A molecular computer that uses enzymes to perform calculations has been built by researchers in Israel.

Itamar Willner, who constructed the molecular calculator with colleagues at the Hebrew University of Jerusalem in Israel, believes enzyme-powered computers could eventually be implanted into the human body and used to, for example, tailor the release of drugs to a specific person’s metabolism.

The team built their computer using two enzymes – glucose dehydrogenase (GDH) and horseradish peroxidase (HRP) – to trigger two interconnected chemical reactions. Two chemical components – hydrogen peroxide and glucose – were used to represent input values (A and B). The presence of each chemical corresponded to a binary 1, while the absence represented a binary 0. The chemical result of the enzyme-powered reaction was determined optically.

The enzyme computer was used to perform two fundamental logic computations known as AND (where A and B must both equal one) and XOR (where A and B must have different values). The addition of two further enzymes – glucose oxidase and catalase – connected the two logical operations, making it possible to add together binary digits using the logic functions.


Intelligent drug delivery

Enzymes are already widely used to assist calculations using specially encoded DNA. These DNA computers have the potential to surpass the speed and power of existing silicon computers because they can perform many calculations in parallel and pack a vast number of components into a tiny space.

But Willner says his enzyme computer is not designed for speed – it can take several minutes to perform a calculation. Rather, he envisages it eventually being incorporated into bio-sensing equipment and used, for example, to monitor and react to a patient’s response to particular dosages of a drug.

“This is basically a computer that could be integrated with the human body,” Willner told New Scientist. “We feel you could implant an enzyme computer into the body and use it to calculate an entire metabolic pathway.”

Martyn Amos from University of Exeter, UK, also sees great potential for such devices. “The development of fundamental devices such as counters is vital for the future success of bio-molecular computers,” he told New Scientist.

“If such counters could be engineered inside living cells, then we can imagine them playing a role in applications such as intelligent drug delivery, where a therapeutic agent is generated at the site of a problem,” Amos says. “Counters would also offer a biological ‘safety valve’, to prevent engineered cells proliferating in an uncontrolled fashion.”

Journal reference: Angewandte Chemie International Edition (vol 45, p 1572)