Aggregation of Cationic Chlorin e6 Derivatives in Water and Aqueous Solutions of Polyvinilpyrrolidone

Dynamic light scattering and electron absorption spectroscopy are used to study aggregation and disaggregation of mono-, di-, and tricationic chlorins (compounds I-III) as potential photosensitizers (PSs) for the photodynamic therapy (PDT) in water and aqueous solutions of polyvinylpyrrolidone (PVP). The average particle size and the nature of particle distribution are determined. Nanoaggregate compounds I-III are formed at the CPS values in the interval of 0.7-1.2 mmol/kg, the particle size increases during the storage of the solution. The size distribution of dispersed phase particles is monomodal only for the PSs with high water solubility. According to the absorption spectra, large (200–300 nm) PS aggregates are destroyed as a result of minor PVP additives, whereas small aggregates are not completely destroyed even in the presence of a 100-fold molar excess of the polymer surfactant.