BLEEDING THROUGH a tampon or pad never makes for a good time. The risk of leaks is annoying and stressful for all women who bleed, and especially for the 20% to 30% whose menstrual flow is so heavy that they sometimes must change their tampons or pads every hour. Some dread leaving their homes for fear of getting caught out.
A new discovery could one day ease that anxiety. Writing in Matter on July 10th, scientists from Virginia Tech described an easy way to turn blood into a thick, semi-solid gel, which could limit leaks and spills from period products. It would be a rare step forward in menstrual care. This is “one of those quality-of-life issues”, says Bryan Hsu, the microbiologist who led the work, regarding which there has not been any progress “in a century”.
The team began by looking for a material that could make blood more solid. They did so by mixing various polymers—molecules whose structure consists of long chains—with pig’s blood and measuring how quickly the resulting concoction flowed down a test tube. After discarding those that produced too runny a gel, they settled on a powder based on alginate, a polymer found in algae. The team’s tests suggested that the positively charged calcium ions in the blood would attract the alginate’s negatively charged molecular chains, creating a tangled web capable of trapping the blood in a firm gel.
The researchers wrapped the alginate powder in a sheet of gauze, to mimic a pad, and taped it to a silicone model of a vagina. They then fed 8 millilitres of blood through the model onto the gauze, roughly double the amount that a regular daytime pad holds. Under these conditions the alginate retained about as much blood as the materials used in commercial pads. But when placed in a centrifuge, to emulate the compressing effect of a sitting person’s weight, the alginate held on to about 78% of the blood, whereas the commercial pad material released more than half. This suggests the gel would be more effective at preventing leaks than a standard pad.
The team also tested the powder as a liner for reusable menstrual cups, which some see as a more sustainable period-product choice. Cups can be kept in for many hours but, as they do not currently come with liners, taking them out is messy. To try to fix that problem, the team added a cotton tube containing the powder to the cup and inserted it into another model vagina, which released 15 millilitres of blood, roughly a menstruating woman’s daily average. The gelled blood stayed neatly within the cup when handled—a result cup-users will recognise as a small miracle. Although such liners would be single-use, Dr Hsu envisions that any future commercial product could be flushed down the toilet rather than go to landfill.
In the past super-absorbent tampons have been linked to toxic-shock syndrome, a life-threatening condition caused by vaginal bacteria, which could potentially feed on the alginate. Though the condition is mercifully rare, the team were keen to minimise the risk. They therefore added an antimicrobial called trimethyl chitosan to the powdered alginate. Adding it in this way means the harmful growth of bacteria can be kept down, while limiting any disturbance to the vaginal microbiome.
The approach “is absolutely a breath of fresh air”, says Linda Griffith of the Massachusetts Institute of Technology, who is a biological engineer and women’s health expert. She has not seen such methods used before. Though the team’s experiments need to be repeated with actual menstrual blood, Dr Griffith anticipates even better results, because menses already have more solid components than ordinary blood does.
A further test awaits: nobody has yet tried an alginate pad or cup liner. The research was informed by the experiences of Dr Hsu’s female colleagues, including one gynaecologist, but “You never know until you get something like this out into the wild how it’s going to work,” says Dr Griffith. With luck, it will not be necessary to throw in the towel.
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