These examples also reveal that the pore size is notably reduced when the dispersed nanoobjects promoted network connectivity. This occurred when nano-objects increased the density of crosslinking, for instance via electrostatic interactions (e.g., amine-functionalized iron oxide NPs/Gel), covalent imide linkages (e.g., PEG-DA-iron oxide NPs/GelMA), dynamic covalent Schiff-bases, (e.g., PDA NPs /oxidized ALG (OALG)) transient boronic bonds (e.g., catechol-modified iron oxide NPs/PVA/borax), or coordination networks (MSNs/HA-DA). Importantly, attention must be paid to an excessive particle content, which can lead to aggregation due to close interaction with the matrix. This was observed for instance with CuO NPs (15%) and graphene QDs (30%) in polysaccharide (CS, CMC) hydrogels and CaP NPs (> 25%) in a DMAEMA/ HEMA-based matrix. In other formulations, the incorporation of nano-objects did not affect the structure of the matrix, which appeared indistinguishable from pristine hydrogels (Figure ). . Adapted with permission. Copyright 2016 American Chemical Society. (b) SEM images of ALG hydrogels either empty (top) and loaded with CLC (bottom). Adapted with permission. Copyright 2020 American Chemical Society.