Table 1.
Overview on publications describing the potential of scCO2 combined with low amounts of additives to reach the required SAL of 10–6 for bacterial spores without high temperature and pressure (TFA = trifluoracetic acid, PAA = peracetic acid).
Fig 1.
108–109 test microorganisms embedded in alginate/agarose cylinders (A). Sudan Red G as indicator for liquid CO2 (18°C, 5,5 MPa) (B) and scCO2. (34–38°C, ~7.3 – ~ 9,0 MPa) (C). Scale bares represent 10 mm.
Fig 2.
Schematic drawing of the custom-made 4-point bending apparatus.
Fig 3.
Inactivation of different microbial cells embedded into alginate/agarose PCD due to scCO2 treatment for different time spans.
The inactivation is displayed as Reduction Factors, RF-values, giving the logarithmic reduction of surviving cells (black bars). Each experiment was performed in triplicate at minimum (n = 3–10). The threshold of detection, i.e. the maximum number of cells that could be quantified for each batch of PCD is given as white bar. For RF-values that reach the threshold of detection no standard deviation (line) is given.
Fig 4.
Box plots visualizing the compressive strength (a) and modulus (b) of alginate hydrogel scaffolds obtained from untreated (non-sterile) and differently sterilized alginate powders.
Each box shows the 25th to 75th percentile of the measured strength and modulus, respectively (n = 6). Squares (□) represent mean values, horizontal bars inside the box show the median value, while upper and lower bars indicate the upper and lower values within 1.5 times the inter-quartile range from the upper and lower quartile (adjacent values are labelled as ×).
Fig 5.
Rheological parameters of alginate/MC pastes, n = 2.
Table 2.
Rheological parameters of alginate/MC pastes.
Fig 6.
Plotted strands of methylcelulose/alginate paste (3:1), 9 x 9 strands, strand width 0.78 mm, A) gamma irradiated MC, B) scCO2 sterilized MC.
Fig 7.
Box plot visualizing the compressive moduli of porous scaffolds from mineralized collagen after treatment with different sterilization procedures.
Each box shows the 25th to 75th percentile of the measured modulus. Squares (□) represent mean values (n = 6), horizontal bars inside the box show the median value, while upper and lower bars indicate the upper and lower values within 1.5 times the inter-quartile range from the upper and lower quartile (adjacent values are labelled as ×).
Fig 8.
Results of bending strength measurement on differently sterilized samples: representative stress-strain curves (a) and box plots visualizing the bending stress values at 5, 10 and 20% deformation (b-d).
Each box shows the 25th to 75th percentile of the measured bending stress. Squares (□) represent mean values (n = 6), horizontal bars inside the box show the median value, while upper and lower bars indicate the upper and lower values within 1.5 times the inter-quartile range from the upper and lower quartile (adjacent values are labelled as ×).
Fig 9.
Alginate beads prepared from steam-sterilized and scCO2 sterilized powders with embedded hMSC.
Left: MTT staining indicates viable cells. Scale bar = 1 mm. Right: Cell numbers calculated from LDH activity after lysis of the embedded cells (n = 4, error bars show standard deviation from the mean).
Fig 10.
Cell numbers calculated from DNA content and ALP activity of hMSC which were cultivated for up to 4 weeks in porous scaffolds from mineralized collagen under osteogenic stimulation.
Scaffolds were sterilized by ethylene oxide exposure, gamma irradiation or scCO2. Data of experiments with hMSC of two different donors were combined (n = 6, each donor n = 3). Because of the different proliferation of the cells, data were normalized to d14 values of gamma irradiated samples, which were set to 1. Error bars show standard deviation from the mean (n = 6).