Anisotropic Particles through Multilayer Assembly

Abstract

The anisotropy in the shape of polymeric particles has been demonstrated to have many advantages over spherical particulates, including bio‐mimetic behavior, shaped‐directed flow, deformation, surface adhesion, targeting, motion, and permeability. The layer‐by‐layer (LbL) assembly is uniquely suited for synthesizing anisotropic particles as this method allows for simple and versatile replication of diverse colloid geometries with precise control over their chemical and physical properties. This review highlights recent progress in anisotropic particles of micrometer and nanometer sizes produced by a templated multilayer assembly of synthetic and biological macromolecules. Synthetic approaches to produce capsules and hydrogels utilizing anisotropic templates such as biological, polymeric, bulk hydrogel, inorganic colloids, and metal–organic framework crystals as sacrificial templates are overviewed. Structure‐property relationships controlled by the anisotropy in particle shape and surface are discussed and compared with their spherical counterparts. Advances and challenges in controlling particle properties through varying shape anisotropy and surface asymmetry are outlined. The perspective applications of anisotropic colloids in biomedicine, including programmed behavior in the blood and tissues as artificial cells, nano‐motors/sensors, and intelligent drug carriers are also discussed.

Micro/Nanosystems for Magnetic Targeted Delivery of Bioagents

“…Besides spherical polymeric capsules, anisotropic LbL-assembled particles of micrometer and nanometer sizes have gained great attention. Kozlovskaya V. and Kharlampieva E. have recently summarized the most interesting results in the field demonstrating that anisotropy in shape results in shape-dependent chemical or physical properties of the vehicle and plays a crucial role in its interaction with various cell types [115]. Obviously, anisotropic LbL constructs are characterized by a more pronounced bio-mimetic behavior, improved deformation, and recovery properties, as well as by a shaped-directed flow, surface adhesion, and motion.…”

Nanoarchitectonics beyond perfect order – not quite perfect but quite useful

“…In addition, anisotropic particles with complex, non-spherical, and asymmetric structures are favored because of their unique advantages, such as anisotropic responses to external forces, anisotropic building blocks for complex structures, which makes them attractive in applications for drug delivery systems, cell culture, and biosensing. 241 For example, Marquis and co-workers adapted dimethyl carbonate as continuous phase, or deforming pre-gelled droplets off-chip at a fluid–fluid interface to synthesize pectin hydrogel microparticles with ellipsoid, torus or mushroom-type morphologies. The connection between microfluidic diffusion-induced self-assembly and surface porosity was revealed by the microstructure of the surface of pectin hydrogel microparticles.…”

Two-Dimensional and Three-Dimensional Ultrathin Multilayer Hydrogels through Layer-by-Layer Assembly

“…The covalent bonds can exist between the same polymer chains or different polymer components in the multilayer hydrogel . Advantageously, the LbL approach of the multilayer hydrogel fabrication can be translated to various geometries, including two-dimensional (2D) and three-dimensional (3D) substrates with spherical and nonspherical shapes. − Moreover, the multilayer hydrogel thickness can be easily and precisely tuned at the nanoscale by increasing the number of polymer layers during the multilayer assembly, while the varied elasticity can be achieved via varying the cross-linking degree . Unlike polymer brushes or self-assembled monolayers, multilayer hydrogels have a high loading capacity toward functional compounds because of the high surface area, which is particularly valuable for sensing and advanced drug delivery applications …”