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Effects of Concentration, Molecular Weight, and Exposure Time of Poly(ethylene glycol) on Cell Fusion

Membrane fusion of L cells and L929 cells was studied in a monolayer using poly(ethylene glycol)(PEG) with eight different molecular weights at varying concentrations. All PEG specimens were free of additives. Cell fusion did not come to completion immediately upon contact with PEG solution, but gradually continued during postincubation. The frequency of membrane fusion increased with increase in the cell density seeded in the culture plate and time of exposure to the PEG solution. Further, with increasing PEG concentration the frequency of fusion markedly increased, regardless of the PEG molecular weight. However, fusion was practically not observed at PEG concentrations lower than 30 w/w%, suggesting that cell fusion is triggered by a physicochemical event associated with the interaction between the cell membrane and PEG molecules. It is likely that the optimum molecular weight of PEG for membrane fusion is around 1000, irrespective of the PEG concentration and the cell type used, though the extent of fusion differs according to cell type. No concerted effect of the molecular weight of PEG was observed on fusogenic ability when mixtures of low and high molecular weights of PEG were used.