Transmembrane transport in inorganic colloidal cell-mimics
Year: 2021
Journal: Nature, Volume 597, SEP 9, page 220
Authors: Xu, Zhe; Hueckel, Theodore; Irvine, William T. M.; Sacanna, Stefano
Hollow colloidal capsules, each with a single micropore, act as artificial cell-like structures that can capture and release payloads such as solid particles or bacteria from the external environment. A key aspect of living cells is their ability to harvest energy from the environment and use it to pump specific atomic and molecular species in and out of their system-typically against an unfavourable concentration gradient(1). Active transport allows cells to store metabolic energy, extract waste and supply organelles with basic building blocks at the submicrometre scale. Unlike living cells, abiotic systems do not have the delicate biochemical machinery that can be specifically activated to precisely control biological matter(2-5). Here we report the creation of microcapsules that can be brought out of equilibrium by simple global variables (illumination and pH), to capture, concentrate, store and deliver generic microscopic payloads. Borrowing no materials from biology, our design uses hollow colloids serving as spherical cell-membrane mimics, with a well-defined single micropore. Precisely tunable monodisperse capsules are the result of a synthetic self-inflation mechanism and can be produced in bulk quantities. Inside the hollow unit, a photoswitchable catalyst(6) produces a chemical gradient that propagates to the exterior through the membrane's micropore and pumps target objects into the cell, acting as a phoretic tractor beam(7). An entropic energy barrier(8,9) brought about by the micropore's geometry retains the cargo even when the catalyst is switched off. Delivery is accomplished on demand by reversing the sign of the phoretic interaction. Our findings provide a blueprint for developing the next generation of smart materials, autonomous micromachinery and artificial cell-mimics.
