Rationally designed bioactive milk-derived protein scaffolds enhanced new bone formation

Recently,a number of studies reported that casein was composed of various multifunctional bioactive peptides such as casein phosphopeptide andβ-casochemotide-1 that bind calcium ions and induce macrophage chemotaxis,which is crucial for bone homeostasis and bone fracture repair by cytokines secreted in the process.We hypothesized that the effects of the multifunctional biopeptides in casein would contribute to improving bone regeneration.Thus,we designed a tissue engineering platform that consisted of casein and polyvinyl alcohol,which was a physical-crosslinked scaffold(milk-derived protein;MDP),via simple freeze-thaw cycles and performed surface modification using 3,4-dihydroxy-L-phenylalanine(DOPA),a mussel adhesive protein,for immobilizing adhesive proteins and cytokines for recruiting cells in vivo(MDP-DOPA).Both the MDP and MDP-DOPA groups proved indirectly contribution of macrophages migration as RAW 264.7 cells were highly migrated toward materials by contained bioactive peptides.We implanted MDP and MDP-DOPA in a mouse calvarial defect orthotopic model and evaluated whether MDP-DOPA showed much faster mineral deposition and higher bone density than that of the no-treatment and MDP groups.The MDP-DOPA group showed the accumulation of host M2 macrophages and mesenchymal stem cells(MSCs)around the scaffold,whereas MDP presented mostly M1 macrophages in the early stage.

Synthesis of an Azobenzene-containing Main-chain Crystalline Polymer and Photodeformation Behaviors of Its Supramolecular Hydrogen-bonded Fibers

The synthesis of a new azobenzene(azo)-containing main-chain crystalline polymer with reactive secondary amino groups in its backbone and photodeformation behaviors of its supramolecular hydrogen-bonded fibers are described. This main-chain azo polymer(namely Azo-MP6) was prepared via first the synthesis of a diacrylate-type azo monomer and its subsequent Michael addition copolymerization with trans-1,4-cyclohexanediamine under a mild reaction condition. Azo-MP6 was found to have a linear main-chain chemical structure instead of a branched one, as verified by comparing its ~1H-NMR spectrum with that of the azo polymer prepared via the polymer analogous reaction of AzoMP6 with acetic anhydride. The thermal stability, phase transition behavior, and photoresponsivity of Azo-MP6 were characterized with TGA,DSC, POM, XRD, and UV-Vis spectroscopy. The experimental results revealed that it had good thermal stability, low glass transition temperature,broad crystalline phase temperature range, and highly reversible photoresponsivity. Physically crosslinked supramolecular hydrogen-bonded fibers with good mechanical properties and a high alignment order of azo mesogens were readily fabricated from Azo-MP6 by using the simple melt spinning method, and they could show "reversible" photoinduced bending under the same UV light irradiation and good anti-fatigue properties.