Protein–Metal-Ion Networks: A Unique Approach toward Metal Sulfide Nanoparticles Embedded In Situ in Nanocomposites

Nanoscale metal sulfides are of tremendous potential in biomedicine. Generally, the properties and performances of metal sulfide nanoparticles (NPs) are highly related to their structures, sizes and morphologies. Recently, a strategy of using sulfur-containing protein–metal-ion networks for preparing metal sulfide embedded nanocomposites was proposed. Within the networks, proteins can play multiple roles to drive the transformation of these networks into protein-encapsulated metal sulfide NPs with ultrasmall size and defined structure (as both a template and a sulfur provider) or metal sulfide NP–protein hydrogels with injecting and self-healing properties (as a template, a sulfur provider, and a gelator) in a controlled manner. In this Concept, the synthesis strategy, the formation mechanism, and the biomedical applications of the gained nanocomposites are presented. Moreover, the challenges and opportunities of using protein–metal ion networks to construct functional materials for biomedical applications are analyzed.