In vitro evaluation for potential calcification of biomaterials used for staple line reinforcement in lung surgery

Bovine pericardium (BPC) and polytetrafluoroethylene (PTFE) have been widely used to reinforce staple lines in lung resection. Since limited information regarding the calcification of these biomaterials is available, we undertook an in vitro study to evaluate their calcification potential. Commercially available BPC and PTFE biomaterials were evaluated and compared with custom-prepared BPC tissue. In vitro calcification was performed via submersion in supersaturated solution in a double-walled glass reactor at 37.0 degrees C +/- 0.1 degrees C, pH 7.4 +/- 0.1, mimicking most ion concentrations of human blood plasma. In processing of calcification, the pH decrease of the solution simulated the addition of consumed H(+), Ca(2+), and PO(4)(3-) ions from titrant solutions, the concentrations of which were based on the stoichiometry of octacalcium phosphate. The molar ion addition with time was recorded, and the initial slope of the curve was computed for each experiment. The rate of calcification developed (molar calcium phosphate ion addition rate per time and total surface area) (R) was computed after that with respect to the relative supersaturation (sigma) used in each experiment. R for custom-prepared BPC tissues was found to be in the range of 0.19 +/- 0.08 to 0.52 +/- 0.19 (n = 17) in sigma range of 0.72 to 1.42. Commercial BPC was found to be 0.016 to 0.052 (n = 4), and PTFE was 0.005 to 0.05 (n = 8) in the same sigma range. Both clinically applied biomaterials, BPC and PTFE, seemed to be calcified with rates of at least one order of magnitude lower than the custom-prepared BPC tissue. This data suggested that BPC and PTFE biomaterials showed a similar, relatively very low tendency for calcification compared with custom-prepared BPC tissue. Although further studies are necessary, staple line reinforcement by these two biomaterials should be considered safe from the calcification point of view.