Multilayered Films Fabricated from Combinations of Degradable Polyamines:  Tunable Erosion and Release of Anionic Polyelectrolytes

Abstract

This investigation sought to develop methods that permit broad and tunable control over the erosion of multilayered polyelectrolyte assemblies and the release of anionic polymers in physiologically relevant media. We report the fabrication and characterization of multilayered films ~60 nm thick using sodium poly(styrene sulfonate) (SPS) and different combinations of three different hydrolytically degradable polyamines (1-3). We investigated two different approaches to film fabrication: 1) fabrication using solutions comprised of defined mixtures of two different polyamines, and 2) fabrication of films composed of different numbers of layers of two different polyamines. In general, films fabricated using polyamine solutions composed of defined mixtures of two different polyamines had erosion and release profiles that were dictated almost entirely by the most hydrophobic polyamine used to fabricate the films. In contrast, the fabrication of films having different numbers of layers of different polyamines permitted broad and tunable control over film erosion and the release of SPS. For example, films having the architecture (1/SPS) n (2/SPS) m released SPS with profiles that were intermediate to those of films fabricated exclusively from polymer 1 or polymer 2. Further, we demonstrated that it is possible to exert systematic control over the release of SPS by varying the relative numbers of layers of (1/SPS) or (2/SPS) incorporated into the films. The approaches reported here provide tunable control over the rate of the release of anionic polymers from surfaces coated with ultrathin multilayered films. This work could, with further development, contribute to the design of ultrathin films that permit tunable control over the release and delivery of therapeutically relevant macromolecules, such as proteins or DNA, from surfaces.

Peeling Back the Layers: Controlled Erosion and Triggered Disassembly of Multilayered Polyelectrolyte Thin Films

“…As described above, we have demonstrated in past studies [35,36] that hydrolytically degradable polymer 1 can be used to fabricate films that erode and sustain the release of anionic polymers from surfaces, generally over periods of ∼ 48 h. As an extension of this work, we demonstrated recently that small changes in the structure of this polymer influence the functional properties of multilayered films and allow measures of temporal control over rates of film erosion and the release of incorporated anionic polymers. [39][40][41] Using sodium poly(styrene sulfonate) (SPS) as a model anionic polymer, we demonstrated that film erosion could be extended by systematically increasing polyamine hydrophobicity. [39] For example, whereas films fabricated from polymer 1 erode and release SPS over a period of ∼ 2 days, films fabricated from polymers 2 and 3-which are more hydrophobic and degrade more slowly than polymer 1-release SPS for prolonged periods (e.g., for up to 6 days and 14 days, respec-tively) when incubated in PBS.…”

“…[40] In addition to the use of polymers 1-3 to extend the erosion of multilayered films, we have also demonstrated that it is possible to tune more broadly the range of times over which these films release anionic polymers by fabricating films using different blends and combinations of polymers 1, 2, or 3. [41] For example, films having the general structure (1/SPS) n (2/ SPS) m (i.e., fabricated using different numbers of layers of polymer 1 and polymer 2) eroded and released SPS with profiles that were intermediate to those of films fabricated from SPS and polymers 1 or 2 alone (Fig. 4).…”

“…[36,39,41,42] Because materials that promote the prolonged or long-term release of DNA could ultimately lead to enhanced therapies, we have also sought to develop new approaches to promoting the disassembly of multilayered films over extended periods. Below, we describe a new approach to gradual film disruption that permits the release of transcriptionally active DNA from surfaces for up to three months.…”

Polyelectrolyte Blend Multilayers: A Versatile Route to Engineering Interfaces and Films

“…Such control over the proportion of a particular component can, in turn, lead to tunable morphology, thickness, and degradation profiles. [16][17][18][19][20][21]23,29] For example, by blending PSS and PAA and alternately depositing this blend with PAH, the film composition can be precisely controlled. [17] Further, we demonstrated that by slightly varying the adsorption conditions, the composition of multilayers assembled using a blend of deoxyribonucleic acid (DNA) oligonucleotides and PSS alternating with PAH could be varied substantially.…”

“…A study by Lynn and coworkers on blends of degradable polyamines with varying alkyl spacer length also found that the film composition can affect the macroscopic properties of the film. [29] In this case, the behavior of the final film was dominated by the more hydrophobic polyamine, where intermediate ratios of hydrophilic to hydrophobic polyamines were used in the adsorption solutions (from 25-90 % hydrophilic polymer). It was only at high fractions of hydrophilic polymer (above 98 %) that the film started to show intermediate polarity.…”