Ingestible sensors—pill-sized electronics that ping your smartphone with data after you pop and swallow—have started to arrive on the market. They don’t do much yet: Mostly they measure pH, temperature, and pressure or monitor whether or not patients have taken their meds. But researchers are cooking up novel sensing technologies to detect a much broader range of medical molecules.
Like say, cramming millions of genetically engineered glowing bacteria inside a AAA-battery-sized capsule to diagnose stomach bleeds—as demonstrated by scientists in Timothy Lu’s lab at MIT.
Lu’s team took L. lactis’s on-switch DNA, coupled it with some code for bacterial bioluminescence, and stuck the whole genetic circuit inside a gut-friendly strain of E. coli commonly sold as a probiotic. Those modified cells went into a body-safe capsule equipped with a semipermeable membrane on one side to let in liquid from the gut. Wireless semiconductors powered by a teeny battery were packed in the capsule too—separated from the cells by a tiny see-through window.
The scientists tested their bacteria-on-a-chip prototype in mice with induced gastrointestinal bleeding and in pigs that had blood piped into their stomachs. When the bacteria hit the heme, they lit up. Not much, but enough for a custom phototransistor to capture it and relay that information to a microprocessor—which sent the signal to an Android app.
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