Journal of Materials Science: Materials in Medicine (2018) 29:94 https://doi.org/10.1007/s10856-018-6096-7

BIOCOMPATIBIL ITY STUDIES

Original Research

In vivo performances of pure Zn and Zn–Fe alloy as biodegradableimplants

Alon Kafri 1● Shira Ovadia2 ● Galit Yosafovich-Doitch2

● Eli Aghion1

Received: 26 February 2018 / Accepted: 5 June 2018© Springer Science+Business Media, LLC, part of Springer Nature 2018

AbstractThe disadvantage of current biodegradable metals such as Mg and Fe is the release of hydrogen gas in vivo that can causegas embolism and the production of voluminous iron oxide that can cause inflammation, respectively. Such considerationshave turned focus towards Zn as an alternative. This is based on the fact that Zn plays a crucial role in many physiologicalprocesses, as well as potentially being biocompatible and capable of with biodegradation. As such, the purpose of the presentstudy was to evaluate the in vivo performance of pure Zinc and Zn–2%Fe implants. The use of iron as an alloying elementwas aimed at accelerating the corrosion rate of pure zinc by a micro-galvanic effect so as to maintain the post-implantationbiodegradation characteristics of the implant. In vivo assessment was carried out using cylindrical disks implanted in theback midline of 16 male Wistar rats for up to 24 weeks. Post-implantation evaluation included monitoring the well-being ofrats, weekly examination of hematological parameters: serum Zn levels, red and white blood cell counts and hemoglobinlevels, X-ray radiography, histological analysis and corrosion rate assessment. The results obtained in terms of well-being,hematological tests and histological analysis of the rats indicate that the in vivo behavior of pure Zn and Zn–2%Fe implantswas adequate and in line with the results obtained by the control group containing inert Ti–6Al–4V alloy implants. Thecorrosion rate of Zn–2%Fe alloy in in vivo conditions was relatively increased compared to pure Zn due to micro-galvaniccorrosion.

Graphical Abstract

1 Introduction

The development of biodegradable metal implants over thelast two decades was mainly focused on two metal candi-dates, Fe− and Mg-based alloys. Although Fe-based alloysexhibit good biocompatibility and excellent mechanicalproperties [1–3], they suffer from severe corrosion thatproduces a voluminous iron oxide layer that can causeinflammation [4]. While Mg-based alloys exhibit superiorbiocompatibility properties [5–8], the release of hydrogengas during corrosion degradation can cause separation oftissues and in extreme cases, gas embolism [9, 10]. Such

* Alon Kafrikafria@bgu.ac.ilKafri09@gmail.com

1 Department of Materials Engineering, Ben-Gurion University ofthe Negev, 8410501 Beer-Sheva, Israel

2 Faculty of Health Science, Ben-Gurion University of the Negev,8410501 Beer-Sheva, Israel

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disadvantages of Mg and Fe as biodegradable implantmaterials have turned the focus of the scientific communitytowards another metal, zinc. As an essential trace element,Zn plays a crucial role in numerous physiological processes,such nucleic acid metabolism, gene expression and signaltransduction [11–13]. The toxicity of abnormal amounts ofzinc in the human body can affect normal growth, as well asprovoking anemia due to the negative effect Zn on ironabsorption [14, 15].

Although the in vitro performance of Zn base material asbiodegradable implant showed promising results [16–24],the in vivo performance of the metal remains relativelyunclear [25–28]. To date, in vivo studies have shown thatpure zinc possesses several relevant properties, such as anti-atherogenic characteristics and adequate mechanical integ-rity in stent applications. However in parallel, pure zincpresents certain disadvantages, such as a reduced corrosionrate in vivo and relatively low mechanical properties[19, 29].

The aim of the present research was to assess the bio-degradation behavior of pure Zinc and Zn–2%Fe implantsin in vivo conditions. Special attention was attributed to theeffect of the implants on well-being, hematological andhistological parameters following subcutaneous implanta-tion in rats. The use of Fe as an alloying element wasdesigned to increase the corrosion rate of pure Zn withouteffecting its biocompatibility [30–32], at the same timepreserving post-implantation degradability of the implant.

2 Materials and methods

The alloys used as structural material for the tested implantswere pure zinc and Zn–2%Fe (in %wt.), designated as Znand Zn–2Fe respectively, as well as Ti–6Al–4V alloy usedas inert implant material in a control group. The preparationof the Zn–2Fe alloy in ingot form was carried out by gravitycasting using pure zinc bars (99.99%) and the designatedamount of pure iron (99%) powder with a particle size ofabout 45 µm. The microstructure examination was obtainedby scanning electron microscopy (SEM) with a JEOL JSM-5600 (JEOL, Tokyo, Japan) with an energy dispersivespectrometer (EDS) detector (Thermo fisher scientific, Ma,USA). Vickers hardness measurements was performed in aZwick/Roell Indentec of Quantarad Technologies, with anapplied load of 3 kg. The alloy was prepared in a graphitecrucible at 750°C with subsequent stirring. The testedimplants were prepared by machining and polishing in theform of cylindrical disks with 7 mm diameter, 2 mm heightand surface roughness of N5. Prior to implantation of thecylindrical disks, they were ultrasonically cleaned in ethanolfor 10 min and in acetone for 5 min before air drying. Allanimal experiments were approved by the Ben-Gurion

University (BGU) Committee for the Ethical Care and Useof Laboratory Animals (BGU-IACUC). In vivo experimentswere carried out according to the Israel Animal welfare law(1994), the NRC Guide for the Care and Use of LaboratoryAnimals (2011) and the BGU animal care and use programapproved by the Association for the Assessment andAccreditation of Laboratory Animal Care International(AAALAC). Animal experiments were carried out in BGUrodent facility.

Sixteen male Wistar rats (Envigo, Jerusalem, Israel) witha mean weight of 270 ± 5 g were selected for in vivoassessment. The rats were divided into 3 groups. The firstgroup was implanted with pure Zn disks (n= 6), the secondgroup was implanted with Zn–2Fe alloy (n= 6) and thethird group was implanted with Ti–6Al–4V alloy (n= 4).

For implantation, all 16 rats were anesthetized with aninhalation anesthesia machine using 3% isoflurane (TerrelPiramal Critical Care, Bethlehem PA) and 500 ml/minoxygen. Two cylindrical disks were aseptically implantedsubcutaneously in the midline of the back of each rat, onebetween the scapulae and the other in the mid-lumbar area.After the surgical incision was sutured, the rats were placedon a heating pad until they recovered from anesthesia andwere ambulatory. For post-operative analgesia, the ratsreceived 100 mg/kg dipyrone (Vitamed PharmaceuticalIndustries, Binyamina, Israel) in their drinking water for3 days. The rats were monitored daily during the first weekfor surgical wound appearance, locomotion in their cage,grooming activity and general well-being. This was fol-lowed by a weekly evaluation of body weight, attitude andincision appearance. Blood was collected from the retro-orbital sinus under isoflurane anesthesia, as describedabove. Whole blood (1 ml) in EDTA, collected for completeblood cell, red blood cell (RBC) and white blood cell(WBC) counts and for determining hemoglobin (HGB)levels, as well as serum (1 ml), for Zn level assessment,were analyzed on the day of implantation (day 0) and at 4,8, 12, 18 and 24 weeks post-implantation.

At weeks 14 and 24, half of each group of rats wasanesthetized with 75 mg/kg ketamine (Vetoquinol, Lure,France) and 5 mg/kg xylazine (Eurovet Animal Health, B.VBladel, Netherlands) administered intraperitoneally.Implanted disks were visualized by X-ray in the lateral andventro-dorsal positions. The rats were euthanized with anintraperitoneal injection of 150 mg/kg pentobarbital (CTSChemical Industries, Hod Hasharon, Israel), followed byimplant and tissue harvest. Tissues from each implantlocation were fixed in 10% formaldehyde for histologicalassessment. Histological analysis of tissues surrounding theimplants assessed inflammation, necrosis and tissue fibrosis.Samples were trimmed, embedded in paraffin and stainedwith hematoxylin & eosin (H&E) and assessed blindly by aveterinary pathologist (Patho-Logica, Ness Ziona, Israel).

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Ex vivo implant degradation assessment included visualexamination of the extracted implants using a stereoscope.Removal of corrosion products from the Zn base materialwas preformed according to ASTM G1 using 10% NH4Clsolution. The corrosion products were weighed to calculatethe related corrosion rate.

Statistical analyses were carried out using one-wayANOVA to identify significance of pairwise comparisons.P < 0.05 was acknowledged as a statistically substantialvariation between means. The error bars shown in the fig-ures represent standard errors relative to mean value.

3 Experimental results

The microstructure of the Zn–2%Fe alloy is shown in cross-section view (Fig. 1), accompanied by an EDS analysis atseveral points (Table 1). Those Fe-rich phases are morecathodic then the Zn matrix thus increasing the corrosionrate by micro-galvanic effect [31, 33]. Hardness measure-ments as a first evaluation of the mechanical properties wasdone.

The hardness of pure Zn and Zn–2%Fe alloy were 40.5± 2.8 and 64 ± 2.2 HV (hardness Vickers), respectively. Theincrease in hardness values is associated with the presenceof the Fe-rich phase.

Post-implantation weight gain by rats containing biode-gradable Zn-based implants, as compared to the control

group containing inert Ti–6Al–4V implants, is shown inFig. 2. All of the rats with Zn-based implants exhibitednormal weight gain, similar to that of the control groupcontaining Ti–6Al–4V implants [34, 35]. Post-implantationassessment including well-being, hair growth and surgicalwound healing exhibited no signs of distress or illness.

Hematological assessment in terms of serum zinc andHGB levels, as well as RBC and WBC counts pre- andpost-implantation of Zn-based materials or Ti6Al4Vimplants are presented in Figs. 3–6, respectively. Thisrevealed a slight increase in serum zinc levels in rats con-taining Zn-based implants, as compared with rats containingTi6Al4V implants, as anticipated. In addition, RBC andWBC counts, as well as HGB levels in rats implanted withZn-based material and Ti6Al4V were similar. This indicatesnot of the tested implants caused anemia or general infec-tion. It should be pointed out that the values for all of thetested hematological parameters were within the normalrange for male rats: Zinc serum, 168–190 [µg/dl]; RBC,7.62–9.99 [106/µl]; HGB 13.6–17.4 [g/dl]; and WBC1.98–11.06 [103/µl] [36, 37] at 24 weeks post-implantation.

Typical radiographic images of rats containing pure zinc,Zn–2Fe, and Ti–6Al–4V implants at 14 and 24 weeks post-implantation are shown in Figs. 7–9, respectively. Eachradiograph shows the two implants that were sub-cutaneously implanted in the midline of the back of the rats.Analysis of the radiographic images clearly indicates that nogas bubbles were present in the vicinity of the implants,

Fig. 1 Microstructure at cross-section of Zn–2%Fe alloy

Table 1 Chemical composition of Zn–2%Fe at different points shownin Fig. 1

El Element [wt.%]

Tested area Zn Fe

Point 1 100 0

Point 2 92.09 ± 1.11 7.91 ± 0.25

Fig. 2 Pre- and post-implantation body weights

Fig. 3 Pre- and post-implantation serum zinc levels

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regardless of whether the implants comprised Zn-basedmaterial or Ti–6Al–4V alloy.

Visual inspection of pure Zn and Zn–2%Fe implantsextracted from rats 14 or 24 weeks post-implantation areshown in Fig. 10. The results clearly show that the corrosiondegradation, reflected in terms of corrosion products,obtained from Zn–2Fe implants was significantly higherthan in the case of pure Zn implants. In addition, noapparent differences in the corrosion of the implants foundat either of the two implantation sites (i.e., between scapulaeand mid-lumbar) were visible. The corrosion rates calcu-lated upon measuring the amounts of corrosion products asa function of implantation time for pure Zn and Zn–2Fealloy is shown in Fig. 11. Such analysis revealed that whilethe corrosion rate of the Ti–6Al–4V implants was nearlyzero, the corrosion rate of the Zn–2Fe implants was almosttwice that of the pure Zn implants. Furthermore, it wasevident that the corrosion rates of the pure Zn and Zn–2Feimplants seen 14 weeks post-implantation were relativelyreduced, as compared to the corrosion rates measured24 weeks post-implantation.

Histological analysis of the tissue located around thepure Zn, Zn–2%Fe and Ti–6Al–4V disc implants taken14 weeks post-implantation are shown in Fig. 12. None ofthe tissues exhibited signs of inflammation or necrosis. Inaddition, no marked differences could be observed betweenthe Zn-based materials and the inert Ti–6Al–4V implantused in the control group. Furthermore, it was again evidentfrom histological analysis that no distinct differences exis-ted between tissues collected from the two implantationsites (i.e., between the scapulae and mid-lumbar).

4 Discussion

Although in vitro assessments of Zn-based alloys haveexhibited promising outcomes [17, 21, 38, 39], Yue et al.[40] indicated that the too low degradation rate is a chal-lenge for future applications of those alloys as biodegrad-able implants. With this in mind, the present study aimed at

Fig. 4 Pre- and post-implantation HGB levels

Fig. 5 Pre- and post-implantation RBC levels

Fig. 6 Pre- and post-implantation WBC levels

Fig. 7 Radiographic assessmentof rats containing two pure Znimplants a 14 and b 24 weekspost-implantation

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evaluating the in vivo behavior of a Zn-based material, aswell as the problem of reduced degradation rate of pure Zn.This was carried out by examining differences between pureZn and Zn–2%Fe alloy that exhibited an increased corro-sion rate post-implantation (Fig. 10), due to the micro-galvanic effect generated by iron addition [31]. It should bepointed out that in both material systems; the sequence of

the corrosion reactions is basically as follows [23]:

Anodic reaction : 2Zn ! 2Zn2þ þ 4e�

Cathodic reaction : O2 þ 2H2Oþ 4e ! 4OH�

2Zn2þ þ 4OH� ! 2Zn OHð Þ2

Fig. 8 Radiographic assessmentof rats containing two Zn–2Fealloy implants a 14 and b24 weeks post-implantation

Fig. 9 Radiographic analysis ofrats containing two Ti–6Al–4Valloy implants a 14 and b24 weeks post-implantation

Fig. 10 Visual images ofcylindrical discs. a, b Pure Znimplants 14 and 24 weeks post-implantation, respectively. c, dZn–2Fe alloy implants 14 and24 weeks post-implantation,respectively

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Zn OHð Þ2! ZnOþ H2O

The formation of Zn(OH)2 and ZnO in vivo, rather thanH2 gas, as obtained with Mg-based implants [41], canexplain the absence of gas bubbles, as revealed by radio-graphic analysis (Figs. 7 and 8). In addition, the formationof ZnO can also explain the reduced corrosion rate of theZn-based material tested at 24 weeks post-implantation,relative to the corrosion rate seen 14 weeks post-

implantation (Fig. 11). This finding is supported by thefindings of Törne et al. [42], who reported that the corrosionrate of pure Zn decreases over time when immersed inactual body fluids. The relatively improved corrosionresistance of pure Zn, as compared to Mg-based materials,was also evident to Bowen et al. [26, 43], who tested pureZn wire implants in the aorta of rats for stent applications.

When considering the in vivo behavior of rats containingpure Zn and Zn–2Fe implants, the main concern ofAndriollo-Sanchez et al. [44] and Prasad et al. [45] was thatan excess of Zinc content would have a detrimental effecton weight gain and can cause anemia. The results obtainedin the present study clearly show that weight gain by ratscontaining Zn-based material was normal and similar to thatof the control group containing inert Ti–6Al–4V implants(Fig. 2). In addition, well-being of the rats bearing the Zn-based implants, including hair growth and surgical woundrecovery, was also satisfactory. Furthermore, hematologicalassessment in terms of zinc serum and HGB levels, as wellas RBC counts, showed no signs of anemia (Figs. 4–6). Thepossible inflammatory effect of Zn-based implants wasevaluated by assessing WBC levels and by histological

Fig. 11 Corrosion rates of pure Zn and Zn–2%Fe alloy implantsmeasured 14 and 24 weeks post-implantation

Fig. 12 Histological analysis ofsubcutaneous tissues at14 weeks post-implantation. a, bpure Zn implants. c, d Zn–2%Feimplants. e, f Ti–6Al–4Vimplants. Implant locations aremarked by asterisks. Slices takenin the cranial and caudalorientations, respectively, areshown for each treatment

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analysis of tissues removed from the vicinity of the implants(Figs. 6 and 12). It was revealed that WBC levels werewithin the normal range, while the histological assessmentexhibited no sign of inflammation or necrosis. These find-ings are in agreement with those reported by Yang et al.[46], who found no inflammation upon degradation of apure Zn stent in rabbits.

Taken together, the in vivo results obtained in the presentstudy indicate that pure Zn and Zn–2%Fe alloy can beconsidered as suitable structural materials for biodegradableimplants. The relatively increased corrosion rate of Zn–2%Fe alloy can be used to increase the degradation rate of theimplants in case were rapid degradation characteristics arerequired.

5 Conclusions

In vivo assessment of rats containing pure Zn and Zn–2%Feimplants in terms of well-being, hematological profiles andhistological analysis was in line with results obtained by thecontrol group containing inert Ti–6Al–4V implants. Theslight increase in serum zinc levels in rats with Zn-basedimplants did not have any detrimental effect on weight gainand did not cause any signs of anemia. The comparativelyincreased corrosion degradation of Zn–2%Fe post-implantation reflects an important benefit in terms of suit-ability as a biodegradable Zn-based implant.

Acknowledgements We thank Mr. Avi Leon for assistance with theexperimental work.

Compliance with ethical standards

Conflict of interest The authors declare that they have no conflictofinterest.

References

1. Schinhammer M, Hänzi AC, Löffler JF, Uggowitzer PJ. Designstrategy for biodegradable Fe-based alloys for medical applica-tions. Acta Biomater. 2010;6:1705–13.

2. Feng Q, et al. Characterization and in vivo evaluation of a bio-corrodible nitrided iron stent. J Mater Sci Mater Med.2013;24:713–24.

3. Liu B, Zheng YF. Effects of alloying elements (Mn, Co, Al, W,Sn, B, C and S) on biodegradability and in vitro biocompatibilityof pure iron. Acta Biomater. 2010;7:1407–20.

4. Pierson D, et al. A simplified in vivo approach for evaluating thebioabsorbable behavior of candidate stent materials. J BiomedMater Res. 2012;100 B:58–67.

5. Levy G, Aghion E. Effect of diffusion coating of Nd on thecorrosion resistance of biodegradable Mg implants in simulatedphysiological electrolyte. Acta Biomater. 2013;9:8624–30.

6. Dunne CF, Levy GK, Hakimi O, Aghion E, Twomey B, StantonKT. Corrosion behaviour of biodegradable magnesium alloys withhydroxyapatite coatings. Surf Coat Technol. 2016;289:37–44.

7. Persaud-Sharma D, Mcgoron A. Biodegradable magnesiumalloys: a review of material development and applications. JBiomim Biomater Tissue Eng. 2012;3:25–39.

8. Ghali E. Corrosion resistance of aluminum and magnesium alloys.Corros Eng Sci Technol. 2010;46:744.

9. Song G. Control of biodegradation of biocompatable magnesiumalloys. Corros Sci. 2007;49:1696–701.

10. Aghion E, Levy G. The effect of Ca on the in vitro corrosionperformance of biodegradable Mg-Nd-Y-Zr alloy. J Mater Sci.2010;45:3096–101.

11. Hambidge KM, Krebs NF. Zinc deficiency: a special challenge. JNutr. 2007;137:1101–5.

12. Plum LM, Rink L, Hajo H. The essential toxin: Impact of zinc onhuman health. Int J Environ Res Public Health. 2010;7:1342–65.

13. Hennig B, Toborek M, McClain CJ. Antiatherogenic properties ofzinc: Implications in endothelial cell metabolism. Nutrition.1996;12:711–7.

14. Piao F, Yokoyama K, Ma N, Yamauchi T. Subacute toxic effectsof zinc on various tissues and organs of rats. Toxicol Lett.2003;145:28–35.

15. Drelich AJ, Bowen PK, LaLonde L, Goldman J, Drelich JW.Importance of oxide film in endovascular biodegradable zincstents. Surf Innov. 2016;4:1.

16. Vojtěch D, Kubásek J, Šerák J, Novák P.Mechanical and corro-sion properties of newly developed biodegradable Zn-based alloysfor bone fixation. Acta Biomater. 2011;7:3515–22.

17. Li HF, et al. Development of biodegradable Zn-1X binary alloyswith nutrient alloying elements Mg, Ca and Sr. Sci Rep.2015;5:10719.

18. Niu J, et al. Research on a Zn-Cu alloy as a biodegradable materialfor potential vascular stents application. Mater Sci Eng C.2016;69:407–413.

19. Bakhsheshi-Rad HR, et al. Thermal characteristics, mechanicalproperties, in vitro degradation and cytotoxicity of novel biode-gradable Zn–Al–Mg and Zn–Al–Mg–xBi alloys. Acta Metall Sin.2017;30:201–11.

20. Dambatta MS, Izman S, Kurniawan D, Hermawan H. Processingof Zn-3Mg alloy by equal channel angular pressing for biode-gradable metal implants. J King Saud Univ. 2017;29:455–61.

21. Mostaed E, et al. Novel Zn-based alloys for biodegradable stentapplications: design, development and in vitro degradation. JMech Behav Biomed Mater. 2016;60:581–602.

22. Tang Z, et al. Design and characterizations of novel biodegradableZn-Cu-Mg alloys for potential biodegradable implants. Mater Des.2017;117:84–94.

23. Katarivas Levy G, Goldman J, Aghion E. The prospects of zinc asa structural material for biodegradable implants—a review paper.Metals. 2017;7:402.

24. Levy GK, et al. Evaluation of biodegradable Zn-1%Mg and Zn-1%Mg-0.5%Ca alloys for biomedical applications. J Mater SciMater Med. 2017;28:174.

25. Xiao C, et al. Indirectly extruded biodegradable Zn-0.05wt%Mgalloy with improved strength and ductility: In vitro and in vivostudies. J Mater Sci Technol. 2018. https://doi.org/10.1016/j.jmst.2018.01.006.

26. Bowen PK, Drelich J, Goldman J. Zinc exhibits ideal physiolo-gical corrosion behavior for bioabsorbable stents. Adv Mater.2013;25:2577–82.

27. Zhao S, et al. Zn-Li alloy after extrusion and drawing: Structural,mechanical characterization, and biodegradation in abdominalaorta of rat. Mater Sci Eng C. 2017;76:301–12.

Journal of Materials Science: Materials in Medicine (2018) 29:94 Page 7 of 8 94

28. Bowen PK, et al. Evaluation of wrought Zn–Al alloys (1, 3, and 5wt % Al) through mechanical and in vivo testing for stent appli-cations. J Biomed Mater Res. 2018;106:245–58.

29. Bakhsheshi-Rad HR, et al. Fabrication of biodegradable Zn-Al-Mg alloy: mechanical properties, corrosion behavior, cytotoxicityand antibacterial activities. Mater Sci Eng C. 2017;73:215.

30. Fransen M, Nazikkol C. Zinc/iron phase transformation studies ongalvannealed steel coatings by X-ray diffraction. Advances.2003;46:291–6.

31. Lee HH, Hiam D. Corrosion resistance of galvannealed steel.Corrosion. 1989;45:852–6.

32. Mueller PP, et al. Histological and molecular evaluation of iron asdegradable medical implant material in a murine animal model. JBiomed Mater Res. 2012;100 A:2881–9.

33. Kafri A, Ovadia S, Goldman J, Drelich J, Aghion E. The suit-ability of Zn–1.3%Fe alloy as a biodegradable implant material.Metals. 2018;8:153.

34. Oner G, Bhaumick B, Bala RM. Effect of zinc deficiency onserum somatomedin levels and skeletal growth in young rats.Endocrinology. 1984;114:1860–3.

35. Cossio-Bolaños M, Gómez Campos R, Vargas R, Vitoria RT,Hochmuller F, de Arruda M. Reference curves for assessing thephysical growth of male Wistar rats. Nutr Hosp. 2013;28:2151–6.

36. Quesenberry KE, Carpenter JW, editors. Small rodents, in ferrets,rabbits and rodents: clinical medicine and surgery. St. Louis, MO:Saunders; 2003, p. 348.

37. Yur F, Bildik A, Belge F, Kilicalp D. Serum plasma and ery-throcyte zinc levels in various animal species. VAN Vet J.2002;13:82–83.

38. Cheng J, Liu B, Wu YH, Zheng YF. Comparative in vitro studyon pure metals (Fe, Mn, Mg, Zn and W) as biodegradable metals.J Mater Sci Technol. 2013;29:619–27.

39. Gong H, Wang K, Strich R, Zhou JG. In vitro biodegradationbehavior, mechanical properties, and cytotoxicity of biodegrad-able Zn-Mg alloy. J Biomed Mater Res. 2015;103:1632–40.

40. Yue R, et al. Microstructure, mechanical properties and in vitrodegradation behavior of novel Zn-Cu-Fe alloys. Mater Charact.2017;134:114–22.

41. Aghion E, Levy G, Ovadia S. In vivo behavior of biodegradableMg-Nd-Y-Zr-Ca alloy. J Mater Sci Mater Med. 2012;23:805–12.

42. Törne K, Larsson M, Norlin A, Weissenrieder J. Degradation ofzinc in saline solutions, plasma, and whole blood. J Biomed MaterRes. 2016;104:1141–51.

43. Bowen PK, et al. Biodegradable metals for cardiovascular stents:from clinical concerns to recent Zn-alloys. Adv Healthc Mater.2016;5:1121–40.

44. Andriollo-Sanchez M, et al. Toxic effects of iterative intraper-itoneal administration of zinc gluconate in rats. Basic Clin Phar-macol Toxicol. 2008;103:267–72.

45. Prasad AS. Clinical, biochemical, and pharmacological role ofzinc. Annu Rev Pharmacol Toxicol. 1979;19:393–26.

46. Yang H, et al. Evolution of the degradation mechanism of purezinc stent in the one-year study of rabbit abdominal aorta model.Biomaterials. 2017;145:92–105.

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