Mechanical properties of decellularized extracellular matrix coated with TiCaPCON film

For the first time the surface of decellularized extracellular matrix (DECM) was modified via deposition of a multicomponent bioactive nanostructured film for improvement of the DECM's mechanical properties. TiCaPCON films were deposited onto the surface of intact and decellularized ulna, radius, and humerus bones by magnetron sputtering of TiC_0.5 + 10%Ca₃(PO₄)₂ and Ti targets in a gaseous mixture of Ar + N₂. The film structure was studied using x-ray diffraction, scanning and transmission electron microscopy, and Raman spectroscopy. The films were characterized in terms of their wettability, as well as adhesion strength to the intact bone and DECM substrates. The mechanical properties of TiCaPCON-coated samples were investigated by compression testing. In addition, humerus bones were evaluated during three-point bending tests. The results indicate that the tightly adhered films, uniformly covering the DECM surfaces, possessed hydrophilic characteristics. A maximum improvement in mechanical properties (250%) was observed for coated humerus samples. In case of decellularized radius bones, the compressive strength also increased by 150% after coating. The positive role of TiCaPCON films was less noticeable for ulna bones because of large data scattering. These results clearly indicate that the films acted as a rigid frame that increased the material compressive strength. Compared with intact bones, fracture in the TiCaPCON-coated DECM samples was characterized by rarer and larger cracks generated under higher critical loads. As a result, the samples were crushed into several large pieces and numerous tiny fragments. Although the film deposition increased the bone stiffness, the bending tests revealed that the flexural strength of the coated samples became 20%-25% lower than the strength of the film-free samples.