Charge-Controlled Permeability of Polyelectrolyte Microcapsules

Abstract

Multilayer microcapsules showing unique charge-controlled permeability have been successfully fabricated by employing poly(styrene sulfonate) (PSS)-doped CaCO3 particles as templates. Encapsulation of the PSS molecules is thus achieved after core removal. Scanning force microscopy (SFM), UV-vis, Raman spectroscopy, and zeta-potential confirm the existence of the PSS molecules in the CaCO3 particles and the resultant microcapsules, which are initially incorporated during the core fabrication process. A part of these additionally introduced PSS molecules interacts with PAH molecules residing on the inner surface of the multilayer wall to form a stable complex, while the other part is intertwined in the capsule wall or in a free state. Capsules with this structure possess many special features, such as highly sensitive permeability tuned by probe charge and environmentally controlled gating. They can completely reject negatively charged probes, but attract positively charged species to form a higher concentration in the capsule interior, as evidenced by confocal microscopy. For example, the capsules completely exclude dextran labeled with fluorescein isothiocyanate (FITC-dextran), but are permeable for dextran labeled with tetramethylrhodamine isothiocyanate (TRITC-dextran) having similar molecular mass (from 4 to 70 kDa), although there are only few charged dyes in a dextran chain. By reversing the charge of the probes through pH change, or by suppressing charge repulsion through salt addition, the permeation can be readily switched for proteins such as albumin or small dyes such as fluorescein sodium salt.

Release of Insulin from Calcium Carbonate Microspheres with and without Layer-by-Layer Thin Coatings

“…The significant variations in the amounts of released insulin from uncoated CaCO 3 microspheres at 300 and 360 min may result from the fact that a burst release of insulin occurred at this stage after Number of bilayers ζPotential / mV induction period. The effects of the LbL film coating and its thickness on the stability and permeability of ions and drugs have been reported [29][30][31][32][33][34]. However, the suppressive effect of the film coatings on the release is more clearly demonstrated here for insulin, probably because of the large size of the protein drug.…”

Freestanding Nanostructures via Layer‐by‐Layer Assembly

“…Polyelectrolyte multilayered microcapsules can be precisely controlled by changing various parameters such as the solution pH, ionic strength, salt concentration, temperature, light, and magnetic field. [35,[73][74][75][76][77] Considering that several recent reviews have already discussed the fabrication, properties, and permeability of LbL microcapsules in great detail, here we restrict ourselves to reviewing some very recent results. [37][38][39][78][79][80] The micromechanical properties of LbL microcapsules filled with polyelectrolyte solutions have been investigated by Vinogradova and co-workers.…”

“…[122] Gao and co-workers have also used CLSM to study microcapsules. [74] Vinogradova et al have measured the Young's modulus of DNA/PAH microcapsules by deformation experiments, and found the Young's modulus values to be in the 100 MPa range. [115] Kharlampieva and Sukhishvili have shown an interesting interplay between hydrogen-bonding and electrostatic interactions in hybrid polymer multilayers.…”

“…For example, CLSM can be used to study the micromechanical properties and permeability of deformed LbL microcapsules using fluorescence markers in liquids. [74,122] Raman scattering is another powerful technique for monitoring the internal stresses and conformational changes in deformed nanostructures. [127][128][129] Surface-enhanced Raman scattering (SERS) can also be utilized to study freestanding LbL structures containing gold and silver nanorods, nanowires, and tubules.…”

Polymeric Hydrogel Nanocapsules: A Thermo and pH Dual-responsive Carrier for Sustained Drug Release

“…Compared to analogous PAAPNIPAm polymer particles [34,38], the PAA-PNIPAm hydrogel capsules show higher loading capacity for Dox. The high loading of Dox in the PAA-PNIPAm hydrogel capsules may arise from the charge controlled permeability mechanism, i.e., negatively charged PAA in the capsules shell at neutral medium induces positively charged Dox to penetrate through the capsule shell and then deposit spontaneously into the interior of the capsules [39,40]. As previously reports, the incubation process usually exhibited lower loading capacity compared to the encapsulation method.…”