Steric stabilization of nanoparticles: Size and surface properties

Nanoparticles of poly-(isobutylcyanoacrylate) (PIBCA), poly-lactic acid (PLA), poly-lactic-co-glycolic copolymer (PLAGA) and poly-epsilon-caprolactone were prepared according to conventional methods. In the preparation of PIBCA nanoparticles different steric stabilizers were used. Formulations included poloxamer 188, polyvinilic alcohol (PVA) or polyethyleneglycol 2000 (PEG 2000), with or without dextran, in order to characterize the influence of different steric stabilizers. All the formulations were tested for their electrophoretic mobility, zeta potential and particle size using DELSA. Particle size measurements were also performed using a PCS technique, employing two sets of apparatus, in an attempt to evaluate the influence of measuring principle and detection angle in the final results. Results indicate that PIBCA nanoparticles can be sterically stabilized by dextran, poloxamer and PVA, but PEG 2000 could need the presence of another steric stabilizer. The good correlation for the same detection angle between PCS and DELSA demonstrates the importance of DELSA in the characterization of size and surface properties associated with colloidal drug carriers like nanoparticles, as demonstrated by PLA, PLAGA and PCL nanoparticles (monodisperse particles). The differences between the two techniques could be explained by different detection angles and strongly suggests an integrated approach using PCS and DELSA when considering polydisperse particle populations.