Figure 6: ALP activities of MC3T3-E1 osteoblast-like cells on HAP, HAP—30% PA, and HAP—30% PA—12 h at 7, 14, and 21 days after obtaining a confluent cell monolayer. At 14 days, the ALP activities of the cells on HAP—30% PA and HAP—30% PA—12 h were significantly higher than that on HAP ( ). The ALP activity at 14 days for HAP—30% PA—12 h was higher than that for HAP—30% PA, but the ALP activity at 21 days was lower than that for HAP—30% PA. Although the ALP activities for HAP and HAP—30% PA gradually increased from 7 to 21 days, the ALP activity for HAP—30% PA—12 h reached its peak at 14 days.