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RESEARCH ARTICLE

Hydrolytic Expansion Induces Corrosion Propagation

for Increased Fe Biodegradation

Cijun Shuai 1,2,3 , Sheng Li , Shuping Peng , Youwen Yang , Chengde Gao *
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4
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1 State Key Laboratory of High-Performance Complex Manufacturing, College of Mechanical and Electrical Engineering,
Central South University, Changsha 410083, China
2 Institute of Bioadditive Manufacturing, Jiangxi University of Science and Technology, Nanchang 330013, China
3 Shenzhen Institute of Information Technology, Shenzhen 518172, China
4 The Key Laboratory of Carcinogenesis of the Chinese Ministry of Health, Xiangya Hospital, Central South University,
Changsha, 410008, China

Abstract: Fe is regarded as a promising bone implant material due to inherent degradability and high mechanical strength, but
its degradation rate is too slow to match the healing rate of bone. In this work, hydrolytic expansion was cleverly exploited
to accelerate Fe degradation. Concretely, hydrolyzable Mg Si was incorporated into Fe matrix through selective laser melting
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and readily hydrolyzed in a physiological environment, thereby exposing more surface area of Fe matrix to the solution.
Moreover, the gaseous hydrolytic products of Mg Si acted as an expanding agent and cracked the dense degradation product
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layers of Fe matrix, which offered rapid access for solution invasion and corrosion propagation toward the interior of Fe
matrix. This resulted in the breakdown of protective degradation product layers and even the direct peeling off of Fe matrix.
Consequently, the degradation rate for Fe/Mg Si composites (0.33 mm/y) was significantly improved in comparison with
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that of Fe (0.12 mm/y). Meanwhile, Fe/Mg Si composites were found to enable the growth and proliferation of MG-63 cells,
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showing good cytocompatibility. This study indicated that hydrolytic expansion may be an effective strategy to accelerate the
degradation of Fe-based implants.
Keywords: Hydrolytic expansion, Biodegradation, Fe-based implants, Selective laser melting, Cytocompatibility
*Corresponding Author: Chengde Gao, State Key Laboratory of High-Performance Complex Manufacturing, College of Mechanical and
Electrical Engineering, Central South University, Changsha 410083, China; gaochengde@csu.edu.cn.
Received: November 12, 2019; Accepted: January 2, 2020; Published Online: January 23, 2020

Citation: Shuai C, Li S, Peng S, et al., 2020, Hydrolytic expansion induces corrosion propagation for increased Fe
biodegradation. Int J Bioprint, 6(1):248. DOI: 10.18063/ijb.v6i1.248

1 Introduction experiments and no acute inflammatory reaction,
systemic, or local toxicity were reported, indicating
Due to natural degradability, favorable mechanical good biocompatibility [4-7] . However, Fe still stays
properties, and acceptable biocompatibility,
biodegradable metals have been extensively intact in vivo even after 6 months, which indicates
[8]
highlighted for fabricating bone implants over that a fast corrosion rate is urgently demanded .
the past years [1-3] . Iron (Fe), which can corrode To increase the corrosion rate of Fe, lots of
in the physiological environment, is considered researches, for example, alloying, surface treatment,
as a typical biodegradable metal. Fe is especially and new fabrication process have been carried
[9]
attractive in load-bearing applications due to its out . Hermawan et al. added manganese (Mn) into
high mechanical strength. The applications of Fe Fe to reduce the corrosion potentials of Fe, thereby
as bone implants have been validated by animal increasing the corrosion rates . Subsequently,
[10]
© 2020 Shuai, et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International
License (http://creativecommons.org/licenses/by-nc/4.0/), permitting all non-commercial use, distribution, and reproduction in any medium, provided the
original work is properly cited.
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