Chondrogenic potential of macroporous biodegradable cryogels based on synthetic poly(alpha-amino acids)

In this study, the potential of highly porous hydrogels based on biodegradable synthetic poly(alpha-amino acids) to support proliferation and chondrogenesis of human dental pulp stem cells (hDPSCs) was investigated. Covalently crosslinked gels with permanent pores were formed under cryogenic conditions by free-radical copolymerization of poly[N-5-(2-hydroxyethyl)-L-glutamine-stat-N-5-(2-methacryloyl-oxy-ethyl)- L-glutamine] (PHEG-MA) with 2-hydroxyethyl methacrylate (HEMA) and N-propargyl methacrylamide (PrMAAm) as minor co-monomers. PrMAAm provided alkyne groups for modifying the gels with cell-supporting moieties (RGDS peptides) by the azide-alkyne "click"-reaction. Two types of gels with different compressive moduli were prepared. Each type was modified with two different concentrations of RGDS peptide. X-ray computed nanotomography (nanoCT) was used to visualize and analyze the 3D-structure of the cryogels. It was shown that modifying the PHEG-MA cryogels within the range of RGDS concentrations examined here had a positive effect on the proliferation of hDPSCs. Immunofluorescence staining for collagen type 2 and aggrecan proved that there was differentiation of hDPSCs into chondrocytes

Lysine-appended polydiacetylene scaffolds for human mesenchymal stem cells

We report on the self-assembly based fabrication of fibrous polymers for tissue engineering applications. Directed self-assembly followed by polymerization of lysine-appended diacetylenes generated a variety of polymers (P1–P5) with distinct chemical properties. The self-assembly along with the conjugated double and triple bonds and rigid geometry of diacetylene backbone imposed a nanofibrous morphology on the resulting polymers. Chemical properties including wettability of the polymers were tuned by using lysine (Lys) with orthogonal protecting groups (Boc and Fmoc). These Lys-appended polydiacetylene scaffolds were compared in terms of their efficiency toward human mesenchymal stem cells adhesion and spreading. Interestingly, polymer P4 containing Lys Nα-NH2 and Lys Nε-Boc with balanced wettability supported cell adhesion better than the more hydrophobic polymer P2 with Nε-Boc and Nα-Fmoc or more hydrophilic polymer P5 containing free Nε and Nα amino groups. The molecular level control in the fabrication of nanofibrous polymers compared with other existing methods for the generation of fibrous polymers is the hallmark of this work.V. Haridas, Sandhya Sadanandan, Pierre-Yves Collart-Dutilleul, Stan Gronthos, and Nicolas H. Voelcke