Spray-coating process development, manufacture, quality assessment and drug release behavior of peripheral drug-eluting stents

Manufacture of peripheral DES requires development of process technologies to accommodate their geometrical and biomechanical specifics. In this study, a spray-coating process for peripheral DES coatings was developed. Peripheral-size, self-expanding nickel titanium stents (7.0 x 40 mm) were coated with the biodegradable polymer poly(L-lactide) (PLLA) incorporated with the immunosuppressant sirolimus (SIR) in a ratio of 82.5/17.5 % w/w. Coating mass was 3400 mu g. A parameter study was conducted to assess optimum coating parameters. The coated DES were evaluated for coating morphology, thickness, and integrity. Drug release behavior was assessed by HPLC. SEM evaluation confirmed a smooth, defect-free PLLA/SIR coating with complete strut coverage. A coating thickness of 5.5 +/- 0.4 mu m was determined by CLSM. SIR release was traced over up to 430 h, exhibiting an initial burst over 30 h, followed by a steady, retarded drug release. Altogether, the results indicate the technical feasibility of self-expanding, peripheral DES.