Nanoparticles eluting stents for coronary intervention: Formulation, characterization and in vitro evaluation

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

Sirolimus-loaded exosomes as a promising vascular delivery system for the prevention of post-angioplasty restenosis

Restenosis remains the main reason for treatment failure of arterial disease. Sirolimus (SIR) as a potent anti-proliferative agent is believed to prevent the phenomenon. The application of exosomes provides an extended-release delivery platform for SIR intramural administration. Herein, SIR was loaded into fibroblast-derived exosomes isolated by ultracentrifugation. Different parameters affecting drug loading were optimized, and exosome samples were characterized regarding physicochemical, pharmaceutical, and biological properties. Cytotoxicity, scratch wound assays, and quantitative real-time PCR for inflammation- and migration-associated genes were performed. Restenosis was induced by carotid injury in a rat carotid model and then exosomes were locally administered. After 14 days, animals were investigated by computed tomography (CT) angiography, morphometric, and immunohistochemical analyses. Western blotting confirmed the presence of specific protein markers in exosomes. Characterization of empty and SIR-loaded exosomes verified round and nanoscale structure of vesicles. Among prepared formulations, desired entrapment efficiency (EE) of 76% was achieved by protein:drug proportion of 2:1 and simple incubation for 30 min at 37 °C. Also, the optimal formulation released about 30% of the drug content during the first 24 h, followed by a prolonged release for several days. In vitro studies revealed the uptake and functional efficacy of the optimized formulation. In vivo studies revealed that %restenosis was in the following order: saline > empty exosomes > SIR-loaded exosomes. Furthermore, Ki67, alpha smooth muscle actin (α-SMA), and matrix metalloproteinase (MMP) markers were less expressed in the SIR-exosomes-treated arteries. These findings confirmed that exosomal SIR could be a hopeful strategy for the prevention of restenosis.

Cardiovascular protection associated with cilostazol, colchicine and target of rapamycin inhibitors

ABSTRACT

An alteration in extracellular matrix production by vascular smooth muscle cells is a crucial event in the pathogenesis of vascular diseases such as aging-related, atherosclerosis and allograft vasculopathy. The human target of rapamycin (TOR) is involved in the synthesis of extracellular matrix by vascular smooth muscle cells. TOR inhibitors reduce arterial stiffness, blood pressure, and left ventricle hypertrophy and decrease cardiovascular risk in kidney graft recipients and patients with coronary artery disease and heart allograft vasculopathy. Other drugs that modulate extracellular matrix production such as cilostazol and colchicine have also demonstrated a beneficial cardiovascular effect. Clinical studies have consistently shown that cilostazol confers cardiovascular protection in peripheral vascular disease, coronary artery disease, and cerebrovascular disease. In patients with type 2 diabetes, cilostazol prevents the progression of subclinical coronary atherosclerosis. Colchicine reduces arterial stiffness in patients with Familial Mediterranean Fever and patients with coronary artery disease. Pathophysiological mechanisms underlying the cardioprotective effect of these drugs may be related to interactions between the cytoskeleton, TOR signaling and cyclic AMP synthesis that remain to be fully elucidated. Adult vascular smooth muscle cells exhibit a contractile phenotype and produce little extracellular matrix. Conditions that upregulate extracellular matrix synthesis induce a phenotypic switch toward a synthetic phenotype. TOR inhibition with rapamycin reduces extracellular matrix production by promoting the change to the contractile phenotype. Cilostazol increases the cytosolic level of cyclic AMP, which in turn leads to a reduction in extracellular matrix synthesis. Colchicine is a microtubule-destabilizing agent that may enhance the synthesis of cyclic AMP.