs). For both methods, divinyl sulfone is used as the linker molecule. Although 1S NPs were capable of resisting both IgG and BSA, 2S NPs exhibited specificity toward IgG adsorption in complex biological fluids, e.g., in a mixture of serums and IgG. The moderate interactions ( K_d ≈ 1.2 μM) between IgG and 2S NPs are 3 orders of magnitude lower than IgG binding with protein A ( K_d 10 nM). Through complementary characterizations and analyses, we rationalize that the surface developed herein with IgG specificity contains two key components: polyzwitterions with a short chain length and sulfone groups with a high density.

Mimicking nature: Phosphopeptide enrichment using combinatorial libraries of affinity ligands

Phosphorylation is a reversible post-translational modification of proteins that controls a plethora of cellular processes and triggers specific physiological responses, for which there is a need to develop tools to characterize phosphorylated targets efficiently. Here, a combinatorial library of triazine-based synthetic ligands comprising 64 small molecules has been rationally designed, synthesized and screened for the enrichment of phosphorylated peptides. The lead candidate (coined A8A3), composed of histidine and phenylalanine mimetic components, showed high binding capacity and selectivity for binding mono- and multi-phosphorylated peptides at pH 3. Ligand A8A3 was coupled onto both cross-linked agarose and magnetic nanoparticles, presenting higher binding capacities (100-fold higher) when immobilized on the magnetic support. The magnetic adsorbent was further screened against a tryptic digest of two phosphorylated proteins (α- and β-caseins) and one non-phosphorylated protein (bovine serum albumin, BSA). The MALDI-TOF mass spectra of the eluted peptides allowed the identification of nine phosphopeptides, comprising both mono- and multi-phosphorylated peptides.

An extracellular polymer at the interface of magnetic bioseparations

FucoPol, a fucose-containing extracellular polysaccharide (EPS) produced by bacterium Enterobacter A47 using glycerol as the carbon source, was employed as a coating material for magnetic particles (MPs), which were subsequently functionalized with an artificial ligand for the capture of antibodies. The performance of the modified MPs (MP-EPS-22/8) for antibody purification was investigated using direct magnetic separation alone or combined with an aqueous two-phase system (ATPS) composed of polyethylene glycol (PEG) and dextran. In direct magnetic capturing, and using pure protein solutions of human immunoglobulin G (hIgG) and bovine serum albumin (BSA), MP-EPS-22/8 bound 120 mg hIgG g(-1) MPs, whereas with BSA only 10 ± 2 mg BSA g(-1) MPs was achieved. The hybrid process combining both the ATPS and magnetic capturing leads to a good performance for partitioning of hIgG in the desired phase as well as recovery by the magnetic separator. The MPs were able to bind 145 mg of hIgG g(-1) of particles which is quite high when compared with direct magnetic separation. The theoretical maximum capacity was calculated to be 410 ± 15 mg hIgG adsorbed g(-1) MPs with a binding affinity constant of 4.3 × 10(4) M(-1). In multiple extraction steps, the MPs bound 92% of loaded hIgG with a final purity level of 98.5%. The MPs could easily be regenerated, recycled and re-used for five cycles with only minor loss of capacity. FucoPol coating allowed both electrostatic and hydrophobic interactions with the antibody contributing to enhance the specificity for the targeted products.

VEGF-targeted magnetic nanoparticles for MRI visualization of brain tumor

This work is focused on synthesis and characterization of targeted magnetic nanoparticles as magnetic resonance imaging (МRI) agents for in vivo visualization of gliomas. Ferric oxide (Fe3O4) cores were synthesized by thermal decomposition and coated with bovine serum albumin (BSA) to form nanoparticles with Deff of 53±9nm. The BSA was further cross-linked to improve colloidal stability. Monoclonal antibodies against vascular endothelial growth factor (mAbVEGF) were covalently conjugated to BSA through a polyethyleneglycol linker. Here we demonstrate that 1) BSA coated nanoparticles are stable and non-toxic to different cells at concentration up to 2.5mg/mL; 2) conjugation of monoclonal antibodies to nanoparticles promotes their binding to VEGF-positive glioma С6 cells in vitro; 3) targeted nanoparticles are effective in MRI visualization of the intracranial glioma. Thus, mAbVEGF-targeted BSA-coated magnetic nanoparticles are promising MRI contrast agents for glioma visualization.

FROM THE CLINICAL EDITOR

This work focuses on synthesis and characterization of targeted magnetic nanoparticles as magnetic resonance imaging (МRI) agents for in vivo visualization of gliomas. The authors utilize the fact that high-grade gliomas have extensive areas of necrosis and hypoxia, which results in increased secretion of angiogenesis vascular endothelial growth factor (VEGF). Monoclonal antibodies against vascular endothelial growth factor (mAbVEGF) were covalently conjugated to crosslinked BSA coated ferric oxide (Fe3O4) nanoparticles. The results show that these targeted nanoparticles are effective in MRI visualization of the intracranial glioma and may provide a new and promising contrast agent.

Biodegradable dextran vesicles for effective haemoglobin encapsulation

Biocompatible and biodegradable dextran–PLA copolymer self-assembled into polymeric vesicles, which could encapsulate the hemoglobin. The encapsulated hemoglobin retained biological activity and could be potentially used as blood substitute.

Doxorubicin-conjugated core-shell magnetite nanoparticles as dual-targeting carriers for anticancer drug delivery

The present study reports the successful synthesis of core-shell nanostructures composed of magnetite nanoparticles (Fe3O4-NPs) conjugated to the anticancer drug doxorubicin, intended for dual targeting of the drug to the tumor sites via a combination of the magnetic attraction and the pH-sensitive cleavage of the drug-particle linkages along with a longer circulation time and reduced side effects. To improve the carrier biocompatibility, the prepared nanocarrier was, finally coated by chitosan. FT-IR analysis confirmed the synthesis of functionalized Fe3O4-NPs, doxorubicin-conjugated Fe3O4-NPs, and chitosan-coated nanocarriers. Scanning electron microscopy (SEM) indicated the formation of spherical nanostructures with the final average particle size of around 50 nm. The vibrating sample magnetometer (VSM) analysis showed that the saturation magnetization value (Ms) of carrier was 6 emu/g. The drug release behavior from the nanocarriers was investigated both in acidic and neutral buffered solutions (pH values of 5.3 and 7.4, respectively) and showed two-fold increase in the extent of drug release at pH 5.3 compared to pH 7.4 during 7 days. The results showed that the dual-targeting nanocarriers responded successfully to the external magnetic field and pH. From the results obtained, it can be concluded that this methodology can be used to target and improve therapeutic efficacy of the anticancer drugs.

Boronic acid-modified magnetic materials for antibody purification

Aminophenyl boronic acids can form reversible covalent ester interactions with cis-diol-containing molecules, serving as a selective tool for binding glycoproteins as antibody molecules that possess oligosaccharides in both the Fv and Fc regions. In this study, amino phenyl boronic acid (APBA) magnetic particles (MPs) were applied for the magnetic separation of antibody molecules. Iron oxide MPs were firstly coated with dextran to avoid non-specific binding and then with 3-glycidyloxypropyl trimethoxysilane to allow further covalent coupling of APBA (APBA_MP). When contacted with pure protein solutions of human IgG (hIgG) and bovine serum albumin (BSA), APBA_MP bound 170 ± 10 mg hIgG g(-1) MP and eluted 160 ± 5 mg hIgG g(-1) MP, while binding only 15 ± 5 mg BSA g(-1) MP. The affinity constant for the interaction between hIgG and APBA_MP was estimated as 4.9 × 10(5) M(-1) (Ka) with a theoretical maximum capacity of 492 mg hIgG adsorbed g(-1) MP (Qmax), whereas control particles bound a negligible amount of hIgG and presented an estimated theoretical maximum capacity of 3.1 mg hIgG adsorbed g(-1) MP (Qmax). APBA_MPs were also tested for antibody purification directly from CHO cell supernatants. The particles were able to bind 98% of IgG loaded and to recover 95% of pure IgG (purity greater than 98%) at extremely mild conditions.

Specificity and regenerability of short peptide ligands supported on polymer layers for immunoglobulin G binding and detection

We demonstrate the specificity, regenerability, and excellent storage stability of short peptide-based systems for detection of immunoglobulin G (IgG). The bioactive component consisted of acetylated-HWRGWVA (Ac-HWRGWVA), a peptide with high IgG binding affinity, which was immobilized onto copolymer matrixes of poly(2-aminoethyl methacrylate hydrochloride-co-2-hydroxyethyl methacrylate) (poly(AMA-co-HEMA)). Surface plasmon resonance (SPR) and quartz crystal microgravimetry (QCM) were utilized with other complementary techniques to systematically investigate interfacial activities, mainly IgG binding performance as a function of the graft density and degree of polymerization of the poly(AMA-co-HEMA) support layer. Results from sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorescence microscopy indicate that the bioactive system is highly specific to IgG and resistant to nonspecific interactions when tested in mixed protein solutions.