Algae microswimmers

25 November 2017 - The biohybrids are coming

zhang2017.PNGIn making-it-move news this week: weaponized spirulina platensis (make-it-move part XIX here) as reported by Li Zhang in Science Robotics (DOI) and the first microswimmer featured in this blog applied in an actual biological system! Spirulina is a microalgae with a natural helical shape and also with natural fluorescence. To prepare this swimmer for microswimming it was dip-coated with iron oxide nanoparticles and then annealed. The original swimmer has by then disintegrated (sorry!) but what is left, a solution of 100 micrometer long magnetic screws can be injected and by virtue of external magnets moved around at will. For this the helical shape is essential. Also importantly the particles are superparamagnetic, a residual magnetic strength would cause them to clutter to together with disastrous consequences. Navigation, fluorescence-based medical imaging and magnetic resonance imaging was demonstrated to track the particle swarm. As a peculiar experimental result the swarm was found to be cytotoxic towards cancer cells. But how? Iron oxide is not cytotoxic. The article concludes that residual spirulina from inside the helix is responsible.

Do it yourself pharma

21 November 2017 - Pharma

Big news in The Netherlands: a dispensing chemist in The Hague is challenging a pharmaceutical company by starting a pharmaceutical production line in the back of his shop rather than being forced to wholesale some really expensive medicine (NOS News). The pharma bro's are Vertex, the product is Orkambi, the disease is cystic fibrosis and the excessive price is over 100 thousand euro's per year for a treatment. The footage accompanying the article is confusing, with a production line you would expect all sort of reactors but on film we have only a line of rota-vapors (containing a brown goo), tiny filtration setup and a tablet press. How to deconstruct the story? Orkambi is a mixture of two compounds: lumacaftor and ivacaftor, so the process going on is probably just the mixing of the two. Still a respectable venture but somewhat less spectacular. The chemist has suppliers in China and expects to be able to serve 750 patients for one fifth of the Vertex price. In the meanwhile all the Dutch government can do is negotiate with Vertex for a better deal. How well they are at that is difficult to tell as these negotiations are strictly confidential.

Spectacular magnet failure

12 November 2017 - Consumer watchdog

klik hier voor de afbeelding op ware grootteThe other day I bought a set of magnets that failed the moment I unpacked them. At 4 euro's not the end of the world but the material failure was spectacular. The button-sized pieces of metal just shattered on any impact, made worse by their large magnetic strength. So before returning them to the store, exactly what did I buy?
With some research done (the packaging just said 'super strong magnets' and nothing else) my bet is that I am dealing with neodymium magnets (NdFeB). The Wikipedia page mentions susceptibility to corrosion. To get some insight into the production process this clip was a delight. A lot can go wrong! In this clip SuperMagnetMan (his real name) visits a Chinese magnet factory. With Chinese can-do a mixture of Neodynium, iron and boron was first strip-casted at 1400°C to a flake-like material, then these flakes were disintegrated in a hydrogen decrepitation step. A jet milling step turned everything into a fine powder and (never knew that) the magnets were pressed into shape with pressures up to 23000 psi. Next followed a sintering process, a machining step , a coating step and finally magnetisation. Watch that clip. The decrepitation step (a metal hydride forms) is an interesting one by itself and can be seen in other youtube clips here and here.

If the magnets are supposed to be coated with nickel or epoxy to protect it from corrosion it is not obvious from visual inspection. Even if everything went well, the magnets can have been over-magnetized. It is almost impossible to pry them apart (they had already cluttered together in the packaging), making them near useless even if they do not shatter. This blog sticks with ferrite from now on.