Design of a novel fibronectin-mimetic peptide-amphiphile for functionalized biomaterials

The interaction of the alpha5beta1 integrin with its ligand, fibronectin, supports numerous adhesive functions and has an important role in health and disease. In recent years, there has been a considerable effort in designing fibronectin-mimetic peptides to target the integrin. However, to date, the therapeutic use of these peptides has been limited, as they cannot accurately mimic fibronectin's binding affinity for alpha5beta1. A peptide-amphiphile (PR_b) was synthesized with a peptide headgroup composed of four building blocks: a spacer; RGDSP, the primary recognition site for alpha5beta1; PHSRN, the synergy binding site; and a linker. The linker was designed to mimic two important criteria: the distance and the hydrophobicity/hydrophilicity between PHSRN and RGD in fibronectin. Human umbilical vein endothelial cells were seeded on different substrates and evaluated in terms of adhesion, spreading, specificity, cytoskeleton organization, focal adhesions, and secretion of extracellular fibronectin. This peptide was shown to perform comparably to fibronectin, indicating that a biomimetic approach can result in the design of novel peptides with therapeutic potential for biomaterial functionalization.     

Indole-based distinctive chemosensors for ‘naked-eye’ detection of CN and HSO4−, associated with hydrogen-bonded complex and their DFT study

Colorimetric detection of anions (HSO₄^? and CN^?) was achieved via analyte triggered colour changing of the dipodal and tripodal sensors in CH₃CN–H₂O (1:1). The sensors exhibited very sharp visual colour changes and fluorescence quenching–enhancing effect upon addition of the HSO₄^? and CN^?. The large downfield shift of the NH proton signals in ¹H-NMR complexation studies and quantum chemical DFT calculations proved the formation of hydrogen-bonded complexes where no proton transfer mechanism was found.     

Green Synthesis of Silver Nanoparticles Using Water Extract from Galls of <Emphasis Type="Italic">Rhus Chinensis</Emphasis> and Its Antibacterial Activity

The green synthesis of silver nanoparticles (AgNPs) has been proposed as a simple, eco-friendly and cost effective alternative to chemical and physical methods. The Rhus chinensis plant is one of the well studied medicinal plant and its galls find excellent clinical and therapeutic applications. The present study reports the use of water extract from galls of R. chinensis as a reducing agent and formation of AgNPs from silver nitrate solution by a green synthesis route. The AgNPs formation was observed visually by color change and the absorbance peak at 450 nm was observed by UV–Visible spectrophotometer. The shape, size, and morphology of synthesized AgNPs were monitored by transmission electron microscopy and field-emission scanning electron microscopy. The face centered cubic structure of AgNPs was confirmed by X-ray diffraction pattern and element composition by energy dispersive X-ray analysis. The Fourier transform infrared spectroscopy spectrum revealed that the presence of components acts as a reducing and capping agent. The antibacterial activity was performed using the agar well diffusion method. Minimum inhibitory concentration and minimum bactericidal concentration were determined by broth dilution and spread plate method respectively. Synthesized nanoparticles were spotted as triangular and hexagonal shape and the particle size was around 150 nm.     

Incorporation and controlled release of silyl ether prodrugs from PRINT nanoparticles

Asymmetric bifunctional silyl ether (ABS) prodrugs of chemotherapeutics were synthesized and incorporated within 200 nm × 200 nm particles. ABS prodrugs of gemcitabine were selected as model compounds because of the difficulty to encapsulate a water-soluble drug within a hydrogel. The resulting drug delivery systems were degraded under acidic conditions and were found to release only the parent or active drug. Furthermore, changing the steric bulk of the alkyl substituents on the silicon atom could regulate the rate of drug release and, therefore, the intracellular toxicity of the gemcitabine-loaded particles. This yielded a family of novel nanoparticles that could be tuned to release drug over the course of hours, days, or months.     

Single molecule imaging of oxygenation of cobalt octaethylporphyrin at the solution/solid interface: thermodynamics from microscopy

For the first time, the pressure and temperature dependence of a chemical reaction at the solid/solution interface is studied by scanning tunneling microscopy (STM), and thermodynamic data are derived. In particular, the STM is used to study the reversible binding of O(2) with cobalt(II) octaethylporphyrin (CoOEP) supported on highly oriented pyrolytic graphite (HOPG) at the phenyloctane/CoOEP/HOPG interface. The adsorption is shown to follow the Langmuir isotherm with P(1/2)(298K) = 3200 Torr. Over the temperature range of 10-40 °C, it was found that ΔH(P) = -68 ± 10 kJ/mol and ΔS(P) = -297 ± 30 J/(mol K). The enthalpy and entropy changes are slightly larger than expected based on solution-phase reactions, and possible origins of these differences are discussed. The big surprise here is the presence of any O(2) binding at room temperature, since CoOEP is not expected to bind O(2) in fluid solution. The stability of the bound oxygen is attributed to charge donation from the graphite substrate to the cobalt, thereby stabilizing the polarized Co-O(2) bonding. We report the surface unit cell for CoOEP on HOPG in phenyloctane at 25 °C to be A = (1.46 ± 0.1)n nm, B = (1.36 ± 0.1)m nm, and α = 54 ± 3°, where n and m are unknown nonzero non-negative integers.     

Directional change of magnetic easy axis of arrays of cobalt nanowires: Role of non-dipolar magnetostatic interaction

Room temperature magnetization of two dimensional (2D) arrays of cobalt nanowires (NWs) having diameter 50 and 150 nm prepared by electrodeposition are studied in details. Diffraction patterns of the NWs reveal that the crystallites of the NWs become more textured on decreasing their diameter. Magnetic hysteresis loop measurements show the magnetic easy axis changes its direction from axial to perpendicular direction of NWs on increasing the length of the NWs. The magnetostatic interaction among the NWs, known as the key factor in defining the easy direction is found not to be dipolar at all the circumstances. An aspect ratio (length/diameter of NWs) dependence of the non-dipolar interaction in 150 nm NWs is evident from the static magnetization as well as from ferromagnetic resonance (FMR) measurements.     

Spectral characteristics of intense red luminescence in Pr:Y2O3 nanophosphor on UV excitation

Detailed structural and spectroscopic characterizations of Pr:Y₂O₃ nanophosphor have been carried out. On ultraviolet light (at 266?nm) excitation, intense red emission along with weak emissions in blue, green and infrared regions have been observed. The phenomena for the observed emission have been thoroughly explained in the present work and it was finally concluded that the?direct excitation through low-lying 4f¹5d band of Pr³⁺ ions and through the conduction band of Y₂O₃ nanophosphor are the main channels for the observed emissions. The calculated quantum efficiency (QE) for the red emission is found to be ~80?% while the CIE coordinates are (0.65, 0.34) quite close to the standard values. These studies clearly indicate that Pr:Y₂O₃ nanophosphors are promising and futuristic red luminescent material for the development of various display devices and UV detectors. Time resolved spectroscopy has been further used to investigate luminescence dynamics.     

Seismic Reflection from an Interface Between an Elastic Solid and a Fractured Porous Medium with Partial Saturation

The theory of Tuncay and Corapcioglu (Transp Porous Media 23:237–258, 1996a) has been employed to investigate the possibility of plane wave propagation in a fractured porous medium containing two immiscible fluids. Solid phase of the porous medium is assumed to be linearly elastic, isotropic and the fractures are assumed to be distributed isotropically throughout the medium. It has been shown that there can exist four compressional waves and one rotational wave. The phase speeds of these waves are found to be affected by the presence of fractures, in general. Of the four compressional waves, one arises due to the presence of fractures in the medium and the remaining three are those encountered by Tuncay and Corapcioglu (J Appl Mech 64:313–319, 1997). Reflection and transmission phenomena at a plane interface between a uniform elastic half-space and a fractured porous half-space containing two immiscible fluids, are analyzed due to incidence of plane longitudinal/transverse wave from uniform elastic half-space. Variation of modulus of amplitude and energy ratios with the angle of incidence are computed numerically by taking the elastic half-space as granite and the fractured porous half-space as sandstone material containing non-viscous wetting and non-wetting fluid phases. The results obtained in case of porous half-space with fractures, are compared graphically with those in case of porous half-space without fractures. It is found that the presence of fractures in the porous half-space do affect the reflection/transmission of waves, which is responsible for raising the reflection and lowering the transmission coefficients.