A woman's reproductive tract is a complex environment. The vagina is naturally acidic (pH 4), but it is altered dramatically by the introduction of semen, which is basic. This combination of acid and base creates a nearly neutral environment in which conception can occur. Only in the presence of semen (or another buffer) can sperm survive and "swim" to an unfertilized egg. This neutral environment may be required for conception to occur, but it is also the condition that allows pathogens like HIV to survive in the vagina and infect susceptible cells within the reproductive tract.
BufferGel works by maintaining the mildly acidic environment of the vagina, and therefore may protect a woman from STD transmission and unwanted pregnancy.
Every microbicide developer faces an enormous challenge: a product must be safe for exposure to the epithelial cells that line the outer surfaces of the vagina and cervix, but must be toxic to the pathogens and infected cells that may be found in semen and could infect the woman (Figure 1). Similarly, a microbicide must be able to kill bacteria that cause disease without killing the normal flora, such as lactobacilli, which is a critical natural protective mechanism of the reproductive tract. Ultimately the challenge includes being safe for use by male partners and so includes creating products that do not cause irritation or epithelial cell damage to men.
BufferGel has met this challenge. Figure 2 shows how BufferGel accomplishes not harming the cells of the reproductive tract but killing or damaging cells that may be infected with pathogens, as well as the pathogens themselves. Figure 3 demonstrates how BufferGel does not inhibit the growth of "good" bacteria, but creates an environment in which the "bad" bacteria and viral pathogens are less likely to survive.