Influence of Polymer Conformation on the Shear Modulus and Morphology of Polyallylamine and Poly(α-l-lysine) Hydrogels

Abstract

Two polyamines with different conformational properties, poly(α-l-lysine) and polyallylamine, were chemically cross-linked to evaluate the effects of polypeptide secondary structures on gel properties. Both cationic gels are highly swollen at low pH and shrink as it increases primarily due to the reduction in of the concentration of associated counterions in the gel as its ionization decreases. Network shear moduli were determined under uniaxial compression. For the polyallylamine gels, the shear modulus (G) scales as φ2 0.31, where φ2 denotes the polymer volume fraction, over the entire pH range. This result is in favorable agreement with the G ∼ φ2 1/3 relationship predicted for networks of flexible chains. Poly(α-l-lysine) gels swollen below pH 11.0 obey the same scaling behavior. At higher pH levels, however, organized secondary structures are believed to develop, and the composition dependence of the modulus at high pH becomes consistent with the scaling relationship predicted for rigid-rod chain networks connected by flexible junctions (G ∼ φ2 3/2). Further evidence of the existence of more organized microstructures in the poly(α-l-lysine) gels at high pH is provided from complementary thermoelasticity and morphological analyses.

Fibroin/collagen hybrid hydrogels with crosslinking method: Preparation, properties, and cytocompatibility

“…6 Following the development of biomedical and pharmaceutical technologies, hydrogels prepared from proteins have been of particular interest, because of their ability to form complex hierarchical structures, as well as their inherent resemblance to the natural ECM and their complex signaling capabilities. [7][8][9][10] Furthermore, cell adhesion and migration are governed not only by chemical signalization processes but also by mechanical interactions. [11][12][13][14] Many researchers have indicated that soft gels (elastic modulus E ¼ 1 kPa) show diffuse and dynamic adhesion complexes, while stiff gels (E ¼ 30-100 kPa) show cells with stable focal adhesion.…”

Effect of β‐Sheet Crystals on the Thermal and Rheological Behavior of Protein‐Based Hydrogels Derived from Gelatin and Silk Fibroin

“…While numerous synthetic polymers exhibit sufficient hydrophilicity to serve as candidate precursors in the preparation of hydrogels,7,8 emerging biomedical and pharmaceutical technologies desire hydrogels that exhibit high levels of biocompatibility and biodegradability. Examples of biomacromolecules ideally suited for this purpose include polysaccharides,9 cellulosics10–12 and proteins 13,14. Hydrogels generated from proteins are particularly advantageous in the food and personal care industries15,16 due to their intrinsic biocompatibility and biodegradability.…”

Experimental optimization of an in situ forming hydrogel for hemorrhage control

“…The PEG and PAA solutions were prepared in acidic and basic buffers, respectively, to reduce hydrolysis and promote protonation. Under such pH conditions, PEG would have minimal hydrolysis24 and PAA amino groups are mostly in a dissociated state 29. The final pHs of the mixed buffers, controlled by each pH and buffering capacity of the solutions, were measured and summarized in Table IV.…”

“…1(c)]. The polymer can form hydrogels through crosslinking with epichlorohydrin28 or N , N ′‐methylenebisacrylamide29 and forming an interpenetrating polymer network with chitosan30 or a polyion complex with alginate 31. The binding capabilities of the polymer with various ions32 have made the material attractive for different chemical and biomedical applications, particularly for clinical use as a phosphate binder to treat renal disease 33.…”