Structure and stability of biodegradable polymer nanoparticles in electrolyte solution
Debasish Saha, Sugam Kumar, Debes Ray, Jitendra Mata, Vinod K. Aswal
Abstract
The structure and stability of biodegradable hydrophobic [Poly(lactic-co-glycolic acid) (PLGA)] and amphiphilic [Poly(ethylene glycol) methyl ether-block-poly(L-lactide-co-glycolide) (PEG-PLGA)] polymer nanoparticles in aqueous electrolyte solution have been investigated by small-angle neutron scattering (SANS), dynamic light scattering (DLS), and ζ-potential measurements. The results show that PLGA forms stable, spherical nanoparticles (size ~ 90 nm, ζ ~ −50 mV) in the aqueous solution. The stability of PLGA nanoparticles rapidly decreases in the presence of NaCl, leading to the formation of micron-sized aggregates even at low salt concentrations (~50 mM), because of the suppression of the stabilizing electrostatic repulsion in the presence of salt. However, the presence of NaCl even at high concentrations (~500 mM) is unable to destabilize the spherical PEG-PLGA nanoparticles (size ~ 35 nm, ζ ~ −15 mV), mostly due to the additional steric repulsion barrier of hydrated PEG shell around the PLGA core, preventing nanoparticles aggregation. Such high stability of PEG-PLGA nanoparticles could be useful for ultra-small nanocarriers (sub-40 nm) applications like deep penetration in tumor tissues, etc.