<i>In Situ</i> Mineralization in Metal-Ion-Coordinated Polymer Hydrogels: Progress, Challenges, and Opportunities

Organic–inorganic composite materials found in nature are produced by organisms via spatiotemporally controlled growth of inorganic minerals in a templating scaffold of organic macromolecules. The outstanding properties and functions of biological composites have motivated long-standing efforts to mimic their manufacture via in situ growth of inorganic minerals in a great variety of bioinspired organic polymer scaffolds. In an attempt to simplify this bioinspired approach to composite manufacture, our group has recently demonstrated that metal-coordinated cross-linked polymer hydrogel networks can act as simple templating scaffolds for in situ mineralization, whereby nucleation and growth of inorganic mineral nanoparticles can be directly targeted to metal-ion-coordinated cross-link sites. This simple and efficient method of hydrogel solidification via in situ metal-coordinated cross-link mineralization could allow the fabrication of novel composite materials due to the unique accessibility to a variety of mineral growth control mechanisms during manufacture. In this Perspective, we first summarize the work that led to the realization of in situ metal-coordinated hydrogel mineralization. Subsequently, the current state-of-the-art in the field will be discussed followed by a description of ongoing challenges and future opportunities.