Immobilization and functional reconstitution of antibody Fab fragment by solid-phase refolding

Screen printed electrode-based biosensor functionalized with magnetic cobalt/single-chain antibody fragments for cocaine biosensing in different matrices

On-site detection of substance abuse is an important approach in the preventive and intervention protocols implementations. It is known that the traditional methods are heavy, time-consuming, and need a high level of logistical requirements. As such, biosensors represent great potential to simplify and improve substance abuse detection. In this study, we have designed a functionalized screen-printed electrode (SPE) electrochemical biosensor with cobalt oxide nanoparticles and single-chain antibody fragments (scFvs) for cocaine detection. Different electrochemical techniques such as differential pulse voltammetry, cyclic voltammetry, and electrochemical impedance spectrometry were used to examine the functionality of the designed biosensor. Furthermore, SEM observations were performed to observe the surface changes after functionalization. The results showed that the linearity ranged between 5.0 and 250 ng/mL and a detection limit of 3.6 ng/mL (n = 6). These results were compared to results obtained from Q-TOF/MS where four different matrices (serum, sweat, urine, and saliva) were spiked with 100 ng/mL cocaine and were analyzed by both methods (Biosensor and Q-TOF/MS). Results showed a higher performance of the biosensor compared to traditional methods. In addition, the selectivity of the biosensor was shown in the presence of different interferents where the designed platform showed a specific response to only cocaine. In conclusion, the designed biosensor proposes great potential for portable and on-site substance abuse detection in addition to boasting the capability of reuse of the SPE and thus, reducing the costs related to such applications.

β-Cyclodextrin-Modified Magnetic Nanoparticles Immobilized on Sepharose Surface Provide an Effective Matrix for Protein Refolding

In this article, we propose an impressive and facile strategy to improve protein refolding using solid phase artificial molecular chaperones consisting of the surface-functionalized magnetic nanoparticles. Specifically, monotosyl-β-cyclodextrin connected to the surface of 3-aminopropyltriethoxysilane (APES)-modified magnetic nanoparticles is immobilized on the sepharose surface to promote interaction with exposed hydrophobic surfaces of partially folded (intermediates) and unfolded states of proteins. Their efficiencies were investigated by circular dichroism spectroscopy and photoluminescence spectroscopy of the protein. Although the mechanism of this method is based on principles of hydrophobic chromatography, this system is not only purging the native protein from inactive inclusion bodies but also improving the protein refolding process. We chose β-cyclodextrin (β-CD) considering multiple reports in the literature about its efficiency in protein refolding and its biocompatibility. To increase the surface area/volume ratio of the sepharose surface by nanoparticles, more β-CD molecules are connected to the sepharose surface to make a better interaction with proteins. We suppose that proteins are isolated in the nanospace created by bound cyclodextrins on the resin surface so intermolecular interactions are reduced. The architecture of nanoparticles was characterized by Fourier transform infrared spectra, X-ray diffraction, scanning electron microscopy images, energy dispersive X-ray spectroscopy, nuclear magnetic resonance (¹H NMR and ¹³C NMR), and dynamic light scattering.

Recombinant antibody production evolves into multiple options aimed at yielding reagents suitable for application-specific needs

BACKGROUND

Antibodies have been a pillar of basic research, while their relevance in clinical diagnostics and therapy is constantly growing. Consequently, the production of both conventional and fragment antibodies constantly faces more demanding challenges for the improvement of their quantity and quality. The answer to such an increasing need has been the development of a wide array of formats and alternative production platforms. This review offers a critical comparison and evaluation of the different options to help the researchers interested in expressing recombinant antibodies in their choice.

RESULTS

Rather than the compilation of an exhaustive list of the recent publications in the field, this review intendeds to analyze the development of the most innovative or fast-growing strategies. These have been illustrated with some significant examples and, when possible, compared with the existing alternatives. Space has also been given to those solutions that might represent interesting opportunities or that investigate critical aspects of the production optimization but for which the available data as yet do not allow for a definitive judgment.

CONCLUSIONS

The take-home message is that there is a clear process of progressive diversification concerning the antibody expression platforms and an effort to yield directly application-adapted immune-reagents rather than generic naked antibodies that need further in vitro modification steps before becoming usable.

High efficiency reduction capability for the formation of Fab׳ antibody fragments from F(ab)2 units

Antibodies have widespread applications in areas ranging from therapeutics to chromatography and protein microarrays. Certain applications require only the fragment antigen-binding (Fab) units of the protein. This study compares the cleavage efficacy of dithiothreitol (DTT), mercaptoethylamine (MEA), and dithiobutylamine (DTBA) – a relatively new reducing agent synthesized in 2012. Pseudo-first order kinetic analyses show DTBA to be ~213 times faster than DTT and ~71 times faster than MEA in the formation of Fab׳ antibody fragments from polyclonal rabbit antibodies. Monoclonal mouse antibodies were also used to show the feasibility of the reduction process on antibodies from a different species and with a different clonality. DTBA cleaved the monoclonal mouse F(ab)₂ units most efficiently, ~2 times faster than DTT ~10 times faster than MEA. Due to the extremely quick reactivity of all the reducing agents in the first five minutes of monoclonal antibody reductions as well as for the DTBA reductions of the polyclonal rabbit antibodies, the pseudo-first order kinetic analyses should be interpreted qualitatively for these results. Nucleophilic sulfides on Fab׳ fragments are preserved in the DTBA reduction process, demonstrated by their reactivity with Ellman׳s reagent. Degradation of the Fab׳ fragments was observed with the monoclonal mouse antibodies after reduction with DTBA or DTT. In conclusion, DTBA is the more efficient reducing agent compared to DTT and MEA, however, the reduction process should be optimized as degradation of the Fab׳ fragments is possible.

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Dithiobutylamine (DTBA) is a relatively new reducing agent synthesized in 2012.

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Antibody cleavage efficiency was compared with DTT, MEA, and DTBA.

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DTBA was able to cleave monoclonal mouse and polyclonal rabbit antibodies.

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Fab׳ nucleophilic sulfides were preserved during the cleavage process.

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DTBA cleavage should be optimized as undesirable byproducts are possible.

Site-specific immobilization of recombinant antibody fragments through material-binding peptides for the sensitive detection of antigens in enzyme immunoassays

The immobilization of an antibody is one of the key technologies that are used to enhance the sensitivity and efficiency of the detection of target molecules in immunodiagnosis and immunoseparation. Recombinant antibody fragments such as VHH, scFv and Fabs produced by microorganisms are the next generation of ligand antibodies as an alternative to conventional whole Abs due to a smaller size and the possibility of site-directed immobilization with uniform orientation and higher antigen-binding activity in the adsorptive state. For the achievement of site-directed immobilization, affinity peptides for a certain ligand molecule or solid support must be introduced to the recombinant antibody fragments. In this mini-review, immobilization technologies for the whole antibodies (whole Abs) and recombinant antibody fragments onto the surfaces of plastics are introduced. In particular, the focus here is on immobilization technologies of recombinant antibody fragments utilizing affinity peptide tags, which possesses strong binding affinity towards the ligand molecules. Furthermore, I introduced the material-binding peptides that are capable of direct recognition of the target materials. Preparation and immobilization strategies for recombinant antibody fragments linked to material-binding peptides (polystyrene-binding peptides (PS-tags) and poly (methyl methacrylate)-binding peptide (PMMA-tag)) are the focus here, and are based on the enhancement of sensitivity and a reduction in the production costs of ligand antibodies. This article is part of a Special Issue entitled: Recent advances in molecular engineering of antibody.

Efficient refolding and immobilization of PMMA-tag-fused single-chain Fv antibodies for sensitive immunological detection on a PMMA plate

In this study, we investigated the efficient refolding and site-specific immobilization of single-chain variable fragments (scFvs) genetically fused with a poly(methylmethacrylate)-binding peptide (PMMA-tag). According to the results of an aggregation test of a scFv-PM in the presence of 0.5 M urea, aggregation was hardly detectable at a weak-alkaline pH (8.5) with lower concentrations of NaCl. Consequently, more than 93% recovery of the anti-RNase scFv-PM model was attained, when it was refolded by dialysis against 50 mM TAPS (pH8.5). These results suggested that the apparent isoelectric point (pI) of a target scFv was decreased to a great extent by the genetic fusion of a PMMA-tag containing 5 acidic amino acids, and, thus, the solubility of the scFv-PM in its semi-denatured form was considerably improved. We also designed alternative peptide-tags composed of plural aspartic acid residues (D5, D10 and D15-tags) to decrease the apparent pI value of the fusion protein. As a consequence, scFv-D5, scFv-D10 and scFv-D15 were also efficiently refolded with yields of more than 95%. It is noteworthy that even scFv-PS-D15, which had both a positively charged polystyrene-binding peptide (PS-tag) and a negatively charged D15-tag, was serially connected at the C-terminal region of scFvs, and also refolded with a yield of 96.1%. These results clearly indicate that controlling the apparent pI value of scFvs by the fusion of oligo-peptides composed of acidic amino acids at the C-terminus resulted in a high degree of recovery via dialysis refolding. According to the results of a sandwich ELISA using scFv-PMs, scFv-D15 and scFv-PS-D15 as ligands, high antigen-binding signals were detected from both the PMMA and phi-PS plates immobilized with scFv-PMs. Furthermore, the high antigen-binding activity of scFv-PMs was maintained in an adsorption state when it was immobilized on the surface of not only PMMA, but also hydrophilic PS (phi-PS) and polycarbonate (PC). These results strongly suggested that a PMMA-tag introduced at the C-terminus of scFvs preferably recognizes ester and/or carboxyl groups exposed on the surface of plastics. The scFv-PM developed in the present study has advantages such as being a ligand antibody, compared with whole Ab and the conventional PS-tag-fused scFvs (scFv-PS), and, thus, it is considerably useful in a sandwich ELISA as well as in various immuno-detection and immuno-separation systems.