In this study the development of stable polyelectrolyte-surfactant complex nanoparticles composed of alginate and cetylpyridinium chloride (CPC), with and without ZnCl2, for therapeutic use, is investigated. The mechanism of CPC binding by alginate was analyzed using a cetylpyridinium cation (CP+) selective membrane electrode. The cooperative nature of the interaction between CP+ and alginate was underlined by the sigmoidal shape of the binding isotherms. The presence of salts was shown to weaken interactions and, moreover, ZnCl2 reduced the cooperativity of binding. The CP+ cations in the form of micellar associates acted as multivalent crosslinkers of the alginate chains where stable dispersions of CP-alginate nanoparticles were formed in water at CP+/alginate charge ratios from 0.2 to 0.8. Characterization of the nanoparticles showed hydrodynamic diameters from 140 to 200 nm, a polydispersity index below 0.2, a negative zeta potential and spherical morphology. The entrapment efficiency of CPC was ˜94%, the loading capacity more than 50% and prolonged release over 7 days were shown. The formulations with noted charge ratios resulted in stable CP-alginate nanoparticles with a potential of treating periodontal disease.