Biologically inspired ‘smart’ materials

Inspiration from nature and its translation to designing the next generation of biomedical devices have received immense attention recently. Biologically inspired materials utilise billions of years of evolution to generate diverse properties that would otherwise be difficult to achieve. These materials have the potential to address many limitations associated with more traditional materials. This issue of ADDR highlights some of the most recent advances in the development of biologically inspired smart materials and systems. These materials/ systems are defined as structures, material systems, sensors, actuators, or other devices that reflect the functionality found in nature and utilise smart materials [1]. Often such designs do not follow traditional engineering paradigms, but are developed through observations of natural phenomena. Bioinspired materials provide new solutions to treat diseases, support tissue regeneration and rebuild body parts and can be derived from synthetic sources (that replicate biological or natural structure, functionality, geometry of morphology), natural materials (derived from natural sources), or composite/hybrids of both classes [2–7]. Historically, natural materials such as wood or ivory were utilised to support fractured bones. In addition, naturally-derived materials have been used to help wound healing and induce skin regeneration [3,7]. Subsequent technological advances resulted in a significant shift towards synthetic materials such as metals and polymers, which were easily accessible, cheaper and satisfied the need from the functional point of view. However, with increasing knowledge and further technological advances it has been recognised that biological processes and structures can provide solutions to real-world problems [8–10]. For example, bioinspired materials offer potential solutions for addressing problems in tissue regeneration, drug delivery and preventivemedicine. Despite advances in engineering of synthetic materials that were reviewed by Kim [2], Hutmacher [6] and Wallace [8], a massive ‘back to nature’movement and appreciation of naturalmaterials are currently underway. The most explored examples of natural materials used in biomedical engineering include collagen [7], tropoelastin [3] and silk [5]. In her review, Abou Neel [7] highlighted that collagen is one of the most abundant proteins in mammals and its role is essential to life. Clinical uses of collagen-derived materials include products that have been shown to be effective for neural repair, as cosmetic for the treatment of dermatologic defects, haemostatic agents, mucosal wound dressing and guided bone regeneration membrane. The paper also highlighted that several other applications of collagen are under investigations [7]. Tropoelastin, which dominates the physical performance of human elastic tissue, has also received increasing appreciation in biomedicine, such as for making engineered constructs to augment