Agnese Magnani

Biological Performance of Materials

The biomaterial science, the study of the application of materials to biological and biomedical problems is a field characterised by medical needs, basic research, advanced technological development, industrial involvement, ethical considerations and regulations. The biological performance of materials largely depends on their bulk and surface properties.

X‐Ray Detected Magnetic Hysteresis of Thermally Evaporated Terbium Double‐Decker Oriented Films

Fabrication of molecular nanostructures and control of the molecular properties at the nanoscale is at the basis of the development of innovative single molecule devices. [ 1 ] Particularly active is the research for the organization of single molecule magnets (SMMs) that have been proposed as ideal candidates for the development of molecular spintronics and data storage devices. [ 2 , 3 ] These molecules are a well known class of compounds characterized by the peculiar presence of a strong axial magnetic anisotropy that induces a slow relaxation in the magnetization and a magnetic hysteresis of molecular origin showing spectacular quantum effects. [ 4 ] Thanks to the surface sensitivity of synchrotron-based techniques it has been possible to provide the proof of concept that SMM behavior is observable in a single layer of magnetic molecules. [ 5 ] First attempts to control at the nanoscale the SMM assembling have been made by opportune functionalization promoting their grafting on specifi c surfaces in order to form monolayer deposits from solution. [ 6 , 7 ] However, cleaner processes, e.g. thermal evaporation, [ 8 ] are required for the development of real devices or to extend the investigation to reactive surfaces, e.g. ferromagnetic metals, and

Conformation of human plasma proteins at polymer surfaces: the effectiveness of surface heparinization

Studies were made on the adsorption of two human plasma proteins, albumin (HSA) and fibrinogen (HFg), onto three different polymeric surfaces: commercial pellethane 2363-80AE (PU); pellethane crosslinked with a poly(amido-amine) (PUPA); and heparinized PUPA, using in situ ATR/FTIR spectroscopy (attenuated total reflection Fourier transform infrared spectroscopy). Conformational changes were found to occur on the two proteins upon adsorption onto bare PU and PUPA, and the protein unfolding on bare PU was also found to be time dependent. On the contrary, the two proteins do not change conformation when they are adsorbed onto the heparinized surface, emphasising the effectiveness of surface heparinization.

Blood-interaction performance of differently sulphated hyaluronic acids

Seven differently sulphated hyaluronic acid derivatives, having a general formula HyalSx where x can be 1, 2, 2.5, 3, 3.5, 3.8, 4, were synthetized. Coagulation tests i.e. whole blood clotting time and thrombin time were performed on these compounds and significant prolongations were observed from HyalS2.5 up to HyalS4. All that means the heparin like activity increases by increasing the sulphation degree of hyaluronic acid. The interaction of each of them with thrombin and FXa was studied in order to understand the mechanism of coagulation inactivation and the role of the sulphate position in the disaccharide unit to favour the protease inhibiting reaction. The bioactivity of HyalSx in terms of FXa and thrombin inactivation increases increasing with sulphation degree but the FXa inactivation seems to be mediated by ATIII, while the aspecific electrostatic interaction seems to play an important role in the inactivation of thrombin. Also the interaction with human serum albumin was studied by ATR/FT-IR technique and no changes of protein conformation was observed, as occurs in the case of heparin.

Micropatterned surfaces for the control of endothelial cell behaviour.

Micropatterned materials were synthesised by photoimmobilising the sulphated hyaluronic acid, adequately functionalised with a photoreactive moiety, on glass substrates. Four different patterns (10, 25, 50 and 100 microns) were obtained. The spectroscopic and microscopic analysis of the microstructured surfaces revealed that the photoimmobilisation process was successful, demonstrating that the photomask was well reproduced on the sample surface. Analysis of endothelial cell behaviour on these micropatterned materials was performed in terms of adhesion, locomotion and orientation. Decreasing the stripe dimensions a more fusiform shape of the adhered endothelial cells was observed. At the same time the cell locomotion and orientation were increased. Furthermore, a photoimmobilisation of stripes of HyalS (10 and 100 microns) was performed on a continuous HyalS layer, in turn immobilised on glass substrate. Being excluded a different chemistry between the stripe and the substrate, the influence of topography on the behaviour of endothelia cells was thus envisaged.

Immobilization of Heparin and Highly-Sulphated Hyaluronic Acid onto Plasma-Treated Polyethylene

Heparin and highly-sulphated hyaluronic acid have been successfully immobilized onto plasma-processed polyethylene via a diamine polyethyleneglycol (PEG) spacer molecule. Two different plasma-processes have been utilized, i.e. a treatment and a deposition process, for providing polyethylene surface with the COOH groups necessary for the immobilization reactions. XPS integrated with derivatization procedures, ATR-FTIR and Water Contact Angle measurements have been carried out for characterizing each modification step: 1) the plasma-process, 2) the immobilization of the spacer molecule and 3) the immobilization of the biomolecules. The thrombin time of the modified surfaces has been measured, and their platelet activation characteristics evaluated. The results indicate a certain nonthrombogenic character of the biomolecule-immobilized polyethylene samples.

Thermal Deposition of Intact Tetrairon(III) Single‐Molecule Magnets in High‐Vacuum Conditions

A tetrairon(III) single-molecule magnet is deposited using a thermal evaporation technique in high vacuum. The chemical integrity is demonstrated by time-of-flight secondary ion mass spectrometry on a film deposited on Al foil, while superconducting quantum interference device magnetometry and alternating current susceptometry of a film deposited on a kapton substrate show magnetic properties identical to the pristine powder. High-frequency electron paramagnetic resonance spectra confirm the characteristic behavior for a system with S = 5 and a large Ising-type magnetic anisotropy. All these results indicate that the molecules are not damaged during the deposition procedure keeping intact the single-molecule magnet behavior.

Cell behaviour on chemically microstructured surfaces

Abstract Micropatterned surfaces with different chemical topographies were synthesised in order to investigate the influence of surface chemistry and topography on cell behaviour. The microstructured materials were synthesised by photoimmobilising natural Hyaluronan (Hyal) and its sulphated derivative (HyalS), both adequately functionalised with a photorective moiety, on glass substrates. Four different grating patterns (10, 25, 50 and 100 μm) were used to pattern the hyaluronan. The micropatterned samples were analysed by Secondary Ions Mass Spectrometry, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy to investigate the chemistry and the topography of the surfaces. The spectroscopic and microscopic analysis of the microstructured surfaces revealed that the photoimmobilisation process was successful, demonstrating that the photomask patterns were well reproduced on the sample surface. The influence of chemical topographies on the cell behaviour was then analysed. Human and 3T3 fibroblasts, bovine aortic and human (HGTFN line) endothelial cells were used and their behaviour on the micropatterned surfaces was analysed in terms of adhesion, proliferation, locomotion and orientation. Both chemical and topographical controls were found to be important for cell guidance. By decreasing the stripe dimensions, a more fusiform shape of cell was observed. At the same time, the cell locomotion and orientation parallel to the structure increased. However, differences in cell behaviour were detected according to both cell type and micropattern dimensions.

The use of hyaluronan and its sulphated derivative patterned with micrometric scale on glass substrate in melanocyte cell behaviour

Surface microfabrication techniques were widely utilised for the spatial control of in vitro cell behaviour. A photo-immobilisation procedure was utilised to create micropatterned surfaces: four different stripe patterns (100, 50, 25 and 10 microm) of hyaluronan (Hyal) and its sulphated derivative (HyalS) on silanised glass substrate were obtained.The morphological analysis showed that the surface topography showed regular stripes of 100, 50, 25 and 10 microm wide and ranging from 300 nm up to 1 microm in thickness. They reproduced the exact photo-mask pattern: glass stripes alternating with polysaccharide ones. On the contrary, Hyal microstructures showed just a topographic pattern as the glass stripes appeared to be covered by a thin layer of the macromolecule by TOF-SIMS. Cell adhesion studies demonstrated that melanocytes adhered and oriented within the first 2h of culture on HyalS microdomains and not on Hyal microstructures where they spread on glass substrate around the patterned area. Double photo-immobilised samples characterised by a 100 microm stripe pattern of Hyal or HyalS on the top of a continuous layer of the two polysaccharides were also created in order to investigate the effect of the topography on cell behaviour. The obtained results demonstrated that melanocytes adhered on HyalS stripes while on the Hyal micropatterned surfaces they spread on silanised glass substrate around the structured area, resulting in the exclusion of the topographic pattern.

Novel polysaccharide hydrogels: characterization and properties

New chemical hydrogels, potentially suitable for biomedical applications, have been synthesized and characterized by 13C NMR, and FT-IR spectroscopy. The polysaccharide components of these hydrogels are hyaluronane, alginate and carboxymethylcellulose, while the novel cross-linking procedure consists of activating the carboxylate moieties by 2-chloro-1-methylpyridinium iodide CMPJ and using 1,3-diaminopropane as a chemical bridge. Varying the amount of CMPJ three series of hydrogels were obtained with different cross-linking degrees (5, 50, 100%). Their percentages were determined by 13C NMR and FT-IR analysis. The morphology of the gels was studied by scanning electron-microscopy and the pore sizes were determined in order to find a relationship with the swelling properties. Cell adhesion, using human hepatocytes, and platelet adhesion studies on the different series of cross-linked compounds allowed us to envisage their utilization as extracellular matrix materials and cardiovascular biomaterials. Copyright