Fig. 2.

Schematic illustration for the preparation and nanostructures of BP-based nanocomposite hydrogels. (A) The BP-based nanocomposite hydrogels embedded with ex-situ NPs: i) CaP NPs, reproduced with permission from Ref. [80], copyright 2014, Elsevier, ii) MgSiO₃ NPs, reproduced with permission from Ref. [77], copyright 2016, Royal Society of Chemistry, iii) Fe₃O₄ NPs, reproduced with permission from Ref. [81], copyright 2019, American Chemistry Society. (B) The BP-based nanocomposite hydrogels embedded with in-situ NPs formed via self-assembly during the gelation process. Reproduced with permission from Ref. [39], copyright 2019, John Wiley and Sons. (C) For hydrogels embedded with ex-situ NPs, the grafted-BP moieties attach onto the surface of nanoparticles; for hydrogels embedded with in-situ NPs, some of the grafted-BP moieties entrap into the center of nanoparticles. Reproduced with permission from Ref. [79], copyright 2017, John Wiley and Sons. (D) The linkage between the attached grafted-BP moieties and the BP–Metal NPs is fully reversible, whereas the linkage between the entrapped grafted-BP moieties and the BP–Metal NPs is not reversible and cannot be restored autogenously. Reproduced with permission from Refs. [79], copyright 2017, John Wiley and Sons.