Biosensing Probe for Quality Control Monitoring of the Structural Integrity of Therapeutic Antibodies

Ideal quality control of therapeutic antibodies involves analytical techniques with high-sensitivity, high-resolution, and high-throughput performance. Few technologies that assess the physicochemical heterogeneity of antibodies, however, meet all the required demands. We developed a biosensing method for the quality control of therapeutic antibodies based on an artificial protein, AF.2A1, which discriminates between the native and the non-native three-dimensional structures of immunoglobulin G (IgG). AF.2A1 specifically recognized non-native IgG spiked into a solution of native IgG, thereby making it possible to detect contamination by a small amount of non-native IgG, which is difficult using conventional size-based separation or spectroscopic techniques. Using AF.2A1 as an analytical probe, we determined the concentration of non-native IgG formed under various pH conditions. The probe was also applicable to accelerated tests of the long-term stability of a therapeutic antibody, allowing monitoring of the formation of non-native IgG at elevated temperatures and extended periods of storage. AF.2A1, a proteinous probe, can be combined with established methods or devices to achieve high-throughput assays and provides the potential for probe-based biosensing for the quality control of therapeutic antibodies.