Bioinspired Viscoelastic Capsules: Delivery Vehicles and Beyond

Abstract

range of rheological properties of capsulecontaining solutions that can be accessed; the formulation of capsule-based solutions displaying a pronounced shear thinning or a yield stress would be key to use them as 3D printable inks. Capsules with much thinner, flexible shells whose structure and surface composition can be varied over a wide range can be fabricated from emulsion drops by solidifying reagents at their surface. This can be achieved, if appropriate reagents are dispersed in the drop and complementary ones in the continuous phase. Once these reagents meet at the drop surface, they solidify through polymerization [21][22][23] or coacervation reactions. [24][25][26][27] Capsules with thin shells can also be produced from a single type of reagent, namely from chemically reactive surfactants, that are cross-linked at the drop surface. [28][29][30][31][32] However, the number of reagents that can be employed to form thin polymeric capsules through these approaches is limited. Flexible capsules that display a narrow size distribution, low permeability toward encapsulants, allow controlled exchanges of reagents, and are mechanically sufficiently stable to withstand significant shear stresses such that they can be processed into macroscopic materials through additive manufacturing techniques remain to be established. These capsules would open up a new field of their use as principal building blocks of macroscopic granular materials with well-defined micrometer-sized structures and locally varying compositions that go far beyond their current use as individually dispersed delivery vehicles.Here, we introduce a new type of viscoelastic, mechanically stable capsules that are composed of bioinspired ionically crosslinked catechol-functionalized block-copolymer surfactants. These capsules present Fe 3+ complexed catechols at their surface such that they have a high affinity to each other. Therefore, they cannot only be used as individually dispersed mobile carrier vehicles that enable triggered release of reagents, but also as principal building blocks of macroscopic soft materials. We demonstrate for the first time that these capsules are mechanically sufficiently stable to serve as principal building blocks of inks that can be 3D printed into macroscopic granular materials with well-defined micrometer-length-scale structures.Emulsion drops are often stabilized with polymeric surfactants that are crucial during drop production and storage. However, once the drops are converted into capsules, surfactants are usually superfluous or even devastating because they irreproducibly change the surface wettability of the Microcapsules are often used as individually dispersed carriers of active ingredients to prolong their shelf life or to protect premature reactions with substances contained in the surrounding. This study goes beyond this application and employs microcapsules as principal building blocks of macroscopic 3D materials with well-defined granular structures. To achieve this goal and inspired by nature, capsules ...

Current Advances of Hollow Capsules as Controlled Drug Delivery Systems

“…The outside layer of the capsule comprises of hydrophilic segments that cover the interior hydrophobic segments. [15][16][17] Over the last decade, different techniques have been used to assist the fabrication of polymersomes such as oil-in-water (O/W) emulsion, [18][19][20][21] and double emulsions (W/O/ W). [22][23][24] Even though the use of these techniques to generate polymeric vesicle is quite simple and easy to conduct, the uniformity and the size of obtained polymersomes are still challenging.…”

From vesicles to materials: bioinspired strategies for fabricating hierarchically structured soft matter

“…Compartments are easier to be processed into superstructures if they are mechanically strengthened prior to their assembly, for example, by transforming them into microcapsules or microparticles. Reagent-loaded microgels [116] and microcapsules [117] can be transferred into aqueous media where they are up-concentrated to undergo a rapid liquid-solid transformation. This liquid-solid transformation enables the jammed compartments to be three-dimensionally printed into macroscopic granular materials.…”

Bioinspired Eggosomes with Dual Stimuli-Responsiveness

“…Recently, micro- and nanoscale containers have attracted great interest due to their diverse range of applications in various industrial products, including pharmaceuticals, biomedical devices, functional foods, and agricultural treatments, especially in the field of drug delivery. − These miniature devices are used to protect active ingredients from degradation during storage but then release them at the required site of action . In the food industry, these tiny containers are being used to fortify foods with bioactive agents, such as vitamins, minerals, and nutraceuticals. , The composition, dimensions, shape, and surface characteristics of these microcontainers can be controlled so that their functional performance can be tailored for specific applications.…”