Biocompatibility and zinc release testing of a zinc-containing vaginal gel

To test the biocompatibility of a zinc-containing vaginal gel, evaluate its ability to release zinc, and to assess the transepithelial permeability of zinc on human vaginal epithelium.

The release and membrane diffusion of zinc from the vaginal gel was tested by a vertical Franz-diffusion cell system. The biocompatibility of the gel was tested on HaCaT cells and reconstructed human vaginal epithelium. MTT assay was used to detect cell viability. Lactate dehydrogenase (LDH) assay was used to access cytotoxicity. The permeability of zinc was tested on the reconstructed human vaginal epithelium. The integrity of the reconstructed human vaginal epithelium after the permeability experiments was measured by transepithelial electric resistance. Zinc levels were determined by inductively coupled plasma optical emission spectrometry.

20 μM zinc sulfate did not decrease cell viability during the 24 and 72-hour treatment. Similarly, cell viability did not decrease significantly after 60 minutes of incubation with the gel and no toxic compound released from the vaginal gel during the 120 minutes diffusion experiment. A total of 72-hour exposure to the zinc-containing vaginal gel showed no cytotoxicity using LDH assay. Using cellulose-acetate membranes, 24.6% of the zinc content of the gel was released and appeared in the acceptor phase after 15 minutes. Zinc had high permeability (2.2 ± 0.8 × 10 cm/s) from the vaginal gel on reconstructed human vaginal epithelium.

The zinc-containing (20 μM) vaginal gel was not toxic. The release of zinc is rapid from the vaginal gel. Zinc permeated rapidly through the vaginal epithelial cell layers.