Polymeric endoluminal gel paving: therapeutic hydrogel barriers and sustained drug delivery depots for local arterial wall biomanipulation.

Polymeric endoluminal paving is a process in which biodegradable polymers may be locally applied percutaneously to blood vessels as endoluminal liners, resurfacing or 'paving', the underlying vascular wall. Depending upon the type of polymer selected, endoluminal polymer layers may function as wall supports, barriers, therapeutic biomaterials or depots for local sustained drug delivery. In the original description of the paving process, that is solid paving, structural polymers were utilized. In this article a second form of paving--gel paving is described. In this process, hydrogel polymers are locally applied or polymerized on vascular endoluminal surfaces. Endoluminal hydrogel layers have been demonstrated to function as physical non-pharmacological barriers limiting cell and protein deposition and effectively reducing underlying arterial wall thrombogenicity. Hydrogel paving layers also provide a means for prolonged local arterial wall drug delivery. In this report an update on gel paving is provided. The overall process of polymeric endoluminal paving is initially reviewed. Gel paving and the rationale for this approach is described. Both thermoreversible as well as photopolymerizable PEG-lactide hydrogel paving systems are outlined. Recent experimental studies with gel paving examining polymer application, haemocompatability and endoluminal surface thromboprotection, effects on post-injury neointimal thickening and local drug delivery, are then reviewed. Finally, the role of gel paving in future approaches to vascular therapy is discussed.