Indeed, the efficacy of nanoparticle diffusion through CF sputum has been shown to be strongly influenced by mucin concentration, being significantly reduced at 25, 30 and 50 mg/ml (to ~ 82%, ~ 72% and ~ 55% respectively), with no effect observed with mucin ≤ 10 mg/ml36. Here, MUC5AC is linked to cystic fibrosis.