Living Computers Figured Out
Dr. Takanari Inoue of Johns Hopkins Medical School has made a bunch of little computers with some of Henrietta Lacks’ old cancerous cervical cells.
(Note: For readers unaware of the story of Henrietta Lacks, please see the recent multiple-journalism-award-winning book The Immortal Life of Henrietta Lacks by Rebecca Skloot. Mrs. Lacks was a poor black tobacco farmer who died of cancer in Johns Hopkins in 1951. Cells which were harvested from her cervix shortly before her death, which will keep dividing so long as they have a suitable home [because they are cancerous], have been cloned in labs across the world, have mutated into many different strains, and have been used in tens of thousands of experiments).
Dr. Inoue, for his part, is working on a line of thought stretching back to before the development of the abacus-- the mechanical representation of mathematical functions. In the 1820s Charles Babbage, father of the computer, began dreaming of his “Analytical Engine,” a big steam-age machine, based on the automatic loom, never fully completed but imagined to use metal punch cards and big columns of gears to do math. Ever since then people have used not only gears but pneumatics, hydraulics, optics, transistors, and even Legos to make the part fundamental to any such machine, called a “logic gate.” Microprocessors are made of hundreds of millions of tiny logic gates. They form the foundation of modern computing.
Logic gates use Boolean logic, named after the English mathematician George Boole, who mapped out a whole algebraic theory of ones and zeros during the same time that Babbage was tinkering with his Analytical Engine plans. Boolean logic gates express three of Boole’s functions. An “AND” gate takes two inputs, both either a one or a zero, and produces zero in all cases except when both inputs are ones. An “OR” gate takes one or two inputs, both either a one or a zero, and produces a one in all cases except when both inputs are zeros. A “NOT” gate takes a one or a zero and reverses it into a zero or a one, respectively. A few hundred million logic gates manipulating a few hundred million ones and zeros per second more or less makes an iPad.
Before Dr. Inoue’s discovery, most attempts at creating cellular logic gates relied on cellular processes that sometimes took minutes or days. Researchers would input a couple ones or zeros and wait until the next morning to see the output. Dr. Inoue aimed to get his cellular gates to work within a few seconds.
His mechanism consisted of Henrietta Lacks' cells genetically modified to produce a quartet of extra, foreign protein molecules normally found in other animals and plants. The cancer cells were also modified to produce an observable response to the bonding of two different pairs of these molecules inside them, which Dr. Inoue knew would only happen under certain chemical conditions that he had all planned out. The ruffling of the cell wall, which the doctor could see under a microscope, symbolized the output of a one, while no ruffling symbolized the output of a zero.
The presence or absence of a pair of immunosuppressive drugs symbolized the input of one one and one zero, two zeroes, two ones, et cetera. For his “OR” gate, Dr. Inoue figured out how to get the cell wall to ruffle when either one or both of the drugs was dripped on the cell-- to always make a one unless both inputs were zero. For his “AND” gate he got his cells to only ruffle when both drugs were added. Then the doctor made some cells whose mode of output was to glow in the dark instead of to ruffle.
Just as logic gates were made with big steel cumbersome gears back in the steam age, and transistors in the machine age, and molecules in the chemical age, they’ll be made with living organisms in the next big age, the biology age. No one knows where such tinkering will lead us, but the results are likely to seem weird. Dr. Inoue’s prototypical cellular logic gates give to us a glimpse of future possibilities similar to the glimpse Babbage’s big gear-and-crank devices once gave to denizens of the 1830s.
Image by CdePaz, courtesy of Creative Commons licensing.