A bio-corrodible nitrided iron stent was developed using a vacuum plasma nitriding technique. In the nitrided iron stents, the tensile strength, radial strength, stiffness and in vitro electrochemical corrosion rate were significantly increased compared with those of the control pure iron stent. To evaluate its performance in vivo, the deployment of the nitrided iron stents in juvenile pig iliac arteries was performed. At 3 or 6 months postoperatively, the stented vessels remained patent well; however, slight luminal loss resulting from intimal hyperplasia and relative stenosis of the stented vessel segment with piglets growth were observed by 12 months; no thrombosis or local tissue necrosis was found. At 1 month postoperatively, a nearly intact layer of endothelial cells formed on the stented vessel wall. Additionally, a decreased inflammation scoring, considerably corroded struts and corrosion products accumulation were seen. These findings indicate the potential of this nitrided iron stent as an attractive biodegradable stent.

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A biodegradable coronary stent is expected to eliminate the adverse events of an otherwise eternally implanting material after vessel remodeling. Both biocorrodible metals and biodegradable polymers have been tried as the matrix of the new-generation stent. Herein, we utilized a metal–polymer composite material to combine the advantages of the high mechanical strength of metals and the adjustable degradation rate of polymers to prepare the biodegradable stent. After coating polylactide (PLA) on the surface of iron, the degradation of iron was accelerated significantly owing to the decrease of local pH resulting from the hydrolysis of PLA, etc. We implanted the metal–polymer composite stent (MPS) into the porcine artery and examined its degradation in vivo, with the corresponding metal-based stent (MBS) as a control. Microcomputed tomography (micro-CT), coronary angiography (CA), and optical coherence tomography (OCT) were performed to observe the stents and vessels during the animal experiments. The MPS exhibited faster degradation than MBS, and the inflammatory response of MPS was acceptable 12 months after implantation. Additionally, we implanted another MPS after 1-year implantation of the first MPS to investigate the result of the MPS in the second implantation. The feasibility of the biodegradable MPS in second implantation in mammals was also confirmed.