Cell suspension, at a density of 2 × 105 cells/mL, was evenly added onto PEKK/TCP dropwise. Four groups were tested in vitro: (1) PEKK + OS (PEKK seeded with hSF-MSCs in osteogenic media), (2) PEKK + SF (PEKK seeded with hSF-MSCs in standard culture media), (3) TCP + OS (TCP seeded with hSF-MSCs in osteogenic media), and (4) TCP + SF (TCP seeded with hSF-MSCs in standard culture media). After 3 days of culture, the standard culture media in the OS groups was changed into an osteogenic media and renewed twice a week while the SF groups were renewed with standard medium at the same frequency. The cellular ALP activity was detected after 1, 4, 7, 14, and 21 days70 (link),71 (link). SigmaFast p-nitrophenyl phosphate tablets (Sigma) dissolved in deionized H2O was used with the cell lysate to detect the ALP level. The absorbance was read in a microplate reader at 405 nm (SpectraMax® M2). The ALP units were standardized to the cell number.
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