Marine glow is a beautiful example for a response of living organisms to mechanical forces. It is caused by dinoflagellates that get stimulated by turbulences in the water and then produce light in a bioluminescence reaction. However, nature counts with billions of years of evolution and more simple approaches must be employed for biomimicry. Because the membrane of polymersomes consists of two hydrophilic layers that enclose a hydrophobic one, polymersomes are simple mimics of the lipid membrane of cells and organelles. In order to prepare mechano-responsive polymersomes that change the permeability of their membrane in response to a mechanical stimulus, we took advantage of the mechanically induced melting of DNA. To this end, amphiphilic block copolymers were synthesized by RAFT polymerisation and the hydrophobic block was then functionalised with the complementary nucleobases adenine and thymine. The resulting PEG-b-poly(hexyl methacrylate-co-thymine methacrylate) and PEG-b-poly(hexyl methacrylate-co-adenine methacrylate) were self-assembled into polymersomes. Adenine and thymine formed hydrogen bonds which could be disrupted by applying shear forces. Thus, the polar nucleobases were exposed to the polymer matrix, which increased the polarity of the hydrophobic leaflet and therefore changed the permeability of the membrane. This permitted the exchange of substrates across the membrane. Horseradish peroxidase was encapsulated into the force-responsive polymersomes. The resulting nanoreactors could be switched on by shearing the polymersome suspension. Luminol reacted with hydrogen peroxide in the presence of horseradish peroxidase containing polymersomes. As a result, luminescence was observed when shear was applied to the system. Therefore, these nanoreactors mimic the dinoflagellate marine glow and could find applications in the shear-induced release of active reagents and drugs.

Marine glow biomimicry by nucleobase-containing shear responsive polymersome nanoreactors

254th National Meeting (2017)

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