*Nature-Inspired Processes and Structures: New Paradigms to Develop Highly Bioactive Devices… DOI: http://dx.doi.org/10.5772/intechopen.82740*

A subject of investigation in the late 1990s was the transformation of wood into inorganic, hierarchically organized materials (e.g., oxidic ceramics such as Al2O3, ZrO2, TiO2, and MnO and nonoxidic ceramics such as SiC, TiC, and ZrC) [92–96]. The synthesis of hierarchically organized bone scaffolds made of SiC is a result of these studies [94], which have the advantage of offering bio-tolerated surfaces and very high fracture strength. Other kinds of biomorphic transformations, conceived recently, were used to manufacture hierarchically organized scaffolds made of HA [3]. The complexity of the apatite phase, in comparison with nitrides, carbides, and oxides, required the settling of a multistep process transformation, where the native wood was sequentially transformed into pure carbon, calcium carbide, calcium oxide, calcium carbonate, and finally HA. Due to their bone-mimicking hierarchical organization, microstructure and composition such a new generation of bioceramics scaffolds promise to offer enhanced integration, osteogenesis, and biomechanical behavior when implanted in vivo [8].

Woods such as rattan have strong similarities to 3D structure and morphology of cortical and spongy bone. Rattan is characterized by channel-like pores (simulating the Haversian system in bone), interconnected with a network of smaller channels (such as the Volkmann system) [3].

There is a precise control of the microstructure, crystallinity, and phase composition, during the multistep transformation process, in which different gas-solid reactions occur where the solid is the template. Calcium, oxygen, carbonate, and phosphate ions were progressively added in the different steps to finally get the HA molecules. The reaction kinetic is controlled throughout the different steps of the transformation process in order to have a precise control of the scaffold microstructure, composition, and bioactivity [95]. Importantly, even in the absence of thermal consolidation treatments, the scaffolds exhibit mechanical strengths comparable to those of spongy bone (~4 MPa) when measured along the channel direction, thanks to the maintenance of the original wood microstructure.

The establishment of biomorphic transformations that are able to transform woods into biomimetic bone scaffolds can provide solutions for long-bone regeneration and can be designed in a custom-made fashion. Selected wood structures could reproduce different bone portions that are characterized by different porosities and pore distributions, as occurring in cortical and spongy bones. Such devices may implement the formation of a biological chamber in vivo that contain a suitable environment that allows to promote and enhance bone formation and remodeling. The implant will thus function as an in vivo bioreactor, thus facing an unsolved clinical problem related to the disappearing of the regenerative process at distances far from the bone-implant interface [20].
