Antibody-Drug Conjugate 2D: Reaction-Diffusion Bystander Model

This is the 2D counterpart to the 3D antibody-drug conjugate (ADC) simulation, built as an independent numerical model rather than a flattened version of the same scene. Free ADC molecules diffuse isotropically through the extracellular space via a proper 2D Brownian random walk and bind antigen-positive tumor cells with first-order kinetics. The real mechanistic difference is in how cleaved payload spreads: instead of computing an instant analytic distance-based sum, this model injects released payload into a continuous concentration field and evolves it every frame by explicitly solving the 2D reaction-diffusion partial differential equation ∂C/∂t = D∇²C − C/τ with finite differences, so the bystander-killing halo you see is the actual numerical solution of a screened-diffusion equation, not an assumed shape. A non-cleavable linker never touches this field at all — its cytotoxic adduct stays locked inside the cell that internalized it. Adjust antigen density, drug-antibody ratio and the diffusion radius (which sets the PDE's diffusion coefficient) and watch the live kill counts for target versus bystander cells.