In the 1950s the US chemist Helen Murray Free, who has died aged 98, was responsible for developing glucose dipsticks. Their use led to much simpler medical screening methods that are still widely used today for pregnancy tests, the diagnosis and monitoring of diabetes, and to detect and monitor a range of kidney, liver and metabolic disorders and other medical conditions.
Before then, without central testing laboratories, if a patient needed to be tested for diabetes the analysis work was done in the doctor’s office: mixing urine with chemicals such as copper sulphate, heating it over a Bunsen burner and looking for a red-orange precipitate indicating sugar. It was time-consuming, restricting the number of tests a doctor carried out, and inconclusive, as it did not differentiate between glucose (indicating diabetes) and other sugars.
Helen, working with her husband, Alfred Free, first refined soluble tablets for diagnostic use, and then invented strips of paper that could be dipped into urine and, later, blood, which would change colour in response to glucose or other substances. The tests they developed meant doctors could easily detect signs of diabetes, pregnancy and a wide range of illnesses in their own consulting rooms. Cheap to manufacture and easy to use, dip-and-read sticks are now ubiquitous in medical screening.
Helen was born in Pittsburgh, Pennsylvania, to James Murray, a coal company salesman, and his wife, Daisy (nee Piper). Her mother died when she was six in the influenza pandemic. From Poland seminary high school in Youngstown, Ohio, in 1941 Helen went to the College of Wooster, Ohio, intending to major in Latin and English.
The government, however, concerned that with so many men drafted into the second world war the US could be deprived of doctors and scientists, was encouraging young women to fill vacancies on science courses. Helen had enjoyed science at school and when a mentor at Wooster suggested she major in chemistry, she agreed, to the bemusement of her Latin professor, who said he could not understand why “this girl wants to give up the marvellous world of mythology to work in a smelly old lab”.
On graduating in 1944, Helen took a job at Miles Laboratories (now Bayer) in Elkhart, Indiana. Miles made Alka-Seltzer effervescent tablets, and its researchers had experimented with embedding chemicals in similar tablets. The result, Clinitest, was launched in 1941. In response to a few drops of urine, the tablets, containing chemicals that detected sugar, would change colour if sugar was present.
After several years of testing ingredients for the company’s vitamin pills, in 1946 Helen moved to Free’s team in Miles’ research division. It was the start of a stellar personal and professional relationship: as well as becoming lifelong research and intellectual partners, they married in 1947 and had six children.
The couple initially worked on improving Clinitest, and then created a second test for diabetes, Acetest: tablets impregnated with the chemical nitroprusside, which turned blue in response to ketones in urine.
Having to put the tablets in a test tube, add drops of urine, and wait for them to fizz and die down, irritated Helen. She said: “It was Al who said, ‘You know, we ought to be able to make this easier and more convenient than tablets, so no one would have to wash out test tubes and mess around with droppers.’”
When Alfred suggested paper strips impregnated with chemicals that could be dipped into urine, she said: “It was like a lightbulb going off.” The pair dipped strips of filter paper into glucose oxidase and peroxidase and dried them in an oven, creating Clinistix, which Miles brought to market in 1956. As well as being more convenient than Clinitest, it was more accurate, as it specifically detected glucose, rather than any sugar.
Although Helen credited her husband with the initial idea for the strips, William Carroll Jr, former president of the American Chemical Society (ACS), said: “I would credit the pair because they came as a pair. They worked together, batted ideas back and forth. Helen’s science was very practical and oriented toward people being able to use it.”
Albustix followed in 1957, a dip-and-read test for protein in the urine, and the Murray Frees were on a roll. How much more convenient, they thought, to test for several things at once with the same strip. Putting two reagents (testing chemicals) on the same strip of paper required an impermeable barrier between the two, but after many experiments they produced Uristix, which could test for both protein and glucose. Finally, in 1981, they produced Multistix, which could test for 10 items in urine and was a useful tool for a wide range of kidney, liver and metabolic disorders.
They also created testing items for blood: in 1964 they developed Dextrostix strips for testing blood glucose and a portable blood glucose meter.
After Helen retired in 1982 from Miles Laboratories, she continued as a consultant at Bayer Healthcare until 2007 and remained a prominent figure in chemistry, becoming president of the ACS in 1993.
She wrote several textbooks, including Urinalysis in Laboratory Practice (1975), and was passionate about demystifying chemistry, chairing the outreach programme National Chemistry Week and helping to establish the Kids & Chemistry project for schoolchildren. A warm and ebullient personality, Helen gave countless public talks, and in her honour the ACS created an annual award for outstanding achievements in public outreach. She was inducted into the US National Women’s Hall of Fame in 2011.
Alfred died in 2000. Helen is survived by their six children, three stepchildren, 17 grandchildren and nine great-grandchildren.