A new method of fluorescein isothiocyanate-labeled lipopolysaccharide

Objective To introduce a new method of fluorescein isothiocyanate (FITC) labeled lipopolysaccharide(LPS).Methods LPS was made monomeric by treatment with triethylamine and labeled with FITC.The concentration of FITC in the final preparation was determined spectrophotometrically and compared with that in the old method of FITC labeled LPS.The bioactivity of FITC LPS,TNF α induction of monocytes by FITC LPS and percentage of monocyte associated FITC LPS binding to the cell surface were measured and were compared with those of native LPS.Results The new technique leaded to a highly efficient labeling (with a FITC to LPS ratio being 1∶1.02) when compared with old one (with a FITC to LPS ratio being 1∶40,P0.05).But the bioactivity of FITC LPS,its capability of TNF α induction in monocytes and efficiency that bound to monocytes behaved indistinctively from those of native LPS(P 0.05 ).Conclusion The method of FITC LPS had a higher labeled percentage,was safe and could maintain the bioactivity of LPS.