Chondroinductive Alginate-Based Hydrogels Having Graphene Oxide for 3D Printed Scaffold Fabrication

Scaffolds
based on bioconjugated hydrogels are attractive for tissue
engineering because they can partly mimic human tissue characteristics.
For example, they can further increase their bioactivity with cells.
However, most of the hydrogels present problems related to their processability,
consequently limiting their use in 3D printing to produce tailor-made
scaffolds. The goal of this work is to develop bioconjugated hydrogel
nanocomposite inks for 3D printed scaffold fabrication through a micro-extrusion
process having improved both biocompatibility and processability.
The hydrogel is based on a photocrosslinkable alginate bioconjugated
with both gelatin and chondroitin sulfate in order to mimic the cartilage
extracellular matrix, while the nanofiller is based on graphene oxide
to enhance the printability and cell proliferation. Our results show
that the incorporation of graphene oxide into the hydrogel inks considerably
improved the shape fidelity and resolution of 3D printed scaffolds
because of a faster viscosity recovery post extrusion of the ink.
Moreover, the nanocomposite inks produce anisotropic threads after
the 3D printing process because of the templating of the graphene
oxide liquid crystal. The in vitro proliferation assay of human adipose
tissue-derived mesenchymal stem cells (hADMSCs) shows that bioconjugated
scaffolds present higher cell proliferation than pure alginate, with
the nanocomposites presenting the highest values at long times. Live/Dead
assay otherwise displays full viability of hADMSCs adhered on the
different scaffolds at day 7. Notably, the scaffolds produced with
nanocomposite hydrogel inks were able to guide the cell proliferation
following the direction of the 3D printed threads. In addition, the
bioconjugated alginate hydrogel matrix induced chondrogenic differentiation
without exogenous pro-chondrogenesis factors as concluded from immunostaining
after 28 days of culture. This high cytocompatibility and chondroinductive
effect toward hADMSCs, together with the improved printability and
anisotropic structures, makes these nanocomposite hydrogel inks a
promising candidate for cartilage tissue engineering based on 3D printing.