Experimental Optimization of a Plasmonic Surface Biofunctionalization, toward the Bimodal Biosensing and Kinetic...

Area of Science:

• Biomedical Engineering
• Immunology
• Analytical Chemistry

Background:

• Soluble PD-1 (sPD1) has a complex role in cancer, influenced by immune checkpoint proteins and antibody therapies.
• Existing biosensor platforms lack the capability for simultaneous quantification and kinetic profiling of sPD1-antibody interactions.
• sPD1 is emerging as a significant liquid biopsy biomarker for immuno-oncologic profiling.

Purpose of the Study:

• To develop and validate a novel surface plasmon resonance (SPR) biosensor.
• To enable simultaneous, label-free quantification and real-time kinetic analysis of sPD1-antibody interactions.
• To assess the biosensor's performance in buffer and human serum for potential clinical monitoring.

Main Methods:

• Development of an SPR refractometric biosensor functionalized with nivolumab.
• Optimization of sensor functionalization and regeneration protocols.
• Label-free quantification and kinetic analysis of sPD1 in buffer and human serum.

Main Results:

• The biosensor achieved a limit of detection of 5 ng/mL and a dynamic range of 8.7 ng/mL to 376 μg/mL for sPD1.
• Quantification of sPD1 in serum demonstrated good recovery (93 ± 5% in 1% serum, 62 ± 30% in 10% serum).
• Determined kinetic constants for the nivolumab-PD1 interaction align with literature values (K_D ≈ 4.66 nM).

Conclusions:

• The dual-mode SPR platform is the first to simultaneously quantify sPD1 and characterize sPD1-antibody kinetics.
• This biosensor provides a powerful tool for research and potential clinical monitoring of immune checkpoint dynamics.
• The platform supports the use of sPD1 as a liquid biopsy biomarker in immuno-oncology.