Influence of PLGA nanoparticles on the deposition of model water-soluble biocompatible polymers by dip coating

Abstract

This work relies on the use of dip-coating at various withdrawal speeds to form nanocomposite films, with a detailed analysis of the influence of the mode of deposition on the nanoparticle (NP) concentration in the dried film. While the deposition of polymer solutions on the one hand and colloidal suspensions of NPs on the other hand have been separately studied by dip coating, their combination is far being a simple superposition of the two separate behaviors. The formation of nanocomposite thin films composed of model water-soluble biocompatible polymers (polyvinyl alcohol - PVA and polyvinylpyrrolidone - PVP) loaded with poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) was studied through a dip coating process. Flat silicon substrates were removed at a controlled withdrawal speed from an aqueous colloidal suspension. Thin films of PLGA NPs with concentrations ranging from 1 to 10 % wt./wt. in PVA or PVP matrices were prepared. The presence of nanoparticles on the well-established process of thin film deposition was examined, as well as the influence of the deposition regime on the nanoparticle concentration in the deposited coating. We demonstrate that the presence of colloidal dispersion of PLGA nanoparticles in water solution of PVA and PVP does not modify the process of film deposition by dip coating. A typical “V” shaped curve was observed, with two well-known deposition regimes: capillary and draining modes respectively obtained at low and high withdrawal speeds. Due to crystallization at low withdrawal speed (favored by slow evaporation of the solvent) it was not possible to identify individual PLGA nanoparticles by AFM in the case of the PVA matrice. Amorphous PVP nanocomposite films were successfully prepared by dip coating, and allowed us to identify individual PLGA nanoparticles with AFM. Because of the prevalence of an evaporation-driven phenomenon at low withdrawal speed, incorporation of NPs was observed over the whole range of withdrawal speeds, showing original behavior compared to recent studies relying on a pure Landau-Levich regime (i.e. non-evaporative systems). Our results indicate that the nanoparticles were not equally retrieved from the solution in the capillary and the draining regimes. This suggests that the balance between the viscous drag and the interfacial effects depends on the deposition mode and calls for a more detailed analysis of the physical processes involved in both regimes.