Claudio Della Volpe

Enzymatically-tailored pectins differentially influence the morphology, adhesion, cell cycle progression and survival of fibroblasts

Improved biocompatibility and performance of biomedical devices can be achieved through the incorporation of bioactive molecules on device surfaces. Five structurally distinct pectic polysaccharides (modified hairy regions (MHRs)) were obtained by enzymatic liquefaction of apple (MHR-B, MHR-A and MHR-alpha), carrot (MHR-C) and potato (MHR-P) cells. Polystyrene (PS) Petri dishes, aminated by a plasma deposition process, were surface modified by the covalent linking of the MHRs. Results clearly demonstrate that MHR-B induces cell adhesion, proliferation and survival, in contrast to the other MHRs. Moreover, MHR-alpha causes cells to aggregate, decrease proliferation and enter into apoptosis. Cells cultured in standard conditions with 1% soluble MHR-B or MHR-alpha show the opposite behaviour to the one observed on MHR-B and -alpha-grafted PS. Fibronectin was similarly adsorbed onto MHR-B and tissue culture polystyrene (TCPS) control, but poorly on MHR-alpha. The Fn cell binding site (RGD sequence) was more accessible on MHR-B than on TCPS control, but poorly on MHR-alpha. The disintegrin echistatin inhibited fibroblast adhesion and spreading on MHR-B-grafted PS, which suggests that MHRs control fibroblast behaviour via serum-adhesive proteins. This study provides a basis for the design of intelligently-tailored biomaterial coatings able to induce specific cell functions.

Numerical models for the evaluation of the contact angle from axisymmetric drop profiles: A statistical comparison

Axisymmetric drop shape analysis (ADSA) is a well-established methodology for estimating the contact angle value and the surface tension of liquids starting from sessile drops images. It consists of an iterative procedure in which a best fit between a theoretical axisymmetric Laplacian curve and an experimental drop profile is performed. When only an evaluation of the geometric contact angle value is needed, a similar numerical approach can be adopted by using simpler algebraic models in place of a Laplace profile, thus allowing more straightforward implementations and shorter computation times. In this work the relative merits of the different methodologies are compared. Beside the standard ADSA procedure, four different mathematical models are examined, namely the circular and elliptical models, the first-order perturbative solution of the Laplace equation, and a cubic spline model. Their relative statistical performances are tested on both calculated and experimental drop profiles. For simulated drops, the actual capability of the models to predict the correct contact angle is also investigated.

Hydrophobic siloxane paper coatings: the effect of increasing methyl substitution

Paper is an organic material widely used in cultural heritage and mainly composed of cellulose mixed with lignin, hemicellulose and small amounts of additives. This paper deals with siloxane coatings on pure cellulose paper, applied by sol–gel dipping in sols prepared with different siloxane precursors (tetraethoxysilane, methyl triethoxysilane, dimethyl diethoxysilane, trimethyl monoethoxysilane). The coated samples were characterized using various techniques (Fourier Transform Infrared Spectroscopy FT-IR, Nuclear Magnetic Resonance NMR and Scanning Electron Microscopy and Energy Dispersive Spectroscopy SEM–EDS), measuring their mechanical properties, flame resistance and contact angles, and a colorimetric test. The coated samples’ behavior was more hydrophobic the higher the methyl number of siloxane precursor, regardless of the coating’s thickness. Increasing the thickness improved the mechanical and thermal properties. The thickest coatings were obtained using a double coating process and a basic catalyst for the hydrolysis step, but this latter condition facilitated the formation of surface agglomerates, which make the paper too stiff and yellow.

Analysis of dynamic contact angle on discoidal samples measured by the Wilhelmy method

Contact angle measurements have been performed using the Wilhelmy microbalance on disc-shaped samples of different thicknesses and these are compared with the theoretical analysis proposed by Dryden and Andrade (D-A). In disagreement with the original D-A results, our conclusion is that not only are the force values well reproducible, but also the determination of the contact angles, by inverting the force equations, provides acceptable estimates. This conclusion is supported by the analysis of error propagation for the various physical and geometrical parameters of the model. By taking into account the thickness of the samples a correction is introduced, the significance of which is analysed with respect to some of the experimental parameters. Moreover, a second method of analysis based on an iterative procedure is proposed; it uses only the force data collected during the immersion of the diameter zone of the disc samples and can be applied to both discoidal (e.g. lenses) and plane disc-shaped samples. Finally, an accurate analysis of the meniscus shape during the immersion leads to a third method for the estimation of contact angles on discs. It requires the detection of the immersion level at which the lateral meniscus becomes perfectly planar. Its use is restricted to the case of thick discs and the precision achieved is not high.

Diffusion in microemulsion systems

Abstract The diffusion coefficients of the system AOT—Water in n-heptane have been measured at 25°C as a function of AOT concentration at four different ratios, R, of H2O to AOT, using the Gouy interferometric technique. The results are in reasonably good agreement with the light scattering data published by previous authors, although some differences have been observed. Density and refractivity data have also been collected and these are discussed briefly.

In situ polymerization of functional monomers in rubbers: 1. Modification of silicone rubbers by a poly(ester thioether amine) based on piperazine

Modified silicone rubber intended mainly for biomedical applications was obtained by in situ polymerization. The process involved swelling of the rubber with a mixture of solvent and monomers, polymerization, and finally evaporating the solvent under reduced pressure. The polymerization system selected was the stepwise hydrogen-transfer polyaddition of 1,4-piperazinediyl diethanethiol to ethylene glycol dimethacrylate, leading to a poly(ester thioether amine). The modified silicone was physically and mechanically characterized by several analytical techniques (Fourier-transform infra-red spectroscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, dynamic contact angle and scanning electron microscopy), and the results obtained were compared with those relative to both the linear guest polymer and the unmodified rubber.