Acid reflux.  Sounds terrible, right?   Where does this acid come from?   Our stomachs, of course.  The acid level in our stomach is critical to breaking down those foods we ingest, so that enzymes can get the nutrients from our food.  And, if we ingest a pathogen or two, then the acid milieu makes toast of them.   Of course, that same acid means that many of the pills we take to feel better or repair our physiological problems get destroyed, too.

So, when a patient has an ulcer (in his stomach) or an associated Helicobacter pylori infection (a microbe that cause ulcers), the physician often prescribes proton pump inhibitors (PPI)  (the purple pill), to stop the acid from destroying the antibiotic or other medicine.  And, as I’ve written often (as recently as last week), these purple pills have tons of side effects.

That’s why Drs. Li, Zhang, and Wang (UCSD) have been working on micromotors, tiny robots, to help make our stomachs more able to accept medicine- but only for a short period of time, so that we can still be protected and digest our food.

Way back in 2014, they (along with Drs. W Gao, R Dong, S. Thamphiwatana, and W. Gao [yes, there were two different W. Gao]) published a paper in ACS (American Chemical Society) Nano.   This research described an in vivo (in a living animal) test, extending the in vitro (literally, under glass- which really means laboratory conditions) of a zinc-based micromotor they were developing.  Basically, those robots used zinc ions to neutralize the pH milieu (the zinc replaces the hydronium [or hydrated hydrogen ions] in the stomach acid, liberating hydrogen gas, which radically changes the pH of the stomach).   In this first case they described, gold nanoparticle robots were the particles being delivered to the mice stomachs.

Now, the research has progressed further.  In this new study, Drs. J. Li, P. Angsantikul, W. Liu, B. de Avila, S. Thamphiwatana, M. Xu, E. Sandraz, X. Wang, J. Delezuk, W. Gao, L. Zhang, and J. Wang, published (in Angewandte Chemie) data  that demonstrated they could neutralize the stomach acid in 20 minutes or so; the stomach pH then returned to normal within a day.

This affords a patient the ability to avoid the PPI therapy that often accompanies certain drugs to ensure their safe passage through the acidic stomach milieu.  This new research uses micromotors based on magnesium (the particles were 20 microns in diameter), coated with a thin layer of gold, and then coated with a pH sensitive polymer (this coating holds the desired drug).  Except for the initial tests, no drug was used; instead a fluorescent compound was added to the coating, so the results could be easily monitored during the testing.

There is a further trick to the design.  Part of the magnesium sphere is left without any coating.  (OK.  Let’s get real.  The microspheres are coated on glass supports- the part contiguous to the glass supports never get coated.) That way when the product hits the stomach, the magnesium can react, displacing the hydronium ions. The released hydrogen gas propels the motors forward at about 60 microns a second.

Just so you know, that’s really slow movement.  It would take the sphere about almost two hours to traverse the distance of a standard (12 inch) ruler.  But, for the purpose intended, the speed is perfect. It lets the spheres penetrate the stomach’s mucus layer and protects the payload from the stomach acid.

Once the pH is acceptable, the polymer coating (which, as I said, is pH sensitive) releases the desired drug.  And, the movement of the micromotors (at 60 microns a second) produce a stirring effect within the stomach, which helps the acidic levels return to normal.  (Note further that it is only a localized region of the stomach that gets fully neutralized; these are nanoparticles.)

These magnesium versions of the micromotors are aimed at treatment of stomach infections and ulcers.  The zinc versions would afford drug usage that would provide relief at  other portions of the gastrointestinal tract.

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