OBJECTIVE To prepare osthole ethylene vinyl acetate(EVA) reservoir type spiral annular vaginal rings using 3D printing technique, to study the effect of prescription factors on the in vitro release of the vaginal ring.

METHODS Fused deposition modeling 3D printing was employed to prepare osthole-loaded ethylene-vinyl acetate 40 (EVA40) spiral ring matrix-type vaginal rings and osthole-loaded EVA40 conventional ring matrix-type vaginal rings using osthole and EVA40. Osthole-loaded EVA spiral ring reservoir-type vaginal rings were fabricated with osthole, EVA40 as the drug-loaded inner core, and ethylene-vinyl acetate 9 (EVA9) as the outer controlled release layer. The single-factor method was used to evaluate the influence of formulation factors on the in vitro drug release of the drug. The Fourier transform infrared spectroscopy (FT-IR) and the scanning electron microscopy (SEM) were applied to characterize the state of osthole in the vaginal rings.

RESULTS All prepared vaginal rings appeared white with smooth surfaces, and their external dimensions were consistent with the software design. The osthole-loaded EVA40 spiral ring matrix-type vaginal rings exhibited higher burst release and higher cumulative release than that of the osthole-loaded EVA40 conventional ring matrix-type vaginal rings. The burst release of osthole from the EVA spiral ring reservoir-type vaginal rings was significantly reduced. The daily drug release rate also decreased with the thickness of the controlled release layer increasing. Infrared spectroscopy and scanning electron microscopy proved that the structure of the osthole did not change and had good compatibility with EVA40.

CONCLUSION  The osthole-loaded EVA spiral ring reservoir-type vaginal ring can reduce the drug burst release and enhance the stable release of drug in the later stage.