pH Responsiveness of Multilayered Films and Membranes Made of Polysaccharides

Abstract

We investigated the pH-dependent properties of multilayered films made of chitosan (CHI) and alginate (ALG) and focused on their postassembly response to different pH environments using a quartz crystal microbalance with dissipation monitoring (QCM-D), swelling studies, ζ potential measurements, and dynamic mechanical analysis (DMA). In an acidic environment, the multilayers presented lower dissipation values and, consequently, higher moduli when compared with the values obtained for the pH used during the assembly (5.5). When the multilayers were exposed to alkaline environments, the opposite behavior occurred. These results were further corroborated by the ability of this multilayered system to exhibit a reversible swelling-deswelling behavior within the pH range from 3 to 9. The changes in the physicochemical properties of the multilayer system were gradual and different from those of individual solubilized polyelectrolytes. This behavior is related to electrostatic interactions between the ionizable groups combined with hydrogen bonding and hydrophobic interactions. Beyond the pH range of 3-9, the multilayers were stabilized by genipin cross-linking. The multilayered films also became more rigid while the pH responsiveness conferred by the ionizable moieties of the polyelectrolytes was preserved. This work demonstrates the versatility and feasibility of LbL methodology to generate inherently pH stimulus-responsive nanostructured films. Surface functionalization using pH responsiveness endows several biomedical applications with abilities such as drug delivery, diagnostics, microfluidics, biosensing, and biomimetic implantable membranes.

Tuning cell adhesive properties via layer-by-layer assembly of chitosan and alginate

“…[47] For viscoelastic materials, the adsorbed mass does not fully couple to the oscillation of the crystal and dampens the oscillation, making the use of the Voigt model more appropriate. [34, 47] The film thickness increased linearly with the deposited layers, as previously reported [27, 34, 44, 54]. A thickness of ~80 nm was estimated for the final 5 bilayers.…”

“…[27, 43] Briefly, the test was performed by immersing uncross-linked and cross-linked multilayers in 0.4 % Trypan blue (Invitrogen, USA) diluted 50-fold in sodium acetate buffer overnight at 37° C. The supernatant absorbance was measured at 580 nm in a microplate reader (Sinergy HT, Bio-Tek, USA). The cross-linking degree was calculated as follows: $$\text{CL}(\%)=\frac{({\text{NH}}_3^{+}\text{non}-\text{Xlinked}\text{solution})-({\text{NH}}_3^{+}\text{Xlinked}\text{solution})}{({\text{NH}}_3^{+}\text{non}-\text{Xlinked}\text{solution})}$$…”

“…Multilayers based on these polysaccharides are stable over a pH range of 3–9, but exhibit high hydration levels and low mechanical strength, which impair cell adhesion. [27–29] Post-assembly modifications can be used to tune these properties, namely adsorption or immobilization of extracellular matrix (ECM) proteins such as laminin (LM) and fibronectin (FN) as well as chemical cross-linking of the films.…”

Tuning the formation and stability of microcapsules by environmental conditions and chitosan structure

“…Driving forces for association between oppositely charged alginate and chitosan and chitosan derivatives in aqueous solution have long been identified as electrostatic in origin [15][16][17]. As a result, the effect of electrostatic interaction on the structure and function (such as stability) of polyelectrolyte complexes (PECs) has been studied [18].…”

Preparation of Layer-by-Layer Films Composed of Polysaccharides and Poly(Amidoamine) Dendrimer Bearing Phenylboronic Acid and Their pH- and Sugar-Dependent Stability

“…LbL films are prepared by an alternate deposition of synthetic polymers [6,7,8] and biopolymers including proteins [9,10,11], polysaccharides [12,13,14], and DNA [15] on the surfaces of solid substrates and nanoparticles. Synthetic dyes and nanomaterials have also been employed as components of LbL films [16,17].…”