Onion-like multilayered polymer capsules synthesized by a bioinspired inside-out technique

Abstract

Diverse structures in nature, such as the spinal disc and the onion have many concentric layers, and are created starting from the core and proceeding outwards. Here, we demonstrate an inside-out technique for creating multilayered polymer capsules. First, an initiator-loaded gel core is placed in a solution of monomer 1. The initiator diffuses outward and induces polymerization, leading to a shell of polymer 1. Thereafter, the core-shell structure is loaded with fresh initiator and placed in monomer 2, which causes a concentric shell of polymer 2 to form around the first shell. This process can be repeated to form multiple layers, each of a distinct polymer, and of controlled layer thickness. We show that these multilayered capsules can exhibit remarkable mechanical resilience as well as stimuli-responsive properties. The release of solutes from these capsules can be tailored to follow specific profiles depending on the chemistry and order of adjacent layers.

Catechol‐Based Molecular Memory Film for Redox Linked Bioelectronics

“…Due to its unique properties, this chitosan-agarose hydrogel has gained increasing attention in materials science. [23][24][25][26][27][28] The memory-film is formed by: (i) casting a blend of chitosan (1.5%) and agarose (1%) onto an indium tin oxide (ITO) electrode; and (ii) electrochemically grafting catechol [29] by immersing the hydrogel coated electrode into a catechol solution (10 × 10 −3 m catechol in phosphate buffer, pH 7.0) and applying an anodic voltage (1.2 V vs Ag/AgCl; various times up to 30 min) for a controlled charge transfer (Q fab = ∫idt). As illustrated in Figure 1a, we adapted the informal nomenclature that is commonly used in the literature to abbreviate chitosan (Chit) and distinguish its two states: the positively charged protonated state (Chit-H + ) and the deprotonated neutral state (Chit 0 ).…”

Multi-Layered Hydrogels for Biomedical Applications

“…This kind of biocompatible multi-layered cellulose hydrogel with controlled architecture has bright application prospects in biomedical application. Zarket and Raghavan developed a novel strategy to constructed onion-like hydrogels in an inside-out fashion (Zarket and Raghavan, 2017 ). Normally, a precursor hydrogel core within water-soluble initiator was prepared first, and then was immersed into a solution containing a monomer (monomer A) and a cross-linker.…”

Under Diffusion Control: from Structuring Matter to Directional Motion

“…(top) pH‐responsive capsule based on the ion‐dependent swelling‐deswelling properties of DMAA‐SA and (bottom) temperature‐responsive capsule based on the LCST property of NIPA. Reproduced with permission . Copyright 2017, Nature Publishing group.…”

“…Recently, a similar approach has been used to synthetize onion‐like capsules composed of alternating layers of poly‐ N , N ′‐dimethylacrylamide‐sodium acrylate (PDMAA‐SA) and poly‐ N ‐isopropyl acrylamide (PNIPAAm) around alginate or chitosan cores. The two polymers are capable of responding to pH and temperature changes, respectively (Figure c) . Different combinations of the polymers in the layer sequence allowed for a) two‐zone independent swelling along the capsule radius and b) implementation of a temperature‐dependent molecular release having a two‐step profile.…”