Artificial Organelles with Orthogonal‐Responsive Membranes for Protocell Systems: Probing the Intrinsic and Sequential Docking and Diffusion of Cargo into Two Coexisting Avidin–Polymersomes

Abstract

The challenge of effective integration and use of artificial organelles with orthogonal‐responsive membranes and their communication in eukaryotic protocells is to understand the intrinsic membrane characteristics. Here, a novel photo‐crosslinked and pH‐responsive polymersome (Psome B) with 2‐(N,N′‐diisopropylamino)ethyl units in the membrane and its respective Avidin‐Psome B hybrids, are reported as good candidates for artificial organelles. Biotinylated (macro)molecules are able to dock and diffuse into Avidin‐Psome B to carry out biological activity in a pH‐ and size‐dependent manner. Combined with another polymersome (Psome A) with 2‐(N,N′‐diethylamino)ethyl units in the membrane, two different pH‐responsive polymersomes for mimicking different organelles in one protocell system are reported. The different intrinsic docking and diffusion processes of cargo (macro)molecules through the membranes of coexisting Psome A and B are pH‐dependent as confirmed using pH titration–dynamic light scattering (DLS). Psome A and B show separated “open”, “closing/opening”, and “closed” states at various pH ranges with different membrane permeability. The results pave the way for the construction of multicompartmentalized protocells with controlled communications between different artificial organelles.

Feedback-Induced and Oscillating pH Regulation of a Binary Enzyme–Polymersomes System

“…38−45 Importantly, pH* of empty Psomes A is 6.5 and that of empty Psomes B is 5.5. 45 The difference in pH* is determined by the different pK a values of DEAEMA (7.0−7.3) and DPAEMA (∼6.0), and pH* is always triggered by environmental conditions.…”

“…To realize our FOPRP, two amphiphilic and photo-cross-linkable pH-responsive block copolymers BCP-A − and BCP-B were synthesized via atom-transfer radical polymerization (ATRP) (Figures S1–S5, details of BCP-A and BCP-B fabrication and characterization in the Supporting Information (SI)). For BCP-A (Figure a), the pH-responsive 2-( N , N ′-diethylamino)­ethyl methacrylate (DEAEMA) and photo-cross-linker 4-(3,4-dimethylmaleimidio)­butyl methacrylate (DMIBMA) are integrated into the hydrophobic part of block copolymer, possessing a hydrophilic PEG tail (Figure a).…”

“…BCP-B consists of PEG in the hydrophilic block and the pH-responsive 2-( N , N ′-diisopropylamino)­ethyl methacrylate (DPAEMA) as well as the UV-active photo-cross-linker 6-(3,4-dimethylmaleimidio)­hexyl methacrylate (DMIHMA) in the hydrophobic block (Figure a). We have previously reported that BCP-A and BCP-B self-assemble into two different pH-responsive polymersomes with specific pH* values (= half power of polymersome swelling) by the pH switch method and subsequential cross-linking under UV irradiation. − Importantly, pH* of empty Psomes A is 6.5 and that of empty Psomes B is 5.5 . The difference in pH* is determined by the different p K a values of DEAEMA (7.0–7.3) and DPAEMA (∼6.0), and pH* is always triggered by environmental conditions.…”

“…The characterization of molar mass, size, and conformational properties of polymeric vesicles by asymmetrical flow-field flow fractionation with light scattering detection (AF4-LS) is well-established. ,− Previously, AF4-LS studies on Psomes A and GOx-Psomes A were reported . First, Psomes morphology was studied at pH 7 and 5 (Figures S13 and S14).…”

“…The aim of the study was to introduce the coupled glucose–GOx reaction and urea–urease reaction in our recently established photo-cross-linked polymersomes A (Psomes A) and B (Psomes B) system to form a binary, artificial organelles system (AOS) with orthogonal-responsive membranes and feedback-induced and oscillating pH-regulating ability (Figure ). The different pH responsiveness of Psomes A − and B should finally trigger the different states (I–VI) of “collapsed”, “closing/opening”, and “open” in the feedback-induced and oscillating pH regulation process of AOS (Figure ).…”