Stéphane Trombotto

Lithography is one of the key steps in micro/nanofabrication, which involves the use of oil-based resists, organic solvents, and toxic chemicals. Nowadays, environmental issues and regulation have raised the need for developing greener materials and processes. Therefore, efforts have been devoted to developing greener resists, in particular, resists based on water-soluble bio-sourced polymers. Among these biopolymers, polysaccharides have gained a strong interest. However, their interaction with silica etching plasmas, in particular, fluorinated plasmas, remains scarcely studied and contradictory results are found in the literature. The present contribution reports on the study of the interaction of two chitosans exhibiting different degrees of N-acetylation with SF6/Ar and CHF3 etching plasmas. The surface modifications and in-depth modifications were studied with x-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, infrared spectroscopy, water contact angle, and size-exclusion chromatography. The effect of neutrals, ions, and vacuum ultraviolet (VUV) was considered. Our results suggest that the chitosan selectivity is greatly influenced by the deposition of a fluorocarbon film and that VUV seems to be involved in scissions of the polymer chains. No significant difference between the two chitosans was observed.

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.