Characterization of the surface activity of a synthetic surfactant with albumin

We previously reported that a human analogue of pulmonary surfactant protein-C (SP-C), SP-CL16 (6-28), with 23 residues was the most active analogue in a reconstituted lipid mixture and had the shortest chain among the poly leucine analogues examined. In this study, we verified the influence of albumin, a component of serum, on the surface activity of surfactant. Surface activity was measured using the Langmuir-Wilhelmy surface balance (WSB), pulsating bubble surfactometer (PBS), and stable microbubble test (MBT). The surface activity of synthetic lung surfactant (SLS) was only slightly influenced by albumin (0.1-10 mg/ml) as compared with that of a ternary mixture of phospholipids. The ternary mixture of phospholipids showed a decrease in surface activity due to albumin. In particular, SLS did not show interaction of surface activity with albumin in vitro (WSB, PBS, and MBT). In contrast, dipalmitoylphosphatidylcholine/phosphatidylglycerol/palmitic acid had significantly weaker surface activity in the presence of albumin. Surfactant-TA showed interaction of surface activity with albumin in the MBT. The number of stable microbubble increased in the presence of albumin at a concentration of 0.1 mg/ml.