Biocompatibility and Degradation Behavior of Molybdenum in an In Vivo Rat Model

Abstract

The biocompatibility and degradation behavior of pure molybdenum (Mo) as a bioresorbable metallic material (BMM) for implant applications were investigated. In vitro degradation of a commercially available Mo wire (ø250 µm) was examined after immersion in modified Kokubo’s SBF for 28 days at 37 °C and pH 7.4. For assessment of in vivo degradation, the Mo wire was implanted into the abdominal aorta of female Wistar rats for 3, 6 and 12 months. Microstructure and corrosion behavior were analyzed by means of SEM/EDX analysis. After explantation, Mo levels in serum, urine, aortic vessel wall and organs were investigated via ICP-OES analysis. Furthermore, histological analyses of the liver, kidneys, spleen, brain and lungs were performed, as well as blood count and differentiation by FACS analysis. Levels of the C-reactive protein were measured in blood plasma of all the animals. In vitro and in vivo degradation behavior was very similar, with formation of uniform, non-passivating and dissolving product layers without occurrence of a localized corrosion attack. The in vitro degradation rate was 101.6 µg/(cm2·d) which corresponds to 33.6 µm/y after 28 days. The in vivo degradation rates of 12, 33 and 36 µg/(cm2·d) were observed after 3, 6 and 12 months for the samples properly implanted in the aortic vessel wall. This corresponds with a degradation rate of 13.5 µm/y for the 12-month cohort. However, the magnitude of degradation strongly depended on the implant site, with the wires incorporated into the vessel wall showing the most severe degradation. Degradation of the implanted Mo wire neither induced an increase in serum or urine Mo levels nor were elevated Mo levels found in the liver and kidneys compared with the respective controls. Only in the direct vicinity of the implant in the aortic vessel wall, a significant amount of Mo was found, which, however, was far below the amounts to be expected from degrading wires. No abnormalities were detected for all timepoints in histological and blood analyses compared to the control group. The C-reactive protein levels were similar between all the groups, indicating no inflammation processes. These findings suggest that dissolved Mo from a degrading implant is physiologically transported and excreted. Furthermore, radiographic and µCT analyses revealed excellent radiopacity of Mo in tissues. These findings and the unique combination with its extraordinary mechanical properties make Mo an interesting alternative for established BMMs.

Bioresorbable, wireless, and battery-free system for electrotherapy and impedance sensing at wound sites

“…After 22 weeks, the micro-CT images confirm that almost all of the Mo resorbs in the body, and the concentration of Mo in the spleen also begins to decrease. In the brain, the concentration of Mo saturates after 22 weeks of implantation, and we expect them to be decreased at a later time point, as previously reported (38).…”

Molybdenum as a Potential Biocompatible and Resorbable Material for Osteosynthesis in Craniomaxillofacial Surgery—An In Vitro Study

“…However, the close fit of the fractured parts and the fact that no new degradation product layer has formed beneath the monolithic layer shows that the cracks do not form in situ, but after removal of the samples from the immersion medium and drying. The cracking of the degradation product layer during drying has been illustrated in the Supplementary Information of Schauer et al [ 33 ].…”

“…In the next steps, the in vivo biocompatibility and the exact degradation rates in complex organisms must be investigated. While Sikora-Jasinska et al showed the biocompatibility and degradation behavior in a flowing system [ 5 ] and Schauer et al demonstrated degradation in the abdominal aorta of rats [ 33 ], the behavior as an osteosynthesis system should be investigated separately. In particular, the degradation and dissolution behavior of molybdenum sheet metal should be investigated under in vivo conditions consistent with implant applications in craniomaxillofacial surgery.…”

“…This oxide dissolves in the form of molybdate ions MoO 4 2− which can be excreted renally [ 31 , 32 ]. While complete absorption has not yet been demonstrated in vivo, in vitro experiments indicate that molybdenum will dissolve completely in a physiological environment [ 29 , 33 ].…”

Zero Waste and Biodegradable Zinc Oxide Thin-Film Transistors for UV Sensors and Logic Circuits

“…[4] By contrast, magnesium (Mg), Zinc (Zn), Tungsten (W), Iron (Fe), Molybdenum (Mo) have been identified as the main alternative choices, due to their biocompatibility and easy of disposal. [6] The sourcing of biodegradable semiconductor materials is another pressing issue in order to reduce e-waste. [5] So far, Ultra-Thin Silicon (UTS) has been used to manufacture biodegradable devices, but silicon electronic manufacture is known to be energy intensive from Life Cycle Assessments (LCAs) studies.…”