Tissue engineering (TE) combines both cells’ biology and engineering to develop bioactive biomaterials to treat tissue regeneration . Among them, biomaterials with electric conductive properties have shown promising potential as bioactive cell substrates for tissue regeneration, especially for electrically active tissues, such as the skeletal muscle system .
Alginate hydrogels possess excellent properties and biocompatibility for a broad range of biomedical applications [3,4]. Nevertheless, they present weak mechanical properties within a few hours in physiological solution . In addition, the hydrophilic nature of alginate hydrogels leads to a lack of cell adhesion and, as a consequence, to an impairment of cellular responsiveness. To overcome these drawbacks of alginate hydrogels, different approaches have been studied, such as surface functionalization or the combination with other natural or synthetic polymers with better mechanical and bioactive properties.
Polycaprolactone (PCL) is a synthetic biocompatible hydrophobic polymer with excellent mechanical properties widely used in different tissue engineering applications and drug delivery [5,6]. Therefore, in this study we have focused on the combination of PCL with calcium-crosslinked sodium alginate (SA) as a promising approach to develop a semi-interpenetrated polymer network (semi-IPN) hydrogel with combined properties and wider range of applications in the biomedical field. In addition, to provide this novel hybrid system with electrical conductive properties to be employed in electroactive tissues (such as musculoskeletal, neural, bone or cardiac), two different concentrations of reduced graphene oxide (rGO 0,5% and 2% wt/wt) were embedded within the polymeric matrix. rGO is a graphene-based material (GBM) with remarkable conductive and mechanical properties which have been previously used regenerative medicine as filler to provide bioactivity in the form of electric conductivity [7-9].
The results show that the SA/PCL/rGO semi-IPN possesses a homogeneous structure based on a complex nano-network with different interactions between the SA chains, rGO nanosheets and Ca+2 ions, while the PCL chains are distributed within the alginate network. The incorporation of rGO significantly increases the electrical conductivity of the nanohybrid hydrogels, with values in the range of muscle tissue. In vitro cultures with C2C12 murine myoblasts revealed that the conductive nanohybrid hydrogels are not cytotoxic and can greatly enhance myoblast adhesion and myogenic differentiation. These novel electroactive nanohybrid hydrogels have great potential for biomedical applications related to regeneration of electroactive tissues, particularly in skeletal muscle tissue engineering.
Financial support from the Spanish Ministry of Science and Innovation (MCINN, AEI/FEDER funds) through the project RTI2018-097862-B-C21 and PID2020-119333RB-I00/AEI/10.13039/501100011033 are acknowledged.