Partition coefficient screening - An effective approach for finding the best conditions for byproduct removal as demonstrated by a bispecific antibody purification case.

In recombinant protein purification, differences in isoelectric point (pI)/surface charge and hydrophobicity between the product and byproducts generally form the basis for separation. For bispecific antibodies (bsAbs), in many cases the physicochemical difference between product and byproducts is subtle, making byproduct removal considerably challenging. In a previous report, with a bsAb case study, we showed that partition coefficient (Kp) screening for the product and byproducts under various conditions facilitated finding conditions under which effective separation of two difficult-to-remove byproducts was achieved by anion exchange (AEX) chromatography. In the current work, as a follow-up study, we demonstrated that the same approach enabled identification of conditions allowing equally good byproduct removal by mixed-mode chromatography with remarkably improved yield. Results from the current and previous studies proved that separation factor determination based on Kp screening for product and byproduct is an effective approach for finding conditions enabling efficient and maximum byproduct removal, especially in challenging cases.

Development and verification of whole column imaging detection-capillary isoelectric focusing method for determination of isoelectric point of pertactin / 中国生物制品学杂志

@#Objective To develop and verify a whole column imaging detection-capillary isoelectric focusing(WCID-CIEF)method for the determination of isoelectric point(pI)of pertactin(PRN).Methods The WCID-CIEF method for the determination of PRN antigen was developed by optimizing the parameters such as the focusing time and final concentration of samples in the WCID-CIEF process,and verified for the specificity,accuracy,repeatability,intermediate precision,durability and inter-batch consistency.Results The optimal focusing time of WCID-CIEF for the determination of PRN antigen pI was 1 min at 1 500 V and 3 min at 3 000 V. The optimal final concentration of PRN antigen was 300 μg/mL. The PRN antigen pI was about 6. 035,and the blank matrix showed no interference peak in the position of each peak of antigen. The method had good specificity,accuracy,repeatability,intermediate precision,durability and consistency among batches.Conclusion The developed WCID-CIEF method is suitable for the pI detection and charge heterogeneity analysis of PRN antigen,which can provide basis for the characterization of PRN antigen and reference for the quality control in the process of development and production of related vaccines.

Resin and loading condition screening for effective and robust byproducts removal by anion exchange chromatography: A case study.

In downstream processing of protein therapeutics, ion exchange (IEX) chromatography is a powerful tool for removing byproducts whose isoelectric point (pI) is appreciably different from that of the product. Although in theory for a given case cation exchange (CEX) and anion exchange (AEX) chromatography should be equally effective for separation, in reality they may show different effectiveness. In the current work, with a case study, we demonstrated that AEX is more effective than CEX chromatography at removing the associated byproducts. In addition, we screened AEX resins and loading conditions to achieve best separation. Finally, we demonstrated that effective separation was achieved with the selected resin/condition, and chromatography performance was comparable between runs conducted at low and high load densities, suggesting that the developed process was relatively robust. The procedure described in this work can be used as a general approach for selecting resin and loading condition that allow for effective and robust removal of byproduct that binds weaker than the product to the selected type of column.

Development and verification of capillary isoelectric focusing-wholecolumn imaging detection method for isoelectric point analysis of recombinant human brain natriuretic peptide / 中国生物制品学杂志

@#Objective To establish and verify a capillary isoelectric focusing-whole column imaging detection(CIEFWCID) method for the analysis of isoelectric point(pI) of recombinant human brain natriuretic peptide.Methods The ampholyte,space-occupying agent,protein concentration,focusing time were optimized by CIEF-WCID method,and the best condition for the detection of recombinant human brain natriuretic peptide was obtained.The repeatability,precision and durability of the developed method were verified,and three batches of recombinant human brain natriuretic peptide produced continuously were analyzed for pI.Results HR AESlyte 8-10.5 was selected as ampholyte,while 25 mmol/L sodium hydroxide as the space-occupying agent;The final concentration of the sample was 87.5 μg/mL and the focusing time was 8min.The relative standard deviation RSD of pI detection was 0.1% after six consecutive injections of the same sample;The RSD of pI detection of six samples was 0.1%;The pI RSD of the main peak was 0.1% at different final concentrations of the sample,and the pI RSD of the sample was 0.1% at different storage time,while the pI markers could not be changed arbitrarily.The pI was detected in three consecutive batches of recombinant human brain natriuretic peptide samples.Conclusion The developed CIEF-WCID method for pI analysis of recombinant human brain natriuretic peptide had good repeatability and precision and might be used for follow-up quality control of recombinant human brain natriuretic peptide.

IgG-like bispecific antibody platforms with built-in purification-facilitating elements.

Assembly of IgG-like asymmetric bispecific antibodies (bsAbs) requires heavy chain heterodimerization and cognate heavy-light chain pairings. Multiple strategies have been developed to solve these chain association issues. While these strategies greatly promote correct chain pairing, they normally cannot prevent low amount of chain mispaired byproducts from being generated. Besides, byproducts can also be generated as a result of discordant chain expression. The existence of various byproducts poses considerable challenges to downstream processing during the production of recombinant IgG-like bsAbs. In many cases, yield is greatly compromised for purity improvement. This mini review introduces eight IgG-like bsAb platforms, which share a common feature: they all contain built-in purification-facilitating elements in addition to chain pairing control designs. These platforms, by simultaneously providing solutions to the two issues associated with bsAb production (i.e., correct chain pairing and efficient purification), improve both efficiency and robustness of bsAb production.

[Preparation of capillary isoelectric focusing with monolithic immobilized pH gradient and its application in determination of isoelectric point of proteins].

A partially filled monolith was prepared by in situ polymerization, and then carrier ampholytes (CAs, pH 3-10) were immobilized on its surface. For effective utilization of capillary isoelectric focusing (cIEF) with the monolithic immobilized pH gradient (M-IPG), a new online platform was established by the introducing of an eight-way injection valve, a three-way valve and a cross-shaped unit. Besides, a capillary coated with hydroxypropyl cellulose (HPC capillary) was prepared and used to determine the isoelectric points (pI) of trastuzumab and etanercept. In parallel, using the newly built capillary isoelectric focusing platform, the pI values of trastuzumab and etanercept were measured with the M-IPG column, and compared with the results obtained using the HPC capillary. It was found that these two cIEF columns can be effectively used to separate proteins and determine the pI values of monoclonal antibodies and fusion proteins in protein drugs. Moreover, the measured pI values were consistent with those estimated using the HPC capillary.

Development of an imaged capillary isoelectric focusing method for characterizing the surface charge of mRNA lipid nanoparticle vaccines.

Lipid nanoparticles (LNPs) have been employed for drug delivery in small molecules, siRNA, mRNA, and pDNA for both therapeutics and vaccines. Characterization of LNPs is challenging because they are heterogeneous mixtures of large complex particles. Many tools for particle size characterization, such as dynamic and static light scattering, have been applied as well as morphology analysis using electron microscopy. CE has been applied for the characterization of many different large particles such as liposomes, polymer, and viruses. However, there have been limited efforts to characterize the surface charge of LNPs and CIEF has not been explored for this type of particle. Typically, LNPs for delivery of oligonucleotides contain at least four different lipids, with at least one being an ionizable cationic lipid. Here, we describe the development of an imaged capillary isoelectric focusing method used to measure the surface charge (i.e., pI) of an LNP-based mRNA vaccine. This method is capable of distinguishing the pI of LNPs manufactured with one or more different ionizable lipids for the purpose of confirming LNP identity in a manufacturing setting. Additionally, the method is quantitative and stability-indicating making it suitable for both process and formulation development.

pI Determination of Native Proteins In Biological Samples.

The electrophoretic mobility of a protein on an immobilized pH-gradient gel (IPG) depends upon its overall positive (acidic) or negative (basic) charge, the principle underlying the IEF technique. In isoelectrofocusing (IEF), a protein with a net positive or negative charge migrates through the pH gradient gel until it reaches the isoelectric point (pI), a pH at which it remains neutral. Thus, the pI of a protein indicates its net charge, a critical determinant of its stability/activity in a given milieu. Conventionally, the first-dimensional IPG-IEF is followed by a second dimension, by which the focused proteins are denatured/reduced and resolved on an SDS-PAGE gel for subsequent immunoblotting to verify the protein identity. The recent development of one-dimensional, vertical IEF followed by immunoblotting enabled concurrent analysis (pI determination) of multiple samples. The protocol described here outlines vertical IEF and immunoblotting under non-denaturing conditions to determine the pI of native proteins in biological samples. © 2019 by John Wiley & Sons, Inc.

Design of a software for calculating isoelectric point of a polypeptide according to their net charge using the graphical programming language LabVIEW.

A software to calculate the net charge and to predict the isoelectric point (pI) of a polypeptide is developed in this work using the graphical programming language LabVIEW. Through this instrument the net charges of the ionizable residues of the polypeptide chains of the proteins are calculated at different pH values, tabulated, pI is predicted and an Excel (-xls) type file is generated. In this work, the experimental values of the pIs (pI) of different proteins are compared with the values of the pIs (pI) calculated graphically, achieving a correlation coefficient (R) of 0.934746 which represents a good reliability for a p < 0.01. In this way the generated program can constitute an instrument applicable in the laboratory, facilitating the calculation to graduate students and junior researchers. © 2017 by The International Union of Biochemistry and Molecular Biology, 46(1):39-46, 2018.