If you were asked to think of something microscopic that moves quickly, chances are that sperm would be the first thing to come to mind. The tiny reproductive cells are able to swim as fast as they do thanks to their long whip-like tails, known as flagella. So, imagine how helpful it might be if sperm-like machines could be used for applications such as delivering medication to targeted areas of the body. Well, that's what scientists at the University of Illinois are in the process of making possible, with the creation of their heart cell-powered "bio-bots."
The body of each bio-bot is made up of a joined head and tail, which together measure a little under 2 mm in length. They're made of an inert flexible polymer called polydimethylsiloxane, which is a type of silicone. Covering the head and the top part of the tail is a coating of fibronectin, a protein that makes up much of the extracellular matrix, and that aids in cell adhesion.
When heart cells are placed on the head/tail junction, they bind with the fibronectin, and also align themselves relative to one another. They also synchronize their expansions and contractions, so they beat in unison. That synced beating causes the tail to whip back and forth, driving the bio-bot forward through a liquid medium.
The technique is illustrated in the following video.
The scientists have also made bots with two tails, which lets them swim faster. It is believed that by giving individual bio-bots even more tails, which could be selectively activated, it would be possible for them to steer themselves. With that capability added, it is hoped that medication- or stem cell-laden bots could then navigate towards specific targets, drawn into them by light or chemical cues.
The research, which is being led by Prof. Taher Saif, is described in a paper that was recently published in the journal Nature Communications.
In related news, a team at Germany's Dresden Institute for Integrative Nanosciences are creating remote-control micro robots known as "spermbots," that are actually propelled by individual sperm cells.
Source: University of Illinois