New approaches in evaluating metallic candidates for bioabsorbable stents (original) (raw)
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Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2010
Limited information exists regarding the in vivo stability of endovascular stents. Nine excised human vascular segments with implanted stents (n ¼ 16) manufactured from stainless steel, nickel-titanium, tantalum, and cobalt-based alloys were analyzed. The stent/tissue components were separated using an established tissue dissolution protocol and control and explanted stents were evaluated by digital optical and electron microscopy. Metallic content in surrounding tissues was measured by mass spectroscopy. Surface alterations, consistent with corrosion mediated by electrochemical and mechanical factors, were observed in 9 of the 16 explanted stents and were absent from control stents. Tissue dissolved from around corroded stents corresponded with a higher metallic content. The effect of these changes in the microtopography of stents on their mechanical properties (fatigue strength and fracture limit) in addition to the potential for released metallic debris contributing to the biological mechanisms of in-stent restenosis supports the need for further investigations. V C 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 95B: 225-238, 2010.
Biodegradable Metal Stents: A Focused Review on Materials and Clinical Studies
Journal of Biomaterials and Tissue Engineering, 2014
Coronary artery disease (CAD) is the most common type of heart disease caused by plaque building up along the inner walls of coronary arteries which narrows the lumen and reduces blood flow. Stenting is the current standard procedure to treat the disease by opening the narrowed arteries and restoring the blood flow. Stenting has been revolutionary evolved from the use of bare metal stents made of corrosion resistant alloys to the incorporation of anti-proliferative drugs in the drug eluting stents. Despite the advantages and limitation of the current stent technology, the permanent presence of stents in the arteries is questionable, especially for some applications, including pediatric, in presence of collateral arteries, and others. Biodegradable stents, designed to support the arterial wall and disappear after its remodelling, therefore constitute an interesting choice, possibly representing the next revolutionary treatment of CAD. Magnesium, iron, zinc and their alloys are among metals have been proposed as biodegradable stent materials. These metals are designed to degrade in vivo through corrosion process without posing toxicity problems to the body and called as biodegradable metals. Stents made of magnesium and its alloys have been the most studied, developed and reached clinical trials in humans, followed by those made of iron which reached in vivo studies in animals. Meanwhile, zinc is just recently proposed with only few studies have been reported. This papers presents a focused review on the development of biodegradable metals for stents.
In-vivo corrosion and local release of metallic ions from vascular stents into surrounding tissue
The Journal of invasive cardiology, 2010
To evaluate retrieved bare metal vascular stents and surrounding tissue. Limited information is available regarding the condition of stent surfaces and their interaction with vascular tissue following implantation. Corrosion of stents presents two main risks: release of metallic ions into tissue and deterioration of the mechanical properties of stents which may contribute to fracture. Release of heavy metal ions could alter the local tissue environment leading to up-regulation of inflammatory mediators and promote in-stent restenosis. Nineteen cases were collected from autopsy, heart explants for transplant, and vascular surgery (23 vessels containing 33 bare metal stents). A method was developed for optimal tissue dissolution and separation of the stent/tissue components without inducing stent corrosion. When available, chemical analysis was performed to assess metallic content in both the control and dissolved tissue solutions. Electron microscopy and digital optical microscopy im...
IJERT-Biodegradable Stent to Prevent Restenosis in Coronary Artery Lesions
International Journal of Engineering Research and Technology (IJERT), 2019
https://www.ijert.org/Biodegradable-Stent-to-Prevent-Restenosis-in-Coronary-Artery-Lesions https://www.ijert.org/research/biodegradable-stent-to-prevent-restenosis-in-coronary-artery-lesions-IJERTCONV7IS02037.pdf Damage and disease in the heart arises the need for developing biomedical implants. Magnesium and its alloys have been intensively studied as biodegradable implant materials, where their mechanical properties make them a potential candidate for many applications. As a biocompatible and biodegradable metal, it has several gains over the metallic implants presently in use, including eliminating the effects of stress shielding, improving (Fe). Bioactivity and degradation studies are evaluated by immersing the samples in simulated body fluid (SBF) for a certain period of biocompatibility concerns in vivo and eliminating the requirement of a second surgery. In this project work magnesium (Mg) is fused with ferrous(Fe) and it was coated with polymer. The bioactivity and degradation studies were assessed by determining the rate of corrosion by weight loss method, polarisation studies and Ac impedance measurements.
Zinc Exhibits Ideal Physiological Corrosion Behavior for Bioabsorbable Stents
Advanced Materials, 2013
Metallic stents are commonly used in percutaneous coronary interventions in patients with pronounced ischemic or coronary heart disease to promote revascularization and retard possible recoil and restenosis of damaged arteries. The benefits of stents during vascular remodeling (i.e. improved procedural success, reduced restenosis, etc.) are numerous and well documented. A traditional coronary stent must remain inert in the human body for many years, but its residence is sometimes terminated after the occurrence of serious side effects.
A review on biodegradable materials for cardiovascular stent application
A stent is a medical device designed to serve as a temporary or permanent internal scaffold to maintain or increase the lumen of a body conduit. The researchers and engineers diverted to investigate biodegradable materials due to the limitation of metallic materials in stent application such as stent restenosis which requires prolonged anti platelet therapy, often result in smaller lumen after implantation and obstruct re-stenting treatments. Biomedical implants with temporary function for the vascular intervention are extensively studied in recent years. The rationale for biodegradable stent is to provide the support for the vessel in predicted period of time and then degrading into biocompatible constituent. The degradation of stent makes the re-stenting possible after several months and also ameliorates the vessel wall quality. The present article focuses on the biodegradable materials for the cardiovascular stent. The objective of this review is to describe the possible biodegradable materials for stent and their properties such as design criteria, degradation behavior, drawbacks and advantages with their recent clinical and preclinical trials.
A new in vitro-in vivo correlation for bioabsorbable magnesium stents from mechanical behavior
Materials science & engineering. C, Materials for biological applications, 2013
Correlating the in vitro and in vivo degradation of candidate materials for bioabsorbable implants is a subject of interest in the development of next-generation metallic stents. In this study, pure magnesium wire samples were corroded both in the murine artery (in vivo) and in static cell culture media (in vitro), after which they were subjected to mechanical analysis by tensile testing. Wires corroded in vivo showed reductions in strength, elongation, and the work of fracture, with additional qualitative changes between tensile profiles. The in vivo degradation was 2.2±0.5, 3.1±0.8, and 2.3±0.3 times slower than corrosion in vitro in terms of effective tensile strength, strain to failure, and sample lifetime, respectively. Also, a combined metric, defined as strength multiplied by elongation, was 3.1±0.7 times faster in vitro than in vivo. Consideration of the utility and restrictions of each metric indicates that the lifetime-based multiplier is the best suited to general use for...
A Review of Material Degradation Modelling for the Analysis and Design of Bioabsorbable Stents
Annals of Biomedical Engineering, 2015
The field of percutaneous coronary intervention has witnessed many progressions over the last few decades, more recently with the advancement of fully degradable bioabsorbable stents. Bioabsorbable materials, such as metallic alloys and aliphatic polyesters, have the potential to yield stents which provide temporary support to the blood vessel and allow native healing of the tissue to occur. Many chemical and physical reactions are reported to play a part in the degradation of such bioabsorbable materials, including, but not limited to, corrosion mechanisms for metals and the hydrolysis and crystallization of the backbone chains in polymers. In the design and analysis of bioabsorbable stents it is important to consider the effect of each aspect of the degradation on the material's in vivo performance. The development of robust computational modelling techniques which fully capture the degradation behaviour of these bioabsorbable materials is a key factor in the design of bioabsorable stents. A critical review of the current computational modelling techniques used in the design and analysis of these next generation devices is presented here, with the main accomplishments and limitations of each technique highlighted.
In vitro host response assessment of biomaterials for cardiovascular stent manufacture
Journal of Materials Science: Materials in Medicine, 2000
The deployment of a vascular stent during angioplasty has greatly reduced the risks of restenosis. However, the presence of the device still induces a host response as well as a mechanical action on the blood vessel wall and an alteration of the haemodynamics. Platelet and in¯ammatory cells can adhere on the stent surface and be activated to produce biochemical signals able to stimulate an excessive proliferation of the smooth muscle cells with the consequent obstruction of the vessel lumen. For these reasons, the host response to two of the materials used in stent manufacture, stainless steel and diamond-like carbon, was investigated in vitro. The data showed that stainless steel induced a higher level of host response both in terms of platelet aggregation and macrophage activation. However, the spreading of in¯ammatory cells was more accentuated on diamond-like carbon. The in¯ammatory cells produced levels of platelet-derived growth factor, a key signal in smooth muscle cell proliferation, similar to stainless steel thus suggesting that carbon coatings may not be able to prevent restenosis.