Insight into purification of monoclonal antibodies in industrial columns via studies of Protein A binding capacity by in situ ATR-FTIR spectroscopy

Application of Raman Spectroscopy to Dynamic Binding Capacity Analysis

Protein A affinity chromatography is a key step in isolation of biotherapeutics (BTs) containing fragment crystallizable regions, including monoclonal and bispecific antibodies. Dynamic binding capacity (DBC) analysis assesses how much BT will bind to a protein A column. DBC reduces with column usage, effectively reducing the amount of recovered product over time. Drug regulatory bodies mandate chromatography resin lifetime for BT isolation, through measurement of parameters including DBC, so this feature is carefully monitored in industrial purification pipelines. High-performance affinity chromatography (HPAC) is typically used to assess the concentration of BT, which when loaded to the column results in significant breakthrough of BT in the flowthrough. HPAC gives an accurate assessment of DBC and how this changes over time but only reports on protein concentration, requires calibration for each new BT analyzed, and can only be used offline. Here we utilized Raman spectroscopy and revealed that this approach is at least as effective as both HPAC and ultraviolet chromatogram methods at monitoring DBC of protein A resins. In addition to reporting on protein concentration, the chemical information in the Raman spectra provides information on aggregation status and protein structure, providing extra quality controls to industrial bioprocessing pipelines. In combination with partial least square (PLS) analysis, Raman spectroscopy can be used to determine the DBC of a BT without prior calibration. Here we performed Raman analysis offline in a 96-well plate format, however, it is feasible to perform this inline. This study demonstrates the power of Raman spectroscopy as a significantly improved approach to DBC monitoring in industrial pipelines.

Methods for addressing host cell protein impurities in biopharmaceutical product development

The high demand for monoclonal antibody (mAb) therapeutics in recent years has resulted in significant efforts to improve their costly manufacturing process. The high cost of manufacturing mAbs derives mainly from the purification process, which contributes to 50%-80% of the total manufacturing cost. One of the main challenges facing industry at the purification stage is the clearance of host cell proteins (HCPs) that are produced and often co-purified with the desired mAb product. One of the issues HCPs can cause is the degradation of the final mAb protein product. In this review, techniques are considered that can be used at different stages (upstream and downstream) of mAb manufacture to improve HCP clearance. In addition to established techniques, many new approaches for HCP removal are discussed that have the potential to replace current methods for improving HCP reduction and thereby the quality and stability of the final mAb product.

Formation of a Conducting Polymer by Different Electrochemical Techniques and Their Effect on Obtaining an Immunosensor for Immunoglobulin G

In this work, a conducting polymer (CP) was obtained through three electrochemical procedures to study its effect on the development of an electrochemical immunosensor for the detection of immunoglobulin G (IgG-Ag) by square wave voltammetry (SWV). The glassy carbon electrode modified with poly indol-6-carboxylic acid (6-PICA) applied the cyclic voltammetry technique presented a more homogeneous size distribution of nanowires with greater adherence allowing the direct immobilization of the antibodies (IgG-Ab) to detect the biomarker IgG-Ag. Additionally, 6-PICA presents the most stable and reproducible electrochemical response used as an analytical signal for developing a label-free electrochemical immunosensor. The different steps in obtaining the electrochemical immunosensor were characterized by FESEM, FTIR, cyclic voltammetry, electrochemical impedance spectroscopy, and SWV. Optimal conditions to improve performance, stability, and reproducibility in the immunosensing platform were achieved. The prepared immunosensor has a linear detection range of 2.0-16.0 ng·mL^-1 with a low detection limit of 0.8 ng·mL^-1. The immunosensing platform performance depends on the orientation of the IgG-Ab, favoring the formation of the immuno-complex with an affinity constant (Ka) of 4.32 × 10⁹ M^-1, which has great potential to be used as point of care testing (POCT) device for the rapid detection of biomarkers.

One-Step Surface Immobilization of Protein A on Hydrogel Nanofibers by Core-Shell Electrospinning for Capturing Antibodies

Nanofibers (NFs) are potential candidates as filter materials for affinity separation owing to their high liquid permeability based on their high porosity. Multiple and complex processes were conventionally performed to immobilize proteins for modifying NF surfaces. A simple method must be developed to immobilize proteins without impairing their biological activity. Herein, we succeeded in fabricating NFs with a core of cellulose acetate and a shell of hydrophilic polyvinyl alcohol immobilized with staphylococcal recombinant protein A by a one-step process based on core-shell electrospinning. A total of 12.9 mg/cm3 of antibody was captured in the fiber shell through high affinity with protein A immobilized in an aqueous environment of the hydrogel. The maximum adsorption site and dissociation constant evaluated by the Langmuir model were 87.8 µg and 1.37 µmol/L, respectively. The fiber sheet withstood triplicate use. Thus, our NF exhibited high potential as a material for membrane chromatography.