This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
This Small Business Technology Transfer (STTR) Phase II project is focused on assessment of our novel siRNA-loaded nanofibrous polyester in a rat carotid artery endothelial cell denudation model, which has been historically used to evaluate the effects of blocking specific genes on arterial healing. The goal of this Phase II proposal is to determine where these siRN-loaded nanofibrous materials can locally release a selected siRNA directly to the implant site and block selected cellular functions within the animal artery that are associated with blood vessel narrowing. Our hypothesis is that selected siRNAs can be incorporated into electrospun nanofibers using our patent-pending proprietary technology. siRNA would then be released from the respective material in a slow, sustained fashion, thereby directing cellular/tissue incorporation and transgene expression. It is anticipated that siRNA-loaded polyester materials will regulate cellular growth in and around the material as compared to untreated nanofibrous materials, thereby preventing blood clotting.
The broader impacts of this research are development of an implantable polyester material that can be used to locally deliver specific siRNA moieties directly at the implant site (i.e. within the artery). There is no other implantable material capable of directly affecting localized cellular function. Thus, this technology when employed as a stent coating or an artificial blood vessel will significantly improve patient outcome after implantation of these materials. Additionally, this type of material could be employed for simple (hernia repair mesh, catheter cuffs) or complex (total implantable heart, ventricular assist devices) devices that would require controlling specific cellular functions.
Intellectual Merits of Technology: This Small Business Technology Transfer (STTR) Phase II project was focused on development of a novel nanofibrous material that will locally release silencing RNA (siRNA) directly to the implant site of medical devices such stents and artificial blood vessels. Over 1.1 million stents and 70,000 prosthetic grafts are implanted annually in the United States, with failure of these devices due to cellular occlusion still persisting. Unregulated cellular growth within the body can have catastrophic consequences as evidenced in cardiovascular disease where abnormal proliferation of neointimal smooth muscle cells is central to lesions of atherosclerosis and restenosis. Our hypothesis is that siRNA can be incorporated into nanofibers of the resulting material using our proprietary technology and subsequently released in a slow, sustained fashion, thereby targeting localized cellular signalling directly around the implant. Specific objectives accomplished in the this Phase II were: 1) synthesis of control and siRNA-loaded nanofibrous materials, 2) characterization of the physical properties of the material, 3) examination of siRNA release and cellular uptake, 4) assessment of siRNA knockdown of targeted cellular mRNA, 5) implantation of control and siRNA-loaded nanofibrous materials in rat carotid denudation model and 6) evaluatation of explanted arterial segments using histological and morphometric techniques. There were several positive outcomes related to this Phase II study. siRNA was directly incorporated into the polymer prior to fiber formation via electrospinning technology. The concentraion of siRNA can be adjusted in the bulk polymer solution, permitting varied release rates and amounts of the siRNA. The resulting siRNA-loaded material can also be sterilized using clinical sterilization techniques. The physical properties of the nanofibrous material was not altered when varying concentrations of siRNA were incorporated. siRNA released from the construct in a slow,sustained fashion upon exposure to simulated blood solutions, with the siRNA structural integrity maintained. siRNA released from the nanofibrous matrix was taken up by smooth muscle cells and showed the ability to target the expression of the selected gene when assisted by a carrier moiety (transfection agent) which helps transport the siRNA into the cell. One setback with evaluating this technology was the need to alter the siRNA sequence in order to provide specificity for the animal implantation studies. This sequence proved to be ineffective at blocking gene expression both in tissue culture and in the implant studies, which was unlike the human siRNA which showed downregulation of our target gene. While our ultimate goal is human use, the technology still needs to be evaluated in an animal model prior to clinical trials. Thus, a different animal siRNA sequence that is comparable in knockdown efficacy to the human siRNA would need to be examined. Commercial Potential: This type of siRNA delivery system is one of the first systems to directly employ the device surface to locally deliver siRNA without the use of any exogenous binder agents to hold the siRNA on the surface, which would improve patient outcome when using a device such as a stent. Development of this type of siRNA-loaded nanofibrous material would have immediate application for endovascular stents and artificial blood vessels. Additionally, this type of material could be employed for simple devices as hernia repair mesh, wound dressings and catheter cuffs to more complex implantable devices such as the total implantable heart and left ventricular assist devices. Other moieties such as bioactive proteins and small synthetic compounds could also be incorporated into this polymer in order to provide additional localized biological effects. The potential market for this siRNA-loaded nanofibrous biomaterial, as shown by the number of potential applicable devices, is extensive. Conservatively, application of this technology to endovascular stents alone has a potential annual market of over $500 million. From this Phase II study, the company has received interest from a major medical device manufacturer to apply this technology onto their existing stent platform. BioSurfaces, Inc. has entered into an agreement with this device manufacturer, who has begun to supply stents as a first step to bring this technology closer to market.