Can a synthetic material communicate with a neuron without carrying drugs, signalling molecules or growth factors?\n\nIn a [new study published in Science](https:\/\/www.science.org\/doi\/10.1126\/science.aeg5583) on 1 October, a team at Northwestern University showed that, at least in cell culture, it can.\n\nThe researchers developed extraordinarily long **supramolecular polymers**: structures made of molecules that assemble through weak, reversible interactions, reaching masses of **billions of daltons**. On the molecular scale, these are enormous structures. Being able to precisely control their length and composition\u2014because we understand their building blocks and the rules governing their assembly\u2014offers a bridge between the nanoscale and the macroscale: **from molecules to cells and tissues**.\n\nThe secret lies in a new growth mechanism. When the available molecules run out, the ends of the filaments fold back on themselves, preventing further elongation. Adding more material, however, allows growth to resume. This makes it possible to build a single filament containing segments with different chemical properties.\n\nAnd it was by playing with the distribution of **electrical charges** that the researchers observed something unexpected.\n\nEntirely positively charged filaments were toxic to neurons, while negatively charged ones were repelled. But inserting a small positive region between negative segments completely changed their behaviour.\n\nThe positive region acted as an anchor on the neuron\u2019s surface, while the negative regions remained mobile nearby. Treated neurons developed **longer, more branched neurites**, showed increased calcium activity and, after 14 days, formed more synapses.\n\nWhat makes this particularly interesting is that these materials **contain no biological signals designed to stimulate neurons**. Their architecture itself appears to produce the effect: the distribution of charges and the movement of the filaments may help recruit proteins already present around the cells.\n\nIn other words, the material does not carry a message.\n\n**Instead, it acts like a promoter at the entrance to a nightclub: it draws in certain proteins already present in the cellular environment, brings them close to the neuron and sets the stage for the right encounters.**<\/p>\n\n\n\n