Layer-by-layer assembly of microcapsules and their biomedical applications

Abstract

Nanoengineered multifunctional capsules with tailored structures and properties are of particular interest due to their multifunctions and potential applications as new colloidal structures in diverse fields. Among the available fabrication methods, the layer-by-layer (LbL) assembly of multilayer films onto colloidal particles followed by selective template removal has attracted extensive attention due to its advantages of precise control over the size, shape, composition, wall thickness and functions of the obtained capsules. The past decade has witnessed a rapid increase of research concerning the new fabrication strategies, functionalization and applications of this kind of capsules, particularly in the biomedical fields such as drug delivery, biosensors and bioreactors. In this critical review, the very recent progress of the multilayer capsules is summarized. First, the advances in assembly of capsules by the LbL technique are introduced with focus on tailoring the properties of hydrogen-bonded multilayer capsules by cross-linking, and fabrication of capsules based on covalent bonding and bio-specific interactions. Then the fabrication strategies which can speed up capsule fabrication are reviewed. In the following sections, the multi-compartmental capsules and the capsules that can transform their shape under stimulus are presented. Finally, the biomedical applications of multilayer capsules with particular emphasis on drug carriers, biosensors and bioreactors are described (306 references).

Influence of charge on encapsulation and release behavior of small molecules in self-assembled layer-by-layer microcapsules

“…The sequential adsorption of polyelectrolytes results in LbL assembled film. Adsorption of polymers on a planar template results in macroscopic LbL assembled planar film (Decher et al, 1992;Kleinfeld & Ferguson, 1994), whereas, LbL film coated on colloidal template results in a three-dimensional nano-and microcapsule (Peyratout & Dahne, 2004;Tong et al, 2012). Upon adsorption of desired number of layers, core template is disintegrated to obtain a core-shell capsular structure (Ibarz et al, 2002;Antipov et al, 2003).…”

“…Upon adsorption of desired number of layers, core template is disintegrated to obtain a core-shell capsular structure (Ibarz et al, 2002;Antipov et al, 2003). LbL assembly has been shown to have control over the size, shell thickness, factors influencing the encapsulation of molecules, controlled release, stimuli responsive release and stability of encapsulated molecules (Peyratout & Dahne, 2004;Tong et al, 2012).…”

Evolution of enzyme catalysts caged in biomimetic gel-shell beads

“…For example, compartments can be built from scratch as mimics that resemble cells in their ability to control access by a semipermeable perimeter compartmentalizing multiple components. Means to construct such functional systems are provided, for example, by polyelectrolyte multilayer technology that is based on the stepwise adsorption of oppositely charged poly-ions on templates 5,6 , so that semipermeability and selective retention of cell-like compartments can be rationally engineered [7][8][9][10][11][12][13] . Nature relies on Darwinian evolution to create or improve functional molecules.…”

Light-controlled drug releasing polymer films combining LbL self-assembly and host-guest interactions

“…Based on this principle, light-responsive host-guest assembly and disassembly between Azo and CD hold great potential to design a reversible drug delivery profile [16,17]. Layer-by-layer (LbL) self-assembly approach is particularly well-suited for fabricating functional multilayer thin films with ultrafine nanometer-scale structure for use as drug delivery vehicles [18][19][20][21]. The traditional means of loading drugs on layers of LbL platform always uses physical adsorption or chemical bonding.…”