Protein-polyelectrolyte interactions: Monitoring particle formation and growth by nanoparticle tracking analysis and flow imaging microscopy

Publication Type:

Journal Article


Eur J Pharm Biopharm, Volume 93, pp. 339-345 (2015)


1873-3441 (Electronic)09

DOI Name (links to online publication)



The purpose of this study was to investigate the formation and growth kinetics of complexes between proteins and oppositely charged polyelectrolytes. Equal volumes of IgG and dextran sulfate (DS) solutions, 0.01mg/ml each in 10mM phosphate, pH 6.2, were mixed. At different time points, samples were taken and analyzed by nanoparticle tracking analysis (NTA), Micro-Flow Imaging (MFI) and size-exclusion chromatography (SEC). SEC showed a huge drop in monomer content (approximately 85%) already 2min after mixing, while a very high nanoparticle (size up to 500nm) concentration (ca. 9x108/ml) was detected by NTA. The nanoparticle concentration gradually decreased over time, while the average particle size increased. After a lag time of about 1.5h, a steady increase in microparticles was measured by MFI. The microparticle concentration kept increasing up to about 1.5x106/ml until it started to slightly decrease after 10h. The average size of the microparticles remained in the low-mum range (1-2mum) with a slight increase and broadening of the size distribution in time. The experimental data could be fitted with Smoluchowski's perikinetic coagulation model, which was validated by studying particle growth kinetics in IgG:DS mixtures of different concentrations. In conclusion, the combination of NTA and MFI provided novel insight into the kinetics and mechanism of protein-polyelectrolyte complex formation.