Biparatopic Nanobody-Based Immunosorbent for the Highly Selective Elimination of Tumor Necrosis Factor-α.

Removing the overexpressed TNF-α by hemoperfusion positively affects clinical treatments for diseases such as autoimmune disease and sepsis. However, clearance ratios of adsorbents targeting TNF-α were limited by the extremely low concentration of TNF-α (mostly <1000 ng/L in sepsis) and hydrophobic interactions. In this work, biparatopic nanobodies (NbC21) with a high affinity of 19.9 pM, which bind to two distinct sites of TNF-α, were constructed as high-affinity ligands for the immunosorbent. The theoretical maximum adsorption capacity estimated from the Langmuir isotherm was up to 18.22 mg/g gel. The prepared immunosorbent (NbC21-sorbent) had an outstanding TNF-α clearance ratio of approximately 96% during the dynamic adsorption test, with a sorbent-to-serum ratio of 1:1000. Additionally, it demonstrated favorable hemocompatibility and a prolonged storage capability. The results indicated that the biparatopic nanobody immunosorbent exhibited significant potential for clinical applications as it met the stringent criteria for both efficacy and safety.

SnoopLigase Enables Highly Efficient Generation of C-C-Linked Bispecific Nanobodies Targeting TNF-α and IL-17A.

Bispecific antibodies (bis-Nbs) have been extensively developed since the concept was devised over the decades. Taking advantage of the superior characteristics of nanobodies, bis-Nbs exhibit an emerging tendency to become the new generation of research and diagnostic tools. Traditional strategies to connect the homo- or heterogeneous monomers are commonly applied, but there are still technical issues to generate the bispecific molecules as efficiently as designed. Here, we utilize SnoopLigase to directly tether the C terminus (C-C) of the tagged nanobodies against tumor necrosis factor-α (TNF-α) and interleukin-17A (IL-17A). Under optimal conditions, the yield of C-C-linked bis-Nbs can reach as high as 70% due to the existence of SnoopLigase. The prepared bis-Nbs possessed similar or even higher affinity as the monomers and significantly inhibited the proliferation and migration of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) induced by TNF-α and IL-17A. This study provides an innovative route for using SnoopLigase to realize a highly efficient generation of C-C-linked bis-Nbs. The approach can be applied to different and multicomponent systems for their potential applications in disease diagnosis and treatment.

An engineered peptide tag-specific nanobody for immunoaffinity chromatography application enabling efficient product recovery at mild conditions.

Camelid-derived nanobody is emerging as a resourceful platform for developing immunoaffinity ligands for chromatography applications. Featured by high affinity and selectivity, BC2 nanobody (BC2-Nb), which can recognize a specific epitope tag (PDRKAAVSHWQQ, termed BC2T), is potential to be developed as a general tool for recombinant protein purification. However, excessively high affinity between binding partners makes the desorption of products less efficient and limits its application. Aiming to improve elution efficiency, structure-guided mutations of BC2-Nb were conducted to adjust the structural flexibility of its antigen-binding site. Six ligand variants were obtained with their binding affinity decreasing by about 100-fold. Among them, one mutated BC2-Nb named 44D was chosen to prepare immunoaffinity resin, and its adsorption and elution performance were well characterized. The site-directed mutation led to the equilibrium dissociation constant (KD) of BC2-Nb changing from 1.4 × 10-9 M to 1.4 × 10-7 M (44D). The resin using 44D as ligand retained a static binding capacity of 19.14 mg/mL toward BC2T-fused enhanced green fluorescent protein (eGFP-BC2T). Significantly improved elution efficiency was obtained with the mutated ligand. Protein recovery reached 94% at pH 3.5 for 44D-based resin, while the resin based on original BC2-Nb could only achieve its highest recovery of 84% at pH 2. In addition, a neutral elution condition (1 M arginine containing 50% propylene glycol, pH 7.4) was also found effective, which allowed a product recovery of 95%. The resin enabled direct capturing of eGFP-BC2T from bacterial lysates, and the one-step purification with the both elution conditions could achieve a product purity of more than 90%. This study provided a promising affinity ligand, and also proved the feasibility of controlling the elution process of nanobody-based affinity resin through the strategy of binding sites modification.

Single and dual functionalization of proteins using site-specific nucleophilic carbon ligations.

We here found that while Meldrum's acid as the reactive warhead allows for the attachment of a single chemical modification on aldehyde-containing proteins, pyrazolone derivatives in combination with a phosphine nucleophile enable protein dual site-specific conjugation with the same or distinct moieties. These reactions are efficient and convergent under biocompatible conditions and allow access to protein bioconjugates with superior stability, homogeneity and flexibility. Our work expands the repertoire of bioconjugation chemistries and offers opportunities to construct bioconjugates with defined structure that have potential for medical and biomaterial applications.

Nanobodies as solubilization chaperones for the expression and purification of inclusion-body prone proteins.

Here, we report a new protocol for enhancing the soluble expression of inclusion body (IB)-prone proteins in E. coli using nanobodies (Nbs) as a molecular-specific chaperone. The specific intracellular binding between the cognate-Nbs and the antigen is successfully achieved and enables the formation of a soluble Nb-antigen complex in E. coli. We further expand this method by adding an epitope tag (EPEA-tag) to the target proteins, and the anti-EPEA Nb was intended to act as the chaperone for in vivo binding with the EPEA tag. Such substitution may develop a "multi-specific" Nb-chaperone that can simultaneously and effectively cope with different IB proteins of interest.

Nanobody-loaded immunosorbent for highly-specific removal of interleukin-17A from blood.

Elimination of overproduced cytokines from blood can relieve immune system disorders caused by hypercytokinemia. Due to the central roles of interleukin-17A (IL-17A) plays in regulating the immunity and inflammatory responses in humans, here, a novel immunosorbent containing anti-IL-17A nanobodies (Nbs) was constructed for IL-17A removal from blood. The theoretical maximum adsorption capacity estimated from the Langmuir isotherm is up to 11.55 mg/g gel, which is almost consistent with the saturated adsorption capacity determined in dynamic adsorption. The in vitro plasma perfusion test demonstrated a remarkable adsorptive performance of the Nb-coupled sorbent since more than 75% IL-17A could be eliminated under the plasma/sorbent ratio of 1000:1. These results indicated the Nb-loaded immunosorbent can provide a simple and economic platform technology for immunoaffinity depletion of single or even multiple cytokines from plasma.

Nanobody-Based high-performance immunosorbent for selective beta 2-microglobulin purification from blood.

Removing ß2-microglobulin (ß2M) from blood circulation is considered to be the most effective method to delay the occurrence of dialysis-related amyloidosis (DRA). The ideal extracorporeal ß2M removal system should be cost-effective, highly specific and having a high capacity. However, the traditional technologies based on size exclusion do not have an adequate specificity, and alternative immunosorbents have limited applications due to low capacity and their high cost. Nanobodies (Nbs), the smallest functional recombinant antibody fragments, offer several advantages to overcome these obstacles. In this study, an anti-ß2M Nb with a C-terminal thiol-tag was successfully prepared from E. coli for site-directed and oriented immobilization and usage as capture ligand in a ß2M-selective immunosorbent. The prepared immunosorbent showed a high binding capacity of up to 7 mg ß2M per mL resin, which is 17 times higher than that of previous studies using single-chain variable antibody fragments (scFv). Furthermore, an exceptional high specificity has been demonstrated as other human serum proteins were not adsorbed during dynamic adsorption experiments. About 80% of the original binding capacity of the immunosorbent was restored after four consecutive easy regenerations, whereas 90% of the original capacity was retained after 1-month storage of the resin. Moreover, the mathematical model fitted very well the in vitro perfusion. The results with this pioneering immunosorbent confirm its possible clinical application and is expected to reach the required clinical effect of immunoadsorption therapy. STATEMENT OF SIGNIFICANCE: Dialysis-related amyloidosis (DRA), associated with the accumulation of ß2-microglobulin (ß2M), is a serious complication of end-stage kidney disease. Removing ß2M from blood circulation by extracorporeal blood purification is considered to be the most effective method to delay the occurrence of DRA. However, the existing methods are incapable to eliminate sufficient quantities of ß2M from circulation, either because of lack of specificity, high cost or for low capacity. In this manuscript, we provide a practical and economic immunosorbent based on anti-ß2M nanobody for DRA. The prepared immunosorbent was reusable and storable, and demonstrated high specificity and realized a high binding capacity of up to 7 mg ß2M per mL resin, which is 17 times higher than that of the previous studies.

High Expression Achievement of Active and Robust Anti-ß2 microglobulin Nanobodies via E.coli Hosts Selection.

Nanobodies (VHHs) overcome many of the drawbacks of conventional antibodies, and the related technologies represent state-of-the-art and advanced applications in scientific research, pharmaceuticals, and therapies. In terms of productivity and economic cost, the cytoplasmic expression of VHHs in Escherichia coli (E. coli) is a good process for their recombinant production. The cytoplasmic environment of the host is critical to the affinity and stability of the recombinant VHHs in soluble form, yet the effects have not been studied. For this purpose, recombinant anti-ß2 microglobulin VHHs were constructed and expressed in four commercialized E. coli hosts, including BL21 (DE3), Rosetta-gami B (DE3) pLysS, Origami 2 (DE3) and SHuffle T7 Express. The results showed that anti-ß2 microglobulin (ß2MG) VHHs expressed in different hosts exhibited distinctive differences in the affinity and structural characteristics. The VHHs expressed in Rosetta-gami B (DE3) pLysS possessed not only the greatest affinity of (equilibrium dissociation constant) KD = 4.68 × 10-8 M but also the highest yields compared with the VHHs expressed in BL21 (DE3), Origami 2 (DE3) and SHuffle T7 Express. In addition, the VHHs expressed in Rosetta-gami B (DE3) pLysS were more stable than the VHHs expressed in the rest three hosts. Thus far, we have successfully realized the high expression of the active and robust anti-ß2MG VHHs in Rosetta-gami B (DE3) pLysS. The underlying principle of our study is able to guide the expression strategies of nanobodies on the context of industrial large-scale production.

Generation and Application of Fluorescent Anti-Human ß2-Microglobulin VHHs via Amino Modification.

The functionalization of VHHs enables their application in almost every aspect of biomedical inquiry. Amino modification remains a common strategy for protein functionalization, though is considered to be inferior to site-specific methods and cause protein property changes. In this paper, four anti-ß2M VHHs were selected and modified on the amino group by NHS-Fluo. The impacts of amino modification on these VHHs were drastically different, and among all th examples, the modified NB-1 maintained the original stability, bioactivity and homogeneity of unmodified NB-1. Specific recognition of VHHs targeting ß2M detected by fluorescence imaging explored the possible applications of VHHs. Via this study, we successfully functionalized the anti-ß2M VHHs through amino modification and the results are able to instruct the simple and fast functionalization of VHHs in biomedical researches.

One-step Preparation of a VHH-based Immunoadsorbent for the Extracorporeal Removal of ß2-microglobulin.

Dialysis-related amyloidosis (DRA), which has been widely recognized to be associated with the accumulation of ß2-microglobulin (ß2-m) in blood, is one of the most common complications in patients receiving long-term dialysis treatment. The most significant side-effect of existing hemodialysis sorbents for the removal of ß2-m from blood is the loss of vital proteins due to non-specific adsorptions. Although the traditional antibodies have the capability to specifically remove ß2-m from blood, high cost limits their applications in clinics. Single domain antibodies derived from the Camelidae species serve as a superior choice in the preparation of immunoadsorbents due to their small size, high stability, amenability, simplicity of expression in microbes, and high affinity to recognize and interact with ß2-m. In this study, we modified the anti-ß2-m VHH by the formylglycine-generating enzyme (FGE), and then directly immobilized the aldehyde-modified VHH to the amino-activated beads. Notably, the fabrication is cost- and time-effective, since all the preparation steps were performed in the crude cell extract without rigorous purification. The accordingly prepared immunoadsorbent with VHHs as ligands exhibited the high capacity of ß2-m (0.75 mg/mL). In conclusion, the VHH antibodies were successfully used as affinity ligands in the preparation of novel immunoadsorbents by the site-specific immobilization, and effectively adsorbed ß2-m from blood, therefore opening a new avenue for efficient hemodialysis.

Oriented Immobilization and Quantitative Analysis Simultaneously Realized in Sandwich Immunoassay via His-Tagged Nanobody.

Despite the advantages of the nanobody, the unique structure limits its use in sandwich immunoassay. In this study, a facile protocol of sandwich immunoassay using the nanobody was established. In brief, ß amyloid and SH2, an anti-ß amyloid nanobody, were used as capture antibody and antigen, respectively. The SH2 fused with His-tag was first purified and absorbed on Co2+-NTA functional matrix and then immobilized through H2O2 oxidation of Co2+ to Co3+ under the optimized conditions. Then, 150 mM imidazole and 20 mM EDTA were introduced to remove the unbound SH2. The immobilized SH2 showed highly-sensitive detection of ß amyloid. It is interesting that the quantification of the sandwich immunoassay was carried out by determining the His-tag of the detection nanobody, without interference from the His-tag of the capture nanobody. The immobilized SH2 detached exhibited outstanding stability during 30 days of storage. Taken together, His6-tag facilitated both the oriented immobilization of capture antibody and quantitative assay of detection antibody in sandwich immunoassay. We propose a facile and efficient sandwich immunoassay method that opens new avenue to the study of His-tagged protein interactions.

A facile method to oriented immobilization of His-tagged BirA on Co3+-NTA agarose beads.

A facile and economical method was established for the oriented immobilization of biotin ligase (BirA) on Co3+-NTA sepharose through H2O2 oxidation of Co2+ and His-tag. His-tag of the BirA were designed at both N-terminal (His-BirA) and C-terminal (BirA-His), respectively. Immobilization of the His-BirA was performed, realized to 92.85% using by 10 mM H2O2 without compromising catalytic activity. Because amounts of ions on matrix were far more than that of the immobilized BirA, EDTA should be used to remove residual ions before catalyzing, while it should be limited to lower than 30 mM, and imidazole ranging from 50 to 250 mM could be added in the catalytic system. When 10 mM EDTA and 50 mM imidazole were used, over 90% of substrates were obtained from the matrix. Moreover, the His-BirA showed higher immobilization rate than the BirA-His, while both of them appeared high catalytic abilities at pH ranging from 6.5 to 9.0, indicating versatile options in the biotinylation of proteins with different pH stabilities. Under the best catalytic conditions, the both immobilized His-BirA and BirA-His exhibited the same activity as the free. When the enzyme was incubated at different pH (pH 3.0, 4.0, 5.0, 10.0 and 11.0) and temperature (40 °C, 50 °C and 60 °C), the immobilized His-BirA showed less pH-sensitive, overall preferable thermo-stability than the free, making it a more desirable option for storage and transportation. More importantly, the reusability of the immobilized His-BirA implied a promising value in industrialization.

Freezing-assisted synthesis of covalent C-C linked bivalent and bispecific nanobodies.

Bi-valent/specific antibodies are coming to the forefront of therapeutic and diagnostic applications for extending the functions of conventional antibodies. Nanobodies as building blocks, due to their small sizes, are prone to synthesizing these homo/hetero-dimers. However, the classical C-terminus to N-terminus (C-N) ligation manner for generating the dimer results in the inhibition of the antigen-binding capacity of the bivalent/specific antibodies. In this study, we designed and constructed several C-terminus to C-terminus (C-C) linked bivalent and bispecific nanobodies against the human ß2-microglobulin via freezing, overcoming the biological function-disrupt raised by the C-N ligation. The nanobody modified by the formylglycine generating enzyme was ligated to a hydrazide or aminooxy bi-functionalized linker. During the process, we discovered that freezing significantly improved the efficiency of hydrazone or oxime formation between the linker and nanobodies, which could not take place at room temperature. By freezing from -10 to -20 °C, up to 50% yield of bivalent nanobodies was achieved within 24 h. The C-C linked nanobody-fusions maintained almost all of its binding activity and exhibited an increase by two orders of magnitudes in affinity kinetics, demonstrating the superiority of C-C over the C-N linking approach.

Photoinitiated Polymerization-Induced Self-Assembly of Glycidyl Methacrylate for the Synthesis of Epoxy-Functionalized Block Copolymer Nano-Objects.

Herein, a novel photoinitiated polymerization-induced self-assembly formulation via photoinitiated reversible addition-fragmentation chain transfer dispersion polymerization of glycidyl methacrylate (PGMA) in ethanol-water at room temperature is reported. It is demonstrated that conducting polymerization-induced self-assembly (PISA) at low temperatures is crucial for obtaining colloidal stable PGMA-based diblock copolymer nano-objects. Good control is maintained during the photo-PISA process with a high rate of polymerization. The polymerization can be switched between "ON" and "OFF" in response to visible light. A phase diagram is constructed by varying monomer concentration and degree of polymerization. The PGMA-based diblock copolymer nano-objects can be further cross-linked by using a bifunctional primary amine reagent. Finally, silver nanoparticles are loaded within cross-linked vesicles via in situ reduction, exhibiting good catalytic properties.

Polymerization-Induced Self-Assembly of Homopolymer and Diblock Copolymer: A Facile Approach for Preparing Polymer Nano-Objects with Higher-Order Morphologies.

Polymerization-induced self-assembly of homopolymer and diblock copolymer using a binary mixture of small chain transfer agent (CTA) and macromolecular chain transfer agent (macro-CTA) is reported. With this system, homopolymer and diblock copolymer were formed and chain extended at the same time to form polymer nano-objects. The molar ratio of homopolymer and diblock copolymer had a significant effect on the morphology of the polymer nano-objects. Porous vesicles, porous nanospheres, and micron-sized particles with highly porous inner structure were prepared by this method. We expect that this method will greatly expand the promise of polymerization-induced self-assembly for the synthesis of a range of polymer nano-objects with unique morphologies.

Facile Preparation of CO2 -Responsive Polymer Nano-Objects via Aqueous Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA).

Carbon dioxide (CO2 )-responsive polymer nano-objects are prepared by photoinitiated reversible addition-fragmentation chain transfer dispersion polymerization of 2-hydroxypropyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) in water at room temperature using a poly(poly(ethylene glycol) methyl ether methacrylate) macromolecular chain transfer agent. Kinetic studies confirm that full monomer conversions are achieved in all cases within 10 min of visible-light irradiation (405 nm, 0.5 mW cm-2 ). The effect of DMAEMA on the polymerization is studied in detail, and pure higher order morphologies (worms and vesicles) are prepared by this particular formulation. Finally, CO2 -responsive property of the obtained vesicles is investigated by dynamic light scattering, visual appearance, and transmission electron microscope.

Low-Temperature Synthesis of Thermoresponsive Diblock Copolymer Nano-Objects via Aqueous Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA) using Thermoresponsive Macro-RAFT Agents.

Photoinitiated reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of 2-hydroxypropyl methacrylate is conducted in water at low temperature using thermoresponsive copolymers of 2-(2-methoxyethoxy) ethyl methacrylate and oligo(ethylene glycol) methacrylate (Mn = 475 g mol(-1) ) as the macro-RAFT agent. Kinetic studies confirm that quantitative monomer conversion is achieved within 15 min of visible-light irradiation (405 nm, 0.5 mW cm(-2) ), and good control is maintained during the polymerization. The polymerization can be temporally controlled by a simple "ON/OFF" switch of the light source. Finally, thermoresponsive diblock copolymer nano-objects with a diverse set of complex morphologies (spheres, worms, and vesicles) are prepared using this particular formulation.

Alcoholic Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA): A Fast Route toward Poly(isobornyl acrylate)-Based Diblock Copolymer Nano-Objects.

We report a fast alcoholic photoinitiated polymerization-induced self-assembly (photo-PISA) formulation via photoinitiated RAFT dispersion polymerization of isobornyl acrylate (IBOA) in an ethanol/water mixture at 40 °C using a monomethoxy poly(ethylene glycol) (mPEG) based chain transfer agent. Polymerization proceeded rapidly via the exposure to visible light irradiation (405 nm, 0.5 mW/cm2), and high monomer conversion (>95%) was achieved within 30 min. Kinetic studies confirmed that good control was maintained during the photo-PISA process, and the polymerization can be activated or deactivated by light. Finally, we demonstrated that a diverse set of complex morphologies (spheres, worms, or vesicles) could be achieved by varying reaction parameters, and a phase diagram was constructed.