In Vitro Bioassay of Endotoxin Using Fluorescein as a pH Indicator in a Macrophage Cell Culture System

Based on the biological activity of endotoxin, we propose a possible new method for detecting endotoxin using a pH- indication system of macrophage culture media. After RAW 264.7 macrophage cells were treated with lipopolysaccharide (LPS), the addition of fluorescein to the LPS-treated media reproductively reduced its absorption and emission spectra (it was a dose-dependent reduction). The advantages of this LPS- detection method were compared with the Limulus Amebocyte Lysate (LAL) test by using purified bacterial LPS (Salmonella minnessota, Escherichia coli, and Pseudomonas aeruginosa). Additionally, the absorption and fluorescence intensity of fluorescein, following treatment of RAW 264.7 cells with a high concentration of Staphylococcus aureus (Gram-positive, lysed bacteria), could not generally be detected by the LAL test, but they were found to be reduced, in a dose-response relationship, with this new system. The macrophage culture system-method might be a good supplement to the LAL assay for detection of LPS, Gram-negative and Gram-positive bacteria.

In vitro study on the neutralizing LPS activity of modeling peptides from the limulus antilipopolysaccharide factor / 第三军医大学学报

Objective To evaluate the endotoxin-neutralizing activity of modeling peptides from the limulus antilipopolysaccharide factor (MPLALFs, Ms) in vitro. Methods The endotoxin-binding activity of Ms was examined by biosensor technique and shown in values of Kon and Kd. The endotoxin-neutralizing effect was analyzed by limulus amebocyte lysate test. Results The biosensor technique results showed that the Kon values of M_0, M_1, M_2, M_3, M_4, M_6, M_8 and M_ 10 binding to LPS 055∶B5 were (840?5.716), (549?6.532), (842?6.530), (627?2.450), (996?5.716), (814?8.982), (556?1.633) and (635?2.449) arc second, of which M_4 and M_1 had the highest and lowest endotoxin-binding activity, respectively. The M_4 reacted to LPS with a Kd of 72.377 ?mol/L. The results obtained by the limulus amebocyte lysate test were the same with those from the biosensor technique. Conclusion M_4 has a potential good endotoxin-neutralizing effect in vitro.