Multilayer Films Assembled from Naturally-Derived Materials for Controlled Protein Release

Abstract

Herein we designed and characterized films composed of naturally derived materials for controlled release of proteins. Traditional drug delivery strategies rely on synthetic or semi-synthetic materials, or utilize potentially denaturing assembly conditions that are not optimal for sensitive biologics. Layer-by-Layer (LbL) assembly of films uses benign conditions and can generate films with various release mechanisms including hydrolysis-facilitated degradation. These use components such as synthetic polycations that degrade into non-natural products. Herein we report the use of a naturally-derived, biocompatible and degradable polyanion, poly(β-l-malic acid), alone and in combination with chitosan in an LbL film, whose degradation products of malic acid and chitosan are both generally recognized as safe (GRAS) by the FDA. We have found that films based on this polyanion have shown sustained release of a model protein, lysozyme that can be timed from tens of minutes to multiple days through different film architectures. We also report the incorporation and release of a clinically used biologic, basic fibroblast growth factor (bFGF), which demonstrates the use of this strategy as a platform for controlled release of various biologics.

Ordered and Kinetically Discrete Sequential Protein Release from Biodegradable Thin Films

“…Subsequent deposition of n -Barrier Film revealed a linear growth (R 2 = 0.992) with 11.7 nm deposited per tetralayer, or ∼3 nm per layer for the combined Lys x-linked + n -Barrier film. This is in striking contrast to our previous data, in which the growth behavior of (chitosan/PMLA/protein/PMLA) n films increases exponentially with up to ∼69.2 nm (R 2 = 0.9999) deposited per tetralayer [23c] , suggesting a significant suppression of exponential growth and interdiffusion.…”

“…In a surface-erosion model, as previously demonstrated for hydrolytically degradable LbL films [23] the therapeutic's location and depth in the film would govern its release order and kinetics; thus, when incorporating a hydrolytically degradable component throughout the film, deposition of a sacrificial barrier layer could putatively delay the onset of release and enable truly sequential release behavior. Herein, we describe our approach to introduce crosslinking in situ (i.e., as the film is deposited) using copper-free click functionalities in a hydrolytically degradable LbL film.…”

“…In an earlier report studying the use of LbL assembled multilayered films [23c] , we found that we could generate protein-loaded thin films using completely naturally-derived materials whose degradation products are generally recognized as safe (GRAS) by the FDA. These films were able to controllably sustain the release of protein over multiple days under physiological conditions.…”

“…These films were able to controllably sustain the release of protein over multiple days under physiological conditions. The growth behavior of these films [23c] and many other protein-containing LbL assembled films [24] has revealed exponential increases in film thickness as a function of layers deposited. This phenomenon has been well documented for certain LbL systems and has been explained by an “in-and-out” diffusion hypothesis that suggests the diffusivity of weakly charged polymeric species (i.e., proteins, polysaccharides, weak polyelectrolytes) in the film contributes significantly to this growth behavior; the diffusion and absorption of excess polyelectrolytes into and out of the film during assembly causes this exponential film growth [24d] .…”

Sustained protein release from hydrogel microparticles using layer-by-layer (LbL) technology

“…hyaluronic acid, chondroitin, heparin and chitosan) and polypeptides (e.g. poly L-lysine, poly L-arginine, poly L-glutamic acid and poly L-aspartic acid) (Hsu et al, 2014). However, to achieve a more sustained and linear release profile, hydrolytic surface degradation of biocompatible and degradable polymers such as poly b-aminoesters (PBAEs) would be more promising (Macdonald et al, 2008).…”