nanoplatelets and HAP ). An alternative example is the synthesis of four different HA derivatives functionalized with thiol, dithiopyridyl, hydrazide or aldehyde groups at ~ 10% that enabled two coupling strategies to be combined in a unique hydrogel. When adding an equal volume of buffered solution of the individual components (at a concentration of 4%), the simultaneous formation of disulfide and hydrazone bonds almost instantaneously yield the crosslinked network in which iron oxide NPs could be incorporated as nanofiller agents by simple mixing. The stabilization of the hydrogel network by formation of covalent chemical bonds can also be obtained using multi-arm PEG derivatives, terminated with opportune functional groups. For example, a 4-arm PEG with succinimidyl ester at each end chain (4-arm-PEG-SG) ensured crosslinking of poly-3-amino-4-methoxybenzoic acid-gelatin (PAMB-Gel) modified with thioketal (TK)-amine (PAMB-Gel-TK) via thiol-catechol Michael-type addition reaction (Figure ). When polymer concentration of 4-arm-PEG-SG and PAMB-Gel-TK was set at 2 and 4%, respectively, complete gelation occurred within 10 s, which is however excessively fast. Reducing the concentration to 1.5 and 3%, respectively, resulted in a fourfold slower gelation. This enabled the formulation to be injected without clogging the needles and to gel in situ, resulting in a sustained release depot of dispersed drug loaded-liposomes. sphingosine-1-phosphate (S1P) (S1P/SS-31/Lipo). Adapted with permission. Copyright 2022, Wiley-VCH.