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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 Refereed/Peer-reviewed

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. Refereed/Peer-reviewed

Calcium deficient hydroxyapatite (CDHA) nanoparticles with a Ca/P ratio of 1.6 were synthesized by accelerated sonochemical process. The synthesis was carried out using calcium nitrate and diammonium hydrogen phosphate in an ultrasonic bath operated at a fixed frequency of 135 kHz and 250 Watts power. The effect of ultrasonic radiation as a function of time over the formation and structure of nanoparticles were investigated using X-ray diffraction, spectroscopy and microscopy methods. The synthesized nanocrystals showed X-ray powder diffraction pattern corresponding to that of hydroxyapatite stoichiometry with CDHA characteristics. HPO2- 4 Fourier transform infrared vibration band observed at 875 cm-1. Transmission electron microscopic analysis confirmed the nanocrystalline nature and growth of acicular, rod and needle-like CDHA nanocrystals morphology with increasing irradiation time. � 2014 American Scientific Publishers. All rights reserved.

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 photoresponsive 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. Refereed/Peer-reviewed

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. Refereed/Peer-reviewed