In vitro study on the feasibility of magnetic stent hyperthermia for the treatment of cardiovascular restenosis

Nanogold-coated stent facilitated non-invasive photothermal ablation of stent thrombosis and restoration of blood flow

In-stent restenosis (ISR) and stent thrombosis (ST) are the most serious complications of coronary angioplasty and stenting. Although the evolution of drug-eluting stents (DES) has significantly restricted the incidence of ISR, they are associated with an enhanced risk of ST. In the present study, we explore the photothermal ablation of a thrombus using a nano-enhanced thermogenic stent (NETS) as a modality for revascularization following ST. The photothermal activity of NETS, fabricated by coating bare metal stents with gold nanorods generating a thin plasmonic film of gold, was found to be effective in rarefying clots formed within the stent lumen in various in vitro assays including those under conditions mimicking blood flow. NETS implanted in the rat common carotid artery generated heat following exposure to a NIR-laser that led to effective restoration of blood flow within the occluded vessel in a model of ferric chloride-induced thrombosis. Our results present a proof-of-concept for a novel photothermal ablation approach by employing coated stents in the non-invasive management of ST.

Sensors-based monitoring and treatment approaches for in-stent restenosis

Cardiovascular disease (CVD) can progressively narrow arteries due to plaque accumulation on the inner walls of the blood vessels, which results in an obstructed blood flow, leading to heart attack, stroke, and even death if the obstruction is severe. A popular treatment for the disease is to use an intravascular mechanical device called the stent to achieve an immediate restoration of blood flow. However, the physical stimulation induced by the stent expansion can cause inflammation of the vessel tissue. As one of the most common post-stenting complications, re-narrowing of the vessel is the main pathology that leads to in-stent restenosis (ISR), induced by the excess growth of the tissue over the deployed stent. The ISR is widely recognized as a significant cause of death globally if early symptoms are not detected. Hence, monitoring and early diagnosis indeed matter when it comes to treatment. The latest technologies for monitoring and treatments of ISR were reviewed in this work, and the potential issues and suggestions related to the reported technologies were presented. The target of this review aims to positively prompt researchers to develop an advanced stent system in terms of its electromechanical performance, size, functional feature, feasibility, and reliability.

Effects of radiofrequency balloon angioplasty on the abdominal aorta in atherosclerotic rabbits

OBJECTIVES

A novel temperature-controlled intravascular radiofrequency balloon angioplasty (RFBA) technique was designed and developed for atherosclerosis (AS) management.

METHODS

After establishing an AS model based on a balloon denudation injury of the abdominal aorta and a high cholesterol diet in rabbits, 46 animals were randomly assigned to the RFBA group (n = 28) or the plain balloon angioplasty (PBA) group (n = 28). The groups were further subdivided based on post-treatment euthanasia times (1 hour, 7 days, 14 days, and 28 days). Histopathological changes were observed by hematoxylin and eosin and Masson's staining. Immunohistochemistry, western blotting, and real-time quantitative polymerase chain reaction were used to detect changes in pro-inflammatory, anti-inflammatory, and apoptotic factors; TGF-β/Smad-2 pathway protein Immune levels; and mRNA levels in tissues, respectively.

RESULTS

The vascular lumen area in the RFBA group was larger than that in the PBA group at the same time points, although the change in the vascular lumen area was not different between groups. The expression of Bax, TGF-β, Smad-2, and Caspase-3 in the RFBA group was significantly higher than that in the PBA group. The expression levels of Bcl-2 in the RFBA group were significantly lower than those in the PBA group.

CONCLUSIONS

At 28 days, RFBA dilated the atherosclerotic blood vessels and thickened the fibrous cap of atherosclerotic plaques to promote plaque stability. RFBA was also found to activate apoptotic factors and the TGF-/Smad-2 inflammatory pathway.

Hybrid Stents Based on Magnetic Hydrogels for Biomedical Applications

Tremendous attention has been given to hydrogels due to their mechanical and physical properties. Hydrogels are promising biomaterials due to their high biocompatibility. Magnetic hydrogels, which are based on hydrogel incorporated magnetic nanoparticles, have been proposed in biomedical applications. The advantages of magnetic hydrogels are that they can easily respond to externally applied magnetic fields and prevent the leakage of magnetic nanoparticles in the surrounding area. Herein, a prototype hybrid stent of magnetic hydrogel was fabricated, characterized, and evaluated for magnetic hyperthermia treatment. First, magnetic hydrogel was produced by a solution of alginate with magnetic nanoparticles in a bath of calcium chloride (5-15 mg mL^-1) in order to achieve the external gelation and optimize the heating rate. The increased concentration (1-8 mg mL^-1) of magnetic nanoparticles inside the hydrogel resulted in almost zero leakage of iron oxide nanoparticles after 15 days, guaranteeing that they can be used safely in biomedical applications. Thus, magnetic hybrid stents, which are based on the magnetic hydrogels, were developed in a simple way and were evaluated both in an agarose phantom model and in an ex vivo tissue sample at 30 mT and 765 kHz magnetic hyperthermia conditions to examine the heating efficiency. In both cases, hyperthermia results indicate excellent heat generation from the hybrid stent and facile temperature control via tuning magnetic nanoparticle concentration (2-8 mg mL^-1). This study can be a promising method that promotes spatially thermal distribution in cancer treatment or restenosis treatment of hollow organs.

Long Non-Coding RNAs Might Regulate Phenotypic Switch of Vascular Smooth Muscle Cells Acting as ceRNA: Implications for In-Stent Restenosis

Coronary in-stent restenosis is a late complication of angioplasty. It is a multifactorial process that involves vascular smooth muscle cells (VSMCs), endothelial cells, and inflammatory and genetic factors. In this study, the transcriptomic landscape of VSMCs’ phenotypic switch process was assessed under stimuli resembling stent injury. Co-cultured contractile VSMCs and endothelial cells were exposed to a bare metal stent and platelet-derived growth factor (PDGF-BB) 20 ng/mL. Migratory capacity (wound healing assay), proliferative capacity, and cell cycle analysis of the VSMCs were performed. RNAseq analysis of contractile vs. proliferative VSMCs was performed. Gene differential expression (DE), identification of new long non-coding RNA candidates (lncRNAs), gene ontology (GO), and pathway enrichment (KEGG) were analyzed. A competing endogenous RNA network was constructed, and significant lncRNA–miRNA–mRNA axes were selected. VSMCs exposed to “stent injury” conditions showed morphologic changes, with proliferative and migratory capacities progressing from G0-G1 cell cycle phase to S and G2-M. RNAseq analysis showed DE of 1099, 509 and 64 differentially expressed mRNAs, lncRNAs, and miRNAs, respectively. GO analysis of DE genes showed significant enrichment in collagen and extracellular matrix organization, regulation of smooth muscle cell proliferation, and collagen biosynthetic process. The main upregulated nodes in the lncRNA-mediated ceRNA network were PVT1 and HIF1-AS2, with downregulation of ACTA2-AS1 and MIR663AHG. The PVT1 ceRNA axis appears to be an attractive target for in-stent restenosis diagnosis and treatment.

Infrared-Emitting Multimodal Nanostructures for Controlled In Vivo Magnetic Hyperthermia

Deliberate and local increase of the temperature within solid tumors represents an effective therapeutic approach. Thermal therapies embrace this concept leveraging the capability of some species to convert the absorbed energy into heat. To that end, magnetic hyperthermia (MHT) uses magnetic nanoparticles (MNPs) that can effectively dissipate the energy absorbed under alternating magnetic fields. However, MNPs fail to provide real-time thermal feedback with the risk of unwanted overheating and impeding on-the-fly adjustment of the therapeutic parameters. Localization of MNPs within a tissue in an accurate, rapid, and cost-effective way represents another challenge for increasing the efficacy of MHT. In this work, MNPs are combined with state-of-the-art infrared luminescent nanothermometers (LNTh; Ag₂ S nanoparticles) in a nanocapsule that simultaneously overcomes these limitations. The novel optomagnetic nanocapsule acts as multimodal contrast agents for different imaging techniques (magnetic resonance, photoacoustic and near-infrared fluorescence imaging, optical and X-ray computed tomography). Most crucially, these nanocapsules provide accurate (0.2 °C resolution) and real-time subcutaneous thermal feedback during in vivo MHT, also enabling the attainment of thermal maps of the area of interest. These findings are a milestone on the road toward controlled magnetothermal therapies with minimal side effects.

A thermosensitive material coated resonant stent for drug delivery on demand

An electromagnetic energy source in the radio-frequency range delivers power to a stent circuit via resonant inductive coupling, allowing a thermally triggered release of gel via Joule heating. A gold-electroplated, medical-grade stainless steel stent, serving as the base of the prototype device, melts a coating made from an emulsion composed mainly of dodecanoic acid. These coated devices produce wirelessly controllable releases of a gel into thermally regulated, stirred water that is near body temperature. The gel is made from salt, water, and gelatine from porcine skin and used to simulate drug release in this study. Thus, this system serves as a proof of concept to show the viability of controlling local drug delivery using this prototype device. Dodecanoic acid, a fatty acid, has a phase transition from solid to liquid near 43[Formula: see text]C and has relatively good biocompatibility. The average melting temperature of two different emulsions was 40.8±0.7[Formula: see text]C, a suitable value for the targeted application. Demonstration of controllable releases used electromagnetic pulses of approximately 180 seconds in duration, illustrating reproducibility of a controllable release phase while remaining relatively inert in the absence of stimuli. Releases were observable through measuring the conductivity of the water, the water temperature, and the stent temperature. This electrothermally active stent device enables wirelessly controlled local delivery with controlled dosage and timing, a concept with a wide range of potential applications. Some relevant examples include inhibiting restenosis or cancer treatment via targeted chemotherapy.

Nanomagnetic Actuation of Hybrid Stents for Hyperthermia Treatment of Hollow Organ Tumors

This paper describes a magnetic nanotechnology that locally enables hyperthermia treatment of hollow organ tumors by using polymer hybrid stents with incorporated magnetic nanoparticles (MNP). The hybrid stents are implanted and activated in an alternating magnetic field to generate therapeutically effective heat, thereby destroying the tumor. Here, we demonstrate the feasibility of nanomagnetic actuation of three prototype hybrid stents for hyperthermia treatment of hollow organ tumors. The results show that the heating efficiency of stent filaments increases with frequency from approximately 60 W/g_Fe (95 kHz) to approximately 250 W/g_Fe (270 kHz). The same trend is observed for the variation of magnetic field amplitude; however, heating efficiency saturates at approximately 30 kA/m. MNP immobilization strongly influences heating efficiency showing a relative difference in heating output of up to 60% compared to that of freely dispersed MNP. The stents showed uniformly distributed heat on their surface reaching therapeutically effective temperatures of 43 °C and were tested in an explanted pig bile duct for their biological safety. Nanomagnetic actuation of hybrid stents opens new possibilities in cancer treatment of hollow organ tumors.

Health Care Monitoring and Treatment for Coronary Artery Diseases: Challenges and Issues

In-stent restenosis concerning the coronary artery refers to the blood clotting-caused re-narrowing of the blocked section of the artery, which is opened using a stent. The failure rate for stents is in the range of 10% to 15%, where they do not remain open, thereby leading to about 40% of the patients with stent implantations requiring repeat procedure within one year, despite increased risk factors and the administration of expensive medicines. Hence, today stent restenosis is a significant cause of deaths globally. Monitoring and treatment matter a lot when it comes to early diagnosis and treatment. A review of the present stent monitoring technology as well as the practical treatment for addressing stent restenosis was conducted. The problems and challenges associated with current stent monitoring technology were illustrated, along with its typical applications. Brief suggestions were given and the progress of stent implants was discussed. It was revealed that prime requisites are needed to achieve good quality implanted stent devices in terms of their size, reliability, etc. This review would positively prompt researchers to augment their efforts towards the expansion of healthcare systems. Lastly, the challenges and concerns associated with nurturing a healthcare system were deliberated with meaningful evaluations.

Local Heat Treatment for Suppressing Gastroduodenal Stent-Induced Tissue Hyperplasia Using Nanofunctionalized Self-Expandable Metallic Stent in Rat Gastric Outlet Model

Despite the promising results from the placement of covered or uncovered self-expandable metallic stent (SEMS) as a nonsurgical therapeutic option for the malignant gastric outlet obstruction (GOO), the long patency of the stent is still limited because of stent-induced tissue hyperplasia. Here, a local heat treatment using a nanofunctionalized SEMS is proposed for suppressing stent-induced tissue hyperplasia during GOO treatment. Highly efficient photothermal gold nanoparticle (GNP) transducer-coated SEMSs (GNP-SEMSs) were prepared for local heat treatment in rat gastric outlet. The in vivo heating temperature in rat gastric outlet model was evaluated and compared with in vitro heating temperature. Three groups of our developed 45 rat gastric outlet models were used: group A, noncoated SEMS only; group B, GNP-SEMS plus local heating; and group C, GNP-SEMS only to investigate in vivo efficacy of GNP-SEMS mediated local heating. Ten rats per group were sacrificed for 4 weeks, and five rats per group were sacrificed immediately after local heat treatment. The in vivo heating temperature was found to be 10.8% lower than the in vitro heating temperatures. GNP-SEMSs were successfully placed through a percutaneous approach into the rat gastric outlet (n = 45). The therapeutic effects of GNP-SEMS were assessed by histologic examination including hematoxylin-eosin, Masson trichrome, immunohistochemistry (TUNEL and CD31), and immunofluorescence (Ki67), and the results showed significant prevention of tissue hyperplasia following stent placement without adjacent gastrointestinal tissue damage. GNP-SEMS-mediated local heating could be an alternative therapeutic option for the suppression of tissue hyperplasia following stent placement in benign and malignant GOOs.

Wirelessly Heating Stents via Radiofrequency Resonance toward Enabling Endovascular Hyperthermia

Thermal therapy known as hyperthermia has served as an effective method for cancer treatment. This therapeutic approach has also been attracting attention for treatment of in-stent restenosis, the most common complication of stenting. Mild heating of stents has been shown to be a possible path to addressing this problem. Despite various studies on stent-based thermotherapy, this area still lacks a clinically viable method and technology. Here, a radiofrequency-powered "hot" stent prototype is reported in vitro and in vivo. An implantable stent device based on medical-grade stainless steel acts as an electrical resonator, or an efficient wireless heater operating only when resonated using tuned external electromagnetic fields. The system architecture uses a custom-developed power transmitter for wireless resonant powering/heating of the stent. An eight-shaped antenna is shown to be highly effective for near-field power transfer to the device and potentially to other smart implants, revealing stent heating efficiencies of up to 120 °C W^-1 , 206% of the level provided by a conventional loop antenna. Testing with swine models, the prototyped system achieves stent heating in blood flow by powering through air and skin tissue in vivo in a fully controlled manner. The results advance stent hyperthermia technology toward possible future clinical application.

Nanofunctionalized Stent-Mediated Local Heat Treatment for the Suppression of Stent-Induced Tissue Hyperplasia

Current therapeutic strategies are insufficient for suppressing stent-induced restenosis. Here, branched gold nanoparticles (BGNP)-coated self-expandable metallic stents (SEMSs) were developed for a local heat-induced suppression of stent-related tissue hyperplasia. Our polydopamine (PDA) coating on SEMS allowed BGNP crystal growth on the surface of SEMSs. The prepared BGNP-coated SEMS showed effective local heating under near-infrared laser irradiation. The effectiveness of BGNP-coated SEMSs for suppressing stent-related tissue hyperplasia was demonstrated in a rat esophageal model ( n = 52). BGNP-coated SEMS placement under fluoroscopic guidance was technically successful in all rats. The placed BGNP-coated SEMS in rat esophagus achieved three different local heat dose ranges (50, 65, and 80 °C) under fluoroscopic image-guided local irradiation. Follow-up endoscopic examination readily monitored the local heating and observed significantly decreased tissue hyperplasia at 4 weeks of local heat treatments (50 and 65 °C). Finally, Western blot, histology, immunohistochemistry (HSP70, αSMA, and TUNEL), and immunofluorescence (Ki67 and BrdU) analyses along with the statistical analysis confirmed that optimized BGNP-coated SEMS-mediated local heat treatments inducing the expression of anti-inflammatory HSP70 effectively suppresses tissue hyperplasia after stent placement in the esophagus. Our local heating with nanofunctionalized stents represents a promising new approach for suppressing stent-related tissue hyperplasia.

Peritoneal dialysis treatment for severe lupus nephritis patients complicated with essential organ dysfunction

The aim of the present study was to evaluate the clinical efficacy of peritoneal dialysis (PD) in patients with severe lupus nephritis (LN) complicated with organ dysfunction. In total, 13 severe LN patients complicated with multiple-organ dysfunction, who underwent PD treatment between November 2003 and September 2010, were enrolled in the study. Six patients received methylprednisolone pulse therapy due to lupus activity and progressive renal failure. These patients were complicated with severe edema, cardiac insufficiency and severe hypoalbuminemia. PD was applied to the patients, followed by the administration of immunosuppressants. Patients were followed-up to review the parameters of renal function, the immunological indexes and the systemic lupus erythematosus disease activity index. The results indicated that the general state of health was markedly improved following PD treatment, with edema abatement and improvement of heart function and physical strength. Serum creatinine levels significantly decreased from 6.3±1.6 to 2.6±1.0 mg/dl. A total of 10 cases ceased PD treatment during the follow-up, while three cases continued PD to the end of the follow-up period. The levels of albumin and hemoglobin exhibited a marked increase from 29.7±5.7 to 35.2±5.5 g/l and 8.7±1.8 to 9.8±1.8 g/l, respectively. There was one case of peritonitis, one case of peritoneal leakage and two cases of pneumonia. Therefore, PD may be a successful treatment method for severe LN patients complicated with essential organ dysfunction. PD not only improved the symptoms of edema and heart failure, but also played an important role in preserving residual renal function and improving the nutritional state of the patients. Thus, PD can be considered as a treatment option for patients with severe LN associated with acute kidney injury, however, selecting a suitable immunosuppressant during PD treatment is essential.