I recently came across this article from Nature. In it, it states that the snails have "tiny biofuel cells that extract electrical power from the glucose and oxygen in the snail’s blood", and that the power obtained is dependent on "how quickly sugar and oxygen can be taken from the creatures' blood". They go on to say that the power obtained decreases over time, and that these implants could power future pacemakers in humans.

Would this application in humans require that a patient eats more and "breathes more" than average? Why does the power output decrease over time, and couldn't that potentially lead to the malfunctioning of a pacemaker?



You'd think if such devices were used in humans, they wouldn't require a change of lifestyle.

They don't say the power always decreases over time:

Katz’s snails, for example, produced up to 7.45 microwatts, but after 45 minutes, that power had decreased by 80%. To draw continuous power, Katz’s team had to ramp down the power they extracted to 0.16 microwatts.

This is really a chemistry question. The glucose has to be brought to the fuel cell some way. In this case, the glucose is oxydized directly in the hemolymph. As oxygen PP in the hemolymph is always greater than glucose concentration(1), your limiting rate (which is related to the power you can get from the device) is that of glucose intake at the fuel cell. Therefore, the more you oxidize glucose per unit time, the greater intake you need to keep the output from dropping.

The glucose intake at the fuel cell is a function of biological parameters such as quantity eaten, metabolic efficiency, metabolic speed, blood flow, but also diffusion. The kinetics of glucose intake at the fuel cell are such that you can't ask for too much power for too long.

I suggest you read the article to get a more detailed answer. Nature news is good, but there's nothing like reading the real paper.

1 http://pubs.acs.org/doi/full/10.1021/ja211714w

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Would this application in humans require that a patient eats more and "breathes more" than average?

From the cellular standview, each glucose and O2 molecule that you substract to the cell for use in a second futile cycle, should be replaced. However, I doubt that the amount of glucose/O2 required per hour will be so important to require additional food intake.

By the way, each cell in the body normally generates electricity from glucose and O2: just think at the electron transport chain during the mitochondrial cellular respiration.

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