This adorable little ant can be trusted to carry quite a lot on its back in the interest of the common good. In that way, it's surprisingly similar to the cells of your immune system, as researchers from MIT and Harvard revealed earlier this month. They've found a way to hook synthetic patches to the surface of B and T cells — and to control the movements of those cells with magnetic fields. Armed with these so-called "backpacks," lymphocytes can now identify growing tumors and infections, as well as personally (or cellularly?) deliver treatments to ailing cells. This could be the first crest of a wave of revolutionary new school supplies in the world of tissue engineering.
This isn't to say that B and T cells will be forced to do our bidding. "The goal is to perturb the cell as little as possible," said Robert Cohen, one of the authors of the paper in Nano Letters. Each synthetic patch only covers a small part of the cell's surface, so the cell can still carry out its normal functions without disturbance. In fact, "backpack" is a near-perfect analogy for this technology. The synthetic patch application consists of three layers of polyelectrolytes (certain types of polymers). Inside, the middle layer is whatever the scientists want the cell to be carrying: examples include a vaccine, a protein marker, or magnetic nanoparticles for controlled direction. The bottom layer of the patch is a polymer that attaches to the surface of the immune cell, and the top layer binds to other cells. If you squint while you're watching this video (courtesy of MIT TechTV), the hordes of marauding B cells kind of look like ants with backpacks: Click to view Now that we know human immune cells can carry a bit of extra load, it's time to start thinking about how we can use that capability to treat cancer or improve our bioimaging — or if you prefer, what kind of pencil boxes and notebooks will go into these new cellular backpacks. Leaf-cutter ant image from Wikimedia Commons. Surface-functionalized cell diagram courtesy American Chemical Society. Tiny backpacks for cells [MIT News Office] Surface functionalization of living cells with multilayer patches [Nano Letters]