Thermo‐Responsive Microcapsules with Tunable Molecular Permeability for Controlled Encapsulation and Release

Abstract

Microcapsules with regulated transmembrane transport are of great importance for various applications. The membranes with a tunable cut‐off threshold of permeation provide advanced functionality. Here, thermo‐responsive microcapsules are designed, whose hydrogel membrane shows a tunable cut‐off threshold of permeation with temperature. To produce the microcapsules, water‐in‐oil‐in‐water (W/O/W) double‐emulsion droplets are microfluidically produced, whose oil shell contains oil‐soluble hydrogel precursor of poly(N, N‐diethylacrylamide) copolymerized with benzophenone (PDEAM‐BP). The PDEAM hydrogels, crosslinked by BP, show volume‐phase transition around 34 °C, which makes the microcapsules with the PDEAM hydrogel membrane thermo‐responsive. The microcapsules show temperature‐dependent changes in radius and membrane thickness. More importantly, the cut‐off threshold of permeation can be reversibly adjusted by temperature control as the degree of swelling decreases with temperature. This enables the molecule‐selective encapsulation and the controlled release of the encapsulants in a programmed manner by adjusting the temperature. The microcapsules can be rendered to be photo‐responsive by encapsulating photothermal polydopamine nanoparticles during the microfluidic operation, which allows the control of the degree of swelling with near‐infrared (NIR) irradiation. The thermo‐ and photo‐responsive microcapsules with a tunable cut‐off threshold are appealing as a new platform for drug carriers, microreactors, and microsensors.

Spatiotemporal control of signal-driven enzymatic reaction in artificial cell-like polymersomes

“…To further confirm this, we estimate the permeability by adapting the simplified solution of Fick’s law 31 , and fitting the normalized fluorescence intensity change acquired from Fig. 1d, e as detailed in the Methods section.…”

“…The permeability of each fluorescent dye molecule was estimated by adapting the simplified solution of Fick’s law and fitting the normalized fluorescence intensity change (I(t)/I(0)) data from Fig. 1d, e , which is related to the normalized concentration change of the diffusing species, C(t)/C(0) 28 , 31 . The permeability of each fluorescent dye molecule ( P ) can be calculated using the following relation: where the R is the average radius of polymersome.…”

Recent advances in the microfluidic production of functional microcapsules by multiple-emulsion templating

“…Polymers can be modified with benzophenone, which enables their crosslinking by ultraviolet exposure in the absence of a photoinitiator through self-initiation. 56 For example, poly( N , N -diethylacrylamide) with lower critical solution temperature (LCST) was modified with benzophenone (PDEAM-BP) dissolved in an organic solvent. This solution was used as the oil phase of W/O/W double-emulsion drops and the polymers were cross-linked by ultraviolet irradiation after the evaporation of the organic solvent to make a network of poly( N , N -diethylacrylamide).…”

“…For example, polymeric shells produced by the consolidation of PDEAM-BP were further stabilized by photocrosslinking. 56,68 Stable shells could also be produced by photopolymerization in the presence of an organic solvent followed by consolidation for a mixture of poly(propylene glycol) diacrylate (PPGDA) and zinc-neutralized poly(acrylic acid- co -butyl acrylate) (Zn-p(AA- co -BA)) ionomer in an organic solvent. 69 The photo-polymerization created a crosslinked network of PPGDA molecules by the formation of covalent bonds.…”

“…Recently, PDEAM-BP was used to make thermo-responsive shells from W/O/W double-emulsion drops. 56 PDEAM itself is hydrophilic, but PDEAM-BP is hardly soluble in water above its LCST and soluble in chloroform owing to the hydrophobicity of BP. The PDEAM shells crosslinked by BP showed a reversible volume-phase transition depending on the temperature near its LCST of around 34 °C.…”