ABSTRACT
Lung surfactants are a composite blend of lipids and some specific proteins which are found in the alveoli and their main role is to decrease the alveolar air/water interface surface tension, hence, averting lung collapse. Deficiency of lung surfactant in premature children (gestation period 26 weeks) results in respiratory distress syndrome (RDS), which can now be treated with surfactant replacement therapy, that is, administration of animal-derived pulmonary surfactant into the airways. Despite so many advantages of surfactant administration therapy, it has some shortcomings: variability from batch to batch, costly source and procedure as well as disease transmission risk. Lung Surfactants are mainly composed of 80% phospholipids (w/w), along with 10% neutral lipids which are generally cholesterol and proteins (SP-A: 5%; SP-B: 2%; SP-C: 2% and SP-D: 1%). Phospholipids, amphiphilic in nature, have one non-polar and another polar part with glycerol linked to one esterified phosphate group (hydrophilic) and two fatty acid chains (hydrophobic). Surface proteins A and D are hydrophilic in nature and help in innate lung immune response while B and C are hydrophobic in nature and decrease the alveoli surface tension. Surfactant replacement therapy is the most trusted and approved treatment in the case of various respiratory pathologies, i.e., neonatal RDS (NRDS), asthma and supplementary treatment for COVID-19. This review provides an insight of using natural surfactants as an alternative candidate to treat different respiratory issues.
