Nanostructured biopolymer/few-layer graphene freestanding films with enhanced mechanical and electrical properties

In the present work, novel freestanding multilayered films based on chitosan
(CHI), alginate (ALG), and functionalized few-layer graphene are developed
through layer-by-layer assembly. First, functionalized few-layer graphene
aqueous suspensions are prepared from graphite by a stabilizer-assisted liquid
phase exfoliation process, using a pyrene derivative as stabilizer. Afterward, the
films are produced and their physical, morphological, thermal, and mechanical
properties are evaluated. Furthermore, their degradation and swelling profiles,
as well as their biological behavior, are assessed. The incorporation of functionalized
few-layer graphene results in films with a nanolayered structure,
lower roughness than the control CHI/ALG films, and hydrophilic behavior.
The mechanical characterization reveals an increase of the Young's modulus,
ultimate tensile strength, and elongation at break due to the incorporation of
the graphene derivative. A decrease in the electrical resistivity of the multilayered
films is also observed. The biological assays reveal improved cytocompatibility
toward L929 cells when functionalized few-layer graphene is incorporated
in the CHI/ALG matrix. Therefore, these new graphene-reinforced multilayered
films exhibit interesting properties and great potential for biomedical applications,
particularly in wound healing and cardiac and bone tissue engineering.