Nephelometry as a simple tool to monitor the disassembly of polymeric nanoparticles

Polymer-based nanoparticles (PNPs) find wide application in e.g. material and pharmaceutical sciences. In order to determine the quality of produced PNPs and understand their function, analytical characterization is essential. Recently, two-dimensional liquid chromatography (2D-LC) has been introduced as an effective means to probe multiple PNP properties, such as size and composition, in an integrated manner. Such approaches involve transformation of PNPs into their constituents between the two LC dimensions by introducing an organic solvent. Employing light scattering, which is mainly caused by intact PNPs, this paper presents nephelometry as a straightforward technique to assess the percentage of organic solvent needed to achieve full disintegration of PNPs. Empty and dye-loaded poly(lactic-co-glycolic acid) (PLGA) based PNPs were exposed to organic solvent-water mixtures of different ratios, while measuring their scattering intensities at a 90° angle when irradiated with a 650 nm light beam. Disruption of the PNPs was marked by a gradual decrease of the scattering intensity with increasing percentages of organic solvent in the PNP suspension. Full disassembly of the PNPs was achieved with 50% acetonitrile in water (v/v). The overall shape of the disassembly profiles and the minimum percentage of organic solvent needed for full PNP disintegration was found to be largely independent of the type and quantity of dye loaded, or the amount of polymer used for PNP formation.