Development of a Novel Biodegradable Metallic Stent Based on Microgalvanic Effect

Abstract

The implementation of biodegradable stents has the potential to revolutionize obstructive coronary artery disease treatment. Limitations still currently exist, however, that prevent biodegradable stents from replacing permanent metallic stents in the global market. The ideal combination of stent properties, including sufficient mechanical strength, controlled degradation, and biocompatibility, has yet to be realized. A novel manufacturing process is proposed that utilizes cold gas-dynamic spraying to fabricate a metal structure with significantly reduced grain size. Iron and stainless steel 316L are combined to form a novel amalgamate with enhanced mechanical strength and a controllable degradation rate, due to the resulting microgalvanic reaction. Flat specimens composed of iron and 316L are fabricated in various compositions, and mechanical and degradation tests were conducted. Femto laser techniques are utilized to produce stents composed of 80% Fe and 20% stainless steel 316L. The in vitro degradation behaviour of the stent is investigated using static and dynamic corrosion tests. It is shown that the corrosion rate can be adjusted to desired values, by varying the weight percentage of iron and stainless steel 316L within the amalgamate.

Recent advances in Fe-based bioresorbable stents: Materials design and biosafety

“…It is worthy to note that the CR value from immersion test was 2.8 g m −2 day −1 at day 1, but declined to 1.1 g m −2 day −1 at day 28, probably due to surface accumulation of corrosion products ( Table 1 ). Such a value (at day 28) is much higher than cast pure iron or porous iron in literatures (0.4–0.8 g m −2 day −1 ) [ 44 , 50 , 54 ]. The acceleration of degradation rate was also observed in the study in which topologically ordered porous structure was achieved by direct metal printing technique [ 40 ].…”

“…For example, the corrosion is decreased in a cell culture medium (that contains inorganic ions, organic compounds and proteins) with respect to that in NaCl solution [ 27 ]. For dynamic immersion tests, the flow rate simulating blood in the human body is set to 40 mL min −1 [ 44 ]. For Fe-based BRS, as reported by Liu et al , the wall shear stress (0.68 Pa), dissolved oxygen (2.8–3.2 mg L −1 ) and pH (7.34–7.45) should be considered as experimental parameters [ 36 ].…”

“…Fe corrosion can be accelerated by introducing second phases into the matrix, e.g. Fe–Mn, Fe–W alloys [ 44 , 47 ]. Besides, surface ions implantation (such as Zn) has been reported for accelerated Fe corrosion [ 49 ].…”

“…However, the results from dynamic immersion tests show a reduced corrosion rate for Fe-X (X = Mn, Co, Al, W, B, S), and only as-rolled Fe–C exhibits increased CR value. Other researchers reported also increased corrosion on Fe-X binary alloys, such as Fe-Zn [ 60 ], Fe–W, Fe-Carbon nanotubes (CNTs) [ 38 ] and porous Fe–W layer on Fe skeleton [ 44 ]. Therefore, alloying is a promising strategy to accelerate the corrosion Fe, but more efforts should be devoted to increase corrosion rate to a higher magnitude.…”

Advances in Bioresorbable Triboelectric Nanogenerators

“…Transient, bioresorbable IMDs, which are designed to degrade and be absorbed by the human body over time, have emerged as an attractive new class of biomedical devices. − Their self-clearing capabilities reduce physical and economic burdens on the patients through periodic replacement to extract the device and allow us to circumvent the potential risks for infection and negative health consequences. ,,− Conventional semipermanent IMDs rarely offer a clinical functionality that takes a short time to manage and treat (e.g., neurostimulation for six months and wound healing for two weeks), since the threat of surgery is much greater than their benefits. ,− In this regard, the use of transient IMDs has broadened the scope of medical applications for IMDs to drug delivery, − monitoring, ,,,,− diagnosis, , and therapeutic applications. ,,, Further advances in materials science have led to the rise of on-demand transient IMDs whose degradation starts by events triggered at the intended time. ,,− While a majority of transient systems employ a passive operation that decays constituent materials gradually in vivo, ,,,− this new class of bioresorbable IMDs with active operation is disintegrated quickly after the application of a corresponding stimulus, ensuring their stable function and avoiding the potential risk of residue materials remaining in the body. ,,,− Continued advances in functional polymers, materials processing, and electronic components will drive progress in IMDs with biosafety and complex capabilities for a variety of ...…”