Biopolymer-based platforms for cell mechanosensing and regenerative medicine

In this talk I will introduce biopolymer-based networks as platforms for cell mechanosensing and regenerative medicine. First, chitosan gels will be presented. Chitosan gels are synthetized through a controlled external ionic gelation.[1] Recently it was reported that the physical-chemical properties of chitosan - as well as the molecular weight and the frequency of two building sugars glucosamine (D unit) and Nacetyl-glucosamine (A unit) along polymer chain - play a key role for the setting up of cylindrical gels characterized by different mechanical behavior at small/large deformations.[2] The ability of chitosan gels to behave as scaffold for cellular infiltration and ensuing anchoring was recently demonstrated.[3] While keeping constant stress relaxation and systematically decoupling overall stiffness from linear elasticity, we have introduced an energy dissipation term (J/mol), that is the molar energy required to deviate from linear stress-strain regime and enter into plastic region.[4] Strikingly, we have unveiled an inverse relationship between substrate energy dissipation and cell response, with high adhesion/high spreading and low adhesion/no spreading detected for substrates at low and high dissipation energy, respectively. Of note, I will show how combinations of facing 5- consecutive sugars (pentads) composing substrates are essential in damping shear stress, thus behaving as cell traction forces dampers. Second, chia (Salvia hispanica) seed mucilage gels will be presented. Chia seed mucilage represents an emerging biomaterial due to its particular tetrasaccharide (repeating unit) composition. Chia gels have shown very interesting mechanical properties.[5] Alkaline Phosphatase enzyme activity assay and Alizarin red staining demonstrated that chia mucilage did not alter in vitro stem cell differentiation. Collectively, this set of experiments revealed an almost inert role associated with chia suspensions, indicating a possible application of chia-based networks as scaffold models to study osteogenesis in vitro.[6]