Cheng et al. (2006b) found that PHBHHx microparticles (0.005–0.10 g l−1) promoted
murine fibroblast L929 cell proliferation and elevated intracellular calcium
concentrations. Ethylene glycol-bis(2-aminoethylether)-N,N,N¢,N¢-tetraacetic acid
inhibited PHBHHx-microparticle-induced cell proliferation by chelating the extracellular
Ca2+ and blocking the PHBHHx particle-induced intracellular Ca2+ concentration
increase. Transwell experiments demonstrated that PHBHHx microparticles
stimulated fibroblast proliferation when separated from cells by a 0.4-μm filter as
effectively as when applied directly to cells. Since the PHBHHx microparticles had
a diameter of 75 μm, the stimulatory effect of PHBHHx particles on cell growth was
attributed to degradation products smaller than 0.4 μm in diameter. The trophic
effect of these microparticles is consistent with our previous reports demonstrating
good biocompatibility for PHBHHx.