Incorporation of Block Copolymer Micelles into Multilayer Films for Use as Nanodelivery Systems

Abstract

This work demonstrates the potential application of stimulus responsive block copolymer micelles as triggerable delivery systems for use within multilayer films. Cationic, pH-responsive micelles of poly[2-(dimethylamino)ethyl methacrylate-block-poly(2-(diethylamino)ethyl methacrylate)] (PDMA-PDEA) were deposited on anionic polystyrene latex particles. The charge reversal of the surface and the amount of adsorbed polymer were monitored by zeta potential measurements and colloidal titrations, respectively. Prior to adsorption, the PDMA-PDEA micelles were loaded with a hydrophobic dye, and UV-vis spectroscopy was used to determine the amount of dye encapsulated within a monolayer of micelles. It was found that subtle chemical modification of the PDMA-PDEA diblock copolymer via permanent quaternization of the PDEA block results in micelles with tunable loading capacities. Multilayers of cationic micelles of partially quaternized PDMA-PDEA and anionic polyelectrolyte (poly(sodium 4-styrene sulfonate)) were deposited on the surface of polystyrene latex particles by sequential adsorption. UV-vis analysis of the dye present within the multilayer after the addition of each layer demonstrates that the micelles are sufficiently robust to retain encapsulated dye after multiple adsorption/washing cycles and can thus create a film that can be increasingly loaded with dye as more micelle layers are adsorbed. Multiple washing cycles were performed on micellar monolayers of PDMA-PDEA to demonstrate how such systems can be used to bring about triggerable release of actives. When performing several consecutive washing steps at pH 9.3, the micelle structure of the PDMA-PDEA micelles in the monolayer is retained, resulting in only a small reduction in the amount of encapsulated dye. In contrast, washing at pH 4, the structure of the micelle layers is severely disrupted, resulting in a fast release of the encapsulated dye into the bulk. Finally, if a sufficient number of micelle/homopolyelectrolyte layers are adsorbed, it is possible to selectively dissolve the latex template, resulting in hollow capsules.

Polyelectrolyte Multilayers Containing Triblock Copolymers of Different Charge Ratio

“…29,30,[37][38][39] Although in most cases random instead of block copolymers have been used, there are several papers that have described the incorporation of diblock copolymers on the multilayer structure. [40][41][42][43][44] It is worth to stress that in almost all the studies the copolymers were adsorbed from solutions of a concentration above the critical micellar one (cmc). [40][41][42] Even though in the present study all the copolymer solutions will have a concentration well below the cmc, 45 it is wellknown that in the case of normal surfactants aggregates can be formed at the surface below the cmc.…”

“…[40][41][42][43][44] It is worth to stress that in almost all the studies the copolymers were adsorbed from solutions of a concentration above the critical micellar one (cmc). [40][41][42] Even though in the present study all the copolymer solutions will have a concentration well below the cmc, 45 it is wellknown that in the case of normal surfactants aggregates can be formed at the surface below the cmc. 46 Recently, Tan et al 47 have studied multilayers containing triblock copolymers and used changes of pH to modify the charge density of the copolymer.…”

Multi-layer films of block copolymer micelles adsorbed to colloidal templates

“…At low pH, it may be expected that the majority of the tertiary amine groups present on the copolymers will be protonated, and thus all samples should demonstrate similar zeta potentials. Inspection of figure 1 shows that this is not the case, with a possible explanation being that the weak/unquaternized PDMA-PDEA micelles show significantly more desorption upon transitioning to low pH following adsorption at pH 9 (Addison et al 2008). Furthermore, rearrangement of the copolymer chains upon exposure to acidic conditions produces layers with significantly different morphologies (see the electronic supplementary material, figure S3; Webber et al 2004).…”

Design and Preparation of a Nanoprobe for Imaging Inflammation Sites

“…Polyamines with appropriate hydrophobicity, including poly[2-(N,N-diethylamino)ethyl methacrylate] (PEAMA), are known to show phase transitions as a function of pH [25][26][27]. Utilizing this character, various environmentally sensitive polymeric materials have been developed.…”