Publications by authors named "Ali Miserez"

77 Publications

Nanolattice-Forming Hybrid Collagens in Protective Shark Egg Cases.

Biomacromolecules 2022 07 24;23(7):2878-2890. Epub 2022 Jun 24.

Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, California 93106, United States.

Nanoscopic structural control with long-range ordering remains a profound challenge in nanomaterial fabrication. The nanoarchitectured egg cases of elasmobranchs rely on a hierarchically ordered latticework for their protective function─serving as an exemplary system for nanoscale self-assembly. Although the proteinaceous precursors are known to undergo intermediate liquid crystalline phase transitions before being structurally arrested in the final nanolattice architecture, their sequences have so far remained unknown. By leveraging RNA-seq and proteomic techniques, we identified a cohort of nanolattice-forming proteins comprising a collagenous midblock flanked by domains typically associated with innate immunity and network-forming collagens. Structurally homologous proteins were found in the genomes of other egg-case-producing cartilaginous fishes, suggesting a conserved molecular self-assembly strategy. The identity and stabilizing role of cross-links were subsequently elucidated using mass spectrometry and small-angle X-ray scattering. Our findings provide a new design approach for protein-based liquid crystalline elastomers and the self-assembly of nanolattices.
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http://dx.doi.org/10.1021/acs.biomac.2c00341DOI Listing
July 2022

Interplay between Interfacial Energy, Contact Mechanics, and Capillary Forces in EGaIn Droplets.

ACS Appl Mater Interfaces 2022 Jun 1;14(24):28074-28084. Epub 2022 Jun 1.

Biological and Biomimetic Materials Laboratory, Center for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 639798, Singapore.

Eutectic gallium-indium (EGaIn) is increasingly employed as an interfacial conductor material in molecular electronics and wearable healthcare devices owing to its ability to be shaped at room temperature, conductivity, and mechanical stability. Despite this emerging usage, the mechanical and physical mechanisms governing EGaIn interactions with surrounding objects─mainly regulated by surface tension and interfacial adhesion─remain poorly understood. Here, using depth-sensing nanoindentation (DSN) on pristine EGaIn/GaO surfaces, we uncover how changes in EGaIn/substrate interfacial energies regulate the adhesive and contact mechanic behaviors, notably the evolution of EGaIn capillary bridges with distinct capillary geometries and pressures. Varying the interfacial energy by subjecting EGaIn to different chemical environments and by functionalizing the tip with chemically distinct self-assembled monolayers (SAMs), we show that the adhesion forces between EGaIn and the solid substrate can be increased by up to 2 orders of magnitude, resulting in about a 60-fold increase in the elongation of capillary bridges. Our data reveal that by deploying molecular junctions with SAMs of different terminal groups, the trends of charge transport rates, the resistance of monolayers, and the contact interactions between EGaIn and monolayers from electrical characterizations are governed by the interfacial energies as well. This study provides a key understanding into the role of interfacial energy on geometrical characteristics of EGaIn capillary bridges, offering insights toward the fabrication of EGaIn junctions in a controlled fashion.
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http://dx.doi.org/10.1021/acsami.2c04043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9227710PMC
June 2022

Complete Sequences of the Velvet Worm Slime Proteins Reveal that Slime Formation is Enabled by Disulfide Bonds and Intrinsically Disordered Regions.

Adv Sci (Weinh) 2022 06 18;9(18):e2201444. Epub 2022 May 18.

Centre for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore, 639798, Singapore.

The slime of velvet worms (Onychophora) is a strong and fully biodegradable protein material, which upon ejection undergoes a fast liquid-to-solid transition to ensnare prey. However, the molecular mechanisms of slime self-assembly are still not well understood, notably because the primary structures of slime proteins are yet unknown. Combining transcriptomic and proteomic studies, the authors have obtained the complete primary sequences of slime proteins and identified key features for slime self-assembly. The high molecular weight slime proteins contain cysteine residues at the N- and C-termini that mediate the formation of multi-protein complexes via disulfide bonding. Low complexity domains in the N-termini are also identified and their propensity for liquid-liquid phase separation is established, which may play a central role in slime biofabrication. Using solid-state nuclear magnetic resonance, rigid and flexible domains of the slime proteins are mapped to specific peptide domains. The complete sequencing of major slime proteins is an important step toward sustainable fabrication of polymers inspired by the velvet worm slime.
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http://dx.doi.org/10.1002/advs.202201444DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9218773PMC
June 2022

Nanocapsules Produced by Nanoprecipitation of Designed Suckerin-Silk Fusion Proteins.

ACS Macro Lett 2021 05 3;10(5):628-634. Epub 2021 May 3.

Univ Lyon, INSA Lyon, CNRS, IMP UMR 5223, F-69622, Villeurbanne, France.

Herein, we report on the precise design of a modular fusion protein amenable to the construction of nanocapsules by nanoprecipitation. The central squid suckerin-derived peptide block provides structural stability, whereas both termini from spider silk fibroins make the protein highly soluble at physiological pH, a critical requirement for the nanoprecipitation process. With this design, nanocapsules consisting of fusion protein shells and oily cores with sizes in the range of 190-250 nm are built in a straightforward manner.
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http://dx.doi.org/10.1021/acsmacrolett.1c00171DOI Listing
May 2021

In vivo liquid-liquid phase separation protects amyloidogenic and aggregation-prone peptides during overexpression in Escherichia coli.

Protein Sci 2022 05;31(5):e4292

Biological and Biomimetic Materials Laboratory (BBML), Center for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore.

Studying pathogenic effects of amyloids requires homogeneous amyloidogenic peptide samples. Recombinant production of these peptides is challenging due to their susceptibility to aggregation and chemical modifications. Thus, chemical synthesis is primarily used to produce amyloidogenic peptides suitable for high-resolution structural studies. Here, we exploited the shielded environment of protein condensates formed via liquid-liquid phase separation (LLPS) as a protective mechanism against premature aggregation. We designed a fusion protein tag undergoing LLPS in Escherichia coli and linked it to highly amyloidogenic peptides, including β amyloids. We find that the fusion proteins form membraneless organelles during overexpression and remain fluidic-like. We also developed a facile purification method of functional Aβ peptides free of chromatography steps. The strategy exploiting LLPS can be applied to other amyloidogenic, hydrophobic, and repetitive peptides that are otherwise difficult to produce.
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http://dx.doi.org/10.1002/pro.4292DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8994509PMC
May 2022

Cephalopod-Mimetic Tunable Photonic Coatings Assembled from Quasi-Monodispersed Reflectin Protein Nanoparticles.

ACS Appl Mater Interfaces 2022 May 27;14(18):21436-21452. Epub 2022 Apr 27.

Centre for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore 639798, Singapore.

The remarkable dynamic camouflage ability of cephalopods arises from precisely orchestrated structural changes within their chromatophores and iridophores photonic cells. This mesmerizing color display remains unmatched in synthetic coatings and is regulated by swelling/deswelling of reflectin protein nanoparticles, which alters platelet dimensions in iridophores to control photonic patterns according to Bragg's law. Toward mimicking the photonic response of squid's skin, reflectin proteins from were sequenced, recombinantly expressed, and self-assembled into spherical nanoparticles by conjugating reflectin B1 with a click chemistry ligand. These quasi-monodisperse nanoparticles can be tuned to any desired size in the 170-1000 nm range. Using Langmuir-Schaefer and drop-cast deposition methods, ligand-conjugated reflectin B1 nanoparticles were immobilized onto azide-functionalized substrates via click chemistry to produce monolayer amorphous photonic structures with tunable structural colors based on average particle size, paving the way for the fabrication of eco-friendly, bioinspired color-changing coatings that mimic cephalopods' dynamic camouflage.
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http://dx.doi.org/10.1021/acsami.2c01999DOI Listing
May 2022

Robust and Long-Term Cellular Protein and Enzymatic Activity Preservation in Biomineralized Mammalian Cells.

ACS Nano 2022 02 10;16(2):2164-2175. Epub 2022 Feb 10.

Center for Micro-Engineered Materials and the Department of Chemical and Biological Engineering, The University of New Mexico, Albuquerque, New Mexico 87131, United States.

Preservation of evolved biological structure and function in robust engineering materials is of interest for storage of biological samples before diagnosis and development of vaccines, sensors, and enzymatic reactors and has the potential to avoid cryopreservation and its associated cold-chain issues. Here, we demonstrate that "freezing cells in amorphous silica" is a powerful technique for long-term preservation of whole mammalian cell proteomic structure and function at room temperature. Biomimetic silicification employs the crowded protein microenvironment of mammalian cells as a catalytic framework to proximally transform monomeric silicic acid into silicates forming a nanoscopic silica shell over all biomolecular interfaces. Silicification followed by dehydration preserves and passivates proteomic information within a nanoscale thin silica coating that exhibits size selective permeability (<3.6 nm), preventing protein leaching and protease degradation of cellular contents, while providing access of small molecular constituents for cellular enzymatic reaction. Exposure of dehydrated silicified cells to mild etchant or prolonged hydrolysis removes the silica, completely rerevealing biomolecular components and restoring their accessibility and functionality.
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http://dx.doi.org/10.1021/acsnano.1c08103DOI Listing
February 2022

Phase-separating peptides for direct cytosolic delivery and redox-activated release of macromolecular therapeutics.

Nat Chem 2022 03 3;14(3):274-283. Epub 2022 Feb 3.

Biological and Biomimetic Material Laboratory (BBML), Center for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore, Singapore.

Biomacromolecules are highly promising therapeutic modalities to treat various diseases. However, they suffer from poor cellular membrane permeability, limiting their access to intracellular targets. Strategies to overcome this challenge often employ nanoscale carriers that can get trapped in endosomal compartments. Here we report conjugated peptides that form pH- and redox-responsive coacervate microdroplets by liquid-liquid phase separation that readily cross the cell membrane. A wide range of macromolecules can be quickly recruited within the microdroplets, including small peptides, enzymes as large as 430 kDa and messenger RNAs (mRNAs). The therapeutic-loaded coacervates bypass classical endocytic pathways to enter the cytosol, where they undergo glutathione-mediated release of payload, the bioactivity of which is retained in the cell, while mRNAs exhibit a high transfection efficiency. These peptide coacervates represent a promising platform for the intracellular delivery of a large palette of macromolecular therapeutics that have potential for treating various pathologies (for example, cancers and metabolic diseases) or as carriers for mRNA-based vaccines.
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http://dx.doi.org/10.1038/s41557-021-00854-4DOI Listing
March 2022

Bioinspired short peptide hydrogel for versatile encapsulation and controlled release of growth factor therapeutics.

Acta Biomater 2021 12 20;136:111-123. Epub 2021 Sep 20.

Center for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798; School of Biological Sciences, Nanyang Technological University, Singapore, 637551. Electronic address:

A short bioinspired octapeptide, GV8, can self-assemble under mild conditions into biodegradable supramolecular physical hydrogels with high storage modulus and good biocompatibility. GV8 hydrogels can encapsulate both single or multiple macromolecular protein-based therapeutics in a simple one-pot formulation manner, making it a promising candidate to address challenges faced by existing synthetic polymer or peptide hydrogels with complex gelation and drug-encapsulation processes. Alongside its versatility, the hydrogel exhibits concentration-dependent storage modulus and controlled drug-release action. We demonstrate that GV8 hydrogels loaded with adipose-derived mesenchymal stem cells (ADMSC) secretome remain mechanically robust, and exhibit promising potential for wound healing applications by preserving secretome activity while maintaining a constant supply of ADMSC secretome to promote epithelial cell migration. Overall, our work highlights the potential of GV8 peptide hydrogel as a versatile and safe carrier for encapsulation and delivery of macromolecular therapeutics. STATEMENT OF SIGNIFICANCE: Supramolecular peptide hydrogels are a popular choice for protein-based macromolecular therapeutics delivery; however, despite the development of abundant hydrogel systems, several challenges limit their adaptability and practical applications. GV8 short peptide hydrogel circumvents these drawbacks and demonstrates the ability to function as a versatile growth factor (GF) encapsulant. It can encapsulate precise concentrations of complex adipose-derived mesenchymal stem cells secretome mixtures with a one-pot formulation approach and perform controlled release of GFs with preserved activity without compromising the self-assembly and mechanical properties of the hydrogel's supramolecular network. The significance of GV8 hydrogel lies in its gelation simplicity and versatility to encapsulate and deliver macromolecular therapeutics, thus representing a promising biomaterial for regenerative medicine applications.
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http://dx.doi.org/10.1016/j.actbio.2021.09.023DOI Listing
December 2021

Bioinspired Functionally Graded Composite Assembled Using Cellulose Nanocrystals and Genetically Engineered Proteins with Controlled Biomineralization.

Adv Mater 2021 Oct 1;33(42):e2102658. Epub 2021 Sep 1.

VTT Technical Research Centre of Finland Ltd, VTT, Espoo, FI-02044, Finland.

Nature provides unique insights into design strategies evolved by living organisms to construct robust materials with a combination of mechanical properties that are challenging to replicate synthetically. Hereby, inspired by the impact-resistant dactyl club of the stomatopod, a mineralized biocomposite is rationally designed and produced in the complex shapes of dental implant crowns exhibiting high strength, stiffness, and fracture toughness. This material consists of an expanded helicoidal organization of cellulose nanocrystals (CNCs) mixed with genetically engineered proteins that regulate both binding to CNCs and in situ growth of reinforcing apatite crystals. Critically, the structural properties emerge from controlled self-assembly across multiple length scales regulated by rational engineering and phase separation of the protein components. This work replicates multiscale biomanufacturing of a model biological material and also offers an innovative platform to synthesize multifunctional biocomposites whose properties can be finely regulated by colloidal self-assembly and engineering of its constitutive protein building blocks.
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http://dx.doi.org/10.1002/adma.202102658DOI Listing
October 2021

Liquid-Liquid Phase Separation of the Green Mussel Adhesive Protein Pvfp-5 is Regulated by the Post-Translated Dopa Amino Acid.

Adv Mater 2022 Jun 26;34(25):e2103828. Epub 2021 Aug 26.

Center for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore, 637553, Singapore.

The underwater adhesive prowess of aquatic mussels has been largely attributed to the abundant post-translationally modified amino acid l-3,4-dihydroxyphenylalanine (Dopa) in mussel foot proteins (MFPs) that make up their adhesive threads. More recently, it has been suggested that during thread fabrication, MFPs form intermediate fluidic phases such as liquid crystals or coacervates regulated by a liquid-liquid phase separation (LLPS) process. Here, it is shown that Dopa plays another central role during mussel fiber formation, by enabling LLPS of Pvfp-5β, a main MFP of the green mussel Perna viridis. Using residue-specific substitution of Tyrosine (Tyr) for Dopa during recombinant expression, Dopa-substituted Pvfp-5β is shown to exhibit LLPS under seawater-like conditions, whereas the Tyr-only version forms insoluble aggregates. Combining quantum chemistry calculations and solution NMR, a transient H-bonding network requiring the two hydroxyl groups of Dopa is found to be critical to enable LLPS in Dopa-mutated Pvfp-5β. Overall, the study suggests that Dopa plays an important role in regulating LLPS of MFPs, which may be critical to concentrate the adhesive proteins at the plaque/substrate interface and therefore produce a more robust adhesive. The findings also provide molecular-level lessons to guide biomanufacturing of protein-based materials such as bioadhesives and load-bearing fibers.
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http://dx.doi.org/10.1002/adma.202103828DOI Listing
June 2022

Liquid-Liquid Phase Separation of Short Histidine- and Tyrosine-Rich Peptides: Sequence Specificity and Molecular Topology.

J Phys Chem B 2021 07 9;125(25):6776-6790. Epub 2021 Jun 9.

School of Biological Sciences, Nanyang Technological University (NTU), 60 Nanyang Drive, Singapore, 637 551.

The increasing realization of the prevalence of liquid-liquid phase separation (LLPS) across multiple length scales of biological constructs, from intracellular membraneless organelles to extracellular load-bearing tissues, has raised intriguing questions about intermolecular interactions regulating LLPS at the atomic level. Squid-beak derived histidine (His)- and tyrosine (Tyr)-rich peptides (HB) have recently emerged as suitable short model peptides to precisely assess the roles of peptide motifs and single residues on the phase behavior and material properties of microdroplets obtained by LLPS. In this study, by systematically introducing single mutations in an HB, we have identified specific sticker residues that attract peptide chains together. We find that His and Tyr residues located near the sequence termini drive phase separation, forming interaction nodes that stabilize microdroplets. Combining quantum chemistry simulations with NMR studies, we predict atomic-level bond geometries and uncover inter-residue supramolecular interactions governing LLPS. These results are subsequently used to propose possible topological arrangements of the peptide chains, which upon expansion can help explain the three-dimensional network of microdroplets. The stability of the proposed topologies carried out through all-atom molecular dynamics simulations predicts chain topologies that are more likely to stabilize the microdroplets. Overall, this study provides useful guidelines for the design of peptide coacervates with tunable phase behavior and material properties. In addition, the analysis of nanoscale topologies may pave the way to understand how client molecules can be trapped within microdroplets, with direct implications for the encapsulation and controlled release of therapeutics for drug delivery applications.
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http://dx.doi.org/10.1021/acs.jpcb.0c11476DOI Listing
July 2021

Structure of a consensus chitin-binding domain revealed by solution NMR.

J Struct Biol 2021 06 18;213(2):107725. Epub 2021 Mar 18.

Biological and Biomimetic Material Laboratory, Center for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 637553, Singapore; School of Biological Sciences, NTU, 60 Nanyang Drive, Singapore 637551, Singapore; NTU Institute of Structural Biology, Experimental Medicine Building (EMB), 59 Nanyang Drive, Level 06-01, Singapore 636921, Singapore. Electronic address:

Chitin-binding proteins (CBPs) are a versatile group of proteins found in almost every organism on earth. CBPs are involved in enzymatic carbohydrate degradation and also serve as templating scaffolds in the exoskeleton of crustaceans and insects. One specific chitin-binding motif found across a wide range of arthropods' exoskeletons is the "extended Rebers and Riddiford" consensus (R&R), whose mechanism of chitin binding remains unclear. Here, we report the 3D structure and molecular level interactions of a chitin-binding domain (CBD-γ) located in a CBP from the beak of the jumbo squid Dosidicus gigas. This CBP is one of four chitin-binding proteins identified in the beak mouthpart of D. gigas and is believed to interact with chitin to form a scaffold network that is infiltrated with a second set of structural proteins during beak maturation. We used solution state NMR spectroscopy to elucidate the molecular interactions between CBD-γ and the soluble chitin derivative pentaacetyl-chitopentaose (PCP), and find that folding of CBD-γ is triggered upon its interaction with PCP. To our knowledge, this is the first experimental 3D structure of a CBP containing the R&R consensus motif, which can be used as a template to understand in more details the role of the R&R motif found in a wide range of CBP-chitin complexes. The present structure also provides molecular information for biomimetic synthesis of graded biomaterials using aqueous-based chemistry and biopolymers.
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http://dx.doi.org/10.1016/j.jsb.2021.107725DOI Listing
June 2021

Fracture toughness of the stomatopod dactyl club is enhanced by plastic dissipation: A fracture micromechanics study.

Acta Biomater 2021 05 13;126:339-349. Epub 2021 Mar 13.

Biological and Biomimetic Materials Laboratory, Center for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, 639798, Singapore; School of Biological Sciences, NTU, 60 Nanyang Drive, 637551, Singapore. Electronic address:

The dactyl club of stomatopods is a biological hammer used to strike on hard-shell preys. To serve its function, the club must be imparted with a high tolerance against both contact stresses and fracture. While the contact mechanics of the club has been established, fracture toughness characterization has so far remained more elusive and semi-quantitative using nanoindentation fracture methods. Here, we used microcantilever fracture specimens with a chevron-notched crack geometry to quantitatively evaluate the fracture response of the impact region of dactyl clubs. The chevron-notched geometry was selected as it minimizes surface-related artefacts due to ion milling, and further allows to carry out fracture tests on samples free of pre-cracks with stable crack propagation even for brittle materials. Both linear elastic as well as elastic-plastic fracture mechanics methods, together with finite element modelling, were employed to analyse the fracture data. We find that crack-tip plastic dissipation is the main mechanism contributing to the fracture properties of the dactyl club material. Our study also suggests that the chevron-notched crack geometry is a suitable method to quantitatively assess the fracture toughness of hard biological materials. STATEMENT OF SIGNIFICANCE: Characterizing the fracture resistance of biomineralized structures is essential to draw their structure-properties relationships. Yet measuring the fracture properties of such materials is often hampered by their small size and irregular shape. Indentation fracture is used to circumvent these issues but does not discriminate between the elastic and elastic-plastic contributions to the fracture resistance. The dactyl club "hammer" of mantis shrimps is a biological material whose fracture properties are central to its function. A microfracture study was conducted using microcantilever specimens with chevron-notched crack geometry to assess the fracture toughness. Adopting linear elastic and elastic-plastic fracture mechanics protocols, we find that plastic dissipation is the major contribution to the fracture response of the hypermineralized impact region of the dactyl club.
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http://dx.doi.org/10.1016/j.actbio.2021.03.025DOI Listing
May 2021

Magnetically responsive peptide coacervates for dual hyperthermia and chemotherapy treatments of liver cancer.

Acta Biomater 2020 07 15;110:221-230. Epub 2020 May 15.

Biological and Biomimetic Materials Laboratory, Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 637553; School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. Electronic address:

Liver cancer is an aggressive malignancy associated with high levels of mortality and morbidity. Doxorubicin (Dox) is often used to slow down liver cancer progression; however its efficacy is limited, and its severe side effects prevent its routine use at therapeutic concentrations. We present a biomimetic peptide that coacervates into micro-droplets, within which both Dox and magnetic nanoparticles (MNPs) can be sequestered. These Dox-loaded Magnetic Coacervates (DMCs) can be used for thermo-chemotherapy, with the controlled release of Dox triggered by an external Alternating Magnetic Field (AMF). The DMCs are internalized by the cells via an energy-independent mechanism which is not based on endocytosis. Application of AMF generates a temperature of 45 °C within the DMCs, triggering their disassembly and the simultaneous release of Dox, thereby resulting in dual hyperthermia and chemotherapy for more efficient cancer therapy. In vitro studies conducted under AMF reveal that DMCs are cytocompatible and effective in inducing HepG2 liver cancer cell death. Thermo-chemotherapy treatment against HepG2 cells is also shown to be more effective compared to either hyperthermia or chemotherapy treatments alone. Thus, our novel peptide DMCs can open avenues in theranostic strategies against liver cancer through programmable, wireless, and remote control of Dox release. STATEMENT OF SIGNIFICANCE: Simultaneous administration of chemical and thermal therapy (thermo-chemotherapy) is more effective in inducing liver cancer cell death and improving survival rate. Thus, there is a keen interest in developing suitable carriers for thermo-chemotherapy. Coacervate micro-droplets display significant advantages, including high loading capacity, fast self-assembly in aqueous environments, and liquid-like behavior. However, they have not yet been explored as carriers for thermo-chemotherapy. Here, we demonstrate that peptide coacervate micro-droplets can co-encapsulate Dox and magnetic nanoparticles and cross the cell membrane. Applying an alternating magnetic field to cells containing drug-loaded coacervates triggers the release of Dox as well as the localized heating by magnetic hyperthermia, resulting in efficient liver cancer cell death by dual thermo-chemotherapy.
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http://dx.doi.org/10.1016/j.actbio.2020.04.024DOI Listing
July 2020

Green biolubricant infused slippery surfaces to combat marine biofouling.

J Colloid Interface Sci 2020 May 14;568:185-197. Epub 2020 Feb 14.

Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 639798, Singapore; School of Biological Sciences, Nanyang Technological University (NTU), 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address:

Hypothesis: Marine biofouling is a global, longstanding problem for maritime industries and coastal areas arising from the attachment of fouling organisms onto solid immersed surfaces. Slippery Liquid Infused Porous Surfaces (SLIPS) have recently shown promising capacity to combat marine biofouling. In most SLIPS coatings, the lubricant is a silicone/fluorinated-based synthetic component that may not be fully compatible with the marine life. We hypothesized that eco-friendly biolubricants could be used to replace synthetic lubricants in SLIPS for marine anti-fouling.

Experiments: We developed SLIPS coatings using oleic acid (OA) and methyl oleate (MO) as infusing phases. The infusion efficiency was verified with confocal microscopy, surface spectroscopy, wetting efficiency, and nanocontact mechanics. Using green mussels as a model organism, we tested the anti-fouling performance of the biolubricant infused SLIPS and verified its non-cytotoxicity against fish gill cells.

Findings: We find that UV-treated PDMS infused with MO gives the most uniform infused film, in agreement with the lowest interfacial energy among all surface/biolubricants produced. These surfaces exhibit efficient anti-fouling properties, as defined by the lowest number of mussel adhesive threads attached to the surface as well as by the smallest surface/thread adhesion strength. We find a direct correlation between anti-fouling performance and the substrate/biolubricant interfacial energy.
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http://dx.doi.org/10.1016/j.jcis.2020.02.049DOI Listing
May 2020

Thermal-Disrupting Interface Mitigates Intercellular Cohesion Loss for Accurate Topical Antibacterial Therapy.

Adv Mater 2020 Mar 19;32(12):e1907030. Epub 2020 Feb 19.

Innovative Centre for Flexible Devices (iFLEX), School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore.

Bacterial infections remain a leading threat to global health because of the misuse of antibiotics and the rise in drug-resistant pathogens. Although several strategies such as photothermal therapy and magneto-thermal therapy can suppress bacterial infections, excessive heat often damages host cells and lengthens the healing time. Here, a localized thermal managing strategy, thermal-disrupting interface induced mitigation (TRIM), is reported, to minimize intercellular cohesion loss for accurate antibacterial therapy. The TRIM dressing film is composed of alternative microscale arrangement of heat-responsive hydrogel regions and mechanical support regions, which enables the surface microtopography to have a significant effect on disrupting bacterial colonization upon infrared irradiation. The regulation of the interfacial contact to the attached skin confines the produced heat and minimizes the risk of skin damage during thermoablation. Quantitative mechanobiology studies demonstrate the TRIM dressing film with a critical dimension for surface features plays a critical role in maintaining intercellular cohesion of the epidermis during photothermal therapy. Finally, endowing wound dressing with the TRIM effect via in vivo studies in S. aureus infected mice demonstrates a promising strategy for mitigating the side effects of photothermal therapy against a wide spectrum of bacterial infections, promoting future biointerface design for antibacterial therapy.
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http://dx.doi.org/10.1002/adma.201907030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7702719PMC
March 2020

Hydrogen bond guidance and aromatic stacking drive liquid-liquid phase separation of intrinsically disordered histidine-rich peptides.

Nat Commun 2019 11 29;10(1):5465. Epub 2019 Nov 29.

Center for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Drive, Singapore, 637553, Singapore.

Liquid-liquid phase separation (LLPS) of intrinsically disordered proteins (IDPs) is involved in both intracellular membraneless organelles and extracellular tissues. Despite growing understanding of LLPS, molecular-level mechanisms behind this process are still not fully established. Here, we use histidine-rich squid beak proteins (HBPs) as model IDPs to shed light on molecular interactions governing LLPS. We show that LLPS of HBPs is mediated though specific modular repeats. The morphology of separated phases (liquid-like versus hydrogels) correlates with the repeats' hydrophobicity. Solution-state NMR indicates that LLPS is a multistep process initiated by deprotonation of histidine residues, followed by transient hydrogen bonding with tyrosine, and eventually by hydrophobic interactions. The microdroplets are stabilized by aromatic clustering of tyrosine residues exhibiting restricted molecular mobility in the nano-to-microsecond timescale according to solid-state NMR experiments. Our findings provide guidelines to rationally design pH-responsive peptides with LLPS ability for various applications, including bioinspired protocells and smart drug-delivery systems.
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http://dx.doi.org/10.1038/s41467-019-13469-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6884462PMC
November 2019

A Short Peptide Hydrogel with High Stiffness Induced by 3-Helices to β-Sheet Transition in Water.

Adv Sci (Weinh) 2019 Nov 10;6(21):1901173. Epub 2019 Sep 10.

Center for Biomimetic Sensor Science School of Materials Science and Engineering Nanyang Technological University Singapore 639798 Singapore.

Biological gels generally require polymeric chains that produce long-lived physical entanglements. Low molecular weight colloids offer an alternative to macromolecular gels, but often require ad-hoc synthetic procedures. Here, a short biomimetic peptide composed of eight amino acid residues derived from squid sucker ring teeth proteins is demonstrated to form hydrogel in water without any cross-linking agent or chemical modification and exhibits a stiffness on par with the stiffest peptide hydrogels. Combining solution and solid-state NMR, circular dichroism, infrared spectroscopy, and X-ray scattering, the peptide is shown to form a supramolecular, semiflexible gel assembled from unusual right-handed 3-helices stabilized in solution by π-π stacking. During gelation, the 3-helices undergo conformational transition into antiparallel β-sheets with formation of new interpeptide hydrophobic interactions, and molecular dynamic simulations corroborate stabilization by cross β-sheet oligomerization. The current study broadens the range of secondary structures available to create supramolecular hydrogels, and introduces 3-helices as transient building blocks for gelation via a 3-to-β-sheet conformational transition.
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http://dx.doi.org/10.1002/advs.201901173DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6839752PMC
November 2019

Three-dimensional structure of Megabalanus rosa Cement Protein 20 revealed by multi-dimensional NMR and molecular dynamics simulations.

Philos Trans R Soc Lond B Biol Sci 2019 10 9;374(1784):20190198. Epub 2019 Sep 9.

School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.

Barnacles employ a protein-based cement to firmly attach to immersed substrates. The cement proteins (CPs) have previously been identified and sequenced. However, the molecular mechanisms of adhesion are not well understood, in particular, because the three-dimensional molecular structure of CPs remained unknown to date. Here, we conducted multi-dimensional nuclear magnetic resonance (NMR) studies and molecular dynamics (MD) simulations of recombinant Megabalanus rosa Cement Protein 20 (rMrCP20). Our NMR results show that rMrCP20 contains three main folded domain regions intervened by two dynamic loops, resulting in multiple protein conformations that exist in equilibrium. We found that 12 out of 32 Cys in the sequence engage in disulfide bonds that stabilize the β-sheet domains owing to their placement at the extremities of β-strands. Another feature unveiled by NMR is the location of basic residues in turn regions that are exposed to the solvent, playing an important role for intermolecular contact with negatively charged surfaces. MD simulations highlight a highly stable and conserved β-motif (β7-β8), which may function as nuclei for amyloid-like nanofibrils previously observed in the cured adhesive cement. To the best of our knowledge, this is the first report describing the tertiary structure of an extracellular biological adhesive protein at the molecular level. This article is part of the theme issue 'Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.
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http://dx.doi.org/10.1098/rstb.2019.0198DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6745475PMC
October 2019

Adhesive Properties of Adsorbed Layers of Two Recombinant Mussel Foot Proteins with Different Levels of DOPA and Tyrosine.

Langmuir 2019 12 11;35(48):15481-15490. Epub 2019 Sep 11.

Consiglio Nazionale delle Ricerche - Istituto di Nanotecnologia (CNR - Nanotec) , c/o Università della Calabria , Ponte P. Bucci, 33/B , 87036 Rende ( CS ), Italy.

Using a surface forces apparatus and an atomic force microscope, we characterized the adhesive properties of adsorbed layers of two recombinant variants of foot protein 5 (PVFP-5), the main surface-binding protein in the adhesive plaque of the Asian green mussel. In one variant, all tyrosine residues were modified into 3,4-dihydroxy-l-phenylalanine (DOPA) during expression using a residue-specific incorporation strategy. DOPA is a key molecular moiety underlying underwater mussel adhesion. In the other variant, all tyrosine residues were preserved. The layer was adsorbed on a mica substrate and pressed against an uncoated surface. While DOPA produced a stronger adhesion than tyrosine in contact with the nanoscopic SiN probe of the atomic force microscope, the two variants produced comparable adhesion on the curved macroscopic mica surfaces of the surface forces apparatus. These findings show that the presence of DOPA is not a sufficient condition to generate strong underwater adhesion. Surface chemistry and contact geometry affect the strength and abundance of protein-surface bonds created during adsorption and surface contact. Importantly, the adsorbed protein layer has a random and dynamic polymer-network structure that should be optimized to transmit the tensile stress generated during surface separation to DOPA surface bonds rather than other weaker bonds.
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http://dx.doi.org/10.1021/acs.langmuir.9b01730DOI Listing
December 2019

Fast and Green Synthesis of an Oligo-Hydrocaffeic Acid-Based Adhesive.

ACS Omega 2018 Dec 31;3(12):18911-18916. Epub 2018 Dec 31.

Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 637553.

A green, mussel-inspired bioadhesive based on oligomerization of hydrocaffeic acid was synthesized in water by an ultrafast one-step reaction in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide as an activating agent. The resulting oligomers exhibited strong wet adhesion when applied to different substrates including glass, stainless steel, and aluminum. Compared to most commercial adhesives, this bioinspired adhesive is produced via a sustainable and green process, i.e., aqueous-based synthesis, one-step reaction, and in the absence of any purification step to obtain the final functional adhesive.
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http://dx.doi.org/10.1021/acsomega.8b01181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6643518PMC
December 2018

Time-Resolved Observations of Liquid-Liquid Phase Separation at the Nanoscale Using in Situ Liquid Transmission Electron Microscopy.

J Am Chem Soc 2019 05 22;141(17):7202-7210. Epub 2019 Apr 22.

Biological and Biomimetic Material Laboratory and Center for Biomimetic Sensor Science, School of Materials Science and Engineering , Nanyang Technological University (NTU) , 50 Nanyang Avenue , Singapore 637553.

Liquid-liquid phase separation (LLPS) of proteins into concentrated microdroplets (also called coacervation) is a phenomenon that is increasingly recognized to occur in many biological processes, both inside and outside the cell. While it has been established that LLPS can be described as a spinodal decomposition leading to demixing of an initially homogeneous protein solution, little is known about the assembly pathways by which soluble proteins aggregate into dense microdroplets. Using recent developments in techniques enabling the observation of matter suspended in liquid by transmission electron microscopy, we observed how a model intrinsically disordered protein phase-separates in liquid environment. Our observations reveal the dynamic mechanisms by which soluble proteins self-organize into condensed microdroplets with nanoscale and millisecond space and time resolution, respectively. With this method, the nucleation and initial growth steps of LLPS could be captured, opening the door for a deeper understanding of biomacromolecular complexes exhibiting LLPS ability.
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http://dx.doi.org/10.1021/jacs.9b03083DOI Listing
May 2019

A diecast mineralization process forms the tough mantis shrimp dactyl club.

Proc Natl Acad Sci U S A 2019 04 11;116(18):8685-8692. Epub 2019 Apr 11.

Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University (NTU), 639798 Singapore;

Biomineralization, the process by which mineralized tissues grow and harden via biogenic mineral deposition, is a relatively lengthy process in many mineral-producing organisms, resulting in challenges to study the growth and biomineralization of complex hard mineralized tissues. Arthropods are ideal model organisms to study biomineralization because they regularly molt their exoskeletons and grow new ones in a relatively fast timescale, providing opportunities to track mineralization of entire tissues. Here, we monitored the biomineralization of the mantis shrimp dactyl club-a model bioapatite-based mineralized structure with exceptional mechanical properties-immediately after ecdysis until the formation of the fully functional club and unveil an unusual development mechanism. A flexible membrane initially folded within the club cavity expands to form the new club's envelope. Mineralization proceeds inwards by mineral deposition from this membrane, which contains proteins regulating mineralization. Building a transcriptome of the club tissue and probing it with proteomic data, we identified and sequenced Club Mineralization Protein 1 (CMP-1), an abundant mildly phosphorylated protein from the flexible membrane suggested to be involved in calcium phosphate mineralization of the club, as indicated by in vitro studies using recombinant CMP-1. This work provides a comprehensive picture of the development of a complex hard tissue, from the secretion of its organic macromolecular template to the formation of the fully functional club.
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http://dx.doi.org/10.1073/pnas.1816835116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6500109PMC
April 2019

Minimal Reconstitution of Membranous Web Induced by a Vesicle-Peptide Sol-Gel Transition.

Biomacromolecules 2019 04 26;20(4):1709-1718. Epub 2019 Mar 26.

Centre for Biomimetic Sensor Science , Nanyang Technological University , 50 Nanyang Drive 637553 , Singapore.

Positive strand RNA viruses replicate in specialized niches called membranous web within the cytoplasm of host cells. These virus replication organelles sequester viral proteins, RNA, and a variety of host factors within a fluid, amorphous matrix of clusters of endoplasmic reticulum (ER) derived vesicles. They are thought to form by the actions of a nonstructural viral protein NS4B, which remodels the ER and produces dense lipid-protein condensates. Here, we used in vitro reconstitution to identify the minimal components and elucidate physical mechanisms driving the web formation. We found that the N-terminal amphipathic domain of NS4B (peptide 4BAH2) and phospholipid vesicles (∼100-200 nm in diameter) were sufficient to produce a gel-like, viscoelastic condensate. This condensate coexists with the surrounding aqueous phase and affords rapid exchange of molecules. Together, it recapitulates the essential properties of the virus-induced membranous web. Our data support a novel phase separation mechanism in which phospholipid vesicles provide a supramolecular template spatially organizing multiple self-associating peptides thereby generating programmable multivalency de novo and inducing macroscopic phase separation.
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http://dx.doi.org/10.1021/acs.biomac.9b00081DOI Listing
April 2019

Biomechanical Design of the Mantis Shrimp Saddle: A Biomineralized Spring Used for Rapid Raptorial Strikes.

iScience 2018 Oct 18;8:271-282. Epub 2018 Oct 18.

Biological and Biomimetic Materials Laboratory, School of Materials Science and Engineering, Nanyang Technological University, Singapore 637553, Singapore; School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address:

Stomatopods deliver one of the fastest strikes in the animal kingdom using their powerful "dactyl clubs." This kinematic performance is enabled by a power amplification device whereby elastic energy is stored in a saddle-shape mineralized bilayer structure. We combined a set of comprehensive micro-mechanical measurements with finite element modeling (FEM) to quantitatively elucidate the saddle biomechanical design. Dynamic nano-scale testing reveals that viscoelastic dissipation is minimized in the highly mineralized layer, whereas micro-bending experiments on miniature cantilevers highlight the critical role of the bilayer arrangement in optimizing storage of elastic energy. FEM shows that the saddle shape prevents stress concentration and the stresses remain well within the elastic range during loading, while the neutral surface coincides with the bilayer interface to prevent interfacial delamination. The study unveils the multi-scale design behind the intriguing ability of the saddle to store a high density of elastic energy using stiff but intrinsically brittle materials. VIDEO ABSTRACT.
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http://dx.doi.org/10.1016/j.isci.2018.08.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6204534PMC
October 2018

Controlling Supramolecular Chiral Nanostructures by Self-Assembly of a Biomimetic β-Sheet-Rich Amyloidogenic Peptide.

ACS Nano 2018 09 21;12(9):9152-9161. Epub 2018 Aug 21.

Department of Health Sciences & Technology , ETH Zurich , Zurich CH-8092 , Switzerland.

Squid sucker ring teeth (SRT) have emerged as a promising protein-only, thermoplastic biopolymer with an increasing number of biomedical and engineering applications demonstrated in recent years. SRT is a supra-molecular network whereby a flexible, amorphous matrix is mechanically reinforced by nanoconfined β-sheets. The building blocks for the SRT network are a family of suckerin proteins that share a common block copolymer architecture consisting of amorphous domains intervened by smaller, β-sheet forming modules. Recent studies have identified the peptide A1H1 (peptide sequence AATAVSHTTHHA) as one of the most abundant β-sheet forming domains within the suckerin protein family. However, we still have little understanding of the assembly mechanisms by which the A1H1 peptide may assemble into its functional load-bearing domains. In this study, we conduct a detailed self-assembly study of A1H1 and show that the peptide undergoes β-strands-driven elongation into amyloid-like fibrils with a rich polymorphism. The nanostructure of the fibrils was elucidated by small and wide-angle X-ray scattering (SAXS and WAXS) and atomic force microscopy (AFM). The presence of His-rich and Ala-rich segments results in an amphiphilic behavior and drives its assembly into fibrillar supramolecular chiral aggregates with helical ribbon configuration in solution, with the His-rich region exposed to the solvent molecules. Upon increase in concentration, the fibrils undergo gel formation, while preserving the same mesoscopic features. This complex phase behavior suggests that the repeat peptide modules of suckerins may be manipulated beyond their native biological environment to produce a wider variety of self-assembled amyloid-like nanostructures.
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http://dx.doi.org/10.1021/acsnano.8b03582DOI Listing
September 2018

Supramolecular propensity of suckerin proteins is driven by β-sheets and aromatic interactions as revealed by solution NMR.

Biomater Sci 2018 Aug;6(9):2440-2447

Center for Biomimetic Sensor Science (CBSS), School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore 637553.

Suckerin proteins are a family of block co-polymer-like structural proteins that self-assemble into robust supramolecular structures - the sucker ring teeth (SRT) - which are located on the arms and tentacles of cephalopods and used to firmly capture preys. Suckerins are promising biomimetic protein-based biopolymers, but the supramolecular interactions stabilizing SRT remain unknown. Here, we report multi-dimensional Nuclear Magnetic Resonance (NMR) spectroscopy structural studies of an engineered suckerin protein composed of two main sequence modules. The protein adopts a dynamic structure with regions in both module 1 (M1: residues A42-A52) and module 2 (M2: residues G30-Y37 and G58-Y65) folding into anti-parallel β-sheets and displaying β-strand propensity, respectively. The obtained structure highlights that aromatic residues present in glycine (Gly)-rich M2 modules are involved in π-π stacking interactions, leading to the stabilization of the structural core. In addition, hydrogen/deuterium (H/D) exchange studies demonstrate a high protection of residues involved in intra-molecular β-sheets. Gaining a better understanding of the molecular structure of suckerin provides key molecular lessons that may be mimicked in the de novo design of peptide- and protein-based biomaterials with applications in medicine, tissue engineering and nanotechnology.
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http://dx.doi.org/10.1039/c8bm00556gDOI Listing
August 2018

Glucose-Responsive Peptide Coacervates with High Encapsulation Efficiency for Controlled Release of Insulin.

Bioconjug Chem 2018 07 26;29(7):2176-2180. Epub 2018 Jun 26.

Centre for Biomimetic Sensor Science, School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Drive , 637553 Singapore.

A new glucose-responsive insulin delivery system is fabricated using biomimetic peptide coacervates derived from the Humboldt squid (Dosidicus Gigas) beak. Both insulin and glucose oxidase are coencapsulated within coacervate microdroplets. The glucose oxidase quickly responds to increasing glucose levels to generate a local acidic environment, thereby rapidly triggering the dissociation of pH-sensitive coacervates to release the insulin cargo. The rate of insulin release is dependent on the glucose level, increases under hyperglycemic conditions, and decreases under normoglycemic conditions. This glucose responsiveness mimics pancreatic β-cell function by releasing insulin according to glucose levels.
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http://dx.doi.org/10.1021/acs.bioconjchem.8b00369DOI Listing
July 2018

Multi-scale structural design and biomechanics of the pistol shrimp snapper claw.

Acta Biomater 2018 06 21;73:449-457. Epub 2018 Apr 21.

Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 639798, Singapore; School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address:

The Arthropoda, the largest phylum of the Animal Kingdom, have successfully evolved to survive various ecological constraints under a wide range of environmental conditions. Central to this survival are the structural designs developed in their exoskeletons and their raptorial appendages for protection and hunting. One such example, the pistol shrimp, is a shallow-water crustacean that is well-known for its aggressive hunting behavior, using its snapper claw to trigger the nucleation of cavitation bubbles that strike targets. In this study, we conducted a multi-scale structural/nanomechanics relationship study of this biotool to analyze its mechanical response to contact stresses. We found that the pistol shrimp snapper claw, which exhibits the capacity to emit a high-velocity water jet during rapid closure actions, is more brittle than other mineralized biotools, exhibiting accelerated wear damage under contact stresses. However, due to an angular offset between the dactylus and pollex of the snapper claw, the appendage never engages in any mechanical contact during the snapping action. This feature is in stark contrast to that reported in other fast raptorial appendages of crustaceans, notably the mantis shrimp dactyl club, which is designed to shatter close range targets in contact mode and exhibits a superior resistance to contact damage and wear. These findings suggest that adaptation of hunting appendages goes beyond their macroscopic morphology, and that multi-scale structural design concomitantly adapted to function, with enhanced structural complexification for tools that are subjected to more intense contact stresses.

Statement Of Significance: The evolution success of crustaceans is largely due to the diversification of their mineralized exoskeletons and hunting appendages, which exhibit a large palette of morphometric characteristics that have adapted to meet particular functions. We explored the "snapper claw" of the pistol shrimp, which is used to generate cavitation bubbles and strike prey. Our multi-scale structure-property relationship study reveals that the snapper claw is more brittle than other fast raptorial appendages - such as the stomatopod dactyl club - because it is not directly subjected to direct contact forces during action. This study implies that when higher mechanical stresses are needed to meet the function, the internal structure is built of a more complex architecture that allows to mitigate internal structural damage.
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http://dx.doi.org/10.1016/j.actbio.2018.04.038DOI Listing
June 2018
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