Abstract
Despite numerous studies on utilizing polymeric vesicles as nanocapsules, fabrication of tunable molecular pathways on transportable vesicle walls remains challenging. Traditional methods for building penetrated channels on vesicular membrane surface often involve regulating the solvent polarity or photo-cross-linking. Herein, we developed a neat, green approach of stimulation by using CO2 gas as “molecular drill” to pierce macroporous structures on the membrane of polymersomes. By simply introducing CO2/N2 gases into the aqueous solution of self-assemblies without accumulating any byproducts, we observed two processes of polymeric shape transformation: “gas breathing” and “gas piercing.” Moreover, the pathways in terms of dimension and time were found to be adjustable simply by controlling the CO2 stimulation level for different functional encapsulated molecules in accumulation, transport, and releasing. CO2-breathing and piercing of polymersomes offers a promising functionality to tune nanocapsules for encapsulating and releasing fluorescent dyes and bioactive molecules in living systems and also a unique platform to mimic the structural formation of nucleus pore complex and the breathing process in human beings and animals.
Highlights
We designed and synthesized an amphiphilic dendritic star-block terpolymer with the ‘graft onto’ strategy using the combination of ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), and click chemistry
We used the nanoprecipitation method to prepare the polymer aqueous solution: 30 mg of the terpolymer were first dissolved in 1 mL THF, a good solvent to all the blocks; 9 mL deionized water was injected at a slow rate of 0.9 mL/h to yield a translucent colloidal solution, and the organic phase was removed by dialysis
Polymer vesicles were stained with phosphotungstic acid (PTA) hydrate
Summary
We designed and synthesized an amphiphilic dendritic star-block terpolymer with the ‘graft onto’ strategy using the combination of ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), and click chemistry. The biodegradable, semi-crystalline PCL with a low glass transition temperature (Tg) of ~− 60 °C was selected to explore new morphologies. This amphiphilic terpolymer can self-assemble into vesicular nanostructures in aqueous solutions with unique properties. When CO2 was introduced into the terpolymer aqueous solution, the PDEAEMA block was gradually protonated, leading to successive variation of the amphiphilic balance and continuous self-expansion of the polymersomes. With stepwise tuning of the CO2 level, the membrane structure and permeability were modulated and macroporous vesicles were observed. Besides serving as nanocarriers in living systems, the vesicles with the ability of shape evolution are in many ways reminiscent of the structure of nucleus pore complex
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