2.10. Cell metabolic activity and injury/death
Samples seeded with VICs were used to assess cell metabolic activity on the different substrates. After 2 and 7 days culture, samples were washed in PBS and incubated with 5 mg/mL MTT reagent in serum free medium (1:10 ratio) for 3 h at 37 °C in 5% CO2. Medium was extracted from each sample and converted dye was solubilized in 1 mL acidic isopropanol (0.04 m HCl in isopropanol) and vortexed to ensure that the dye dissolved completely. The solution was then transferred to a 96-well plate and read in a plate reader at 570 nm with background subtraction at 650 nm. Cell injury and death was measured via a commercially available lactate dehydrogenase (LDH) cytotoxicity assay (Promega, Fitchburg, WI). Briefly, cardiomyocytes were cultured on SANF scaffolds for 24 h and incubated with conditioned medium using the assay kit for 30 min at 37 °C. Absorbance at 490 nm was measured using a commercially available plate reader. Cells seeded on fibronectin treated PDMS coated glass coverslips served as a comparison.
2.11. Statistical analysis
All data were expressed as mean ± standard error (SEM). Statistical comparisons were done on normally distributed data using analysis of variance (ANOVA) and Tukey's post-hoc tests. ANOVA on ranks followed by Dunn's or Tukey's pairwise comparison was used to analyze data that was not normally distributed. A p-value of less than 0.05 was used as a measure for statistical significance.