Polyelectrolyte Multilayered Capsules as Biomedical Tools

Abstract

Polyelectrolyte multilayered capsules (PEMUCs) obtained using the Layer-by-Layer (LbL) method have become powerful tools for different biomedical applications, which include drug delivery, theranosis or biosensing. However, the exploitation of PEMUCs in the biomedical field requires a deep understanding of the most fundamental bases underlying their assembly processes, and the control of their properties to fabricate novel materials with optimized ability for specific targeting and therapeutic capacity. This review presents an updated perspective on the multiple avenues opened for the application of PEMUCs to the biomedical field, aiming to highlight some of the most important advantages offered by the LbL method for the fabrication of platforms for their use in the detection and treatment of different diseases.

Keywords: biomedical; capsules; controlled release; drug delivery; layer-by-layer; multilayers; polyelectrolyte.

Figure 1

Sketch representing the use of dip-coating deposition for the fabrication of LbL materials using a negatively charged flat substrate as template. Reprinted from Mateos-Maroto et al. [42], with permission under Open access CC BY 4.0 license, https://creativecommons.org/licenses/by/4.0/ (accessed 20 January 2021).

Figure 2

Schematic representation of the most common methodologies used for fabricating PEMUCs using colloidal particles as templates. Reprinted from Yan et al. [52], Copyright (2014), with permission from American Chemical Society.

Figure 3

Sketch of the fabrication of PEMUCs using immobilized colloids as templates. The different letters indicate the different steps of the process. (a) Immersion of the immobilized colloid into the first layering solution and subsequent rinsing (the rinsing step is not shown for simplicity). (b) Immersion on the second layering solution and subsequent rinsing. (c) The coated colloids are recovered from the agarose matrix. The steps (a,b) are repeated until the desired number of layers is obtained. Reprinted from Richardson et al. [74], Copyright (2013), with permission from John Wiley and Sons.

Figure 4

Sketch representing the experimental approach for the assembly process of LbL PEMUCS using a tubular reactor. Reprinted from Elizarova et al. [80], Copyright (2016), with permission from Elsevier.

Figure 5

Sketch representing an experimental configuration for the assembly of LbL PEMUCS using a microfluidic device. (a) General view representing the inputs and outputs of the assembly process. (b) Expanded view of the process of deposition of one bilayer. Reprinted from Kantak et al. [88], Copyright (2011), with permission from The Royal Society of Chemistry.

Figure 6

Idealized representation of the dependences of the adsorbed amount on the number of bilayers for LbL polyelectrolyte multilayers undergoing linear and non-linear growth. Reprinted from Mateos-Maroto et al. [42], with permission under Open access CC BY 4.0 license, https://creativecommons.org/licenses/by/4.0/ (accessed 20 January 2022).

Figure 7

Change in the ξ potential with the alternate deposition of PAH and PSS layers onto positively charged liposomes with different charge density (indicated by %DODAB) from polyelectrolyte solutions with concentration 1 g/L, and ionic strength fixed at 10 mM. Reprinted from Mateos-Maroto et al. [71], Copyright (2021), with permission from American Chemical Society.

Figure 8

Idealized representation of polyelectrolyte layers and counterions in polyelectrolyte multilayers presenting intrinsic and extrinsic compensation mechanisms. Reprinted from Mateos-Maroto et al. [42], with permission under Open access CC BY 4.0 license, https://creativecommons.org/licenses/by/4.0/ (accessed 20 January 2022).

Figure 9

Idealized representation of the fabrication procedure used for obtaining multicapsules. Reprinted with permission from Städler et al. [150], Copyright (2009), American Chemical Society.

Figure 10

Sketch representing a general perspective of the encapsulation using the RP-LbL approach. Reprinted from Mak al. [179], Copyright (2009), with permission from American Chemical Society.

Figure 11

Scheme of different type of stimuli that can be exploited for encapsulation and release of encapsulated compounds from LbL materials. Reproduced from Skirtach at al. [37], Copyright (2011), with permission from The Royal Society of Chemistry.

Figure 12

Sketch of the fabrication for LbL of different types of capsules for theranosis purposes. (a) Co-precipitation method. (b) Direct drug adsorption. MB: Microbeads, MC: Microcapsules. Reprinted from Kalinechenko et al. [36], with permission under Open access CC BY 4.0 license, https://creativecommons.org/licenses/by/4.0/ (accessed 20 January 2022).