Abstract
Some marine plankton called dinoflagellates emit light in response to the movement of surrounding water, resulting in a phenomenon called milky seas or sea sparkle. The underlying concept, a shear‐stress induced permeabilisation of biocatalytic reaction compartments, is transferred to polymer‐based nanoreactors. Amphiphilic block copolymers that carry nucleobases in their hydrophobic block are self‐assembled into polymersomes. The membrane of the vesicles can be transiently switched between an impermeable and a semipermeable state by shear forces occurring in flow or during turbulent mixing of polymersome dispersions. Nucleobase pairs in the hydrophobic leaflet separate when mechanical force is applied, exposing their hydrogen bonding motifs and therefore making the membrane less hydrophobic and more permeable for water soluble compounds. This polarity switch is used to release payload of the polymersomes on demand, and to activate biocatalytic reactions in the interior of the polymersomes.
Highlights
Many biological processes are intimately related to mechanical stimulation.[1]
Block copolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of 95 mol % hexyl methacrylate and 5 mol % pentafluorophenyl methacrylate from a PEG-based chain transfer agent
A 1:1 mixture of the two amphiphilic block copolymers that carried either adenine or thymine in their hydrophobic block was self-assembled into polymersomes, yielding uni- and multi-compartmental vesicles (ADEN/THYM polymersomes) (Characterisation of polymersomes: Figure 1 and Supporting Information 4)
Summary
Many biological processes are intimately related to mechanical stimulation.[1]. For instance, the sense of touch, hearing, proprioception, and the control of blood pressure are regulated by mechanically responsive proteins that control the flux of ions and other molecules across cell membranes.[2]. Bio-inspired artificial systems that take this concept as a blueprint are nanoreactors that can be activated by changing the permeability of the reactor shell through mechanical forces This would allow to switch on chemical reactions on demand by shear stress that is generated, e.g., in flow conditions or during turbulent stirring, and allow to pursue new concepts in catalytic systems engineering. We functionalised amphiphilic block copolymers with a small percentage of nucleobases in their hydrophobic block producing complementary polymers that were self-assembled into polymersomes The membrane of these vesicles should be impermeable to water soluble compounds when the nucleobases are paired and permeable when the base pairs are cleaved by mechanical stimulation. By encapsulating enzymes into the vesicles, biocatalytic nanoreactors were obtained that could be transiently switched on by hydrodynamic shear stress, for example, to start bioluminescence reactions
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