Design and synthesis of organic–inorganic hybrid capsules for biotechnological applications

Abstract

Organic-inorganic hybrid capsules, which typically possess a hollow lumen and a hybrid wall, have emerged as a novel and promising class of hybrid materials and have attracted enormous attention. In comparison to polymeric capsules or inorganic capsules, the hybrid capsules combine the intrinsic physical/chemical properties of the organic and inorganic moieties, acquire more degrees of freedom to manipulate multiple interactions, create hierarchical structures and integrate multiple functionalities. Thus, the hybrid capsules exhibit superior mechanical strength (vs. polymeric capsules) and diverse functionalities (vs. inorganic capsules), which may give new opportunities to produce high-performance materials. Much effort has been devoted to exploring innovative and effective methods for the synthesis of hybrid capsules that exhibit desirable performance in target applications. This tutorial review firstly presents a brief description of the capsular structure and hybrid materials in nature, then classifies the hybrid capsules into molecule-hybrid capsules and nano-hybrid capsules based upon the size of the organic and inorganic moieties in the capsule wall, followed by a detailed discussion of the design and synthesis of the hybrid capsules. For each kind of hybrid capsule, the state-of-the-art synthesis methods are described in detail and a critical comment is embedded. The applications of these hybrid capsules in biotechnological areas (biocatalysis, drug delivery, etc.) have also been summarized. Hopefully, this review will offer a perspective and guidelines for the future research and development of hybrid capsules.

Polymer–inorganic microcapsules fabricated by combining biomimetic adhesion and bioinspired mineralization and their use for catalase immobilization

“…The main shortcomings for industrial application of enzymes are the operation instability and recycling difficulty, which can be overcome through enzyme immobilization [3]. Among numerous immobilization carriers [4][5][6][7][8][9], microcapsules with a semi-permeable wall and a lumen have gained great attention and already been utilized as an enzyme bioreactor. Theoretically, the capsule lumen could be loaded with a large quantity of enzymes, whereas the semi-permeable capsule wall could allow the diffusion of substrate(s) and product(s) [6].…”

“…Among numerous immobilization carriers [4][5][6][7][8][9], microcapsules with a semi-permeable wall and a lumen have gained great attention and already been utilized as an enzyme bioreactor. Theoretically, the capsule lumen could be loaded with a large quantity of enzymes, whereas the semi-permeable capsule wall could allow the diffusion of substrate(s) and product(s) [6]. In general, ideal microcapsules for constructing an enzyme bioreactor should possess good biocompatibility, moderate hydrophilicity, suitable wall structures, and robust mechanical stability.…”

Multi-layer microcapsules: fresh insights and new applications

“…The silica surface can adsorb different small molecules and prevent the leakage of low-molecular-weight chemicals from microcapsules. In addition, silica is nontoxic and can be dissolved in biological environments [5]. These hybrid microcapsules with the ability to encapsulate small-molecule drugs can also be synthesized through LbL assembly of PE, inorganic nanoparticles (INPs), and graphene oxide (GO) (Figure 1(c,d)) [7,8].…”

“…Attempts to use hydrophobic polymers such as polylactic acid, for multilayer shell build-up in nonaqueous solution, could reduce the permeability, but probably not enough to retain small molecules. Alternatively, introduction of inorganic structures into LbL microcapsules can generate impermeable capsules with high mechanical strength [5]; such hybrid microcontainers combining the physicochemical properties of organic and inorganic components can extend their applications in drug delivery systems (DDSs).…”

Design and Construction of Hybrid Microcapsules with Higher‐Order Structure and Multiple Functions

“…In this regard, polymer/inorganic nanocomposite particles with various morphologies are by far the most common and most studied system. The combination of organic polymers with inorganic materials in a competitive and promising way can remarkably alter the practical performance like chemical, mechanical, optical, electrical, rheological, and surface properties 19, 20, 21. Therefore, the incorporation of inorganic nanoparticles into the membrane can endow the generated proteinosomes with some advanced inorganic nanoparticle functionalities (e.g., luminescent, magnetic, and catalytic properties) 22, 23.…”