Examining layer-by-layer assembly of polyelectrolyte-drug interactions using Quartz Crystal Microbalance with Dissipation

The incorporation of drug molecules into layer-by-layer (LbL) assemblies attracts great interest in biomedical applications. This work describes the preparation and characterization of LbL multilayers including drugs, namely ibuprofen (IBF-Na) and Diclofenac sodium salt (DCF-Na) as anionic molecules. The main aim is to enhance the drug loading capacity within the LbL assembly. The effects of drug-LbL multilayered films obtained from poly(diallyl dimethylammonium chloride) (PDADMAC)/IBF-Na and PDADMAC/DCF-Na interactions on multilayer growth and loading of model molecules are examined using UV-Visible and Quartz-Crystal Microbalance with Dissipation (QCM-D). The wet mass of PDADMAC/IBF-Na is found to be 67.2 ng/cm(2), while PDADMAC/DCF-Na film exhibits 201.6 ng/cm(2) mass adsorption. Furthermore, the multilayer stabilities are assessed against neutral, acidic, and basic solutions. The results demonstrate that the LbL films have robustness, without any signs of multilayer degradation. By the way, the incorporation of IBF-Na into the feed solution leads to the formation of a rigid structure, whereas the inclusion of DCF-Na results in a comparatively flexible structure. The use of a higher molecular weight and more polar drug in the feed causes a noticeable rise in surface hydrophilicity and surface roughness. PDADMAC/IBF-Na and PDADMAC/DCF-Na display average contact angles of 46 +/- 1.3 degrees and 76 +/- 2 degrees while they have roughness values of 5.9 and 8.0 nm, respectively. LbL multilayers fabricated from a polycation and anionic drug can be considered as a promising material platform for controlled drug loading due to their tunable physicochemical and morphological properties as well as surface wettability.