(1−3) Tissue engineering, as an alternative to treat missing or damaged tissue, has steadily garnered interest since the popularization of the field by Green and Gallico in the late 1970s and early 1980s. There are, however, significant issues with grafting as a treatment plan, including donor site morbidity, limited availability, rejection, and disease transfer, depending on whether auto-, allo-, or xenografts are used. Surgical grafting remains the primary treatment for patients suffering from severe tissue damage that requires replacement of the damaged tissue. Taking advantage of the bioactivity of PP and the tunable physicochemical properties of the synthetic PEG hydrogels, the presented MoDPEG+ hydrogels show great promise for tissue regeneration. To showcase their potential use in application-driven research, the MoDPEG+ hydrogels were straightforwardly (i) 3D printed using the SLA technique and (ii) produced via high-energy visible light (HEV-TEC) to populate damaged soft-tissue or bone cavities. Importantly, cells could adhere and proliferate on MoDPEG+ hydrogels due to the bioactive PP, while MoDPEG hydrogels were bio-inert as cells moved away from the hydrogel or were distributed in a large cluster on the hydrogel surface. All hydrogels showed good biocompatibility in vitro toward human skin cells and murine macrophages, with cell viability above 91%. PP reduced the swelling ratios compared with the pristine hydrogels (MoDPEG).

The addition of PP (1, 4, or 8 wt %) within the PEG hydrogels increased the storage moduli, with the 8 wt % PP hydrogels showing the highest storage moduli.

The PP-incorporated PEG hydrogels (MoDPEG+) showed tunable storage moduli ranging from 1080 ± 290 to 51,400 ± 200 Pa. In this study, placenta powder (PP), made from decellularized human placenta, was physically incorporated into synthetic poly(ethylene glycol) (PEG)-based hydrogels via UV-initiated thiol-ene coupling (TEC). Human placenta is a source of extracellular matrix for tissue engineering.

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