Topical reinforcement of the cervical mucus barrier to sperm

Capturing sperm with chitosans

Many women would prefer a nonhormonal, on-demand contraceptive that does not have the side effects of existing methods. Here, Schimpf and colleagues studied reinforcement of the cervical mucus barrier with chitosans as a potential contraceptive method. In vitro, chitosans passively diffused into human cervical mucus and decreased the ability of sperm to penetrate the mucus. The authors then developed a gel using a 36.2-kDa chitosan and applied it to ewes before artificial insemination, resulting in markedly reduced numbers of sperm in the distal cervix and uterus without irritating the vaginal epithelium. Although further studies showing contraceptive effect are needed, these findings suggest that chitosan gels might serve as an alternative to current hormonal and nonhormonal contraceptive methods.


Close to half of the world’s pregnancies are still unplanned, reflecting a clear unmet need in contraception. Ideally, a contraceptive would provide the high efficacy of hormonal treatments, without systemic side effects. Here, we studied topical reinforcement of the cervical mucus by chitosan mucoadhesive polymers as a form of female contraceptive. Chitosans larger than 7 kDa effectively cross-linked human ovulatory cervical mucus to prevent sperm penetration in vitro. We then demonstrated in vivo using the ewe as a model that vaginal gels containing chitosan could stop ram sperm at the entrance of the cervical canal and prevent them from reaching the uterus, whereas the same gels without chitosan did not substantially limit sperm migration. Chitosan did not affect sperm motility in vitro or in vivo, suggesting reinforcement of the mucus physical barrier as the primary mechanism of action. The chitosan formulations did not damage or irritate the ewe vaginal epithelium, in contrast to nonoxynol-9 spermicide. The demonstration that cervical mucus can be reinforced topically to create an effective barrier to sperm may therefore form the technological basis for muco-cervical barrier contraceptives with the potential to become an alternative to hormonal contraceptives.


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