Non-polymer drug-eluting coronary stents

Circular RNAs: Biogenesis, Biological Functions, and Roles in Myocardial Infarction

Non-coding RNAs have been excavated as important cardiac function modulators and linked to heart diseases. Significant advances have been obtained in illuminating the effects of microRNAs and long non-coding RNAs. Nevertheless, the characteristics of circular RNAs are rarely mined. Circular RNAs (circRNAs) are widely believed to participate in cardiac pathologic processes, especially in myocardial infarction. In this review, we round up the biogenesis of circRNAs, briefly describe their biological functions, and summarize the latest literature on multifarious circRNAs related to new therapies and biomarkers for myocardial infarction.

Stent Thrombosis and Restenosis with Contemporary Drug-Eluting Stents: Predictors and Current Evidence

Iterations in stent technologies, advances in pharmacotherapy, and awareness of the implications of implantation techniques have markedly reduced the risk of stent failure, both in the form of stent thrombosis (ST) and in-stent restenosis (ISR). However, given the number of percutaneous coronary interventions (PCI) performed worldwide every year, ST and ISR, albeit occurring at a fairly low rate, represent a public health problem even with contemporary DES platforms. The understanding of mechanisms and risk factors for these two PCI complications has been of fundamental importance for the parallel evolution of stent technologies. Risk factors associated with ST and ISR are usually divided into patient-, lesion-, device- and procedure-related. A number of studies have shown how certain risk factors are related to early (1 month) versus late/very late ST (between 1 month and 1 year and >1 year, respectively). However, more research is required to conclusively show the role of time-dependence of risk factors also in the incidence of ISR (early [1 year] or late [>1 year]). A thorough risk assessment is required due to the complex etiology of ST and ISR. The most effective strategy to treat ST and ISR is still to prevent them; hence, it is crucial to identify patient-, lesion-, device- and procedure-related predictors.

Bioresponsive starPEG-heparin hydrogel coatings on vascular stents for enhanced hemocompatibility

Hydrogel coatings can improve the biocompatibility of medical devices. However, stable surface bonding and homogeneity of hydrogel coatings are often challenging. This study exploits the benefits of biohybrid hydrogels of crosslinked four-armed poly(ethylene glycol) and heparin to enhance the hemocompatibility of cobalt‑chromium (CoCr) vascular stents. A bonding layer of dual silane and poly(ethylene-alt-maleic anhydride) (PEMA) treatment was applied to the stent to provide covalent immobilization and hydrophilicity for the homogeneous spreading of the hydrogel. A spray coating technology was used to distribute the aqueous solution of the reactive hydrogel precursors onto the sub-millimeter struts of the stents, where the solution polymerized to a homogeneous hydrogel film. The coating was mechanically stable on the stent after ethanol dehydration, and the stents could be stored in a dry state. The homogeneity and stability of the coating during stent expansion were verified. Quasistatic and dynamic whole blood incubation experiments showed substantial suppression of the pro-coagulant and inflammatory activity of the bare metal by the coating. Translation of the technology to industrial coating devices and future surface modification of stents with anti-inflammatory hydrogels are discussed.

The combination of medical devices and medicinal products revisited from the new European legal framework

Medical devices and medicinal products have many similarities in their nature, scope or specific medical purposes, and despite the differences in their principal means of action, they are often used in combination. Indeed, many medicinal products depend on medical devices for their administration, and it is increasingly common for medical devices to contain medicinal substances to support their action. Therefore, the combination of medicinal products and medical devices provides additional benefits for patients. However, their higher technical complexity requires a strengthening of their authorisation and certification requirements. In this regard, more comprehensive requirements and classification rules are introduced by a new European regulation on medical devices that fully applies from May 26^th 2021. On account of their therapeutic significance, this review aims at gaining insight into the borderline between medical devices and medicinal products in this new 2021 regulatory framework. For the first time, any item containing a medical device and a medicinal product will have both parts evaluated. Through exemplification of both marketed and investigational devices incorporating medicinal substances and drug-device combinations, the new European requirements and their implications are thoroughly illustrated herein.

Surface engineering at the nanoscale: A way forward to improve coronary stent efficacy

Coronary in-stent restenosis and late stent thrombosis are the two major inadequacies of vascular stents that limit its long-term efficacy. Although restenosis has been successfully inhibited through the use of the current clinical drug-eluting stent which releases antiproliferative drugs, problems of late-stent thrombosis remain a concern due to polymer hypersensitivity and delayed re-endothelialization. Thus, the field of coronary stenting demands devices having enhanced compatibility and effectiveness to endothelial cells. Nanotechnology allows for efficient modulation of surface roughness, chemistry, feature size, and drug/biologics loading, to attain the desired biological response. Hence, surface topographical modification at the nanoscale is a plausible strategy to improve stent performance by utilizing novel design schemes that incorporate nanofeatures via the use of nanostructures, particles, or fibers, with or without the use of drugs/biologics. The main intent of this review is to deliberate on the impact of nanotechnology approaches for stent design and development and the recent advancements in this field on vascular stent performance.

Drug-Eluting Stents and Balloons-Materials, Structure Designs, and Coating Techniques: A Review

Controlled drug delivery is a matter of interest to numerous scientists from various domains, as well as an essential issue for society as a whole. In the treatment of many diseases, it is crucial to control the dosing of a drug for a long time and thus maintain its optimal concentration in the tissue. Heart diseases are particularly important in this aspect. One such disease is an obstructive arterial disease affecting millions of people around the world. In recent years, stents and balloon catheters have reached a significant position in the treatment of this condition. Balloon catheters are also successfully used to manage tear ducts, paranasal sinuses, or salivary glands disorders. Modern technology is continually striving to improve the results of previous generations of stents and balloon catheters by refining their design, structure, and constituent materials. These advances result in the development of both successive models of drug-eluting stents (DES) and drug-eluting balloons (DEB). This paper presents milestones in the development of DES and DEB, which are a significant option in the treatment of coronary artery diseases. This report reviews the works related to achievements in construction designs and materials, as well as preparation technologies, of DES and DEB. Special attention was paid to the polymeric biodegradable materials used in the production of the above-mentioned devices. Information was also collected on the various methods of producing drug release coatings and their effectiveness in releasing the active substance.

Polymer microparticles with a cavity designed for transarterial chemo-embolization with crystalline drug formulations

Transarterial chemo-embolization with drug-eluting embolic beads (DEB-TACE) is still evolving. Recent developments include the introduction of radiopaque (X-ray imageable) drug-eluting particles. Here, we report on conceptually different radiopaque polymeric drug-eluting embolic particles, which are (i), cross-linked poly(methacrylates); (ii), radiopaque; (iii), microporous. Furthermore, the particles are not perfectly spherical: they have a large indentation in the sense that they are either a spherical/cup-shaped or ellipsoid/mouth-shaped. The micropores and the large indentation can confer useful features upon the particles, since they can be filled with a crystalline lipophilic chemotherapeutic drug. It is important, in this respect that (i), many potent chemotherapeutics are lipophilic and crystalline; (ii), available drug-eluting beads (DEBs) have the limitation that they can only be used in combination with water-soluble chemotherapeutic agents. Cup- and mouth-shaped particles were obtained in a Cu(0) catalyzed free-radical polymerization reaction. The microparticles could be charged with crystalline drug, in such a manner that the crystals reside in both the micropores and the large cavity, and in quantities that would be required for effective local chemotherapy. The antifungal drug voriconazole, lipophilic, and crystalline, was used to demonstrate this. We believe that the ability of the microporous/cavitated DEBs to carry lipophilic chemotherapeutic drugs is especially important. DEB-TACE is likely to become a cornerstone method of interventional oncology in the years ahead, and the new embolic particles described herein hold the promise of becoming scope widening for the technique.

Recent Advances in Manufacturing Innovative Stents

Cardiovascular diseases are the most distributed cause of death worldwide. Stenting of arteries as a percutaneous transluminal angioplasty procedure became a promising minimally invasive therapy based on re-opening narrowed arteries by stent insertion. In order to improve and optimize this method, many research groups are focusing on designing new or improving existent stents. Since the beginning of the stent development in 1986, starting with bare-metal stents (BMS), these devices have been continuously enhanced by applying new materials, developing stent coatings based on inorganic and organic compounds including drugs, nanoparticles or biological components such as genes and cells, as well as adapting stent designs with different fabrication technologies. Drug eluting stents (DES) have been developed to overcome the main shortcomings of BMS or coated stents. Coatings are mainly applied to control biocompatibility, degradation rate, protein adsorption, and allow adequate endothelialization in order to ensure better clinical outcome of BMS, reducing restenosis and thrombosis. As coating materials (i) organic polymers: polyurethanes, poly(ε-caprolactone), styrene-b-isobutylene-b-styrene, polyhydroxybutyrates, poly(lactide-co-glycolide), and phosphoryl choline; (ii) biological components: vascular endothelial growth factor (VEGF) and anti-CD34 antibody and (iii) inorganic coatings: noble metals, wide class of oxides, nitrides, silicide and carbide, hydroxyapatite, diamond-like carbon, and others are used. DES were developed to reduce the tissue hyperplasia and in-stent restenosis utilizing antiproliferative substances like paclitaxel, limus (siro-, zotaro-, evero-, bio-, amphi-, tacro-limus), ABT-578, tyrphostin AGL-2043, genes, etc. The innovative solutions aim at overcoming the main limitations of the stent technology, such as in-stent restenosis and stent thrombosis, while maintaining the prime requirements on biocompatibility, biodegradability, and mechanical behavior. This paper provides an overview of the existing stent types, their functionality, materials, and manufacturing conditions demonstrating the still huge potential for the development of promising stent solutions.