Anisotropic Diffusion of Polyelectrolyte Chains within Multilayer Films

Xu, Li; Kozlovskaya, Veronika; Kharlampieva, Eugenia; Ankner, John F.; Sukhishvili, Svetlana A.

doi:10.1021/mz200075x

Cited by 49 publications

(81 citation statements)

References 20 publications

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“…We observed that HDFs displayed a moderate preference for aligning with the direction in which the slides were dipped during the dip coating process (Figures 3B & 4). Cells without any preferential alignment would be expected to have an average orientation of 45° (Figures 3B & 4 & Supplementary Figure 2); however, we saw that HDFs on PEDOT-PSS-based multilayer films had an average orientation of 38.6° ± 1.5° (Figure 4A & E), whereas HDFs on PEDOT-S-based multilayer films had an average orientation of 35.3° ± 1.8° (Figure 4B & E), which is likely to be because the polymer chains were aligned during the dip coating process as is commonly observed for multilayer films prepared in this fashion [34], and fibroblasts are known to respond to features on such length scales [35,36]. Interestingly, electrical stimulation of HDFs on the conductive substrates led to an increase in their propensity to align with the direction of the DC current passed through the substrate (akin to their behavior when a DC current is passed through the culture medium) [37], and we found that HDFs on PEDOT-PSS-based multilayer films had an average orientation of 27.7° ± 1.7° (Figure 4C & E), whereas HDFs on PEDOT-S-based multilayer films had an average orientation of 32.1° ± 1.1° (Figure 4C & E).…”

Section: Resultsmentioning

confidence: 83%

Conducting Polymer-Based Multilayer Films for Instructive Biomaterial Coatings

Hardy

Chow

et al. 2015

Future Sci. OA

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Aim:To demonstrate the design, fabrication and testing of conformable conducting biomaterials that encourage cell alignment.Materials & methods:Thin conducting composite biomaterials based on multilayer films of poly(3.4-ethylenedioxythiophene) derivatives, chitosan and gelatin were prepared in a layer-by-layer fashion. Fibroblasts were observed with fluorescence microscopy and their alignment (relative to the dipping direction and direction of electrical current passed through the films) was determined using ImageJ.Results:Fibroblasts adhered to and proliferated on the films. Fibroblasts aligned with the dipping direction used during film preparation and this was enhanced by a DC current.Conclusion:We report the preparation of conducting polymer-based films that enhance the alignment of fibroblasts on their surface which is an important feature of a variety of tissues.

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Section: Resultsmentioning

confidence: 83%

Conducting Polymer-Based Multilayer Films for Instructive Biomaterial Coatings

Hardy

Chow

et al. 2015

Future Sci. OA

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“…[21][22][23] There are some recent studies which have used the FRAP phenomenon to study diffusion of proteins in PEMs as well as inter-diffusion of the components of the PEM system within the multilayer stack. [24,25] These studies assumed an analytical model of fluorescence recovery which is (a) more appropriate for a closed system such as a cell and (b) assumed only diffusion to be the mechanism of recovery while ignoring other effects such as adsorption and desorption of the molecules to the PEM matrix. To increase the rigor in the analysis of FRAP data from thin films, we studied the transport of molecules in PEMs surrounded by an aqueous medium numerically, incorporating the effect of additional transport pathways such as the surrounding medium and considering the effect of finite film thickness.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence Recovery After Photobleaching in Ultrathin Polymer Films

Prakash

Pahal

Varma

2017

Preprint

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Fluorescence recovery after photobleaching (FRAP) is a widely used technique to study transport of molecules in biological systems. Recently, FRAP has been used to study molecular transport in polyelectrolyte multilayers (PEMs). Through numerical simulations verified by experiments, we show that the FRAP behaviour of PEM films in an aqueous medium differs significantly from that in previously explored systems such as single cells. This is because fluorescence recovery can take place through the aqueous medium surrounding the PEM film. Our simulations show the critical role of the time scale of the different processes namely, diffusion through PEM, diffusion through surrounding medium and the unbinding rate of fluorophore labelled species in the interpretation of FRAP data. An important conclusion from our numerical and experimental study is that, for ultrathin PEM films ~ 100 nm thicknesses, recovery is dominated through solution medium and hence, classical FRAP analysis is not sufficient to probe diffusion in PEM. Our numerical study reveals several aspect of FRAP phenomena in thin polymer films which are critical for the proper interpretation of experimental data.

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“…The self‐roughening behavior of exponentially growing PEM films is essentially a pressure‐induced wrinkling behavior, which is caused by the diffusion of polyelectrolytes into the films during the assembling process . Since molecular diffusion can be affected dramatically by the presence of steric hindrance, the formation of surface wrinkles could be affected by changing the internal construction of these PEM films. In this study, we fabricated a self‐wrinkling PEM film capable of being covalently cross‐linked under UV light.…”

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confidence: 99%

Spatially Confining Surface Roughness on Exponentially Growing Polyelectrolyte Multilayer Films

Chen

Huang

Ferreira

et al. 2019

Adv Materials Inter

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approach is direct and effective, how to manipulate the formation of such roughness features remains to be explored. A study on this issue may provide an approach for controlling the surface profiles of these PEM films and facilitate constructing various functional surfaces.The self-roughening behavior of exponentially growing PEM films is essentially a pressure-induced wrinkling behavior, which is caused by the diffusion of polyelectrolytes into the films during the assembling process. [16,17] Since molecular diffusion can be affected dramatically by the presence of steric hindrance, [22,23] the formation of surface wrinkles could be affected by changing the internal construction of these PEM films. In this study, we fabricated a self-wrinkling PEM film capable of being covalently crosslinked under UV light. Such PEM film was LbL assembled from branched polyethylenimine (PEI) and a photoreactive poly(acrylic acid) (PAA) derivative. We found that the wrinkling behavior of this film can be suppressed by applying a pre-crosslinking process, which can produce steric hindrance within the films against the diffusion of oncoming polyelectrolytes. With the aid of photolithography, the surface wrinkling of the film can be "turned off" regioselectively and confined on the areas unexposed to UV irradiation, thus leading to a film with patterned surface roughness. This can provide a spatial control over the properties of film surfaces and thus pave the way for novel applications, such as marine antifouling and tunable wettability.Branched PEI (Figure 1A) and a PAA derivative were alternately assembled onto substrates to generate a photocross-linkable PEM film. The PAA derivative (PAA-N 3 ) was synthesized by modifying PAA with phenyl azido groups via amidation reaction ( Figure 1B) and its grafting ratio was calculated to be 5.3% ( Figure 1C). Figure 1D shows the thickness of (PEI/PAA-N 3 ) n films as a function of the number of layers. The (PEI/PAA-N 3 ) n films grow exponentially in the initial ten layers and linearly in the following layers. Such growth mode of PEM systems generally results from the diffusion of polyelectrolyte chains ''in'' and "out'' of the whole film, as verified by previous studies. [24][25][26] The introduction of phenyl azido groups allows a (PEI/PAA-N 3 ) n film to be covalently cross-linked under UV light. This cross-linking reaction was studied through UV-vis spectroscopy (Figure 2A). The absorption peak at 270 nm corresponds to the π-π* transition of phenyl azido groups. [27][28][29] Upon UV irradiation, it drops off and exhibits a blueshift, which can be ascribed to the dissociation of phenyl azido groups into Introducing roughness features onto materials' surface can serve as an efficient strategy for novel or enhanced surface functionality. Surface roughness can be developed spontaneously on exponentially growing polyelectrolyte multilayer films without any postassembly treatment. This is essentially a pressure-induced wrinkling behavior, which is associated with the diffusion of polyelectro...

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Anisotropic Diffusion of Polyelectrolyte Chains within Multilayer Films

Cited by 49 publications

References 20 publications

Conducting Polymer-Based Multilayer Films for Instructive Biomaterial Coatings

Conducting Polymer-Based Multilayer Films for Instructive Biomaterial Coatings

Fluorescence Recovery After Photobleaching in Ultrathin Polymer Films

Spatially Confining Surface Roughness on Exponentially Growing Polyelectrolyte Multilayer Films

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