Strong Response of Multilayer Polyelectrolyte Films to Cationic Surfactants

Abstract

The influence of common cationic surfactants on the physical properties of differently composed polyelectrolyte films prepared by the layer-by-layer (LbL) technology was investigated. Free-standing polyelectrolyte films as microcapsules showed a fast, strong response to the addition of less than 1 mM cationic surfactant cetyltrimethylammonium bromide (CeTAB). As a function of the polyelectrolyte composition, the behavior of the capsules varied from negligible changes to complete disintegration via strong swelling. The response of microcapsules consisting of (poly(allylamine hydrochloride)(PAH)/poly(styrene sulfonate)(PSS))(4) was associated with a 5-fold volume increase, a fast switch of permeability, and in the case of fluorescently labeled films a 4-fold increase in fluorescence intensity. The kinetics and strengths of the interaction process were investigated by confocal laser scanning microscopy (CLSM) and fluorescence spectroscopy. Also, the relative stabilities of the polycation/polyanion and surfactant/polyanion complexes were determined. A mechanism was suggested to explain the interactions between the cationic surfactants and polyelectrolyte capsules. The strong response can be exploited in potential applications such as the triggered release of drugs or other encapsulated materials, the fluorescence-based detection of cationic detergents, and a switchable stopper in microchannels. However, the high sensitivity of LbL films to traces of cationic surfactants can also limit their applicability to the encapsulation of drugs or other materials because pharmaceutical or technical formulations often contain cationic surfactants as preservatives such as benzalkonium salts (BAC). It was demonstrated that undesired capsule opening can be effectively prevented by cross-linking the polyelectrolyte multilayers.

Label‐Free Bioanalysis Based on Low‐Q Whispering Gallery Modes: Rapid Preparation of Microsensors by Means of Layer‐by‐Layer Technology

“…Although the LbL‐coated WGM beads have some advantages over dye‐doped particles in view of versatility of the approach, the LbL film is in addition responsive to the environment, which might influence the WGM signal as well. Several studies have shown that polyelectrolyte (PE) multilayer films change their thickness and density or even partially disassemble at high ionic strength, high or low pH, or by addition of ions which form strong complexes with one polyelectrolyte of the film such as cationic amphiphiles with PSS . Although the PAH/PSS is known to be one of the most stable polyelectrolyte combinations, such effects can limit the applicability of LbL‐coated WGM sensors.…”

Polyelectrolytes as Building Blocks for Next-Generation Membranes with Advanced Functionalities

“…When weak polyelectrolytes are used to build the multilayer 131 or when the wastewater to treat contains small, charged molecules (like surfactants), 178 PEM-based membranes can suffer from stability issues. In these cases, the stability of PEM membranes can be further increased via covalent cross-linking.…”

Self‐assembly and applications of nucleic acid solid‐state films

“…45 Intriguingly a recent article claims that the addition of cationic surfactants to LbL-prepared polyelectrolyte films can prompt a strong burst release as a function of the LbL film composition which may limit their applications in drug delivery, although the degradation can be prevented by crosslinking the polymers. 130 Thin NA-polymer films have been studied for drug and gene delivery applications including local gene delivery to cells and vascular delivery from stent coatings. The rate of release can be controlled with additives.…”

“…One recent report describes the use of linear PEI/polyacrylic acid/polyethylene glycol LbL films patterned with a PDMS stamp to delivery siRNA at high N/P ratios with relatively high transfection efficiency 45. Intriguingly a recent article claims that the addition of cationic surfactants to LbL‐prepared polyelectrolyte films can prompt a strong burst release as a function of the LbL film composition which may limit their applications in drug delivery, although the degradation can be prevented by crosslinking the polymers 130…”