A Combination of Short and Simple Surfactant Protein B and C Analogues as a New Synthetic Surfactant: In Vitro and Animal Experiments

PURPOSE: Pulmonary surfactants for preterm infants contain mostly animal-derived surfactant proteins (SPs), which are essential for lowering surface tension. We prepared artificial pulmonary surfactants using synthetic human SP analogs and performed in vitro and in vivo experiments. MATERIALS AND METHODS: We synthesized peptide analogues that resemble human SP-B (RMLPQLVCRLVLRCSMD) and SP-C (CPVHLKRLLLLLLLLLLLLLLLL). Dipalmitoylphosphatidylcholine (DPPC), phosphatidylglycerol (PG), and palmitic acid (PA) were added and mixed in lyophilized to render powdered surfactant. Synsurf-1 was composed of DPPC:PG:PA:SP-B (75:25:10:3, w/w); Synsurf-2 was composed of DPPC:PG:PA:SP-C (75:25:10:3, w/w); and Synsurf-3 was composed of DPPC:PG:PA:SP-B:SP-C (75:25:10:3:3, w/w). We performed in vitro study to compare the physical characteristics using pulsating bubble surfactometer and modified Wilhelmy balance test. Surface spreading and adsorption test of the surfactant preparations were measured. In vivo test was performed using term and preterm rabbit pups. Pressure-volume curves were generated during the deflation phase. Histologic findings were examined. RESULTS: Pulsating bubble surfactometer readings revealed following minimum and maximum surface tension (mN/m) at 5 minutes: Surfacten® (5.5±0.4, 32.8±1.6), Synsurf-1 (16.7±0.6, 28.7±1.5), Synsurf-2 (7.9±1.0, 33.1±1.6), and Synsurf-3 (7.1±0.8, 34.5±1.0). Surface spreading rates were as follows: Surfacten® (27 mN/m), Synsurf-1 (43 mN/m), Synsurf-2 (27 mN/m), and Synsurf-3 (27 mN/m). Surface adsorption rate results were as follows: Surfacten® (28 mN/m), Synsurf-1 (35 mN/m), Synsurf-2 (29 mN/m), and Synsurf-3 (27 mN/m). The deflation curves were best for Synsurf-3; those for Synsurf-2 were better than those for Surfacten®. Synsurf-1 was the worst surfactant preparation. Microscopic examination showed the largest aerated area of the alveoli in the Synsurf-3 group, followed by Synsurf-1 and Surfacten®; Synsurf-2 was the smallest. CONCLUSION: Synsurf-3 containing both SP-B and SP-C synthetic analogs showed comparable and better efficacy than commercially used Surfacten® in lowering surface tension, pressure-volume curves, and tissue aerated area of the alveoli.

Comparison of Synthetic Surfactant with Modified Bovine Surfactant in Neonatal Respiratory Distress Syndrome

PROPOSE: This study was designed to compare the efficacy of a synthetic surfactant (Exosurf) and a modified bovine surfactant (SurfactenR) in the treatment of neonatal respiratory distress syndrome. METHODS: A total of 90 infants with respiratory distress syndrome who were admitted to neonatal intensive care unit at Samsung Medical Center between October 1994 to September 1996 were includeeach surfactant. RESULTS: There was no significant difference in between two groups regarding birth weight, gestational age, and initiation of treatment after birth. ExosurfR group received less supplemental oxygen therapy and ventilator care. Survival rate were 81.3R in Exosurf group and 79.2% in SurfactenR group. The incidences of patent ctus arteriosus in the ExosurfR and SurfactenR groups were 75% and 62.5%, grade 3-4 intcular hemorrhage were 18.8% and 10.4%, respectively,' retinopathy of prematurity were 9.4% and 18.8%, respectively. There was significant improvernent of a/APO2 and VI at 30 minutes and 2 hours after the treatment in SurfactenR group', 2 hours and 6 hours after the treatment in ExosurfR group, however, dynamic compliance and respiratory resistance did not improve during 24 hours. CONCLUSION: Although SurfactenR treatment appears to induce faster improvement in oxygenation and pulmonary function than ExosurfR treatment, this study does not reveal any difference in clinical outcomes among those who received two different surfactant preparations.