Cited by 839
Massachusetts Institute of Technology
Publishes on Polymer Surface Interaction Studies, Surface Modification and Superhydrophobicity, Hydrogels: synthesis, properties, applications. 3 papers and 1.5k citations.
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Nanostructured polyelectrolyte multilayer thin films electrostatically assembled alternately from such polymers as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were investigated for their in vitro cell interactions. Not surprisingly, NR6WT cells, a highly adhesive murine fibroblast cell line, attached to many different multilayer combinations tested. However, PAH/PAA multilayers constructed at pH deposition conditions of 2.0/2.0 were completely bioinert. Analogous cell interactions were observed with PAH/poly(methacrylic acid) (PAH/PMA), PAH/sulfonated poly(styrene) (PAH/SPS), and poly(diallyldimethylammonium chloride)/SPS (PDAC/SPS) systems, thereby suggesting a general trend in the fibroblasts' response to multilayers. Specifically, highly ionically stitched films attracted cells, whereas weakly ionically cross-linked multilayers, which swell substantially in physiological conditions to present richly hydrated surfaces, resisted fibroblast attachment. Thus, by manipulating the multilayer pH or ionic strength assembly conditions or both, which in turn dictate the molecular architecture of the thin films, one may powerfully direct a single multilayer combination to be either cell adhesive or cell resistant.
The systematic design of materials that alter their macroscopic properties in response to environmental stimuli continues to provide a basis for stimuli-responsive applications in biomaterials and microelectronics. We report discrete volume phase transitions in ultrathin polyelectrolyte multilayers (PEMs) driven by changes in environmental pH of the post-assembled film. These films exhibit a history-dependent swelling behavior and molecular conformational memory. We illustrate that the same two polymerspoly(allylamine hydrochloride)/poly(styrenesulfonic acid) (PAH/SPS)can be incorporated into a multilayer film with specifically designed molecular architectures (by virtue of assembly pH conditions) that enable them to be either virtually insensitive or highly responsive to small changes in post-assembly pH. We thus provide a general design strategy for PEMs that exhibit multiple conformational states and related phenomena. We further demonstrate the ability to spatially regulate the affinity of molecular species to PEMSspecifically, by virtue of pH-triggered conformational changes in the PEM. Finally, we show the potential of these materials for sustained molecular release.