Physiomimetic biocompatibility evaluation of directly printed degradable porous iron implants using various cell types

Additively manufactured (AM) degradable porous metallic biomaterials offer unique opportunities for sat-isfying the design requirements of an ideal bone substitute. Among the currently available biodegradable metals, iron has the highest elastic modulus, meaning that it would benefit the most from porous de-sign. Given the successful preclinical applications of such biomaterials for the treatment of cardiovascu-lar diseases, the moderate compatibility of AM porous iron with osteoblast-like cells, reported in earlier studies, has been surprising. This may be because, as opposed to static in vitro conditions, the biodegra-dation products of iron in vivo are transported away and excreted. To better mimic the in situ situations of biodegradable biomaterials after implantation, we compared the biodegradation behavior and cyto-compatibility of AM porous iron under static conditions to the conditions with dynamic in situ-like fluid flow perfusion in a bioreactor. Furthermore, the compatibility of these scaffolds with four different cell types was evaluated to better understand the implications of these implants for the complex process of natural wound healing. These included endothelial cells, L929 fibroblasts, RAW264.7 macrophage-like cells, and osteoblastic MG-63 cells. The biodegradation rate of the scaffolds was significantly increased in the perfusion bioreactor as compared to static immersion. Under either condition, the compatibility with L929 cells was the best. Moreover, the compatibility with all the cell types was much enhanced under physiomimetic dynamic flow conditions as compared to static biodegradation. Our study highlights the importance of physiomimetic culture conditions and cell type selection when evaluating the cytocompat-ibility of degradable biomaterials in vitro .Statement of SignificanceAdditively manufactured (AM) degradable porous metals offer unique opportunities for the treatment of large bony defects. Despite the successful preclinical applications of biodegradable iron in the car-diovascular field, the moderate compatibility of AM porous iron with osteoblast-like cells was reported. To better mimic the in vivo condition, we compared the biodegradation behavior and cytocompatibility of AM porous iron under static condition to dynamic perfusion. Furthermore, the compatibility of these scaffolds with various cell types was evaluated to better simulate the process of natural wound healing. Our study suggests that AM porous iron holds great promise for orthopedic applications, while also high-lighting the importance of physio-mimetic culture conditions and cell type selection when evaluating the cytocompatibility of degradable biomaterials in vitro .(c) 2023 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the performance of AM porous iron by comparing its biodegradation behavior and cytocompatibility under static and dynamic conditions. The research finds that the biodegradation rate of AM porous iron significantly increases under in situ-like conditions, and its compatibility with various cell types is enhanced.