Novel bifurcation stents coated with bioabsorbable nanofibers with extended and controlled release of rosuvastatin and paclitaxel

"Hot-dog-string" drug-eluting degradable stents for treating stenosis in tortuous arteries

Despite advances in cardiovascular technology, treating stenosis in tortuous arteries with balloon-expandable stents, typically deployed in a straight orientation, remains a challenge. This study developed novel balloon-expandable "hot-dog-string" (HDS) drug-eluting poly(ε-caprolactone) (PCL) nanofibrous stents using solvent casting and coaxial electrospinning techniques. A unique HDS geometry was designed for the PCL stent backbone, while aspirin and sirolimus were loaded into the core-sheath structured poly(lactic-co-glycolic acid) (PLGA) nanofibers, which were then wrapped around the degradable stent. In vitro characterization of the biodegradable HDS stent and drug-eluting nanofibers was conducted. The results indicate that the biodegradable HDS stents exhibited excellent mechanical properties and superior flexibility, allowing them to navigate curved sections of a simulated in vitro vessel model more effectively than metallic stents. The core-sheath structure of the nanofibers enabled sustained release of high concentrations of aspirin and sirolimus over 14 and 23 days, respectively, with sirolimus effectively inhibiting smooth muscle cell proliferation. Moreover, in vivo animal tests showed that the rabbits remained in good health with excellent vessel patency following stent placement. By implementing the innovative design and techniques proposed in this study, we anticipate fabricating biodegradable drug-eluting HDS stents of various sizes for diverse cardiovascular applications at curved lesions.

Minimal invasive treatment of urethral strictures: An experimental study of the effect of paclitaxel coated balloons in the wall of strictured rabbit's urethra

PURPOSE

The aim of this study is the evaluation of the distribution of paclitaxel (PTX) released by a coated balloon in the layers of rabbit's urethra.

METHODS

18 rabbits were included. A laser device was used for the stricture formation. After two weeks, dilation of the strictured urethra was performed by using Advance 35LP PTA balloons and Advance 18 PTX PTA balloons. The experimental models were divided into 3 groups. The group Α included two rabbits without any intervention except for the stenosis procedure. Group B compromised six rabbits that underwent dilation with Advance 35LP PTA balloons. Group C consisted of 10 rabbits to which dilation with both Advance 35LP PTA balloons and Advance 18 PTX PTA balloons was applied. Histological evaluation and Immunohistochemistry were performed on all specimens.

RESULTS

Inflammation, fibrosis and ruptures were detected in the specimens of the study. In specimens of Group C the decrease of inflammation and fibrosis rate was greater. Anti-PTX antibody was detected in the epithelium, lamina propria and smooth muscle layer of all specimens of urethras that have been harvested immediately and 1 day after the dilation with Advance 18 PTX PTA balloon and it was not observed in any layer of the urethral wall of the rest of the examined specimens of Group C.

CONCLUSIONS

PTX's enrichment was detected in the smooth muscle layer of all specimens that have been harvested immediately and 24h after the dilation with Advance 18 PTX PTA balloons. PTX may play an inhibitive role in the recurrence of the stenosis.

Multimodal effects of asymmetric coating of coronary stents by electrospinning and electrophoretic deposition

Drug-eluting stents (DESs) are drug-coated vascular implants that inhibit smooth muscle cell proliferation and limit in-stent re-stenosis. However, traditional DESs release a single drug into the blood and cannot cope with complex mechanisms in atherosclerosis and body responses. The present study aimed to develop a novel multimodal stent by fabricating asymmetric coating with electrophoretic deposition and electrospinning. Herein, we use heparin-loaded alginate (Hep/Alg) and atorvastatin calcium-loaded polyurethane (AtvCa/PU) coatings on the stent luminal and abluminal surfaces, respectively. Scanning electron microscopy (SEM) micrographs showed that the alginate coatings had uniformity and thin thickness. Meanwhile, the PU fibers were formed without beads, with an acceptable diameter and suitable mechanical properties. PU nanofiber revealed minimal degradation in a 1-month study. The release of AtvCa and Hep continued for 8 days without a significant initial burst release. None of the stent coatings were cytotoxic or hemolytic, and PU nanofibers supported the survival of human umbilical endothelial cells (HUVEC) with high adhesion and flattened morphologies. The results indicate that electrophoretic deposition and electrospinning have significant potential for achieving asymmetric coating on stents and a promising approach for dual drug release for multimodal effects in vascular stent applications.

Enhanced Diabetic Wound Healing Using Electrospun Biocompatible PLGA-Based Saxagliptin Fibrous Membranes

Delayed diabetic wound healing is an adverse event that frequently leads to limb disability or loss. A novel and promising vehicle for the treatment of diabetic wounds is required for clinical purposes. The biocompatible and resorbable poly (lactic-co-glycolic acid) (PLGA)-based fibrous membranes prepared by electrospinning that provide a sustained discharge of saxagliptin for diabetic wound healing were fabricated. The concentration of released saxagliptin in Dulbecco’s phosphate-buffered saline was analyzed for 30 days using high-performance liquid chromatography. The effectiveness of the eluted saxagliptin was identified using an endothelial progenitor cell migration assay in vitro and a diabetic wound healing in vivo. Greater hydrophilicity and water storage were shown in the saxagliptin-incorporated PLGA membranes than in the pristine PLGA membranes (both p < 0.001). For diabetic wound healing, the saxagliptin membranes accelerated the wound closure rate, the dermal thickness, and the heme oxygenase-1 level over the follicle areas compared to those in the pristine PLGA group at two weeks post-treatment. The saxagliptin group also had remarkably higher expressions of insulin-like growth factor I expression and transforming growth factor-β1 than the control group (p = 0.009 and p < 0.001, respectively) in diabetic wounds after treatment. The electrospun PLGA-based saxagliptin membranes exhibited excellent biomechanical and biological features that enhanced diabetic wound closure and increased the antioxidant activity, cellular granulation, and functionality.

Harnessing Therapeutic Potentials of Statins Using Nanofibrous Carriers

Statins are a wide category of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor drugs extensively prescribed for hypercholesterolemia. In fact, many studies showed beneficial effects of these agents on a variety of related illnesses, which include increased atherosclerotic plaque stability, decreased proliferation of vascular smooth muscle, platelet aggregation, the dampening of vascular inflammation, and also anabolic effects on bone tissue. Therefore, these drugs are considered as pleiotropic agents having different clinical applications other than those for which they were initially developed. Controlled drug delivery is an efficient way of delivery in tissue engineering. Amongst different controlled release formulations, nanofibers are a novel, alternative, widely used agent because of their unique properties. These include their sustained release of drug, a high drug-loading capacity, flexible shapes with a high surface-to-volume ratio, and superior porosity. Electrospinning is an economic and a simple method employed to produce nanofibers. In this report, studies related to statin nanofiber applications have been reviewed and their results have been summarized. Four different applications of statin nanofibers have been reported, including bone generation, endothelial stenosis and thrombosis, peripheral nerve injury, and anti-inflammatory action. Studies carried out both in vitro and in vivo showed effectiveness of statins in bone healing, aneurysm, and the healing of sciatic nerve injury. In addition, statins showed apoptosis effects and anti-inflammatory effects, with dose-dependent reduction of IL-6 and dose-independent reduction of TNF-α. Despite these promising results, validation via clinical trials is yet to be performed. The scope of statins in their pleiotropic range of actions is still not completely explored, and studies are still needed to enlighten different useful aspects of such drugs.

Cardiovascular Stents: A Review of Past, Current, and Emerging Devices

One of the leading causes of morbidity and mortality worldwide is coronary artery disease, a condition characterized by the narrowing of the artery due to plaque deposits. The standard of care for treating this disease is the introduction of a stent at the lesion site. This life-saving tubular device ensures vessel support, keeping the blood-flow path open so that the cardiac muscle receives its vital nutrients and oxygen supply. Several generations of stents have been iteratively developed towards improving patient outcomes and diminishing adverse side effects following the implanting procedure. Moving from bare-metal stents to drug-eluting stents, and recently reaching bioresorbable stents, this research field is under continuous development. To keep up with how stent technology has advanced in the past few decades, this paper reviews the evolution of these devices, focusing on how they can be further optimized towards creating an ideal vascular scaffold.

Recent advances in nanomaterials for therapy and diagnosis for atherosclerosis

Atherosclerosis is a chronic inflammatory disease driven by lipid accumulation in arteries, leading to narrowing and thrombosis. It affects the heart, brain, and peripheral vessels and is the leading cause of mortality in the United States. Researchers have strived to design nanomaterials of various functions, ranging from non-invasive imaging contrast agents, targeted therapeutic delivery systems to multifunctional nanoagents able to target, diagnose, and treat atherosclerosis. Therefore, this review aims to summarize recent progress (2017-now) in the development of nanomaterials and their applications to improve atherosclerosis diagnosis and therapy during the preclinical and clinical stages of the disease.

Nanostructure-Enabled and Macromolecule-Grafted Surfaces for Biomedical Applications

Advances in nanotechnology and nanomaterials have enabled the development of functional biomaterials with surface properties that reduce the rate of the device rejection in injectable and implantable biomaterials. In addition, the surface of biomaterials can be functionalized with macromolecules for stimuli-responsive purposes to improve the efficacy and effectiveness in drug release applications. Furthermore, macromolecule-grafted surfaces exhibit a hierarchical nanostructure that mimics nanotextured surfaces for the promotion of cellular responses in tissue engineering. Owing to these unique properties, this review focuses on the grafting of macromolecules on the surfaces of various biomaterials (e.g., films, fibers, hydrogels, and etc.) to create nanostructure-enabled and macromolecule-grafted surfaces for biomedical applications, such as thrombosis prevention and wound healing. The macromolecule-modified surfaces can be treated as a functional device that either passively inhibits adverse effects from injectable and implantable devices or actively delivers biological agents that are locally based on proper stimulation. In this review, several methods are discussed to enable the surface of biomaterials to be used for further grafting of macromolecules. In addition, we review surface-modified films (coatings) and fibers with respect to several biomedical applications. Our review provides a scientific update on the current achievements and future trends of nanostructure-enabled and macromolecule-grafted surfaces in biomedical applications.