Analytical strategy for studying the formation and stability of multilayered films containing gold nanoparticles.

The design of layer-by-layer (LbL) polyelectrolyte films including nanoparticles is a growing field of innovation in a wide range of biomedical applications. Gold nanoparticles (AuNPs) are very attractive for further biomolecule coupling to induce a pharmacological effect. Nanostructured LbL films coupled with such metallic species show properties that depend on the conditions of construction, i.e. the polymer nature and dissolution buffer. Tripartite LbL films (polycation, AuNP, and polyanion) were evaluated using two different polycationic polymers (poly(allylamine hydrochloride) (PAH), poly(ethylene imine) (PEI)) and various medium conditions (salts, i.e. phosphate, Tris or Tris-NaCl buffers, and concentration). AuNP incorporation and film stability were analysed by visible spectrophotometry, capillary zone electrophoresis, a quartz crystal microbalance, and high-performance liquid chromatography. The ideal compromise between AuNP loading and film stability was obtained using PAH prepared in Tris-NaCl buffer (0.01-0.15 M). This condition allowed the formation of a LbL film that was more stable than the film with PEI and provided an AuNP quantity that was 4.8 times greater than that of the PAH-PBS-built film. In conclusion, this work presents an analytical strategy for the characterization of nanostructured multilayer films and optimization of LbL films enriched with AuNPs to design biomedical device coatings.

Quality control of gold nanoparticles as pharmaceutical ingredients.

Nanoparticles are being developed for a wide range of medical applications such as, controlled release, drug delivery systems or imagery, theranostics, implants…. For the moment, there is no legal definition of nanoparticles or nanomaterials for therapeutic use. The specific case of gold nanoparticles is not an exception: their current definition as nanoparticle material does not correspond to classic pharmaceutical ingredients as described in Pharmacopoeias. In this study, more than 30 different batches of citrate stabilized gold nanoparticles (AuNP) were synthesized and analyzed thanks to both classical approaches (UV-Vis spectrophotometry, dynamic light scattering coupled or not to electrophoresis …) and capillary zone electrophoresis (CZE) coupled to diode array detection to assess their purity and impurity profiles. These techniques led to the beginning of defined specifications, a key step for the use of gold nanoparticles as pharmaceutical ingredients. CZE was demonstrated suitable to evaluate a batch-to-batch quality control, to monitor the purification processes and to follow the stability of 18 different batches for 20 days. Finally, commercially available AuNP samples were tested and the results compared to the provided certificates of analysis.