Electrostatic Assembly/Disassembly of Nanoscaled Colloidosomes for Light‐Triggered Cargo Release

Abstract

Colloidosome capsules possess the potential for the encapsulation and release of molecular and macromolecular cargos.H owever,t he stabilization of the colloidosome shell usually requires an additional covalent crosslinking which irreversibly seals the capsules,and greatly limits their applications in large-cargos release.H erein we report nanoscaled colloidosomes designed by the electrostatic assembly of organosilica nanoparticles (NPs) with oppositely charged surfaces (rather than covalent bonds), arising from different contents of ab ridged nitrophenylene-alkoxysilane [NB;3nitro-N-(3-(triethoxysilyl)propyl)-4-(((3-(triethoxysilyl)propyl)-amino)methyl)benzamid] derivative in the silica. The surface charge of the positively charged NPs was reversed by light irradiation because of aphotoreaction in the NB moieties, which impacted the electrostatic interactions between NPs and disassembled the colloidosome nanosystems.T his design was successfully applied for the encapsulation and light-triggered release of cargos.Colloidosomes can be formed by the assembly of colloidal particles on emulsion droplets leading to capsule morphologies. [1][2][3][4][5] Va rious colloidal nanobuilding blocks have been used to design colloidosomes such as iron oxide NPs, [6] nanodiamonds, [7] polymeric rod-shaped microparticles, [8] silica NPs, [9,10] cubic metal-organic frameworks NPs, [11] and mixtures of these NPs. [9,10] Thek ey interest of such structures is their important internal volume combined with the properties of the nanobuilding blocks in the shell, which promise many applications as witnessed by few pioneering studies involving enzyme encapsulation, [12,13] bacteria encapsulation, [14] biocatalysis, [3] and passive release or delivery by interparticle pores. [15][16][17] Colloidal NPs assemble at the interface of emulsion droplets during the colloidosome formation in order to decrease interfacial energy of the system. [18] Thea ssembly at the liquid-liquid interface requires that particles should be neither completely wetted by the oil phase nor by the aqueous phase. [19] To adjust the wettability of NPs,t he hydrophobization of the surface of colloids is usually carried out. This can be achieved by physical interactions with additives (e.g. surfactants), [7,9,20] or chemical functionalization. [21,22] Ty pically,c olloidal particles with partially hydrophobic surfaces, such as silica NPs functionalized with organosilane, [23,24] are chosen as nanobuilding blocks of colloidosomes.T hese colloidal NPs assemble at the oil/water (o/w) or water/oil (w/o) interfaces of emulsion droplets, [17] which is much analogous to the behavior of surfactants.Many applications of colloidosomes are nonetheless compromised by several challenges such as the stability of the hollow structure and the accessibility of the internal volume.Controlled release and delivery applications require that the colloidosome carriers be:( 1) stabilized after the emulsion stage, [17] (2) non-permeable to ensure the transportation of the loaded active entities ...

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“…This induced electrostatic interactions leading to surface charge reversion or “flipping” by which the positive charges turned to negative and thus the repulsive forces between negative charges disassembled the colloidosomes and resulted in drug release. 180 …”

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“…(d) Schematic of formation of the stable colloidosome vehicles via self-assembly of oppositely charged NPs (NBSN-1 and NBSN-2) in an oil/water emulsion and their disassembly by light irradiation (365 nm laser for 10 min). Reprinted with permission from ref 118; copyright 2015, John Wiley and Sons. (e) Light-induced self-assembly of nonphotoresponsive NPs functionalized with COOH-terminated ligands within a protonated merocyanine (MCH + )-containing photoswitchable medium.…”

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