Pleiotrophin (PTN) is a heparin‐binding growth factor that plays a significant role in tumor growth and angiogenesis. We have previously shown that in order for PTN to induce migration of endothelial cells, binding to both α_νβ₃ integrin and its receptor protein tyrosine phosphatase beta/zeta (RPTPβ/ζ) is required. In the present study we show that a synthetic peptide corresponding to the last 25 amino acids of the C‐terminal region of PTN (PTN_112–136) inhibited angiogenesis in the in vivo chicken embryo chorioallantoic membrane (CAM) assay and PTN‐induced migration and tube formation of human endothelial cells in vitro. PTN_112–136 inhibited binding of PTN to α_νβ₃ integrin, and as shown by surface plasmon resonance (SPR) measurements, specifically interacted with the specificity loop of the extracellular domain of β₃. Moreover, it abolished PTN‐induced FAK Y397 phosphorylation, similarly to the effect of a neutralizing α_νβ₃‐selective antibody. PTN_112–136 did not affect binding of PTN to RPTPβ/ζ in endothelial cells and induced β₃ Y773 phosphorylation and ERK1/2 activation to a similar extent with PTN. This effect was inhibited by down‐regulation of RPTPβ/ζ by siRNA or by c‐src inhibition, suggesting that PTN_112–136 may interact with RPTPβ/ζ. NMR spectroscopy studies showed that PTN_112–136 was characterized by conformational flexibility and absence of any element of secondary structure at room temperature, although the biologically active peptide segment 123–132 may adopt a defined structure at lower temperature. Collectively, our data suggest that although PTN_112–136 induces some of the signaling pathways triggered by PTN, it inhibits PTN‐induced angiogenic activities through inhibition of PTN binding to α_νβ₃ integrin. J. Cell. Biochem. 112: 1532–1543, 2011.

Many current research efforts focus on alternative electroacoustic transduction devices having no moving parts, in order to achieve sufficient audio performance from compact solid state devices. Thermoacoustic loudspeakers are transducers based on the conversion of A/C current signals to thermal energy, causing a local fluctuation of air pressure which generates acoustic waves. A thermoacoustic actuator does not involve any movement of solid components in order to generate an acoustic wave and it is based on a mechanism of a "virtual" piston produced by vibrating air molecules via alternating heat transfer to the medium. This work examines such novel and alternative audio transduction technologies based on a novel hybrid thermoacoustic transducer prototype which was developed at the University of Patras through the cooperation between Audio and Acoustic Technology Group and Solid State Physics Laboratory. This hybrid solid state device without moving parts is based on the thermoacoustic method of sound reproduction and preliminary measurements of its performance are presented. The theoretical principles of these systems are also simulated, resulting into comparisons with the measured performance of the prototype.

We describe a novel technique for the characterization of the mean pore radius of self-ordered porous anodic alumina membranes. We have studied the flow of liquids through cylindrical membrane pores under conditions of very low Reynolds number (Re ≪ 1). We find that the flow data are well-described by Poiseuille's law. Characterization is achieved through the application of the Hägen-Poiseuille equation on flow measurements conducted in a simple and compact experimental setup. This setup allows for the monitoring of flow as a result of the pressure difference between the two sides of the membrane without the use of sophisticated and costly laboratory equipment. The proposed method has been tested by flow experiments using liquids of various viscosities. Good agreement is found between the results obtained from the flow data and the pore radii measured by scanning electron microscopy. Consistent results for the mean pore radius for the same membrane have been obtained in all cases.

The electrostatic complexation of the protein beta-lactoglobulin (β-LG) with the anionic polysaccharide chondroitin sulfate (CS) and the subsequent stabilization by thermal treatment were studied to achieve the well-defined nanoparticles (NPs). The formation of the well-defined NPs was obtained at pH 4 with a hydrodynamic radius from 60 to 80 nm. NP aggregation was observed at pH 1.5 because of the loss of the anionic charge of chondroitin sulfate on the surface of the NPs. After thermal treatment, the NPs exhibited stability against a pH increase to pH 7 while a stronger aggregation at pH 1.5 was observed. Core-shell structures were found at pH 7 after thermal treatment, indicating a possible mechanism of partial disintegration. The addition of Tween 80 (T80) before thermal treatment led to the formation of T80 self-assemblies inside the NPs. This caused an increase in the hydrophobicity of the inner and outer surfaces of the NPs as it was observed by fluorescence spectroscopy. The ζ-potential of the complexes and NPs was about −20 mV while the presence of T80 did not affect it. FTIR spectra verified changes of the secondary structure of β-LG in its complexes with CS and T80. The thermally treated NPs exhibited high surface and overall hydrophobicity and stability in high salinity and biocompatible solutions. The thermally treated NPs showed colloidal and physicochemical stability for 1 month, which were enhanced by the addition of T80. Due to the nature of the precursors and their colloidal properties, the NPs are highly promising for applications as biocompatible drug delivery nanocarriers while T80 acts as an agent to modify their properties.