Fig. 5.
Self-induced capture of proteinosomes by enzyme-mediated vesicle-to-coacervate transitions. a Graphic showing restructuration of a mixed population of proteinosomes (green) containing encapsulated GOx (blue circle) and urease (Uase, grey circle) in the presence of non-encapsulated fatty acid vesicles (red) containing HRP (yellow circle) (state 1) into a nested proteinosome-in-coacervate micro-architecture (state 2) after addition of urea, followed by transformation into a vesicle-in-proteinosome structure (state 3) after addition of glucose. b Time-dependent plot showing sequential increase in pH after addition of 20 mM urea (at t1 = 0, black squares) to a mixed population of fatty acid vesicles and urease/GOx-containing proteinosomes, and associated rapid increase in absorbance (purple circles) due to the transformation of vesicles into micelle coacervate micro-droplets above pH 8.9. Subsequent addition of 10 mM glucose (at t2 = 0) produces a decrease in pH, and an associated rapid decrease in absorbance due to disassembly of the micelle coacervate droplets into vesicles below pH 8.9. The conversion from state 1 to 3 as labelled in a is highlighted. c–f Time series of optical microscopy images showing self-induced capture of a urease/GOx-containing proteinosome (arrow) via urease-mediated transformation of fatty acid vesicles into micelle coacervate droplets in the presence of urea (20 mM; time t0) (see Supplementary Movie 4). Scale bars, 50 μm. g–j As for c–f, but imaged by confocal fluorescence microscopy showing single proteinosome (white arrow) and vesicles (g) followed by formation of fatty acid coacervate droplets and initial stages of wetting of the urease/GOx-containing proteinosome 20 min after addition of urea (h). Capture of the proteinosome occurs via the interfacial coalescence of several coacervate droplets (i, j); scale bars, 50 μm. k, l Confocal fluorescence microscopy images of a single urease/GOx-containing FITC-labelled proteinosome (green fluorescence) in the presence of RITC-HRP-loaded fatty acid vesicles before (k) and after (l) sequential addition of urea (20 mM, 180 min) and glucose (10 mM, 240 min). Initially, vesicles containing RITC-HRP (red fluorescence) are excluded from the proteinosome lumen (ratio of red fluorescence inside vs. outside the proteinosomes, IIN/IOUT = 0.5 ± 0.1), whilst after enzyme-mediated pH-induced host–guest protocell assembly and reconfiguration, many of the vesicles are located along with their payload in the proteinosome interior (IIN/IOUT = 2.1 ± 0.1); scale bars, 50 μm