In vitro testing of ten bone cements after different time intervals from polymerization

Abstract

Biological response of cells to implanted bone cement is a fundamental but often neglected issue in successful cemented implants. In this study, ten acrylic bone cements for orthopedics were assayed using two different in vitro testing methods on L929 cells. The cements were mixed as prescribed, cured for either 1 h or 7 days and then extracted in minimum essential medium (MEM) according to the ISO standard for the preparation of samples. For the evaluation of cytotoxicity, the neutral red uptake assay (NRU) and the incorporation of propidium iodide (PI) were used to detect the viability/death of cells. The two methods were shown to be well correlated (p < 0.0001) in the case of both the 1-h and the 7-day extracts. Two cements, i.e. CERIM LT and CMW2, were found to be toxic after 1-h curing through both the spectrophotometric NRU assay and the cytofluorometric assay with PI. After 7-day curing, these two cements, as well as the Zimmer-low viscosity cement, were toxic according to the NRU assay. The toxic effect of all the cements disappeared after dilution of extracts 1:2 with MEM, except in the case of CERIM LT. In the search for the component inducing the toxic effect, the possible contribution of the residual monomer was discarded on the basis of literature data and the influence of various other factors was analyzed, including the contrast medium (barium sulphate or zirconium dioxide) and the concentrations of N,N-dimethyl-paratoluidine and of benzoyl peroxide (< 1% or > or = 1%). Unlike zirconium dioxide, barium sulphate was found to damage the cells at the 1-h endpoint. Benzoyl peroxide at concentration > or = 1% was found to affect cells at the same endpoint, whereas dimethylparatoluidine had no effect regardless of the proportion.

Cytotoxic effect of bone cements in HL-60 cells: Distinction between apoptosis and necrosis

“…These conclusions are consistent with previous results using different cell culture systems: we found that CMW1 acts on apoptosis-driving genes in human lymphocytes, and Cerim LT and CMW2, as well as Zimmer LV and CMW1, have been shown to be cytotoxic to L929 fibroblastic cells after 24 h. 22,5 Oxygen-derived free radicals are involved in apoptosis/necrosis, and a relationship between their concentration and the mode of cell death is likely to exist. We also suggest that the response of cells to toxic agents may depend not only on their concentration, but also on the persistence of the insult over time.…”

“…5 In this article, the mechanism of cell death induced in vitro by ten cements currently employed in prosthetic surgery, mainly hip replacements, was studied.…”

Material properties and in vitro biocompatibility of a newly developed bone cement

“…These results confirm the findings of another group, which analyzed cell proliferation of various acrylic bone cements added at different time intervals after polymerization 31,32 . They found that cytotoxic effects of these cements are inversely proportional to their polymerization time, which means that toxicity of PMMA-based cements decreases with proceeding polymerization time.…”

Interleukin-6 expression by osteoblast-like MG63 cells challenged with four acrylic bone cements

“…In other experiments, we found that the undiluted extract of CMW 2 ® was cytotoxic for the mammalian broblasts, while the viability of the cells incubated with CMW 1 ® was 70% of the control [18]. Toxicity was correlated to the content of barium sulphate and benzoyl peroxide, but not to N,N-dimethyl-paratoluidine.…”