Browsing by Author "Balu, R"

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    3D printed graphene aerogels using conductive nanofibrillar network formulation
    (Elsevier, 2023-06) Tran, TS; Balu, R; Mata, JP; Dutta, NK; Choudhury, NR
    Despite recent progress in 3D printing of graphene, formulation of aqueous 3D printable graphene inks with desired rheological properties for direct ink writing (DIW) of multifunctional graphene macrostructures remains a major challenge. In this work, we develop a novel 3D printable pristine graphene ink in aqueous phase using conductive nanofibrillar network formulation by controlling the interfacial interactions between graphene and PEDOT:PSS nanofibrils. The formulated inks, tailored for energy applications, provide excellent 3D printability for fabricating multilayer 3D structures (up to 30 layers) with spanning features and high aspect ratio. The 3D printed aerogels, comprising interconnected networks of graphene flakes and PEDOT:PSS nanofibrils, exhibit excellent electrical conductivity as high as ∼630 S m − 1 and can be converted into conductive hydrogels via swelling in water/electrolyte. The formulated graphene inks were used for fabricating 3D printed supercapacitor electrodes (power density of 11.3 kW kg−1 and energy density of 7.3 Wh kg−1) with excellent performance and durability. © 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.
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    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
    (American Chemical Society, 2016-06-09) Balu, R; Mata, JP; Knott, RB; Elvin, CM; Hill, AJ; Choudhury, NR; Dutta, NK
    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. © 2016 American Chemical Society
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    Structural ensembles reveal intrinsic disorder for the multi-stimuli responsive bio-mimetic protein rec1-resilin
    (Springer Nature, 2015-06-04) Balu, R; Knott, RB; Cowieson, NP; Elvin, CM; Hill, AJ; Choudhury, NR; Dutta, NK
    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. © 2017 Macmillan Publishers Limited, part of Springer Nature
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    Structural evolution of photocrosslinked silk fibroin and silk fibroin-based hybrid hydrogels: a small angle and ultra-small angle scattering investigation
    (Elsevier, 2018-07-15) Whittaker, JL; Balu, R; Knott, RB; de Campo, L; Mata, JP; Rehm, C; Hill, AJ; Dutta, NK; Choudhury, NR
    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 3 nm 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 20 nm 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. © 2018 Elsevier B.V.
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    Tuning the hierarchical structure and resilience of resilin-like polypeptide hydrogels using graphene oxide
    (American Chemical Society, 2020-11-24) Balu, R; Dorishetty, P; Mata, JP; Hill, AJ; Dutta, NK; Choudhury, NR
    Resilin-like polypeptides (RLPs) are an important class of intrinsically disordered multistimuli-responsive bioelastomers. The nanostructure of RLPs in solution has been extensively studied in the past few years, from dilute to molecular crowding conditions, and with the addition of rigid biopolymers. Modification of the hierarchical network structure of RLP hydrogels using graphene oxide (GO) as an additive is a burgeoning prospect for their application in the bioelectronic and biomedical fields. In this work, we systemically study the influence of incorporating GO into RLP (Rec1) hydrogels for tuning their physicochemical properties and understanding the gel–cell interactions. The nature of GO interaction with the Rec1 hydrogel is deduced from the change in structure and properties. Contrast-matching small-angle and ultra-small-angle neutron-scattering techniques were used to investigate the network structure of the Rec1 hydrogel and how this structure is modified in the presence of GO. Incorporation of GO in the Rec1 hydrogel matrix results in an increase in the micromechanical resilience, equilibrium water swelling ratio, micropore size, cross-linked domain size; with a decrease in the cross-link density, mass fractal cluster size, local compressive elastic modulus, and cell inert characteristics. These property combinations achieved with the addition of GO further open up the available structure–property design window for RLP applications. © 2020 American Chemical Society