Mammalian cell survival and processing in supercritical CO2

We demonstrate that mammalian cells can survive for 5 min within high-pressure CO2. Cell survival was investigated by exposing a range of mammalian cell types to supercritical CO2 (scCO(2)) (35 C, 74 bar; 1 bar = 100 kPa) for increasing exposure and depressurization times. The myoblastic C2C12 cell line, 3T3 fibroblasts, chondrocytes, and hepatocytes all displayed appreciable but varying metabolic activity with exposure times up to 1 min. With depressurization times of 4 min, cell population metabolic activity was >= 70% of the control population. Based on survival data, we developed a single-step scCO(2) technique for the rapid production of biodegradable poly(DL-lactic acid) scaffolds containing mammalian cells. By using optimum cell-survival conditions, scCO(2) was used to process poly(DL-lactic acid) containing a cell suspension, and, upon pressure release, a polymer sponge containing viable mammalian cells was formed. Cell functionality was demonstrated by retention of an osteogenic response to bone morphogenetic protein-2 in C2C12 cells. A gene microarray analysis showed no statistically significant changes in gene expression across 4,418 genes by a single-class t test. A significance analysis of microarrays revealed only eight genes that were down-regulated based on a delta value of 1.0125 and a false detection rate of 0.