# The Effect of Human Blood Plasma Conditioning Films on Platelet Tungsten Bag Surface Properties
## 3 Results
### Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR)  
Using ATR-FTIR, the human plasma conditioned surfaces (Figure 4a/b), human plasma and S. epidermidis (Figure 4c/d) and human plasma and _Ser. marcscens_ (Figure 4e/f) were analysed. For the human plasma conditioned, human plasma and_S. epidermidis_ and human plasma and _Ser. marcscens_ conditioned surfaces, on the rough, smooth and flat surfaces, at both 1 h (a, c and e) and 24 h (b, d and f). Note that these spectra are substrate subtracted in order to better resolve new IR bands associated with adsorption of the plasma and/or organism. Note that it is not possible to differentiate between the organisms and the plasma. The positive peaks are the new adsorption-related IR bands and the negative peaks relate to there being slightly less substrate related absorptions in the sample than the substrate reference. This is due better contact between the internal reflection element (IRE) and the treated samples than between the untreated substrate controls and the IRE. ATR-FTIR of the pPVC substrates has been discussed in a previous paper [23]--assignments for the negative peaks can be found here. Figure 3: Determination of elements present according to atomic weight as determined by EDX on the (**a**) rough, (**b**) smooth and (**c**) flat surfaces. Surfaces had CFs applied for 1 h or 24 h with human plasma, human plasma with _S. epidermidis_ (Plasma Se) or plasma with _Ser. marcscens_ (Plasma Sm). (\(n=3\)). Data presented as mean \(\pm\) SE. Human plasma in isolation showed strongest adsorption (amide I and II bands at 1635 cm\({}^{-1}\) and 1575 cm\({}^{-1}\), respectively and the O-H and N-H stretching at 3266 cm\({}^{-1}\)) on to the rough surfaces with only a slight increase after 24 h, indicating rapid adsorption to an almost limiting level (Figure 4a,b). Resolvable levels of plasma adsorption were not observed on the smooth and flat surfaces, even after 24 h.  
_S. epidermidis_ and human plasma interestingly showed no resolvable adsorption on to the smooth and flat surfaces after 1 h and 24 h. A small amount of adsorption was evident on the rough surface after 1 h (amide I (1635 cm\({}^{-1}\)) (Figure 4c)), after 24 h the level of adsorption appeared to reduce to non-resolvable levels observed on the smooth and flat surfaces. This observation at first thought appears to unexpected, though after further consideration it may be proposed that the _S. epidermidis_ and human plasma interact so strongly with each other that all the adsorption active groups are used in the latter interaction and are not available for interaction with the substrate, resulting in no adsorption. In the case of the rough surface a small amount of (maybe plasma) adsorption occurred initially, though with time interaction with the _S. epidermidis_ (or vice-versa - or a combination of both) led to its removal from the surface. Figure 4: ATR-FTIR of human plasma conditioning films after **(a)** 1 h and **(b)** 24 h, _S. epidermidis_ and human plasma conditioning films after **(c)** 1 h and **(d)** 24 h, and _Ser. marcescens_ and human plasma conditioning films after **(e)** 1 h and **(f)** 24 h, after subtraction of non-conditioned control surfaces. Note that scale differs for e/f due to absorbance intensity. (\(n=3\)). _Ser. marcescens_ and human plasma showed no resolvable adsorption on to the smooth and flat surfaces after 1 h whilst the rough surface showed a small amount of adsorption after this period (Figure 4e). After 24 h adsorption of _Ser. marcescens_ and human plasma on to the flat surface increased significantly, so much so that the absorbance scale had to be increased three-fold to accommodate the amide I peak (Figure 4f). Adsorption of this combination on to the rough surface also increased significantly after 24 h, to roughly twice the levels seen with plasma alone. The smooth surface also showed increased adsorption to broadly similar levels to that of plasma alone on the rough surface.