This is a top-down, 2D-native counterpart of the 3D chitosan flocculation simulation — the same population of chitosan chain segments and anionic cells, the same screened-Coulomb force law and the same Henderson–Hasselbalch protonation model, just viewed as a flat plane (a thin wound-bed cross-section) instead of an orbiting 3D box.
α(pH) = 1 / (1 + 10^(pH − pKa)), pKa ≈ 6.5
net chain charge density q ∝ DDA × α(pH)
F(r) = k · q₊q₋ / r² · exp(−r / λ_D)
λ_D (nm) ≈ 0.304 / √I(mol/L) (checked against literature: ≈0.78 nm at 0.15 M saline)
Chitosan is a linear polysaccharide of glucosamine units carrying a free primary amine (–NH₂, pKa ≈ 6.5). Below that pKa the amines protonate to –NH₃⁺, turning the chain into a polycation. Erythrocyte and bacterial membranes carry a net negative surface charge (sialic acid / lipopolysaccharide); the resulting electrostatic attraction is a screened Coulomb (Yukawa) interaction, with the screening length set by the Debye–Hückel relation for the wound fluid's ionic strength. This is the accepted mechanism behind chitosan's rapid, coagulation-cascade-independent hemostasis (used in dressings such as Celox and HemCon): a densely protonated chain electrostatically bridges and aggregates red cells into a physical plug at the wound surface.
- Wound pH — lower pH raises α, giving each chain more positive charge (acidic dressings and infected/healing wounds are typically pH 4–6.5; chronic wounds can drift to pH 7.5–9, where chitosan loses most of its charge).
- Degree of deacetylation — the fraction of units that even carry a free amine; higher DDA (more deacetylated chitin) means a higher maximum charge density.
- Ionic strength — physiological saline (~0.15 M) already screens the charge to a sub-nanometre range; higher exudate salinity shortens λ_D further and weakens long-range attraction, visibly slowing flocculation.
- Chain density — how much chitosan polymer is present relative to the cell population, i.e. dressing dose.
Drag on the canvas to pan the view and scroll to zoom in on a cluster of flocculated cells.