Application of the critical packing parameter of physiologically active compounds in biological models
Amphiphilic compounds in an aqueous environment can aggregate and form structures with different physicochemical properties. This process enables, inter alia, the formation of lipid bilayers, which constitute the skeleton of cell membranes, but also intracellular membrane structures, the properties of which ensure the proper course of life processes. Other self-assembly structures are vesicles and three-dimensional structures, which in recent years have been used as drug delivery systems, especially for drugs poorly soluble in water. Self-assembling and formation of stable structures are caused by two opposing phenomena: hydrophobic and hydrophilic interaction. These intermolecular interactions of amphiphiles in the water environment determine the optimal area of the molecule at the interface surface and the entire three-dimensional structure of this molecule, which can be described by successive characteristic quantities: the volume of the hydrocarbon chain and the maximum effective length of this chain. A convenient and frequently used parameter, which contains information about the above values, is the critical packing parameter (CPP). Physiological factors (temperature, pH, and digestive enzymes activity) affect amphiphilic compounds, which is reflected in the change of the CPP parameter value and the structures formed by these molecules. Knowing the CPP of a compound and how it changes in the physiological environment, the course of the self-organization of the compound in the organism can be predicted. This review presents the literature values of CPP of amphiphilic compounds present in biological membranes, administered as drugs, and used as drug delivery systems, as well as the changes in the value of this parameter during physiological processes. The presented articles report on structural changes occurring during the digestive processes, antimicrobial activity, and also pathological processes. The described methods for determining the CPP value, both experimental and theoretical, show that this parameter is a convenient tool that can be used in the process of designing drugs or drug delivery systems, as well as in assessing the side effects of drugs and other biologically active compounds administered to the organism.
Keywords: CPP, critical packing parameter, lipid self-assembly, biolipids.
© Farm Pol, 2022, 78(5): 249–262