Interplay of the Assembly Conditions on Drug Transport Mechanisms in Polyelectrolyte Multilayer Films

Abstract

The layer-by-layer film deposition is a suitable strategy for the design and functionalization of drug carriers with superior performance, which still lacks information describing the influence of assembly conditions on the mechanisms governing the drug release process. Herein, traditional poly(acrylic acid)/poly(allylamine) polyelectrolyte multilayers (PEM) were explored as a platform to study the influence of the assembly conditions such as pH, drug loading method, and capping layer deposition on the mechanisms that control the release of calcein, the chosen model drug, from PEM. Films with 20−40 bilayers were assembled at pH 4.5 or 8.8, and the drug loading process was carried out during-or post-film assembly. Release data were fitted to three release models, namely, Higuchi, Ritger−Peppas, and Berens−Hopfenberg, to investigate the mechanism governing the drug transport, such as the apparent diffusion and the relaxation time. The postassembly drug loading method leads to a higher drug loading capacity than the during-assembly method, attributed to the washing out of calcein during film assembly steps in the latter method. Higuchi's and Ritger−Peppas' model analyses indicate that the release kinetic constant increased with the number of bilayers for the postassembly method. The opposite trend is observed for the during-assembly method. The Berens−Hopfenberg release model enabled the decoupling of each drug transport mechanism's contribution, indicating the increase of the diffusion contribution with the number of bilayers for the postassembly method at pH 4.5 and the increase of the polymer relaxation contribution for the during-assembly method at pH 8.8. Deborah's number, which represents the ratio of the polymer relaxation time to the diffusion time, follows the trends observed for the relaxation contribution for the conditions investigated. The deposition of the capping phospholipid layer over the payload also favored the polymer relaxation contribution in the drug release, featuring new strategies to investigate the drug release in PEM.

Polyelectrolyte Multilayer Films as a Potential Buccal Platform for Drug Delivery

“…The size of the morphological units is 500 nm in diameter. The densely packed structure for films implies a good efficiency of drugs, suggesting capacity for prolonged release [29]. AFM was used to investigate the multilayer films' surface morphology.…”

“…The size of the morphological units is about 500 nm in diameter. The densely packed structure for films implies a good entrapment efficiency of drugs, suggesting capacity for prolonged release [29]. Scanning electron microscopy (Figure 5) revealed the presence of numerous morphological units on the surface of the multilayer films, which are due to polyelectrolyte interactions between chitosan and casein and the formation of interpenetrating layers.…”

Simplifying Molecular Transport in Polyelectrolyte Multilayer Thin Films

“…The PEM stacks offer incorporation of wide range of materials, including biomolecules within the PEM matrix. [ 8–12 ] The ability to tune the PEM's architecture with nanometer precision is very promising aspect for using them in biomedical applications. Understanding the molecular dynamics of the participating species, either in situ [ 13–21 ] or ex situ, [ 22–26 ] is useful to further tune the PEM architecture for specific applications.…”

Weak Polyelectrolytes as Nanoarchitectonic Design Tools for Functional Materials: A Review of Recent Achievements

“…The same phenomenon controls the hardness and elastic modulus of PAH/PAA multilayers [ 100 ], leading to lower values being obtained for PAH(pH 7.5)/PAA(pH 3.5) when both polyelectrolytes have a smaller charge density than for PAH(pH 6.5)/PAA(pH 6.5). Consequently, the assembly pH has been demonstrated to influence the drug transport mechanism in PAH/PAA multilayer films ( Figure 3 ) [ 95 ]. In contrast, when the LbL film buildup relies on H-bonding, increasing the ionization rate of weak polyelectrolytes follows the opposite trend: for instance, the buildup of PAA/poly(vinylpyrrolidone) multilayers was hindered at pH values where PAA had a high charge density [ 93 , 101 ].…”