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Drug-eluting stent with bioabsorbable polymer coating, smart polymers allow more subtle control and timing of drug delivery

Drug-eluting stent with bioabsorbable polymer coating, smart polymers allow more subtle control and timing of drug delivery

The SYNERGY� Everolimus-Eluting Platinum Chromium Coronary Stent System by Boston Scientific Corporation received CE Mark approval for featuring an ultra-thin abluminal (outer) bioabsorbable polymer coating. It is unique in that its proprietary PLGA polymer and everolimus drug coating dissipate by three months. This innovation has the potential to improve post-implant vessel healing and will eliminate long-term polymer exposure, a possible cause of late adverse events. Drug release and polymer absorption occur in parallel and are complete at about three months after stent implantation. This exciting advance may improve long-term safety and efficacy compared to current durable polymer DES and perhaps even reduce the need for prolonged dual antiplatelet therapy. In addition to its innovative coating, the foundation of the stent is a proprietary platinum chromium alloy and an enhanced stent design which allow for thinner struts, increased visibility and an extremely low crossing profile for easier deliverability. The Stent will be available in a full range of sizes to select centers in Europe and other geographies by early 2013. This limited market release is expected to provide additional data to support the clinical and economic benefits of this novel bioabsorbable technology.

Better control over the delivery of drugs to specific sites in the body at specific times would reduce unwanted side effects and improve medical treatment dramatically. �Smart� polymers are promising materials for controlling drug delivery, since they change their properties in response to specific stimuli. However, they usually require continuous stimulation to maintain these changes. Now, researchers led by Takao Aoyagi at the MANA, National Institute for Materials Science, Japan, have developed an approach that could allow more subtle control and timing of drug delivery. The new technique uses hydrogels, which are a type of �smart� polymer made of water-soluble long-chain molecules. The team first showed that they could control the acidity inside a hydrogel by loading it with a compound called o-NBA. This releases protons, which increases acidity, when irradiated with UV light. When o-NBA-loaded hydrogel was irradiated, acidity increased inside; if only part of the gel was irradiated, acidity throughout increased gradually as protons diffused. The hydrogel was loaded with o-NBA and L-DOPA, a precursor of the brain chemical dopamine that is used in the treatment of Parkinson�s disease. The change of acidity in the gel upon UV irradiation caused L-DOPA to be released because the acidity disrupted the interaction of L-DOPA with the molecules in the gel. Irradiation with UV not only enhanced overall L-DOPA release from the hydrogel, but also caused an extra �explosive� release five hours after irradiation. This allowed the drug release to be timed, as well as triggered, in a controlled way. Being able to control the release of drugs from hydrogels by triggering a change in acidity could help to design programmable drug delivery techniques that offer improved targeting of treatment.

 
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65 mm  R PVC plant

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