Structural Changes of the Lipid Model Systems in the Presence of Enzymes or Silver Nanoparticles

Abstract

This work aimed to study the interaction of silver nanoparticles (AgNP) and lipases with models of biological membranes based on natural phospholipid and cholesterol. The crude phosphatidylcholine from egg yolk (PCe1) and synthetic cholesterol (Chol) were obtained from Sigma-Aldrich. Porcine pancreatic lipase (PPL) was obtained by purification from the hog pancreas. AgNP dispersion was prepared by the well-known citrate method. Measurement of surface tension (ST) was carried out using a BPA-1P device. The equilibrium surface tension (eST) was obtained by calculating the ST-time isotherms using the ADSA program. The particle sizes were determined by the dynamic light scattering method. An addition of AgNPs led to a pronounced decrease in both ST and eST (whereas almost no changes occurred by lipase addition), and AgNPs destructed the large lipid particles. The average lipid particle diameter values changed drastically, whereas the effective particle diameter values were almost the same by lipase addition. Thus, the interactions of AgNPs or lipase with the mixture of natural phospholipid and cholesterol have had entirely different features. These effects are interesting for modeling the interactions of inorganic and organic compounds with biological membranes.