title: Enzyme Induced Stiffening of Nanoparticle-Hydrogel Composites with Structural Color.
abstract: The passive monitoring of biological environments by soft materials has a variety of nanobiotechnology applications; however, invoking distinct transitions in geometric, mechanical or optical properties remains a prevalent design challenge. We demonstrate here that close-packed nanoparticle-hydrogel composites can progress through a substantial shift in such properties by the use of a chemical-to-physical cross-link transition mediated by the catalytic activity of different proteases. Catalytic cleavage of the original hydrogel network structure initiates the self-assembled formation of a secondary, physically cross-linked network, causing a 1200% increase in storage modulus. Furthermore, this unique mechanism can be fabricated as a 3D photonic crystal with broad (∼240 nm), visible responses to the targeted enzymes. Moreover, the material provided threshold responses, requiring a certain extent of proteolytic activity before the transition occurred. This allowed for the fabrication of Boolean logic gates (OR and AND), which responded to a specific assortment of proteases. Ultimately, this mechanism enables the design of stimuli-responsive hydrogels, which can proceed through a secondary network formation, after an energetic barrier has been breached. Protease responsive hydrogel nanocomposites, described here, could offer avenues in degradation-stiffening and collapsing materials for a variety of biomaterial applications.
authors.affiliation: Fischell Department of Bioengineering, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Omar B
authors.initials: OB
authors.lastname: Ayyub
authors.affiliation: Fischell Department of Bioengineering, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Kofinas
mesh_terms: D055162:Biocatalysis; D002918:Chymotrypsin / Q000737:chemistry*; D003116:Color; D020100:Hydrogels / Q000737:chemistry*; D050866:Liquid Crystals; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D009842:Oligopeptides / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D014357:Trypsin / Q000737:chemistry*
chemical_list: D020100:Hydrogels; D009842:Oligopeptides; D011092:Polyethylene Glycols; D012822:Silicon Dioxide; D002918:Chymotrypsin; D014357:Trypsin
keywords: hydrogel; nanoparticle; photonic crystal; protease; self-assembly