Whispering Gallery Modes-based biosensors for real-time monitoring and binding characterization of antibody-based cancer immunotherapeutics

• Published in: Sensors and actuators. B, Chemical Vol. 346; p. 130512
• Main Authors: Álvarez Freile, Jimena, Choukrani, Ghizlane, Zimmermann, Kerstin, Bremer, Edwin, Dähne, Lars
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.11.2021; Elsevier Science Ltd
• Subjects: Antibodies; Antigens; Binding; Biosensors; Cancer immunotherapy; Drug development; Growth factors; IgG antibody; Immunotherapy; Label-free analytics; Ligands; Microparticles; Optical biosensor; Proteins; Real time; Receptors; Sensors; Surface properties; Whispering Gallery Modes; Whispering Gallery Modes; Label-free analytics; Cancer immunotherapy; Drug development; Optical biosensor
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2021.130512

[Display omitted] •Protein G-coated microsensors based on Whispering Gallery Modes for label-free monitoring of Antigen-Antibody interactions.•Cell-sized sensors imitate cancer cell properties with cell surface biomarkers and immune checkpoint blockade targets.•Protein G binding capacity saturation allowed for interactions in which both ligand and analyte were Fc-fusion proteins.•Extra “Blocking” with an irrelevant IgG was required when Fc-fusion proteins were immobilized due to incomplete saturation. Development of novel protein-based drugs such as antibodies or immunocytokines and initial validation of target binding typically occurs in 2D settings with e.g., surface plasmon resonance or reflection interferometry using antigen-coated planar sensors. However, a versatile tool to assess binding characteristics of tumour-targeting therapeutics where specific biochemical interactions can be monitored in real-time and in a more realistic 3D interaction setting is currently lacking. Here, we report on the development of versatile small optical 3D biosensors using protein G-coated spherical microparticles based on Whispering Gallery Modes (WGMs). These sensors allowed for an oriented immobilization of theoretically any immunoglobulin G (IgG) and IgG crystallizable fragment domain (Fc)-tagged protein and have been carefully optimized for specific detection of antigen-antibody interactions, as illustrated using the Epithelial Growth Factor Receptor (EGFR) antibody Cetuximab and Program Death Ligand 1 (PD-L1) antibody Atezolizumab. When both ligand and analyte contained an Fc-fragment, protein G binding capacity saturation followed by a “blocking” step with an irrelevant IgG enabled the label-free detection of Fc-tagged antigens with corresponding cognate ligands, as identified using EGFR-Fc, PD-L1-Fc and different members from the tumour necrosis factor receptor family, such as CD27-Fc and 4−1BB-Fc. Thus, WGMs and developed protein G-coated biosensors provide a widely applicable tool to evaluate binding of immunotherapeutics to their targets on the sensor surface, imitating cell surface properties.