Custom silicone elastomers for improved mechanical performance and reduced hormone binding in a dapivirine/levonorgestrel vaginal ring

Karl Malcolm, Yahya Dallal Bashi, Clare F. McCoy, Diarmaid Murphy, Peter Boyd, Brid Devlin, Kyle Kleinbeck, Patrick Spence, Bindi Dangi, Bashir Hansraj, Nicole McMullen, Leanne Brown, Francois Martin, Matthew Kihara

Research output: Contribution to conferencePosterpeer-review

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We previously reported the chemical binding of levonorgestrel (LNG) to vaginal rings manufactured from addition-cure silicone elastomers. Here, three custom silicones were evaluated for manufacture of a multipurpose technology (MPT) vaginal ring (VR) releasing dapivirine (DPV) and LNG with the aim of reducing LNG binding and improving mechanical performance.

Silbione® Biomedical D160 silicone elastomers (Lots 07117-13, 14 and 15) were supplied by Elkem Silicones. Matrix-type VRs containing 200mg DPV and 320mg non-micronised LNG (nmLNG) were manufactured by injection molding (100°C/95 sec). Elastomer 14 was also used to prepare VRs containing 200mg DPV with 240, 160 or 80mg nmLNG. Various mechanical tests were performed on the VRs and assay values for DPV and LNG were determined. In vitro release testing was performed for the VRs using two different media – IPA:water (1:1 v/v) and sodium acetate buffer with 2% Solutol® HS15.

All three silicones showed similar cure profiles and viscosities conducive to practical ring manufacture and performance (Table 1).

DPV+LNG rings manufactured from Silicone 14 (selected for further study due to its relatively long working time) showed high LNG recovery and good mechanical properties (Table 2).

In vitro DPV release from the Elkem 14 VRs did not change significantly in repsonse to varied nmLNG loading, while LNG release was significantly correlated with initial nmLNG loading.

These new silicone materials, and particularly variation 07117-14, offered desirable mechanical performance and acceptable LNG recovery values for further development of a silicone based MPT ring.
Original languageEnglish
Publication statusPublished - 27 Mar 2021
Event4th HIV Research for Prevention Conference (HIVR4P // Virtual) - Virtual
Duration: 27 Jan 202104 Feb 2021


Conference4th HIV Research for Prevention Conference (HIVR4P // Virtual)
Abbreviated titleHIV R4P
Internet address


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