RGD-mimic polyamidoamine-montmorillonite composites with tunable stiffness as scaffolds for bone tissue-engineering applications

This paper reports on the development of montmorillonite (MMT)-reinforced hydrogels, based on a peptidomimetic polyamidoamine carrying guanidine pendants (AGMA1), as substrates for the osteo-induction of osteoblast precursor cells. AGMA1 hydrogels of various degrees of crosslinking responded favourably to MMT reinforcement, giving rise to composite hydrogels with shear storage modulus G', when fully swollen in water, up to 200 kPa, i.e. 20 times higher than the virgin hydrogels and of the same order or higher than other hydrogel-based composites proposed for orthopaedic applications. This significant improvement was ascribed to the effective interpenetration between the polymer matrix and the inorganic filler. AGMA1-MMT hydrogels, when evaluated as scaffolds for the osteogenic differentiation of mouse calvaria-derived pre-osteoblastic MC3T3-E1 cells, proved able to support cell adhesion and proliferation and clearly induced differentiation towards the osteoblastic phenotype, as indicated by different markers. In addition, AGMA1-MMT hydrogels proved completely degradable in aqueous media at pH 7.4 and did not provide any evidence of cytotoxicity. The experimental evidence suggests that AGMA1-MMT composites definitely warrant potential as scaffolds for osteoblast culture and bone grafts.