Label-Free Glycoprofiling with Multiplex Surface Plasmon Resonance: A Tool To Quantify Sialylation of Erythropoietin

Application of lectin immobilized on polyHIPE monoliths for bioprocess monitoring of glycosylated proteins

In-process monitoring of glycosylated protein concentration becomes very important with the introduction of perfusion bioprocesses. Affinity chromatography based on lectins allows selective monitoring when carbohydrates are accessible on the protein surface. In this work, we immobilized lectin on polyHIPE type of monoliths and implemented it for bioprocess monitoring. A spacer was introduced to lectin, which increased binding kinetics toward Fc-fusion protein, demonstrated by bio-layer interferometry. Furthermore, complete desorption using 0.25 M galactose was shown. Affinity column exhibited linearity in the range between 0.5 and 8 mg/ml and flow-unaffected binding for the flow-rates between 0.5 and 8 ml/min. Long-term stability over at least four months period was demonstrated. No unspecific binding of culture media components, including host cell proteins and DNA, was detected. Results obtained by affinity column matched concentration values obtained by a reference method.

Application of Lectin Microarrays for Biomarker Discovery

Many proteins in living organisms are glycosylated. As their glycan patterns exhibit protein-, cell-, and tissue-specific heterogeneity, changes in the glycosylation levels could serve as useful indicators of various pathological and physiological states. Thus, the identification of glycoprotein biomarkers from specific changes in the glycan profiles of glycoproteins is a trending field. Lectin microarrays provide a new glycan analysis platform, which enables rapid and sensitive analysis of complex glycans without requiring the release of glycans from the protein. Recent developments in lectin microarray technology enable high-throughput analysis of glycans in complex biological samples. In this review, we will discuss the basic concepts and recent progress in lectin microarray technology, the application of lectin microarrays in biomarker discovery, and the challenges and future development of this technology. Given the tremendous technical advancements that have been made, lectin microarrays will become an indispensable tool for the discovery of glycoprotein biomarkers.

GlycoBIST: A System for Automatic Glycan Profiling of a Target Protein Using Milli-Bead Array in a Tip

Lectin is a biomolecule that recognizes a specific part of glycans and, thus, has been used widely as a probe for glycoprotein analysis. Owing to the wide repertoire in nature combined with the recent two decades of advances in microarray technology, the multiplexed use of lectins has been widely used for glycan profiling of endogenous proteins. Because protein glycosylation is recognized as being biologically important and is expected to be a reliable disease marker, lectin microarray analysis with highly sensitive detection has been used to discover disease-relevant glycosylation alterations. However, the conventional system is limited to research purposes; thus, its implementation in clinical settings is warranted. Here, we provide an automatic glycan profiling method using GlycoBIST. A unique array format is used for 10-plexed lectin-glycoprotein interaction analysis on 1-mm-sized beads, which are arranged vertically in a capillary-shaped plastic tip. Using a one-boxed autopipetting machine, the whole process (including interaction, washing, and detection) is performed automatically and serially, resulting in reproducible measurements. In this article, a typical method for glycan profiling of a purified glycoprotein and the fabrication of GlycoBIST tips is explained. © 2020 by John Wiley & Sons, Inc. Basic Protocol 1: Fabrication of a GlycoBIST tip Basic Protocol 2: Automatic profiling of a target glycoprotein using GlycoBIST.

Feasibility Study for Bedside Production of Recombinant Human Acid α-Glucosidase: Technical and Financial Considerations

OBJECTIVE

The high cost of orphan drugs limits their access by many patients, especially in low- and middle-income countries. Many orphan drugs are off-patent without alternative generic or biosimilar versions available. Production of these drugs at the point-of-care, when feasible, could be a cost-effective alternative.

METHODS

The financial feasibility of this approach was estimated by setting up a small-scale production of recombinant human acid alpha-glucosidase (rhGAA). The commercial version of rhGAA is Myozyme™, and Lumizyme™ in the United States, which is used to treat Pompe disease. The rhGAA was produced in CHO-K1 mammalian cells and purified using multiple purification steps to obtain a protein profile comparable to Myozyme™.

RESULTS

The established small-scale production of rhGAA was used to obtain a realistic cost estimation for the magistral production of this biological drug. The treatment cost of rhGAA using bedside production was estimated at $3,484/gram, which is 71% lower than the commercial price of Myozyme ™.

CONCLUSION

This study shows that bedside production might be a cost-effective approach to increase the access of patients to particular life-saving drugs.

High-Throughput Quantification and Glycosylation Analysis of Antibodies Using Bead-Based Assays

A novel version of bead -based assays with fluorescence detection enables the high-throughput analysis of antibodies and proteins. The protocols are carried out in special 384-well plates, require very few manual interventions, and are easy to automate. Here we describe how the technology can be used to determine antibody titers and screen for product glycosylation, a critical quality attribute, early in cell line and bioprocess development.

Identification of methionine oxidation in human recombinant erythropoietin by mass spectrometry: Comparative isoform distribution and biological activity analysis

BACKGROUND

Oxidative degradation of human recombinant erythropoietin (hrEPO) may occur in manufacturing process or therapeutic applications. This unfavorable alteration may render EPO inefficient or inactive. We investigated the effect of methionine/54 oxidative changes on the amino acid sequences, glycoform distribution and biological activity of hrEPO.

METHODS

Mass spectrometry was applied to verify the sequence and determine the methionine oxidation level of hrEPO. Isoform distribution was studied by capillary zone electrophoresis method. In vivo normocythemic mice assay was used to assess the biological activity of three different batches (A, B, and C) of the proteins.

RESULTS

Nano-LC/ESI/MS/MS data analyses confirmed the amino acid sequences of all samples. The calculated area percent of three isoforms (2-4 of the 8 obtained isoforms) were decreased in samples of C, B, and A with 27.3, 16.7, and 6.8% of oxidation, respectively. Specific activities were estimated as 53671.54, 95826.47, and 112994.93 mg/mL for the samples of A, B, and C, respectively.

CONCLUSION

The observed decrease in hrEPO biological activity, caused by increasing methionine oxidation levels, was rather independent of its amino acid structure and mainly associated with the higher contents of acidic isoforms.

A Novel Fiber Optic Surface Plasmon Resonance Biosensors with Special Boronic Acid Derivative to Detect Glycoprotein

We proposed and demonstrated a novel tilted fiber Bragg grating (TFBG)-based surface plasmon resonance (SPR) label-free biosensor via a special boronic acid derivative to detect glycoprotein with high sensitivity and selectivity. TFBG, as an effective sensing element for optical sensing in near-infrared wavelengths, possess the unique capability of easily exciting the SPR effect on fiber surface which coated with a nano-scale metal layer. SPR properties can be accurately detected by measuring the variation of transmitted spectra at optical communication wavelengths. In our experiment, a 10° TFBG coated with a 50 nm gold film was manufactured to stimulate SPR on a sensor surface. To detect glycoprotein selectively, the sensor was immobilized using designed phenylboronic acid as the recognition molecule, which can covalently bond with 1,2- or 1,3-diols to form five- or six-membered cyclic complexes for attaching diol-containing biomolecules and proteins. The phenylboronic acid was synthetized with long alkyl groups offering more flexible space, which was able to improve the capability of binding glycoprotein. The proposed TFBG-SPR sensors exhibit good selectivity and repeatability with a protein concentration sensitivity up to 2.867 dB/ (mg/mL) and a limit of detection (LOD) of 15.56 nM.

Glycan profiling of proteins using lectin binding by Surface Plasmon Resonance

Glycan profiling of proteins was studied through their lectin binding activity by Surface Plasmon Resonance (SPR). To validate the method, we monitored specific lectin binding with sequential removal of sugar moieties from human transferrin using specific glycosidases. The results clearly indicated that glycans on the protein can be identified by their selective binding activity to various lectins. Using this method, we characterized Fc glycosylation profiles of therapeutic peptibodies and antibodies expressed in mammalian cells (CHO and HEK 293 6E cells), with E. coli expressed proteins as the negative controls. We observed that antibodies expressed in CHO cells did not contain any sialic acid, while antibodies expressed in 293 6E cells contained sialic acid. CHO cell expressed antibodies were also more heavily fucosylated than the ones expressed by 293 6E cells. We further applied this method to measure the fucose composition of glycan engineered mouse antibodies, as well as to determine mannose composition of human antibody variants with depletion or enrichment of high mannose. The glycan profiles generated using this method were comparable to results from 2-AB labeled glycan analysis of normal-phase separated glycans, and Fc gamma receptor binding activity of the glycan engineered antibodies were consistent with their glycan profiles. Hence, we demonstrated that SPR lectin binding analysis can be a quick alternative method to profile protein glycosylation.

Nanotechnology in Glycomics: Applications in Diagnostics, Therapy, Imaging, and Separation Processes

This review comprehensively covers the most recent achievements (from 2013) in the successful integration of nanomaterials in the field of glycomics. The first part of the paper addresses the beneficial properties of nanomaterials for the construction of biosensors, bioanalytical devices, and protocols for the detection of various analytes, including viruses and whole cells, together with their key characteristics. The second part of the review focuses on the application of nanomaterials integrated with glycans for various biomedical applications, that is, vaccines against viral and bacterial infections and cancer cells, as therapeutic agents, for in vivo imaging and nuclear magnetic resonance imaging, and for selective drug delivery. The final part of the review describes various ways in which glycan enrichment can be effectively done using nanomaterials, molecularly imprinted polymers with polymer thickness controlled at the nanoscale, with a subsequent analysis of glycans by mass spectrometry. A short section describing an active glycoprofiling by microengines (microrockets) is covered as well.

Effects of Interfacial Properties of a Surface Modified Surface Plasmon Resonance Chip on Protein Immobilization Performance

In order to confirm the correlation between interfacial properties of modified surface plasmon resonance (SPR) chips and their SPR responses to immobilized anti-IgG, SPR chips were modified by mercaptoundecanoic acid, poly(ethylene glycol) diacrylate (PEG), PEG-based copolymer and cyclodextrin coupled PEG using self-assembled or radical polymerization methods. The resulting interfacial properties such as film thickness and hydrophilicity were characterized by AFM, elliptic polarization scanners and contact angle meter. Immobilization of human IgG on the modified chips was achieved by EDC/NHS activation through an amide bond. The association between fixed IgG and free anti-IgG was reflected by the variation of SPR responses and the binding ability was evaluated by Langmuir isotherms. As observed, the adsorption between IgG and anti-IgG was affected by the interfacial properties of different modifiers, such that a chip with a thinner and more hydrophilic layer may result in a higher SPR response, producing a larger adsorption equilibrium constant for protein interaction.