Label-free optical biosensor measuring real-time biomolecular association (kon) and dissociation (koff) kinetics on a gold sensor chip.
Specifications & Metrics
measures
Real-time association rate (kon), dissociation rate (koff), equilibrium affinity (Kd), and drug residence time
Core Principles & Analysis
First demonstrated for biosensing in 1983 by Bo Liedberg, Claes Nylander, and Ingemar Lundström at the Linköping Institute of Technology (and commercialized by Biacore in 1990), SPR detects refractive-index changes within ~300 nm of a thin gold film excited by polarized light under total internal reflection.
A target protein is immobilized on a carboxymethylated dextran gold chip while microfluidics flow a small-molecule or antibody analyte across the surface; mass accumulation shifts the resonance reflection angle in real time (1 Response Unit ≈ 1 pg/mm² of bound mass) without radioactive or fluorescent labels.
Fitting the rising association phase and buffer-wash dissociation phase of the sensorgram directly resolves the bimolecular on-rate (kon), unimolecular off-rate (koff), drug–target residence time (τ = 1/koff), and equilibrium dissociation constant (Kd = koff / kon).