CO2-breathing and piercing polymersomes as tunable and reversible nanocarriers

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.

Figure 1. Schematic illustration of CO₂-responsive vesicles with shape evolution.

Gas-sensitive structural transition of amphiphilic dendritic star-block terpolymers (top). Terpolymer self-assembly into vesicles, reversible gas-driven controlled self-assembly and shape transformation (bottom).

Figure 2. Self-assemblies of the terpolymer in its aqueous solution.

(a,b) TEM images of the self-assemblies at different magnifications and (c) DLS curve to show the size distribution of the self-assemblies.

Figure 3. Self-assemblies of the terpolymer in its aqueous solution under CO₂ stimulation.

TEM images of the self-assemblies after CO₂ treatment for (a,b) 20 min, (c,d) 30 min, and (e,f) 50 min at different magnifications and SEM image (g) after CO₂ treatment for 50 min. (h) Rh and zeta potential as a function of CO₂ aeration time in the period of 0–60 min.

Figure 4. Gas-controlled reversible morphological transition.

(a) Variation in the diameter and interfacial tension of the terpolymer self-assemblies upon alternating CO₂/N₂ stimulation. (b) SEM images of the self-assemblies after N₂ treatment.

Figure 5. Regional isomerization in the terpolymer.

(a) Schematic illustrations of the changes of the vesicular radius and internal regional isomerization on vesicle membrane under CO₂ stimulation. (b) DSC curves of 220P-star-PCL and 220P-star-PCL-b-PDEAEMA-b-PEG. (c,d) POM images of 220P-star-PCL (c) and 220P-star-PCL-b-PDEAEMA-b-PEG (d) crystallized at 45 °C.

Figure 6. Controlled release of RB from the vesicles.

(a) Fluorescence intensity at the wavelength of 580 nm as a function of time for vesicles containing RB with (red circles) or without (black squares) CO₂ stimulation and RB aqueous solutionin the prensence of CO₂ stimulation. Fluorescence emission spectra of (b) vesicle + RB without CO₂ stimulus and (c) vesicle + RB with CO₂ stimulation.