Complexes of cellulose model particles with polycations: composition, properties and cytotoxicity

Cellulose particles of 200-250 nm size, stable for 18 days in a water-salt medium, are proposed as a model of biodegradable microplastics. The particles are characterized by means of dynamic light scattering, laser microelectrophoresis, differential scanning calorimetry, thermogravimetry (TG) and IR spectroscopy. The complexation of cellulose particles with toxicants - cationic polymers (kaustamin, poly-l-lysine hydrobromide and poly(N-ethyl-4-vinylpyridinium) bromide), as well as the composition of the resulting complexes and their ability to dissociate into the initial components in water-salt media is discussed. It is demonstrated that the complexation is followed by the surface charge neutralization and enlargement of the particles. The interaction is electrostatic in nature: the salt addition causes the dissociation of the complexes into individual components. The cytotoxicity of the individual cellulose particles and their complexes with polycations towards fibroblast cells is investigated using MTT assay. Cellulose particles are found to be non-toxic, but at the same time, cellulose-polycation complexes demonstrate cytotoxicity comparable to the cytotoxicity of individual polycations of the same concentration. The findings of the work should be taken into account when discussing the potentially harmful effects of microplastics on ecosystems.