Effects of RGD, KRSR, and KSSR on alkaline phosphatase specific activity in osteoblast-like MG63 cells. (a) Alkaline phosphatase activity increased on PLL-g-PEG surfaces compared with TCPS and SLA surfaces . There was no effect of KSSR on alkaline phosphatase activity. (b) Addition of either RGD or KRSR decreased alkaline phosphatase activity. The effect of combining RGD and KRSR caused a further decrease in alkaline phosphatase activity at high peptide densities. (a) **P<0.05, PEG surfaces vs. SLA. (b) +P<0.05, RGD vs. KRSR alone (0 RGD) ; ‡P<0.05, KRSR vs. RGD alone (0 KRSR).