Heart disease
Numerous treatments have been developed for atherosclerotic vascular diseases and for those patients with severe artery blockage, coronary artery bypass grafting or coronary artery stenting are required. Vascular stents are ‘spring-like’ cylindrical and hollow metal-based implantable devices for the treatment of vessel related blockages. Vascular stenting is the procedure of implanting a thin metal (such as Ti, stainless steel, Nitinol or CoCr alloys) tube into the part of the artery blocked by plaque accumulation in order to prop it open and re-establish blood flow. A standard treatment for clogged and damaged arteries is implanting a vascular stent, which holds the artery open and releases drugs such as paclitaxel.
Nanotechnology solutions
Nanosurfaces on metallic vascular stents
The researchers of Brown University have designed a synthetic vascular polymeric grafts and metallic vascular stents using novel nanotechnology approaches. They have demonstrated for the first time that when compared with implants which are nano-smooth, those with nano-scale surface features mimic the natural vessel walls to attract more endothelial cells and promote their growth, thus, accelerating the re-formation of an endothelium to prohibit re-blocking of the artery. They have shown that nanosurfaces on metallic vascular stents and polymeric vascular grafts can save the implant from suffering a detrimental inflammatory response.
Nanoburrs with drug load
MIT and Harvard researchers have designed new particles which they call nanoburrs can cling to damaged artery walls and slowly release cancer drugs with nanoparticles to clear cardiovascular disease. The nanoburrs are particles coated with tiny protein fragments that allow them to stick to damaged arterial walls. Once stuck, they can release drugs such paclitaxel, which inhibits cell division and helps prevent growth of scar tissue that can clog arteries. The nanoburrs are among the first particles that can zero in on damaged vascular tissue unlike previously developed nanoparticles that seek out and destroy tumors.
Mechanism
The nanoburrs are targeted to a structure known as the basement membrane, which lines the arterial walls but is only exposed when those walls are damaged. To build their nanoparticles they used the most successful, a seven-amino-acid sequence called C11, to coat the outer layer of their nanoparticles.
The inner core of the 60-nanometer-diameter particles carries the drug, which is bound to a polymer chain called PLA. A middle layer of soybean lecithin, a fatty material, lies between the core and the outer shell, which consists of a polymer called PEG that protects the particles as they travel through the bloodstream.
The drug can only be released when it detaches from the PLA polymer chain, which occurs gradually by a reaction called ester hydrolysis. The longer the polymer chain, the longer this process takes, so the researchers can control the timing of the drug’s release by altering the chain length.
The researchers claim that the nanoburr’s structure could make it easier to manufacture, because the targeted peptides are attached to an outer shell and not directly to the drug-carrying core, which would require a more complicated chemical reaction. The design also reduces the risk of the nanoparticles bursting and releasing drugs prematurely. They can be injected intravenously at a site distant from the damaged tissue. Because the particles can deliver drugs over a longer period of time, and can be injected intravenously, patients would not have to endure repeated and surgically invasive injections directly into the area that requires treatment.
But the British Heart Foundation warned the technology was some years from being used in patients.