Antimicrobial Nanoparticle Surface: Bacterial Kill-Curve Simulator

Nanoparticle Coating

Surface coverage 40 particles

Initial bacterial load 50 cells

Exposure time-scale 1.0x

Live kill curve

Bacterial population vs. exposure time (log scale)

Population left

Log reduction

0.00

Exposure time

0.0 h

Rate constant k

–

How it works

Silver and ZnO nanoparticles kill bacteria mainly by two overlapping routes: silver slowly releases Ag⁺ ions that bind bacterial membrane proteins and disrupt the electron-transport chain, while ZnO (especially under ambient light) generates short-lived reactive oxygen species (ROS: ⋅OH, O₂⁻, H₂O₂) at its surface that oxidize the cell membrane directly. Both mechanisms scale with how much active agent reaches a bacterium, so the local concentration around each nanoparticle falls off with distance the way a diffusing point source does:

C(r)  = C₀ · exp( -(r / r₀)² )
dN/dt = -k · C · N          (Chick–Watson first-order kinetics)
P(die in Δt) = 1 - exp( -k · C · Δt )

Each bacterium accumulates whichever local concentration it wanders through as it moves across the surface, and every simulated instant it faces the same instantaneous death probability real disinfection kinetics predicts — not a scripted timer. Summed over the whole population this reproduces the textbook exponential die-off curve (a straight line on the log-scale chart), and the "log reduction" readout is the same metric (3-log = 99.9% killed) hospitals use to rate antimicrobial coatings. Silver's ions diffuse further but act more slowly (lower k, larger r₀); ZnO's photocatalytic ROS is more potent up close but has a shorter effective reach — switch coatings to compare the two real kill curves.

Bacteria wander the coated surface — the glow marks each nanoparticle's active zone