Is purified poly(ethylene glycol) able to induce cell fusion?

Preparations of poly(ethylene glycol) 6000 (PEG) from five different commercial sources have been purified, and their ability to fuse hen erythrocytes has been investigated. Quantitative assessments of cell fusion showed that before purification one of the preparations (PEG Wako), was able to induce limited fusion (5-6%) of erythrocytes with conditions (1 min incubation with 50% w/w PEG) under which the other four unpurified preparations of PEG were inactive. On purification, PEG (Wako) became inactive. By contrast, when erythrocytes were incubated with 45% w/w PEG for 15 min, extensive fusion (23-27%) occurred with all five unpurified preparations of PEG. Under these conditions, the fusogenic properties of four of the preparations of PEG were unaffected by purification: fusion induced by PEG (Wako) was, however, decreased on purification from 27% to 19%. It appears that polymeric poly(ethylene glycol) is itself able to fuse cells, but that some commercial preparations, e.g. PEG (Wako), have enhanced fusogenic properties resulting from the presence of contaminating substances. No relationship between the absorbance at 290 nm of PEG and its fusogenic properties was found in this study. The addition of small quantities of fusogenic lipid-soluble compounds to PEG was, however, observed to enhance cell fusion by up to 50%.