Seung-Wuk LEE - Academia.edu (original) (raw)
Papers by Seung-Wuk LEE
Nature Communications, 2014
Many materials in nature change colours in response to stimuli, making them attractive for use as... more Many materials in nature change colours in response to stimuli, making them attractive for use as sensor platform. However, both natural materials and their synthetic analogues lack selectivity towards specific chemicals, and introducing such selectivity remains a challenge. Here we report the self-assembly of genetically engineered viruses (M13 phage) into targetspecific, colourimetric biosensors. The sensors are composed of phage-bundle nanostructures and exhibit viewing-angle independent colour, similar to collagen structures in turkey skin. On exposure to various volatile organic chemicals, the structures rapidly swell and undergo distinct colour changes. Furthermore, sensors composed of phage displaying trinitrotoluene (TNT)-binding peptide motifs identified from a phage display selectively distinguish TNT down to 300 p.p.b. over similarly structured chemicals. Our tunable, colourimetric sensors can be useful for the detection of a variety of harmful toxicants and pathogens to protect human health and national security.
In nature, helical macromolecules such as collagen, chitin and cellulose are critical to the morp... more In nature, helical macromolecules such as collagen, chitin and cellulose are critical to the morphogenesis and functionality of various hierarchically structured materials 1–3. During tissue formation, these chiral macromolecules are secreted and undergo self-templating assembly, a process whereby multiple kinetic factors influence the assembly of the incoming building blocks to produce non-equilibrium structures 1,4. A single macromolecule can form diverse functional structures when self-templated under different conditions. Collagen type I, for instance, forms transparent corneal tissues from orthogonally aligned nematic fibres 5 , distinctively coloured skin tissues from cholesteric phase fibre bundles 6,7 , and mineralized tissues from hierarchically organized fibres 8. Nature's self-templated materials surpass the functional and structural complexity achievable by current top-down and bottom-up fabrication methods 9–12. However, self-templating has not been thoroughly explored for engineering synthetic materials. Here we demonstrate the biomimetic, self-templating assembly of chiral colloidal particles (M13 phage) into functional materials. A single-step process produces long-range-ordered, supramolecular films showing multiple levels of hierarchical organization and helical twist. Three distinct supramolecular structures are created by this approach: nematic orthogonal twists, cholesteric helical ribbons and smectic helicolidal nanofilaments. Both chiral liquid crystalline phase transitions and competing interfacial forces at the interface are found to be critical factors in determining the morphology of the templated structures during assembly. The resulting materials show distinctive optical and photonic properties, functioning as chiral reflector/filters and structural colour matrices. In addition, M13 phages with genetically incorporated bio-active peptide ligands direct both soft and hard tissue growth in a hierarchically organized manner. Our assembly approach provides insight into the complexities of hierarchical assembly in nature and could be expanded to other chiral molecules to engineer sophisticated functional helical-twisted structures. As building blocks for the self-templating process we chose to use the bacterial virus M13 phage. Various viral particles have previously been used as model liquid crystal systems 13–16 and to create functional materials for nanoparticle synthesis and assembly 17,18 , for energy storage 19 and in tissue engineering 20,21. In particular, M13 was chosen for its helical, nanofibrous shape, for its monodispersity and for its ability to display multiple functional motifs (Fig. 1a). We then assembled the phage into large-area films by creating an apparatus to pull substrates vertically from phage suspensions at precisely controlled speeds (Supplementary Movie 1). As the substrates were pulled, evaporation proceeded fastest near the air–liquid–solid contact line resulting in the local accumulation and deposition of phage particles on the substrate at the meniscus (Fig. 1b). Two factors were critical to self-templating assembly. The first was the local induction of chiral liquid-crystal phase transitions at the meniscus; that is, twisted nematic (cholesteric) and chiral smectic structures (Supplementary
Nature Communications, 2014
Many materials in nature change colours in response to stimuli, making them attractive for use as... more Many materials in nature change colours in response to stimuli, making them attractive for use as sensor platform. However, both natural materials and their synthetic analogues lack selectivity towards specific chemicals, and introducing such selectivity remains a challenge. Here we report the self-assembly of genetically engineered viruses (M13 phage) into targetspecific, colourimetric biosensors. The sensors are composed of phage-bundle nanostructures and exhibit viewing-angle independent colour, similar to collagen structures in turkey skin. On exposure to various volatile organic chemicals, the structures rapidly swell and undergo distinct colour changes. Furthermore, sensors composed of phage displaying trinitrotoluene (TNT)-binding peptide motifs identified from a phage display selectively distinguish TNT down to 300 p.p.b. over similarly structured chemicals. Our tunable, colourimetric sensors can be useful for the detection of a variety of harmful toxicants and pathogens to protect human health and national security.
In nature, helical macromolecules such as collagen, chitin and cellulose are critical to the morp... more In nature, helical macromolecules such as collagen, chitin and cellulose are critical to the morphogenesis and functionality of various hierarchically structured materials 1–3. During tissue formation, these chiral macromolecules are secreted and undergo self-templating assembly, a process whereby multiple kinetic factors influence the assembly of the incoming building blocks to produce non-equilibrium structures 1,4. A single macromolecule can form diverse functional structures when self-templated under different conditions. Collagen type I, for instance, forms transparent corneal tissues from orthogonally aligned nematic fibres 5 , distinctively coloured skin tissues from cholesteric phase fibre bundles 6,7 , and mineralized tissues from hierarchically organized fibres 8. Nature's self-templated materials surpass the functional and structural complexity achievable by current top-down and bottom-up fabrication methods 9–12. However, self-templating has not been thoroughly explored for engineering synthetic materials. Here we demonstrate the biomimetic, self-templating assembly of chiral colloidal particles (M13 phage) into functional materials. A single-step process produces long-range-ordered, supramolecular films showing multiple levels of hierarchical organization and helical twist. Three distinct supramolecular structures are created by this approach: nematic orthogonal twists, cholesteric helical ribbons and smectic helicolidal nanofilaments. Both chiral liquid crystalline phase transitions and competing interfacial forces at the interface are found to be critical factors in determining the morphology of the templated structures during assembly. The resulting materials show distinctive optical and photonic properties, functioning as chiral reflector/filters and structural colour matrices. In addition, M13 phages with genetically incorporated bio-active peptide ligands direct both soft and hard tissue growth in a hierarchically organized manner. Our assembly approach provides insight into the complexities of hierarchical assembly in nature and could be expanded to other chiral molecules to engineer sophisticated functional helical-twisted structures. As building blocks for the self-templating process we chose to use the bacterial virus M13 phage. Various viral particles have previously been used as model liquid crystal systems 13–16 and to create functional materials for nanoparticle synthesis and assembly 17,18 , for energy storage 19 and in tissue engineering 20,21. In particular, M13 was chosen for its helical, nanofibrous shape, for its monodispersity and for its ability to display multiple functional motifs (Fig. 1a). We then assembled the phage into large-area films by creating an apparatus to pull substrates vertically from phage suspensions at precisely controlled speeds (Supplementary Movie 1). As the substrates were pulled, evaporation proceeded fastest near the air–liquid–solid contact line resulting in the local accumulation and deposition of phage particles on the substrate at the meniscus (Fig. 1b). Two factors were critical to self-templating assembly. The first was the local induction of chiral liquid-crystal phase transitions at the meniscus; that is, twisted nematic (cholesteric) and chiral smectic structures (Supplementary