A device to apply user-specified strains to biomaterials in culture

An apparatus was developed to apply user-specified displacements to biomate rial samples in culture, The device allowed cyclic waveforms of bandwidth 0 Hz to 20 Wt to be applied under physiologic thermal (37.5 degreesC) and [C O2] (5%) conditions. For a 0 Hz to 20 Hz bandwidth signal similar in shape to a ventricular pressure waveform, the mean displacement error was 0.26% o f the full-scale output, The maximum overshoot was 0.700%. Environmental sy stem evaluation tests demonstrated a specimen cartridge temperature of 37.2 0 +/- 0.15 degreesC during cyclic loading and 37.23 +/- 0.21 degreesC durin g static conditions. [CO2] was 5.29 +/- 0.54% during cyclic loading and 5.2 5 +/- 0.61% during static conditions. Laminar flow applied at the loading r od entrances to the specimen cartridge ensured the sample remained sterile during testing. As a preliminary evaluation, polyurethane samples were seed ed with fetal foreskin fibroblasts and subject to intermittent cyclic displ acements. Results demonstrated enhanced cell proliferation and increased [P GE(2)] for samples subjected to 10% strain compared with unstrained control s, ii next step will be to evaluate cell response sensitivity to strain mag nitude, duration, direction, and frequency. The long-term intent is to esta blish mechanical loading configurations that induce acceptable or adaptatio n-inducing responses for use in implant design and tissue engineering appli cations.