Design of injectable organic-inorganic hybrid for bone tissue repair.

Injectable bone substitutes are rapidly gained success in tissue engineering applications for their less invasive surgical aspect. Here, the design and the characterization of a novel degradable paste of PCL reinforced with nanocrystals of hydroxyapatite have been presented aiming to mimic natural tissue. Nanohydroxyapatite has been successfully synthesized via sol-gel technique. Dynamic and steady state viscoelastic properties of the solutions and paste were investigated to control the kinetic of phase transition. Correspondingly, the morphology and composition were characterized via TEM, EDAX, and thermal analysis. Injection test underlines the completely ability of the paste of being injected without altering its features. Preliminary biological study showed that the composite paste is not cytotoxic. The synergistic rheological and biological properties, combined with the positive effect of chemical synthesis method indicate that the composite paste is very suitable as local bone substitute in low-load areas.

Layer-by-layer self-assembly of chitosan and poly(γ-glutamic acid) into polyelectrolyte complexes.

Chitosan (Ch) is a nontoxic and biocompatible polysaccharide extensively used in biomedical applications. Ch, as a polycation, can be combined with anionic polymers by layer-by-layer (LbL) self-assembly, giving rise to multilayered complexed architectures. These structures can be used in tissue engineering strategies, as drug delivery systems, or artificial matrices mimicking the extracellular microenvironment. In this work, Ch was combined with poly(γ-glutamic acid) (γ-PGA). γ-PGA is a polyanion, which was microbially produced, and is known for its low immunogenic reaction and low cytotoxicity. Multilayered ultrathin films were assembled by LbL, with a maximum of six layers. The interaction between both polymers was analyzed by: ellipsometry, quartz crystal microbalance with dissipation, Fourier transform infrared spectroscopy, atomic force microscopy, and zeta potential measurements. Ch/γ-PGA polyelectrolyte multilayers (PEMs) revealed no cytotoxicity according to ISO 10993-5. Overall, this study demonstrates that Ch can interact electrostatically with γ-PGA forming multilayered films. Furthermore, this study provides a comprehensive characterization of Ch/γ-PGA PEM structures, elucidating the contribution of each layer for the nanostructured films. These model surfaces can be useful substrates to study cell-biomaterial interactions in tissue regeneration.