Thursday, April 10, 2025
4/10/2025
Tin-Silver Alloy as a Degradable Biomaterial: Biocompatibility Assessment - Project Summary/Abstract A component of the Essure® Micro Insert Female Sterilization device is comprised, in part, of a tin-silver (Sn-Ag) solder, a metal alloy which had never been previously implanted into the human body cavity and for which there is little to no peer-reviewed scientific literature of its use in the human body. The Essure® insert received premarket approval from the US Food and Drug Administration in 2002 as a non-surgical, non-hormonal alternative to tubal ligation. The device utilized dacron fibers to initiate a fibrotic immune reaction occluding the fallopian tube over the course of three months. These fibers were held in place with a 316L Stainless Steel coil (SS), and soldered with Sn-Ag to an outer, shape memory Nickel-Titanium coil (Ni-Ti), which expanded to the diameter of the fallopian tube. Additionally, two platinum- iridium (Pt-Ir) radiopaque markers were on the coils to assist in the insertion process. After only about 15 years on the market, the patient-reported adverse events rose rapidly, resulting in an FDA-mandated 522 post-market surveillance study and the voluntarily withdrawal of the implant from the global market by Bayer Healthcare. To investigate the failure of the device, several retrieval analyses were performed by our lab. While the device was intended to remain permanently implanted in Essure®, these investigations demonstrate evidence that Sn-Ag is a degradable alloy, where severe corrosion of the Sn-Ag solder resulted in fragmentation of the device as well as the release of oxides, chlorides, and phosphates into surrounding tissue. We observed that Sn-Ag corrosion in vivo induced a densely fibrotic tissue response where fibrous tissue grew into and became strongly attached to the porous metal. These observations led us to hypothesize that Sn-Ag may be used as a beneficial degradable alloy that can induce fibrous tissue attachment to metal surfaces. In the current R03 proposal we seek to explore the biological interaction of this biodegradable Sn-Ag alloy and assess its biocompatibility. This basic information is lacking in the biomaterials literature and will provide a basis for consideration of Sn-Ag as a degradable metallic biomaterial. Due to the lack of scientific peer reviewed work regarding the use of Sn-Ag as a biomaterial or its behavior in vivo, this proposal aims to 1. Assess the material for cytocompatibility in vitro and 2. Assess the material/tissue interface in vivo using an animal model. An assessment of cytocompatibility following exposure to various concentrations of corrosion products will allow for a deeper understanding of the local effects caused by implantation of the biomaterial. Compared to the ex vivo retrieval investigations, an animal model will allow for greater understanding of the blood metal ion concentrations over implantation time, systemic effects, and provides an opportunity to better assess the possibility of stimulating fibrous tissue ingrowth as seen in the human retrievals. Due to the usefulness of Sn-Ag as a solder in contact with other alloys, evaluating the alloy on its own as well as in conjunction with an additional metal alloy will provide more translation into real-world applications as a degradable metallic biomaterial. This work will provide insight and understanding of current phenomena experienced by women with Essure®, as well as provide insight into novel applications for Sn-Ag as a degradable metallic biomaterial.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).