Publications by authors named "Naba K Dutta"

40 Publications

Polyelectrolyte Gels: Fundamentals, Fabrication and Applications.

Gels 2021 Sep 18;7(3). Epub 2021 Sep 18.

School of Engineering, STEM College, RMIT University, Melbourne, VIC 3000, Australia.

Polyelectrolyte gels are an important class of polymer gels and a versatile platform with charged polymer networks with ionisable groups. They have drawn significant recent attention as a class of smart material and have demonstrated potential for a variety of applications. This review begins with the fundamentals of polyelectrolyte gels, which encompass various classifications (i.e., origin, charge, shape) and crucial aspects (ionic conductivity and stimuli responsiveness). It further centralises recent developments of polyelectrolyte gels, emphasising their synthesis, structure-property relationships and responsive properties. Sequentially, this review demonstrates how polyelectrolyte gels' flourishing properties create attractiveness to a range of applications including tissue engineering, drug delivery, actuators and bioelectronics. Finally, the review outlines the indisputable appeal, further improvements and emerging trends in polyelectrolyte gels.
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http://dx.doi.org/10.3390/gels7030148DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8482214PMC
September 2021

Emerging bioadhesives: from traditional bioactive and bioinert to a new biomimetic protein-based approach.

Adv Colloid Interface Sci 2021 Oct 14;296:102521. Epub 2021 Sep 14.

School of Engineering, RMIT University, Melbourne, VIC 3000, Australia. Electronic address:

Bioadhesives have reached significant milestones over the past two decades. Research has shown not only to produce adhesives capable of adhering to dry tissue but recently wet tissue as well. However, most bioadhesives developed have exhibited high adhesion strength yet lack other properties required for versatility in application, such as elasticity, biocompatibility and biodegradability. Adapting from limitations met from early bioadhesives and meeting the current demand allows novel bioadhesives to reach new milestones for the future. In this review, we overview the progression and variations of bioadhesives, current trends, characterisation techniques and conclude with future perspectives for bioadhesives for tissue engineering applications.
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http://dx.doi.org/10.1016/j.cis.2021.102521DOI Listing
October 2021

3D Printable Soy/Silk Hybrid Hydrogels for Tissue Engineering Applications.

Biomacromolecules 2021 09 30;22(9):3668-3678. Epub 2021 Aug 30.

School of Engineering, RMIT University, Melbourne, VIC 3000, Australia.

The development of protein-based 3D printable hydrogel systems with tunable structure and properties is a critical challenge in contemporary biomedicine. Particularly, 3D printing of modular hydrogels comprising different types of protein tertiary structure, such as globular and fibrous, has not yet been achieved. Here we report the extrusion-based 3D printing of hybrid hydrogels photochemically co-cross-linked between globular soy protein isolate (SPI) and fibrous silk fibroin (SF) for the first time. The hierarchical structure and organization of pristine SPI and SF, and 1:3 (SPI/SF) hybrid inks under various shear stress were investigated using in situ rheology combined with small-/ultra-small-angle neutron scattering (Rheo-SANS/USANS). The hybrid ink exhibited an isotropic mass fractal structure that was stable between tested shear rates of 0.1 and 100 s (near printing shear). The kinetics of sol-gel transition during the photo-cross-linking reaction and the micromechanical properties of fabricated hydrogels were investigated using photorheology and atomic force microscopy, where the hybrid hydrogels exhibited tunable storage and Young's moduli in the range of 13-29 and 214-811 kPa, respectively. The cross-link density and printing accuracy of hybrid hydrogels and inks were observed to increase with the increase in SF content. The 3D printed hybrid hydrogels exhibited a micropore size larger than that of solution casted hydrogels; where the 3D printed 1:3 (SPI/SF) hybrid hydrogel showed a pore size about 7.6 times higher than that of the casted hydrogel. Moreover, the fabricated hybrid hydrogels exhibit good mouse fibroblast cell attachment, viability, and proliferation, demonstrating their potential for tissue engineering applications.
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http://dx.doi.org/10.1021/acs.biomac.1c00250DOI Listing
September 2021

Mixed-Matrix Membrane Fabrication for Water Treatment.

Membranes (Basel) 2021 Jul 23;11(8). Epub 2021 Jul 23.

Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, VIC 3000, Australia.

In recent years, technology for the fabrication of mixed-matrix membranes has received significant research interest due to the widespread use of mixed-matrix membranes (MMMs) for various separation processes, as well as biomedical applications. MMMs possess a wide range of properties, including selectivity, good permeability of desired liquid or gas, antifouling behavior, and desired mechanical strength, which makes them preferable for research nowadays. However, these properties of MMMs are due to their tailored and designed structure, which is possible due to a fabrication process with controlled fabrication parameters and a choice of appropriate materials, such as a polymer matrix with dispersed nanoparticulates based on a typical application. Therefore, several conventional fabrication methods such as a phase-inversion process, interfacial polymerization, co-casting, coating, electrospinning, etc., have been implemented for MMM preparation, and there is a drive for continuous modification of advanced, easy, and economic MMM fabrication technology for industrial-, small-, and bulk-scale production. This review focuses on different MMM fabrication processes and the importance of various parameter controls and membrane efficiency, as well as tackling membrane fouling with the use of nanomaterials in MMMs. Finally, future challenges and outlooks are highlighted.
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http://dx.doi.org/10.3390/membranes11080557DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8402158PMC
July 2021

Additive Manufacturing of Polymer Materials: Progress, Promise and Challenges.

Polymers (Basel) 2021 Feb 28;13(5). Epub 2021 Feb 28.

School of Engineering, Chemical and Environmental Engineering, RMIT University, Melbourne 3000, Australia.

The use of additive manufacturing (AM) has moved well beyond prototyping and has been established as a highly versatile manufacturing method with demonstrated potential to completely transform traditional manufacturing in the future. In this paper, a comprehensive review and critical analyses of the recent advances and achievements in the field of different AM processes for polymers, their composites and nanocomposites, elastomers and multi materials, shape memory polymers and thermo-responsive materials are presented. Moreover, their applications in different fields such as bio-medical, electronics, textiles, and aerospace industries are also discussed. We conclude the article with an account of further research needs and future perspectives of AM process with polymeric materials.
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http://dx.doi.org/10.3390/polym13050753DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7957542PMC
February 2021

Microroughness induced biomimetic coating for biodegradation control of magnesium.

Mater Sci Eng C Mater Biol Appl 2021 Feb 30;121:111811. Epub 2020 Dec 30.

Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, VIC, Australia. Electronic address:

Herein we explore a combination of anodization induced micro-roughness and biomimetic coating on pure magnesium (Mg) metal at different applied voltages to control adhesion, biodegradation, and corrosion performance in simulated body fluid solution. The anodic film was fabricated using two different potentials, 3 and 5 V, respectively, to create microroughness on the Mg surface. The microroughened Mg surface was subsequently coated with a biomimetic silk thin film; and the characteristics of the treated Mg-substrates were evaluated using various spectroscopic, microscopic, immersion, and electrochemical techniques. A number of independent measurements, including hydrogen evolution, weight loss and electrochemical methods were employed to assess the corrosion characteristics. The silk-coated anodized samples revealed dramatically reduced degradation rate in terms of volume of hydrogen gas generation and weight loss compared to the respective anodized but uncoated, which revealed that optimized biomimetic silk-coated Mg surface (anodized at 5 V and subsequently biomimetic silk-coated ANMg) exhibited the best corrosion performance among all other tested samples. The ANMg Silk showed the highest polarization resistance (46.12 kΩ·cm), protection efficiency (>0.99) and lowest corrosion rate (only 0.017 mm/year) relative to untreated Mg (8.457 mm/year), and anodized Mg (1.039 for anodized at 3 V and 0.986 for anodized at 5 V) surface due to the formation of a pore-free dense biomimetic protective film over Mg surface. The results of the cytotoxicity test confirm that silk-coated samples are significantly less cytotoxic compared to bare and anodized Mg samples. With enhanced corrosion resistance and cytocompatibility, silk-coated Mg could be a potential material for clinical applications.
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http://dx.doi.org/10.1016/j.msec.2020.111811DOI Listing
February 2021

Resilin-mimetics as a smart biomaterial platform for biomedical applications.

Nat Commun 2021 01 8;12(1):149. Epub 2021 Jan 8.

Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, VIC, 3000, Australia.

Intrinsically disordered proteins have dramatically changed the structure-function paradigm of proteins in the 21 century. Resilin is a native elastic insect protein, which features intrinsically disordered structure, unusual multi-stimuli responsiveness and outstanding resilience. Advances in computational techniques, polypeptide synthesis methods and modular protein engineering routines have led to the development of novel resilin-like polypeptides (RLPs) including modular RLPs, expanding their applications in tissue engineering, drug delivery, bioimaging, biosensors, catalysis and bioelectronics. However, how the responsive behaviour of RLPs is encoded in the amino acid sequence level remains elusive. This review summarises the milestones of RLPs, and discusses the development of modular RLP-based biomaterials, their current applications, challenges and future perspectives. A perspective of future research is that sequence and responsiveness profiling of RLPs can provide a new platform for the design and development of new modular RLP-based biomaterials with programmable structure, properties and functions.
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http://dx.doi.org/10.1038/s41467-020-20375-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7794388PMC
January 2021

Nanofiltration for Arsenic Removal: Challenges, Recent Developments, and Perspectives.

Nanomaterials (Basel) 2020 Jul 6;10(7). Epub 2020 Jul 6.

Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, Victoria 3000, Australia.

Arsenic (As) removal is of major significance because inorganic arsenic is highly toxic to all life forms, is a confirmed carcinogen, and is of significant environmental concern. As contamination in drinking water alone threatens more than 150 million people all over the world. Therefore, several conventional methods such as oxidation, coagulation, adsorption, etc., have been implemented for As removal, but due to their cost-maintenance limitations; there is a drive for advanced, low cost nanofiltration membrane-based technology. Thus, in order to address the increasing demand of fresh and drinking water, this review focuses on advanced nanofiltration (NF) strategy for As removal to safeguard water security. The review concentrates on different types of NF membranes, membrane fabrication processes, and their mechanism and efficiency of performance for removing As from contaminated water. The article provides an overview of the current status of polymer-, polymer composite-, and polymer nanocomposite-based NF membranes, to assess the status of nanomaterial-facilitated NF membranes and to incite progress in this area. Finally, future perspectives and future trends are highlighted.
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http://dx.doi.org/10.3390/nano10071323DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7407220PMC
July 2020

Magnesium Alloys With Tunable Interfaces as Bone Implant Materials.

Front Bioeng Biotechnol 2020 10;8:564. Epub 2020 Jun 10.

Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, VIC, Australia.

Magnesium (Mg) based biodegradable materials are a new generation orthopedic implant materials that are intended to possess same mechanical properties as that of bone. Mg alloys are considered as promising substitutes to permanent implants due to their biodegradability in the physiological environment. However, rapid corrosion rate is one of the major constraints of using Mg alloys in clinical applications in spite of their excellent biocompatibility. Approaches to overcome the limitations include the selection of adequate alloying elements, proper surface treatment, surface modification with coating to control the degradation rate. This review focuses on current advances on surface engineering of Mg based biomaterials for biomedical applications. The review begins with a description of corrosion mechanism of Mg alloy, the requirement for appropriate surface functionalization/coatings, their structure-property-performance relationship, and suitability for biomedical applications. The control of physico-chemical properties such as wettability, surface morphology, surface chemistry, and surface functional groups of the coating tailored by various approaches forms the pivotal part of the review. Chemical surface treatment offers initial protection from corrosion and inorganic coating like hydroxyapatite (HA) improves the biocompatibility of the substrate. Considering the demand of ideal implant materials, multilayer hybrid coatings on Mg alloy in combination with chemical pretreatment or inorganic HA coating, and protein-based polymer coating could be a promising technique to improve corrosion resistance and promote biocompatibility of Mg-based alloys.
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http://dx.doi.org/10.3389/fbioe.2020.00564DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297987PMC
June 2020

Bioprintable tough hydrogels for tissue engineering applications.

Adv Colloid Interface Sci 2020 Jul 25;281:102163. Epub 2020 Apr 25.

Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, Victoria 3000, Australia. Electronic address:

Bioprinting is an advanced fabrication approach to engineer complex living structures as the conventional fabrication methods are incapable of integrating structural and biological complexities. It offers the versatility of printing different cell incorporated hydrogels (bioink) layer by layer; offering control over spatial resolution and cell distribution to mimic native tissue architectures. However, the bioprinting of tough hydrogels involve additional complexities, such as employing complex crosslinking or reinforcing mechanisms during printing and pre/post printing cellular activities. Solving this complexity requires attention from engineering, material science and cell biology perspectives. In this review, we discuss different types of bioprinting techniques with focus on current state-of-the-art in bioink formulations and pivotal characteristics of bioinks for tough hydrogel printing. We discuss the scope of transition from 3D to 4D bioprinting and some of the advanced characterization techniques for in-depth understanding of the 3D printing process from the microstructural perspective, along with few specific applications and conclude with the future perspectives in biofabrication of hydrogels for tissue engineering applications.
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http://dx.doi.org/10.1016/j.cis.2020.102163DOI Listing
July 2020

A Sustainable Biomineralization Approach for the Synthesis of Highly Fluorescent Ultra-Small Pt Nanoclusters.

Biosensors (Basel) 2019 Oct 29;9(4). Epub 2019 Oct 29.

Chemical and Environment Engineering, School of Engineering, RMIT University, Melbourne, VIC 3000, Australia.

Herein we report the first example of a facile biomineralization process to produce ultra-small-sized highly fluorescent aqueous dispersions of platinum noble metal quantum clusters (Pt-NMQCs) using a multi-stimulus responsive, biomimetic intrinsically disordered protein (IDP), Rec1-resilin. We demonstrate that Rec1-resilin acts concurrently as the host, reducing agent, and stabilizer of the blue-green fluorescent Pt-NMQCs once they are being formed. The photophysical properties, quantum yield, and fluorescence lifetime measurements of the synthesized Pt-NMQCs were examined using UV-Vis and fluorescence spectroscopy. The oxidation state of the Pt-NMQCs was quantitatively analyzed using X-ray photoelectron spectroscopy. Both a small angle X-ray scattering technique and a modeling approach have been attempted to present a detailed understanding of the structure and conformational dynamics of Rec1-resilin as an IDP during the formation of the Pt-NMQCs. It has been demonstrated that the green fluorescent Pt-NMQCs exhibit a high quantum yield of ~7.0% and a lifetime of ~9.5 ns in aqueous media. The change in photoluminescence properties due to the inter-dot interactions between proximal dots and aggregation of the Pt-NMQCs by evaporation was also measured spectroscopically and discussed.
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http://dx.doi.org/10.3390/bios9040128DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6956208PMC
October 2019

3D Bioprinted Nanocellulose-Based Hydrogels for Tissue Engineering Applications: A Brief Review.

Polymers (Basel) 2019 May 17;11(5). Epub 2019 May 17.

Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, Victoria 3000, Australia.

Nanocellulosic materials, such as cellulose nanocrystals, cellulose nanofibers, and bacterial nanocellulose, that display high surface area, mechanical strength, biodegradability, and tunable surface chemistry have attracted great attention over the last decade for biomedical applications. Simultaneously, 3D printing is revolutionizing the field of biomedical engineering, which enables the fast and on-demand printing of customizable scaffolds, tissues, and organs. Nanocellulosic materials hold tremendous potential for 3D bioprinting due to their printability, their shear thinning behavior, their ability to live cell support and owing to their excellent biocompatibility. The amalgamation of nanocellulose-based feedstocks and 3D bioprinting is therefore of critical interest for the development of advanced functional 3D hydrogels. In this context, this review briefly discusses the most recent key developments and challenges in 3D bioprinting nanocellulose-based hydrogel constructs that have been successfully tested for mammalian cell viability and used in tissue engineering applications.
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http://dx.doi.org/10.3390/polym11050898DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6572377PMC
May 2019

Evolution of the Interfacial Structure of a Catalyst Ink with the Quality of the Dispersing Solvent: A Contrast Variation Small-Angle and Ultrasmall-Angle Neutron Scattering Investigation.

ACS Appl Mater Interfaces 2019 Mar 4;11(10):9934-9946. Epub 2019 Mar 4.

Chemical and Environmental Engineering, School of Engineering , RMIT University , Melbourne , Victoria 3000 , Australia.

The electrocatalyst layer (ECL) of the proton-exchange membrane fuel cell (PEMFC) is commonly fabricated from colloidal catalyst ink containing carbon-supported catalyst nanoparticles (NPs), ionomer stabilizer, and dispersion medium (DM). The structure, stability, and aggregate size distribution of fuel cell catalyst ink are critically dependent on the quality of DM. However, understanding of the influence of the quality of DM on the hierarchical structure of the ECL is lacking. This work presents a systematic investigation of the effects of reducing alcohol content in isopropyl alcohol/water (IPA/HO) binary mixtures as DM on the structural evolution of water-rich (green) catalyst ink using contrast-variation small-angle and ultrasmall-angle neutron scattering techniques. Both qualitative and quantitative information are extracted from the data to obtain information about the size, structure, and organization of the catalyst ink using different model functions fit to the experimental data. The catalyst ink prepared using 70% IPA (commonly employed in industry and extensively reported in the literature) is shown to consist of randomly distributed globular carbon aggregates (mean radius of gyration of ∼178.9 nm) stabilized by an ionomer mass fractal shell (thickness of ∼13.0 nm), which is dispersed in the matrix of rodlike (∼1.3 nm radius and ∼35.0 nm length) negatively surface-charged ionomer NPs. These well characterized baseline data are then compared and contrasted with DM formulations of lower IPA content. A sequential reduction in IPA content of DM shows a progressive increase in the ionomer NP radius and electrostatic repulsion, concomitantly with the decrease in the carbon aggregate size and ionomer shell thickness of the catalyst ink. Therefore, the changes in the interfacial structure via adjustments of the DM composition can be used as a controlling parameter to tailor the hierarchical structure of the colloidal fuel cell catalyst ink and to further optimize the performance of the ECL.
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http://dx.doi.org/10.1021/acsami.8b20645DOI Listing
March 2019

Sulfonated Thiophene Derivative Stabilized Aqueous Poly(3-hexylthiophene):Phenyl-C-butyric Acid Methyl Ester Nanoparticle Dispersion for Organic Solar Cell Applications.

ACS Appl Mater Interfaces 2018 Dec 10;10(50):44116-44125. Epub 2018 Dec 10.

Future Industries Institute , University of South Australia , Mawson Lakes , South Australia 5095 , Australia.

Aqueous dispersions of poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) nanoparticles (NPs) have been fabricated using a thiophene-based surfactant 2-(3-thienyl)ethyloxybutylsulfonate sodium salt (TEBS) for the first time via the mini-emulsion process. The use of TEBS resulted in a stable colloidal dispersion of P3HT:PCBM NPs, of which the effect of various fabrication parameters is investigated. The fabricated NPs were characterized by dynamic light scattering, scanning electron microscopy, UV-visible spectroscopy, contrast-variation small and ultra-small angle neutron scattering, and cyclic voltammetry. The internal structure and electrochemical performance of TEBS-stabilized P3HT:PCBM NPs were compared to those of sodium dodecyl sulfate-stabilized core-shell (PCBM-P3HT) NPs at the same surfactant concentration. Neutron scattering and cyclic voltammetry results reveal a homogeneous distribution of small de-mixed P3HT and PCBM domains in the internal structure of TEBS-stabilized P3HT:PCBM NPs, reminiscent of cast film. Moreover, electron microscopy images show evidence of diffused NP surface/interface upon drying (without annealing), which indicates that the thiophene-containing TEBS may improve compatibility and film-forming properties of fabricated P3HT:PCBM NPs, and consequently be more suited for conventional film-processing methods for organic solar cell applications.
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http://dx.doi.org/10.1021/acsami.8b15589DOI Listing
December 2018

Structural evolution of photocrosslinked silk fibroin and silk fibroin-based hybrid hydrogels: A small angle and ultra-small angle scattering investigation.

Int J Biol Macromol 2018 Jul 12;114:998-1007. Epub 2018 Mar 12.

Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia; School of Engineering, RMIT University, La Trobe Street, Melbourne, VIC 3000, Australia. Electronic address:

Regenerated Bombyx mori silk fibroin (RSF) is a widely recognized protein for biomedical applications; however, its hierarchical gel structure is poorly understood. In this paper, the hierarchical structure of photocrosslinked RSF and RSF-based hybrid hydrogel systems: (i) RSF/Rec1-resilin and (ii) RSF/poly(N-vinylcaprolactam (PVCL) is reported for the first time using small-angle scattering (SAS) techniques. The structure of RSF in dilute to concentrated solution to fabricated hydrogels were characterized using small angle X-ray scattering (SAXS), small angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) techniques. The RSF hydrogel exhibited three distinctive structural characteristics: (i) a Porod region in the length scale of 2 to 3nm due to hydrophobic domains (containing β-sheets) which exhibits sharp interfaces with the amorphous matrix of the hydrogel and the solvent, (ii) a Guinier region in the length scale of 4 to 20nm due to hydrophilic domains (containing turns and random coil), and (iii) a Porod-like region in the length scale of few micrometers due to water pores/channels exhibiting fractal-like characteristics. Addition of Rec1-resilin or PVCL to RSF and subsequent crosslinking systematically increased the nanoscale size of hydrophobic and hydrophilic domains, whereas decreased the homogeneity of pore size distribution in the microscale. The presented results have implications on the fundamental understanding of the structure-property relationship of RSF-based hydrogels.
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http://dx.doi.org/10.1016/j.ijbiomac.2018.03.044DOI Listing
July 2018

Engineering DN hydrogels from regenerated silk fibroin and poly(N-vinylcaprolactam).

J Mater Chem B 2016 Sep 14;4(33):5519-5533. Epub 2016 Jul 14.

Future Industries Institute, Mawson Lakes Campus, University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia.

The development of novel hydrogels that possess adequate elasticity and toughness to withstand mechanically active environments, along with being biocompatible, remains a significant challenge in the design of materials for tissue engineering applications. In this study, a family of regenerated silk fibroin (RSF) based double network (DN) hydrogels were fabricated for the first time using a rapid one-pot method. The DN hydrogels combine the rigid covalently crosslinked RSF with the softer poly(N-vinylcaprolactam) (PVCL) through strong physical interactions. The formation of these DN hydrogels resulted in an improvement of the water uptake capacity, elasticity and toughness compared to the individual RSF hydrogel. The elasticity of the RSF/PVCL DN hydrogels was closer to that of native cartilage, which makes them promising materials for cartilage regeneration applications. An in vitro study on adhesion, proliferation and differentiation of a mouse pre-chondrocyte cell line (ATDC5) conducted using microscopic analysis, a cell proliferation assay and RT-PCR confirmed the cells cultured on the less stiff hydrogels demonstrated the most favourable chondrogenic response. Thus, this study demonstrates the potential of RSF-based hybrid hydrogels for cartilage tissue engineering applications.
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http://dx.doi.org/10.1039/c6tb01055eDOI Listing
September 2016

Effects of Crowding and Environment on the Evolution of Conformational Ensembles of the Multi-Stimuli-Responsive Intrinsically Disordered Protein, Rec1-Resilin: A Small-Angle Scattering Investigation.

J Phys Chem B 2016 07 28;120(27):6490-503. Epub 2016 Jun 28.

School of Chemical Engineering, The University of Adelaide , Adelaide, SA 5005, Australia.

In this study, we explore the overall structural ensembles and transitions of a biomimetic, multi-stimuli-responsive, intrinsically disordered protein (IDP), Rec1-resilin. The structural transition of Rec1-resilin with change in molecular crowding and environment is evaluated using small-angle neutron scattering and small-angle X-ray scattering. The quantitative analyses of the experimental scattering data using a combination of computational models allowed comprehensive description of the structural evolution, organization, and conformational ensembles of Rec1-resilin in response to the changes in concentration, pH, and temperature. Rec1-resilin in uncrowded solutions demonstrates the equilibrium intrinsic structure quality of an IDP with radius of gyration Rg ∼ 5 nm, and a scattering function for the triaxial ellipsoidal model best fit the experimental dataset. On crowding (increase in concentration >10 wt %), Rec1-resilin molecules exert intermolecular repulsive force of interaction, the Rg value reduces with a progressive increase in concentration, and molecular chains transform from a Gaussian coil to a fully swollen coil. It is also revealed that the structural organization of Rec1-resilin dynamically transforms from a rod (pH 2) to coil (pH 4.8) and to globular (pH 12) as a function of pH. The findings further support the temperature-triggered dual-phase-transition behavior of Rec1-resilin, exhibiting rod-shaped structural organization below the upper critical solution temperature (∼4 °C) and a large but compact structure above the lower critical solution temperature (∼75 °C). This work attempted to correlate unusual responsiveness of Rec1-resilin to the evolution of conformational ensembles.
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http://dx.doi.org/10.1021/acs.jpcb.6b02475DOI Listing
July 2016

A multi-responsive intrinsically disordered protein (IDP)-directed green synthesis of fluorescent gold nanoclusters.

J Mater Chem B 2015 Aug 23;3(32):6580-6586. Epub 2015 Jul 23.

Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.

Herein we demonstrate the green synthesis of fluorescent gold nanoclusters (AuNCs) using a multi-responsive intrinsically disordered protein (IDP) polymer, Rec1-resilin, as a multi-functional template. In a controlled environment, Rec1-resilin acts simultaneously as the directing agent and the reducer, and performs the role of a highly efficient stabilizer once AuNCs are formed. The evolution of the photophysical properties and the chemical states of AuNCs formed are measured using UV-Vis, fluorescence and X-ray photoelectron spectroscopy. Circular dichroism (CD) spectroscopy measures the intrinsically disordered nature of Rec1-resilin stabilizing AuNCs. High resolution transmission electron microscopy (HR-TEM) reveals the detailed structure and morphology of the generated AuNCs of <1.5 nm size. A local ordering resembling that of a face-centered cubic (FCC) structure with evidence of twinning was observed for the generated AuNCs. The AuNCs so formed exclude the use of toxic reducing agents and display excellent water dispersibility, photostability and environmental stability towards aggregation.
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http://dx.doi.org/10.1039/c5tb00659gDOI Listing
August 2015

Tunable Thermoresponsiveness of Resilin via Coassembly with Rigid Biopolymers.

Langmuir 2015 Aug 3;31(32):8882-91. Epub 2015 Aug 3.

†Ian Wark Research Institute, University of South Australia, Mawson Lakes Boulevard, Adelaide, South Australia 5095, Australia.

The ability to tune the thermoresponsiveness of recombinant resilin protein, Rec1-resilin, through a facile coassembly system was investigated in this study. The effects of change in conformation and morphology with time and the responsive behavior of Rec1-resilin in solution were studied in response to the addition of a rigid model polypeptide (poly-l-proline) or a hydrophobic rigid protein (Bombyx mori silk fibroin). It was observed that by inducing more ordered conformations and increasing the hydrophobicity the lower critical solution temperature (LCST) of the system was tuned to lower values. Time and temperature were found to be critical parameters in controlling the coassembly behavior of Rec1-resilin in both the model polypeptide and more complex protein systems. Such unique properties are useful for a wide range of applications, including drug delivery and soft tissue engineering applications.
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http://dx.doi.org/10.1021/acs.langmuir.5b01014DOI Listing
August 2015

Structural ensembles reveal intrinsic disorder for the multi-stimuli responsive bio-mimetic protein Rec1-resilin.

Sci Rep 2015 Jun 4;5:10896. Epub 2015 Jun 4.

Ian Wark Research Institute, University of South Australia, Mawson Lakes campus, Mawson lakes, South Australia 5095, Australia.

Rec1-resilin is the first recombinant resilin-mimetic protein polymer, synthesized from exon-1 of the Drosophila melanogaster gene CG15920 that has demonstrated unusual multi-stimuli responsiveness in aqueous solution. Crosslinked hydrogels of Rec1-resilin have also displayed remarkable mechanical properties including near-perfect rubber-like elasticity. The structural basis of these extraordinary properties is not clearly understood. Here we combine a computational and experimental investigation to examine structural ensembles of Rec1-resilin in aqueous solution. The structure of Rec1-resilin in aqueous solutions is investigated experimentally using circular dichroism (CD) spectroscopy and small angle X-ray scattering (SAXS). Both bench-top and synchrotron SAXS are employed to extract structural data sets of Rec1-resilin and to confirm their validity. Computational approaches have been applied to these experimental data sets in order to extract quantitative information about structural ensembles including radius of gyration, pair-distance distribution function, and the fractal dimension. The present work confirms that Rec1-resilin is an intrinsically disordered protein (IDP) that displays equilibrium structural qualities between those of a structured globular protein and a denatured protein. The ensemble optimization method (EOM) analysis reveals a single conformational population with partial compactness. This work provides new insight into the structural ensembles of Rec1-resilin in solution.
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http://dx.doi.org/10.1038/srep10896DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4455251PMC
June 2015

Separator Membrane from Crosslinked Poly(Vinyl Alcohol) and Poly(Methyl Vinyl Ether-alt-Maleic Anhydride).

Nanomaterials (Basel) 2015 Mar 25;5(2):398-414. Epub 2015 Mar 25.

Ian Wark Institute, University of South Australia, Mawson Lakes 5095, Australia.

In this work, we report separator membranes from crosslinking of two polymers, such as poly vinyl alcohol (PVA) with an ionic polymer poly(methyl vinyl ether-alt-maleic anhydride) (PMVE-MA). Such interpolymer-networked systems were extensively used for biomedical and desalination applications but they were not examined for their potential use as membranes or separators for batteries. Therefore, the chemical interactions between these two polymers and the influence of such crosslinking on physicochemical properties of the membrane are systematically investigated through rheology and by critical gel point study. The hydrogen bonding and the chemical interaction between PMVE-MA and PVA resulted in highly cross-linked membranes. Effect of the molecular weight of PVA on the membrane properties was also examined. The developed membranes were extensively characterized by studying their physicochemical properties (water uptake, swelling ratio, and conductivity), thermal and electrochemical properties using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermo-gravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). The DSC study shows the presence of a single in the membranes indicating compatibility of the two polymers in flexible and transparent films. The membranes show good stability and ion conductivity suitable for separator applications.
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http://dx.doi.org/10.3390/nano5020398DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5312902PMC
March 2015

Fabrication and characterisation of an electrospun tubular 3D scaffold platform of poly(vinylidene fluoride-co-hexafluoropropylene) for small-diameter blood vessel application.

J Biomater Sci Polym Ed 2014 31;25(18):2023-41. Epub 2014 Oct 31.

a Ian Wark Research Institute , University of South Australia, Mawson Lakes Campus , Mawson lakes , South Australia, Australia.

In this research, nanofibrous 3D tubular (~4-mm-diameter tube) scaffolds of poly (vinylidene fluoride-co-hexafluoropropylene) were fabricated by electrospinning. The role of surface charge in the success of these scaffolds for potential small-diameter artificial vascular grafts has been investigated using streaming potential study. Prior to endothelial cell culture, surface properties such as wettability and the surface charge of these tubular scaffolds were evaluated using unmodified and fibrinogen-adsorbed surfaces to understand their interaction with surrounding environment. The tubular scaffolds constructed using electrospinning show similar mechanical properties such as tensile strength and elastic modulus as those of native vessels. Whilst endothelial cell proliferation on unmodified tubes, as analysed by scanning electron microscopy, was found to be moderate, a simple process of dynamic fibrinogen adsorption was seen to enhance the endothelialisation of these tubular grafts. The high negative zeta potential values, high strength, robustness and structural reliability of the scaffolds represent them to be promising biomaterials for vascular graft applications.
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http://dx.doi.org/10.1080/09205063.2014.968018DOI Listing
July 2015

Facile and rapid ruthenium mediated photo-crosslinking of Bombyx mori silk fibroin.

J Mater Chem B 2014 Oct 28;2(37):6259-6270. Epub 2014 Jul 28.

Ian Wark Research Institute, University of South Australia, Mawson Lakes, Adelaide, SA 5095, Australia.

A facile and rapid ruthenium catalysed photo-crosslinking method was employed to prepare Bombyx mori silk fibroin hydrogels for the first time that may be used for biomedical applications. The gels have been characterised by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), photo-acoustic Fourier transform infrared spectroscopy (PA-FTIR), and X-ray diffraction (XRD). We have reported the tuning of the properties of the chemically crosslinked gels through hydration level. DSC and DMA measurements have shown that the molecular chain dynamics and mechanical properties are dependent on the moisture/water content. The structural changes upon gelation were examined through the use of DSC, PA-FTIR and XRD, which confirmed that the gels were less crystalline than the original silk powder. Finally, the biocompatibility and hence, the potential tissue engineering application of the silk fibroin hydrogel was also assessed by culturing chondrocyte progenitor cells for up to one week on the engineered fibroin surfaces.
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http://dx.doi.org/10.1039/c4tb00698dDOI Listing
October 2014

Multi-responsive biomaterials and nanobioconjugates from resilin-like protein polymers.

J Mater Chem B 2014 Sep 8;2(36):5936-5947. Epub 2014 Aug 8.

Ian Wark Research Institute, University of South Australia, Mawson Lakes, Adelaide, South Australia 5095, Australia.

Nature, through evolution over millions of years, has perfected materials with amazing characteristics and awe-inspiring functionalities that exceed the performance of man-made synthetic materials. One such remarkable material is native resilin - an extracellular skeletal protein that plays a major role in the jumping, flying, and sound production mechanisms in many insects. It is one of the most resilient (energy efficient) elastomeric biomaterials known with a resilience of ∼97% and a fatigue life in excess of 300 million cycles. Recently, resilin-like polypeptides (RLPs) with exquisite control over the amino acid sequence (comprising repeat resilin motifs) and tuneable biological properties and/or functions have been generated by genetic engineering and cloning techniques. RLPs have been the subject of intensive investigation over a decade and are now recognized to be multi-functional and multi-stimuli responsive; including temperature (exhibiting both an upper and a lower critical solution temperature), pH, moisture, ion and photo-responsive with tuneable photo-physical properties. Such unusual multi-stimuli responsiveness has scarcely been offered and reported for either synthetic or natural biopolymers. Furthermore, the directed molecular self-assembly property of RLPs also exhibits promise as efficient templates for the synthesis and stabilization of metal nanoparticles. These developments and observations reveal the opportunities and new challenges for RLPs as novel materials for nanotechnology, nanobiotechnology and therapeutic applications. In this review, we discuss and highlight the design and synthesis of different RLPs, their unique molecular architecture, advanced responsive behaviour, and functionality of hydrogels, solid-liquid interfaces, nanoparticles and nanobioconjugates derived from RLPs.
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http://dx.doi.org/10.1039/c4tb00726cDOI Listing
September 2014

An16-resilin: an advanced multi-stimuli-responsive resilin-mimetic protein polymer.

Acta Biomater 2014 Nov 6;10(11):4768-4777. Epub 2014 Aug 6.

CSIRO Manufacturing, Clayton, Victoria 3168, Australia.

Engineered protein polymers that display responsiveness to multiple stimuli are emerging as a promising class of soft material with unprecedented functionality. The remarkable advancement in genetic engineering and biosynthesis has created the opportunity for precise control over the amino acid sequence, size, structure and resulting functions of such biomimetic proteins. Herein, we describe the multi-stimuli-responsive characteristics of a resilin-mimetic protein, An16-resilin (An16), derived from the consensus sequence of resilin gene in the mosquito Anopheles gambiae. We demonstrate that An16 is an intrinsically disordered protein that displays unusual dual-phase thermal transition behavior along with responsiveness to pH, ion, light and humidity. Identifying the molecular mechanisms that allow An16 to sense and switch in response to varying environments furthers the ability to design intelligent biomacromolecules.
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http://dx.doi.org/10.1016/j.actbio.2014.07.030DOI Listing
November 2014

Work Function Engineering of Graphene.

Nanomaterials (Basel) 2014 04 3;4(2):267-300. Epub 2014 Apr 3.

Ian Wark Research Institute, University of South Australia, Mawson Lakes Campus, 5095 Adelaide, Australia.

Graphene is a two dimensional one atom thick allotrope of carbon that displays unusual crystal structure, electronic characteristics, charge transport behavior, optical clarity, physical & mechanical properties, thermal conductivity and much more that is yet to be discovered. Consequently, it has generated unprecedented excitement in the scientific community; and is of great interest to wide ranging industries including semiconductor, optoelectronics and printed electronics. Graphene is considered to be a next-generation conducting material with a remarkable band-gap structure, and has the potential to replace traditional electrode materials in optoelectronic devices. It has also been identified as one of the most promising materials for post-silicon electronics. For many such applications, modulation of the electrical and optical properties, together with tuning the band gap and the resulting work function of zero band gap graphene are critical in achieving the desired properties and outcome. In understanding the importance, a number of strategies including various functionalization, doping and hybridization have recently been identified and explored to successfully alter the work function of graphene. In this review we primarily highlight the different ways of surface modification, which have been used to specifically modify the band gap of graphene and its work function. This article focuses on the most recent perspectives, current trends and gives some indication of future challenges and possibilities.
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http://dx.doi.org/10.3390/nano4020267DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5304665PMC
April 2014

Engineering interaction between bone marrow derived endothelial cells and electrospun surfaces for artificial vascular graft applications.

Biomacromolecules 2014 Apr 13;15(4):1276-87. Epub 2014 Mar 13.

Ian Wark Research Institute, University of South Australia , Mawson Lakes Campus, South Australia, Australia.

The aim of this investigation was to understand and engineer the interactions between endothelial cells and the electrospun (ES) polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) nanofiber surfaces and evaluate their potential for endothelialization. Elastomeric PVDF-HFP samples were electrospun to evaluate their potential use as small diameter artificial vascular graft scaffold (SDAVG) and compared with solvent cast (SC) PVDF-HFP films. We examined the consequences of fibrinogen adsorption onto the ES and SC samples for endothelialisation. Bone marrow derived endothelial cells (BMEC) of human origin were incubated with the test and control samples and their attachment, proliferation, and viability were examined. The nature of interaction of fibrinogen with SC and ES samples was investigated in detail using ELISA, XPS, and FTIR techniques. The pristine SC and ES PVDF-HFP samples displayed hydrophobic and ultrahydrophobic behavior and accordingly, exhibited minimal BMEC growth. Fibrinogen adsorbed SC samples did not significantly enhance endothelial cell binding or proliferation. In contrast, the fibrinogen adsorbed electrospun surfaces showed a clear ability to modulate endothelial cell behavior. This system also represents an ideal model system that enables us to understand the natural interaction between cells and their extracellular environment. The research reported shows potential of ES surfaces for artificial vascular graft applications.
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http://dx.doi.org/10.1021/bm401825cDOI Listing
April 2014

Interaction of platelets with poly(vinylidene fluoride-co-hexafluoropropylene) electrospun surfaces.

Biomacromolecules 2014 Mar 18;15(3):744-55. Epub 2014 Feb 18.

Ian Wark Research Institute, University of South Australia , Mawson Lakes Campus, South Australia, Australia.

Platelets are the major contributors in the process of thrombosis and in the failure of biomedical implants. A number of factors influence the platelet interaction with foreign surfaces such as surface morphology, surface chemistry, and adsorbed proteins. This study examined the effect of surface topography and chemistry of pristine and fibrinogen-adsorbed solvent cast (SC) and electrospun (ES) samples of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) on platelet adhesion, activation, and aggregation. Qualitative and quantitative studies of fibrinogen adsorption were performed using time-of-flight secondary ion mass spectrometry (ToF-SIMS), while SEM, aggregometry, and liquid scintillation analyses were performed to evaluate platelet adhesion, aggregation, and serotonin release. While little or no platelet adhesion was observed on pristine ES surfaces, considerable adhesion, and measurable aggregation and serotonin release were observed on pristine SC surfaces. Notably, increased adhesion of platelets was observed following fibrinogen adsorption on SC surface with considerable aggregation and serotonin release compared with ES samples, where limited aggregation and platelet adhesion was observed. A further comparison of platelet adhesion, aggregation, and serotonin release was performed with plasma-adsorbed SC and ES surfaces. SC surfaces showed enhanced platelet adhesion, aggregation, and serotonin release compared to ES surfaces. This study shows that the morphology of samples plays a critical role on the biocompatibility of samples by altering the adsorption and adhesion of biomolecules and cells. The low level of adhesion, low aggregation, and serotonin release of platelets, even in the presence of fibrinogen and plasma-derived proteins, suggested that ES samples have the least thrombogenicity.
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http://dx.doi.org/10.1021/bm4015396DOI Listing
March 2014

Near superhydrophobic fibrous scaffold for endothelialization: fabrication, characterization and cellular activities.

Biomacromolecules 2013 Nov 4;14(11):3850-60. Epub 2013 Oct 4.

Ian Wark Research Institute, University of South Australia , Mawson Lakes Campus, South Australia, Australia.

In this work, we have applied an electrospinning method to control wettability and further hydrophobic modification of a hydrophobic polymer mat of poly(vinylidene fluoride-co-hexafluoropropylene). A correlation between the processing parameters, rheological properties of polymer solutions, and electrospinning ability was made using the polymer's critical entanglement concentration, the boundary between the semidilute unentangled regime and the semidilute entangled regime. The wetting behavior, structural and thermal characteristics of electrospun (ES) mats were evaluated and compared with solvent cast sample using advancing and receding contact angle analyses, differential scanning calorimetry, and small-angle X-ray scattering. To demonstrate the feasibility, the best optimized ES samples were examined for their potential and ability to support bone marrow derived endothelial cell seeding efficiency, adhesion and proliferation. Our studies show that, while different processing techniques can effectively modulate physical and morphological changes such as porosity and hydrophobicity, the cellular adhesion and proliferation are highly time-dependent and controlled by chemical factors. As such, these results suggest that it is the interplay of both physical and chemical factors that determine the endothelialization of porous near superhydrophobic scaffolds. The developed electrospun samples demonstrate their feasibility for endothelialization.
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http://dx.doi.org/10.1021/bm400938nDOI Listing
November 2013

The effect of hydration on molecular chain mobility and the viscoelastic behavior of resilin-mimetic protein-based hydrogels.

Biomaterials 2011 Nov 24;32(33):8462-73. Epub 2011 Aug 24.

Ian Wark Research Institute, University of South Australia, Mawson Lakes Blvd., Mawson Lakes, South Australia 5095, Australia.

The outstanding rubber-like elasticity of resilin and resilin-mimetic proteins depends critically on the level of hydration. In this investigation, water vapor sorption and the role of hydration on the molecular chain dynamics and viscoelastic properties of resilin-mimetic protein, rec1-resilin is investigated in detail. The dynamic and equilibrium swelling behavior of the crosslinked protein hydrogels with different crosslink density are reported under various controlled environments. We propose three different stages of hydration; involving non-crystallizable water, followed by condensation or clustering of water around the already hydrated sites, and finally crystallizable water. The kinetics of water sorption for this engineering protein is observed to be comparable to hydrophilic polymers with a diffusion coefficient in the range of 10(-7) cm(2) s(-1). From the comparison between the absorption and desorption isotherms at a constant water activity, it has been observed that rec1-resilin exhibits sorption hysteresis only for the tightly bound water. Investigation of molecular mobility using differential scanning calorimetry, indicates that dehydrated crosslinked rec1-resilin is brittle with a glass transition temperature (T(g)) of >180 °C, which dramatically decreases with increasing hydration; and above a critical level of hydration rec1-resilin exhibits rubber-like elasticity. Nanoindentation studies show that even with little hydration (<10%), the mechanical properties of rec1-resilin gels change dramatically. Rheological investigations confirm that the equilibrium-swollen crosslinked rec1-resilin hydrogel exhibits outstanding elasticity and resilience of ∼ 92%, which exceeds that of any other synthetic polymer and biopolymer hydrogels.
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http://dx.doi.org/10.1016/j.biomaterials.2011.07.064DOI Listing
November 2011
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