DNA computers inside living animals

DNA computing
Image by CSIRO Australia via WikiCommons.

This post is part of a series on the bio-computing.

Today I want to talk about an experiment that simultaneously excites and scares me. Scientists have created nano-robots out of DNA and used them to make tiny computers that function inside a living animal. These DNA robots could conceivably be used to control individual cells and ultimately a whole animal. The thought of biological robots is not science fiction any more.

DNA origami robots are sequences of DNA that are folded around a ‘payload’ which can be any protein or smaller DNA sequence e.g. an antibody or an enzyme. The DNA robots are activated by binding to a separate DNA sequence called a key. When the robots bind to the key, they change shape and release their payload.

In this experiment, the DNA keys were used as logic gates. Logic gates are the basis of computing. In modern computing, information is converted into a binary code called bits which is usually shown as 0 and 1 or Hi and Lo, and often correspond to high and low voltage. The voltage turns the logic gates on and off. Logic gates can be connected together into the complex circuits that make up the microprocessors and memory cells inside our computers.

Three different types of DNA robots were used in this experiment. Effector robots (E-robots) contained an antibody that recognised cockroach blood cells. Positive regulator robots (P-robots) contained a key DNA sequenced needed to activate the E-robots. Negative regulator robots (N-robots) contained a lock that jammed the gate on the E-robots and stopped them from opening to release the blood cell antibody.

These three robot types were used in combination to create various computational logic gates such as AND and OR. For example, to create and AND gate, an E-robot can be programmed to only open if two keys, called X and Y, are present. To create an OR gate, a P1-robot can be programmed to open only if it binds to the key X. Then if the P1-robot contains the key needed to open a P2-robot (called key Y) and the P2-robot contains the key to activate the E-robot, the E-robot can be activated if only X is present, or if only Y is present or if X and Y are present.

At this stage each DNA-robot logic gate circuit can only process two pieces of information and so is only a two bit ‘processor’. But the processors can be linked together to form a computing circuit that could achieve four and eight-bit computing like the old school Atari 800. And the amazing this is that this works inside living cells.

Here’s the rest of the bio-computing series:

Can biological computers become a reality?

Synthetic DNA and living computers

How DNA is made

The Scientific Papers:

Amir et al. Universal computing by DNA origami robots in a living animal. Nature Nanotechnology. 2014.

Douglas et al. A logic-gated nanorobot for targeted transport of molecular payloads. Science. 2012.

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