Complex Materials: The Tough Life of Bone

Bone was a crucial biological material for the evolution of large terrestrial organisms and is today essential for most of our daily activities and well-being. From an engineering perspective, this living material features highly desirable properties for modern load-bearing structures. It is made of abundant and environmental-friendly building blocks, which are combined into a tough and durable structure that can continuously modify itself to adapt to changes in the mechanical load imposed by the surroundings. In this review article, we compile and discuss scientific findings that allow us to understand bone as a complex system with properties that emerge from cell-mediated interactions of molecules and particles at multiple length scales. Analogous to other complex systems, such interactions lead to self-organization, hierarchical structures and adaptive behavior without the need of a central controlling unit. A rich range of physical, chemical and biological phenomena provide a framework for information to be generated and processed in this complex system. Understanding the interplay between such underlying phenomena and their emerging properties should help the diagnosis and treatment of bone-related medical conditions and might provide guidelines for the future development of more sustainable materials and engineering structures.骨骼是大型陆生生物演化进程中不可或缺的关键生物材料，时至今日，它亦是维系人类绝大多数日常活动与健康福祉的核心物质。从工程学视角审视，这种活体材料具备现代承重结构所亟需的诸多优异特性。其由储量丰富且环境友好的构筑单元构成，这些单元组装形成坚韧耐用的结构，且可自主持续调节以适配外界施加的机械载荷变化。在本篇综述文章中，我们整理并探讨了相关科学发现，这些成果助力我们将骨骼认知为一类复杂系统：其特性源自多尺度下分子与颗粒经细胞介导的相互作用。与其他复杂系统相仿，这类相互作用无需中央调控单元，即可自发催生自组织现象、层级化结构与自适应行为。丰富多样的物理、化学与生物现象，为该复杂系统内信息的生成与处理提供了底层支撑框架。厘清这类底层现象与其涌现特性之间的相互作用，将有助于骨相关疾病的诊断与治疗，同时也可为未来开发更具可持续性的材料与工程结构提供指导性思路。