SP-B and SP-C analogues within CHF5633 synthetic surfactant probed by fluorescence labeling

Surfactant replacement therapy, commonly consisting of bovine or porcine lung surfactant extracts, is a lifesaving treatment for preterm newborns that suffer for respiratory distress syndrome (RDS). Recently, a synthetic surfactant, CHF5633, has been developed by Chiesi Farmaceutici (Italy) for the treatment of neonatal RDS. CHF5633 contains two phospholipids forming multilamellar vesicles and two peptides which are analogues of surfactant protein B and surfactant protein C. By conjugating the solvatochromic fluorophore dansyl to the peptides we aimed at characterizing their environment and distribution within the formulation. The fluorescence properties of dansyl-conjugated SP-B Analogue and SP-C Analogue were characterized in different solvents and compared with their emission properties when individually formulated in CHF5633. Both peptides exhibited a close interaction with the phospholipid matrix, as observed for the natural counterparts. In particular, SP-C Analogue is more deeply inserted in the phospholipid bilayer compared to SP-B Analogue. The localization of the fluorescent peptides within CHF5633 did not experience significant changes over a storage period of nine months.