Controlled Electrodissolution of Polyelectrolyte Multilayers: A Platform Technology Towards the Surface‐Initiated Delivery of Drugs

Boulmedais, Fouzia; Tang, Clarence; Keller, Beat; Vörös, János

doi:10.1002/adfm.200400406

Cited by 98 publications

(116 citation statements)

References 81 publications

(90 reference statements)

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“…Desorption experiments beginning after 5 and 10 min of adsorption, i.e., before the continuous regime, exhibit characteristic time constants of 220 and 240 min, respectively (based on exponential fits). After 90 min of adsorption, i.e., within the continuous regime, the time constant is initially 160 min and decreases to 140 min when the potential is increased, at 1 h of desorption, to 1.7 V. Previous studies have shown similar desorption of LbL films (19,20).…”

Section: Resultsmentioning

confidence: 62%

“…The influence of an applied electric potential on the adsorption of charged macromolecules (mainly proteins) has been the subject of several previous investigations (19,20,(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44). Although most of these studies note an influence of substrate potential on adsorption, changes are typically within a factor of two or so, and to our knowledge no continuous adsorption has been reported.…”

Section: Discussionmentioning

confidence: 99%

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Continuous polyelectrolyte adsorption under an applied electric potential

Ngankam

Tassel

2007

Proc. Natl. Acad. Sci. U.S.A.

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Interactions between charged macromolecules (e.g., proteins, nucleic acids, polyelectrolytes) and charged surfaces govern many natural and industrial processes. We investigate here the influence of an applied electric potential on the adsorption of charged polymers, and report the following significant result: the adsorption of certain amine side chain-containing polycations may become continuous, i.e., asymptotically linear (or nearly linear) in time over hours, upon the application of a modest anodic potential. Employing optical waveguide lightmode spectroscopy (OWLS) and an indium tin oxide (ITO) substrate, we show that asymptotic kinetics, and the adsorbed mass at the onset of the asymptotic regime, depend sensitively on polymer chemistry (in particular, side chain volume and charge location), increase with applied potential and ionic strength (conditions favoring a thicker initial layer), and are independent of bulk polymer concentration (suggesting postadsorption events to be rate limiting). X-ray photoelectron spectra reveal a suppressed polymer charge within layers formed via continuous adsorption, but no evidence of electrochemical reactions. We propose a mechanism based on polymer-polymer binding within the adsorbed layer, enabled by suppressed electrostatic repulsion and/or enhanced ionic correlations near the conducting surface, and stabilized by short-range attractive interactions. Continuous adsorption under an applied electric potential offers the possibility of nanoscale films of tailored polymer content realized in a single step.optical waveguide lightmode spectroscopy ͉ poly(L-lysine) ͉ protein adsorption ͉ indium tin oxide I nteractions between charged macromolecules and charged surfaces are ubiquitous in nature (e.g., protein-cell membrane) and are often exploited in technological applications. For example, weakly charged colloidal systems such as paints, inks, and waste water may be stabilized through an adsorbed layer of charged polymer (polyelectrolyte) (1, 2), and polyelectrolyte films containing functional entities (e.g., biomolecules, nanoparticles) may serve as sensors, separation membranes, and electrochemical components (3, 4). Adsorption is usually spontaneous, with electrostatic interactions naturally playing a key role. These interactions, and therefore the adsorption process itself, may be controlled through solution variables such as salt concentration and pH (5-12). However, there generally exists an upper limit to the extent of polyelectrolyte adsorption. The typical situation is for adsorption to be quite rapid (usually at a transport limited rate) and then to saturate, corresponding to the point where interfacial charge accumulation suppresses additional (net) adsorption (1). A clever way to avoid this limit is through the layer-by-layer (LbL) method, where a substrate is alternately exposed to solutions of oppositely charged polyelectrolytes (3, 13). Each exposure results in an increase in adsorbed mass and an overall interfacial charge reversal. The LbL method allows one t...

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Section: Resultsmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Continuous polyelectrolyte adsorption under an applied electric potential

Ngankam

Tassel

2007

Proc. Natl. Acad. Sci. U.S.A.

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“…[108][109][110][111][112] The insulin could be released from an electrode coated with an insulin-containing LbL film in response to an applied electric potential, because the pH around the electrode surface would be acidified by the electrolysis of H2O. However, the operating variables, such as pH, ionic strength, and the magnitude of electrode potential, have to be carefully addressed, because some drugs can be electrochemically oxidized or reduced at an electrode.…”

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confidence: 99%

Layer-by-layer Thin Films and Microcapsules for Biosensors and Controlled Release

2012

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We present an overview of the preparation and properties of layer-by-layer (LbL) deposited thin films and microcapsules in relation to their use in the development of biosensors and controlled release systems. Enzyme biosensors can be constructed by immobilizing enzymes on the surface of electrodes by LbL deposition without loss of their catalytic activity. In addition to synthetic polymers, binding proteins, such as avidin and lectin, are also used for constructing LbL films through avidin-biotin and lectin-sugar interactions. The performance characteristics of LbL film-based biosensors can be tuned by controlling the number of layers and by the choice of film components. The permeability of polyelectrolyte LbL films to ions and molecules is discussed in relation to the use of the films for eliminating interference in biosensors. The possible use of polysaccharide LbL film-coated electrodes for the construction of biosensors is highlighted, and examples of LbL film-and microcapsule-based optical sensors are described. We then focus on the use of LbL films and microcapsules as vehicles for controlled release, in particular on recent progress in the controlled release of insulin from LbL films and microcapsules. LbL films composed of insulin and polymers are sensitive to environmental pH, and release insulin in response to pH changes, suggesting that insulin LbL films can be used in the development of orally administered insulin. The construction of glucose-dependent insulin release systems using LbL insulin microcapsules functionalized with phenylboronic acid, lectin, and glucose oxidase is also examined.

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“…LbL films have been used for constructing molecular architectures [11][12][13], stimuli-sensitive systems [2,[14][15][16][17], optical and electrochemical devices [5,10,[18][19][20][21][22], and controlled release systems [23][24][25][26][27][28].…”

Section: Open Accessmentioning

confidence: 99%

Ion Permeability of Free-Suspended Layer-by-Layer (LbL) Films Prepared Using an Alginate Scaffold

2013

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Abstract:Layer-by-layer (LbL) films were prepared over an aperture (diameter 1-5 mm) on a glass plate to study ion permeation across free-suspended LbL films. LbL films were prepared by depositing alternating layers of poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) on the surface of a glass plate with an aperture filled with an alginate gel, followed by dissolution of the alginate gel. PAH-PSS films prepared in this way showed permeability to inorganic salts, depending on the size and charge. Permeability to alkali metal chlorides depended on the Stokes radius of the alkali metal cations. The effect of the type of halide was negligible because of the halides' smaller ionic radii. Permeation of multivalent ions such as Ru(NH 3 ) 6 3+ and [Fe(CN) 6 ] 3− was severely suppressed owing to Donnan exclusion.

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Controlled Electrodissolution of Polyelectrolyte Multilayers: A Platform Technology Towards the Surface‐Initiated Delivery of Drugs

Cited by 98 publications

References 81 publications

Continuous polyelectrolyte adsorption under an applied electric potential

Continuous polyelectrolyte adsorption under an applied electric potential

Layer-by-layer Thin Films and Microcapsules for Biosensors and Controlled Release

Ion Permeability of Free-Suspended Layer-by-Layer (LbL) Films Prepared Using an Alginate Scaffold

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