@article {19345, title = {Biomedical Films of Graphene Nanoribbons and Nanoflakes with Natural Polymers}, journal = {RSC Advances}, volume = {7}, year = {2017}, month = {2017-05-01 00:00:00}, pages = {27578{\textendash}27594}, publisher = {Royal Society of Chemistry}, abstract = {

Graphene and its derivatives are promising as reinforcement for polymer nanocomposites. Additionally to
their inherent outstanding mechanical properties, these nanoparticles may be functionalized to enhance
their compatibility with the polymeric matrix and provide specific chemical and physical properties. In
this work, new freestanding films (FS) based on chitosan (CHI), alginate (ALG) and functionalized
graphene were developed using the layer-by-layer assembly. Suspensions of functionalized graphene
nanoflakes (f-GF) and nanoribbons (f-GNR) were prepared from expanded graphite (EG) and multiwalled
carbon nanotubes (MWNTs), respectively. The graphene nanoflakes and MWNTs were covalently
functionalized using a 1,3-dipolar cycloaddition reaction that allowed the nanoparticles exfoliation. f-
GNR and f-GF suspensions were characterized to demonstrate that graphene nanoflakes and MWNTs
were successfully functionalized and exfoliated. Then, the layer-by-layer deposition of CHI, ALG and
both types of functionalized graphene was investigated and FS films were produced. The morphology,
thermal and mechanical characteristics of the produced FS films were assessed. Their degradation and
swelling profiles as well as their biological behavior were evaluated. The incorporation of f-GF resulted in
smoother films while the incorporation of f-GNR resulted in rougher films. When compared with the
CHI/ALG bi-component films. Both graphene containing films remained hydrophobic. The graphene
incorporation in the multilayered FS was estimated to be 1.7 wt\% for f-GF and 2.5 wt\% for f-GNR. The
presence of functionalized graphene did not affect the thermal stability of the films, it increased the
storage modulus and the dynamic mechanical response at 1 Hz and 37 C, and decreased the electrical
resistivity. The biological assays revealed cytocompatibility towards L929 cells when both f-GF and f-
GNR were incorporated in the CHI/ALG matrix. In conclusion, these new f-GF and f-GNR reinforced FS
films present great potential for use in biomedical applications such as films for wound healing or
cardiac and bone engineering.

}, keywords = {functionalized graphene, layer by layer assembly, natural polymers}, issn = {20462069}, doi = {10.1039/C7RA04173J}, url = {http://pubs.rsc.org/-/content/articlehtml/2017/ra/c7ra04173j}, author = {Silva, M. and Caridade, S. G. and Vale, A. C. and Cunha, E. and Sousa, M. P. and Mano, J. F. and Paiva, M. C. and Alves, N. M.} }