Syringes with rubber-coated plungers and inactivation of surfactant

Injectable drugs are generally administered to newborns with 1 mL syringes. During in-vitro measurements of surface tension with a pulsating bubble surfactometer, we noticed that surfactant was inactivated after repeated aspiration into a 1 mL syringe with a rubber-coated plunger. Inactivation did not take place, however, when we used rubber-free two-part syringes with polyethylene pistons. Results of further studies showed that the silicone fluid used to lubricate the rubber surface of the syringe was inactivating the surfactant. Our findings suggest that contact with rubber surfaces should be avoided in the handling of surfactant material for biophysical assessment or clinical use.