A device for imposing cyclic strain to cells growing on implant alloys

The objective of this study was to develop a unique device for applying well-characterized cyclic, strain to cells growing on implant alloys. The device is based on the four-point bending principle and utilizes an electric motor, belt, and cam system to cyclically deflect a commercially pure titanium plate with cell culture wells in the middle of the plate. Analyses demonstrated that 182 +/- 3, 366 +/- 9, and 984 +/- 7 microstrain may be cyclically generated in culture areas from 0.5 to 10 Hz for up to 72 h. UMR-106 osteoblast-like cells growing on the titanium plate were subjected to these strain magnitudes at 1.5 Hz for periods of 4 or 24 h. Cells were checked for viability, total protein as a general indicator of cell number, and alkaline phosphatase activity (ALP) as an indicator of bone cell func-tion. Cells strained at 984 +/- 7 microstrain exhibited 21%-24% more protein but 45%-49% less ALP activity than cells strained at 182 +/- 2 or 366 +/- 9 microstrain. Decreased ALP activity may indicate impaired mineralization. Results indicate the device is suitable for applying known, cyclic strain to cells growing on implant alloys and evaluating cellular responses to strain while growing on implant alloys.