This month I performed measurements of polyelectrolyte films by ellipsometry in order to assess their thickness. I also prepared series of samples for the analysis of cytotoxicity. Preliminary measurements were performed using AFM nanoindentation mode. Recently obtained results were presented as the poster entitled “Effect of genipin cross-linking on physico-chemical properties and cellularization process of PLL/HA multilayer polyelectrolyte films” during „2nd Joint PhD seminar”. This work was focused on biocompatibility improvement of polymer coatings by chemical cross-linking and further by films endothelialization. The integration of biomedical implants in human organism is dependent on the chemical composition and topography of the surface as well as the mechanical properties of an applied materials. While in the past most of the clinically used materials were developed only based on their acceptance by the body, today beneficial interactions of implants with cells and proteins gather more and more importance. Current development in cardiovascular devices is related to the biocompatibility improvement through manufacturing surfaces mimicking extracellular matrix components. This dynamic microenvironment facilitates covering an internal surface of implant by cell monolayer which mask the material from an inflammatory response and reduce risk of thrombosis. The aim of this study was to improve properties of blood contacting material such as polyurethane, by the “layer by layer” polyelectrolyte multilayer film formation on its surface in order to control implant endothelialisation. However, application of polyelectrolyte coatings as biomaterials for cell attachment has been limited due to their gel like characteristic. Herein, we attempt to improve the cellular adhesion properties of films through chemical cross-linking with a genipin. Hyaluronan (HA), poly-L-lysine (PLL) were used to assemble [PLL-HA]n films in two different thickness variants, 12 and 24 bi-layers respectively. The effects of genipin cross-linking on the internal composition, surface topography, nano-hardness of multilayers and as a consequence on cellular processes were investigated. Fourier Transform Infrared Spectroscopy (FTIR) measurements shown a slight changes in the internal structure of multilayers cross-linked with various genipin concentration. Atomic force microscopy (AFM) confirmed that cross-linking affected film topography and stiffness. Cellular adhesion, proliferation and functionality studies using endothelial cells, carried out on both variants of film thickness, demonstrated significant differences. The [PLL–HA]24 film was shown to better improve endothelialization, especially for higher concentrations of the cross-linker.

In October verified function , which returns six variants of twinning in the parameterization Rodriguez by calculating the six- point normal to the plane of twinning , for example, 101 or 102 for the input vector Rodriguez. If n is a vector normal to the plane hkl crystallographic system , and g is the passive rotation matrix of the S- > C , all twinning planes normal to get the formula: n_i = g ^ - 1.OperatorSymetry_i.n . Being in possession of six planes normal to the twinning in the crystal hexagon , we can transform the orientation g to find the orientation of the twin . Having done this by the formula g ' = g.Transpose [ RotationMatrix [ Pi, Gn [ [ i]] ] ] I found that I made a mistake , because , although confusion with the orientation g was confusion twin , the sense of displacement systems gig ' was unfounded. It is assumed as follows from the formula , the orientation of the coordinate system that rotates around g n_i normal through an angle of 180 degrees, this movement takes place by way of rotation around the line perpendicular to the n_i (lying in the plane of twinning ) and at the same time parallel to the unit cell of a suitable vector a_i . Simply put this is a rotation around a_i about 86 degrees in the case of twin 102 and 56 degrees in the case of twin 101 ( shortest turnover ) . Confirmation of these relationships were based on an analysis of the orientation of the twin on the experimental map. First, select a place on the map where the confusion found twin 102 two grains. Then selected two orientations forming the above confusion , and the first of them were propagated rotation relative to the symmetry operators a total of six (because each is repeated twice , so not twelve ) crystallographic directions a_i rotated additionally actively transposing the matrix g according to : a_i = g ^ -1. Hex [ [ i]] . and , where a marked unit vector [ 1,0,0 ] . To find variants of twinning should rotate 102 g with respect to the input orientation a_i an angle of 86 degrees according to : g.Transpose [ RotationMatrix [ angle , Ga [ [ i]] ] ] .

I decided to find a way for finding maxima in the
5-paremter grain boundary distribution function.
From the computational point of view, it is
a very complex (and time-consuming) task.
With reduction of the investigated
domain to the fundamental zone, it can be done quite efficiently,
but the question arises if some information is missing.
At least we lose, the information about multiplicities of boundaries,
however, still most of the maxima should be found.

The most interesting things from this month:

-during research stay in Budapest I had opportunity to perform in-situ heating of the melt spun ribbons in TEM
- I have received positive review of my article
- I have carried out microhardness measurements of melt spun ribbons
- in order to prepare compact samples I have pulverized firs series of melt spun ribbons using vibration micro mill
- I have participated in the Joint PhD Seminar at the AGH University

In the beginning of this month presented a seminar in the Institute of Metallurgy and Materials Science PAS. The seminar was connected with the beginning of the PhD procedure and it was entitled: “Application of three-dimensional orientation microscopy to microstructure characterization”. The supervisor of the work is Prof. dr hab. inż. Marek Faryna and the assistant supervisor is dr inż. Anna Sypień.