nystatin-a1 and 1-2-distearoylphosphatidylethanolamine

From the point of view of pharmaceutical design, development of carrier system of antimicrobial agents with functional properties should be required. We introduced here the development-process of liposomal formulations of polyene macrolide antibiotics, amphotericin B (AmB) and nystatin as injectable dosage forms. Both development of the effective encapsulation method of these drugs in liposomes and investigation of the encapsulation mechanism and the molecular states of them are important to determine the optimum lipid composition for therapeutic uses. Enhanced encapsulation of these hydrophobic drugs, long-circulation in blood and high targetability are the required functional properties for the carrier system. Low encapsulation of AmB in liposomes has been overcome by the incorporation of polyethylene glycol-lipid derivatives, DSPE-PEG. Both the hydration with 9% sucrose solution and the complex formation between AmB and DSPE-PEG contribute not only to the enhanced encapsulation of AmB in liposomes but also to the stability and long-circulation properties in blood. Encapsulation mechanism and the molecular states of AmB in liposomes were also investigated by several methods. AmB-encapsulating PEG liposomes (PEG-L-AmB) with optimum lipid composition also showed reduced toxicity and higher therapeutic efficacy on murine model of pulmonary aspergillosis than that of conventionally used AmB formulations. Further enhanced therapeutic effects was observed by using AmB-encapsulating PEG immunoliposomes (34A-PEG-L-AmB) carrying monoclonal antibodies at the distal ends of the PEG chains. On the contrary to AmB, encapsulation characteristics of nystatin were apparently different from that of AmB, though the chemical structure is very similar. Self-association of nystatin with sterol-free lipid membrane dominantly influences on the encapsulation characteristics. Many experiments about the encapsulation of antimicrobial agents in liposomes have been demonstrated by many researchers, but there are not so much drugs developed for commercially used. Optimization of the formulation of functional drug-carrier system should be important for the practical uses.

Topics: Amphotericin B; Animals; Anti-Bacterial Agents; Communicable Diseases; Drug Carriers; Drug Design; Liposomes; Lung; Nystatin; Phosphatidylethanolamines; Polyethylene Glycols; Solvents

This work presents the investigations of the interactions between nystatin, a polyene antibiotic, and phospholipids with various head groups (phosphatidylcholine and phosphatidylethanolamine) and acyl chains of different length and saturation degree. The experiments were performed with the Langmuir monolayer technique. Among phosphatidylethanolamines, DMPE, DPPE and DSPE were studied, while phosphatidylcholines were represented by DSPC and DOPC. The influence of the antibiotic on the molecular organization of the phospholipid monolayer was analysed with the compression modulus values, while the strength of nystatin/phospholipid interactions and the stability of the mixed monolayers were examined on the basis of the excess free energy of mixing values. The results obtained proved a high affinity of nystatin towards phospholipids. Nystatin was found to interact more strongly with phosphatidylcholines than with phosphatidylethanolamines. The most negative values of the excess free energy of mixing observed for the antibiotic and DOPC mixtures prove that nystatin favors the phospholipid with two unsaturated acyl chains. The results imply that nystatin/phospholipid interactions compete in the natural membrane with nystatin/sterol interactions, thereby affecting the antifungal activity of nystatin and its toxicity towards mammalian cells.

Topics: Antifungal Agents; Membranes; Models, Chemical; Models, Statistical; Nystatin; Phosphatidylcholines; Phosphatidylethanolamines; Phospholipids; Polyenes; Pressure; Surface Properties; Thermodynamics

In this study, we characterized the encapsulation of amphipathic nystatin into liposomes with or without cholesterol (CH) and a polyethylene glycol derivative, distearoyl-N-(monomethoxy poly(ethylene glycol)succinyl)phosphatidylethanolamine (DSPE-PEG). The highest encapsulation efficacy of nystatin into liposomes (151 microg nystatin/mg lipid) was obtained with a cholesterol-free lipid composition containing 6 mol% of DSPE-PEG. The encapsulation efficacy was decreased by the incorporation of CH and improved by the incorporation of DSPE-PEG. In liposomes composed of dipalmitoylphosphatidylcholine (DPPC)/CH (2:1, mol/mol), the highest encapsulation efficacy of nystatin liposomes (84 microg/mg lipid) was achieved by the addition of DSPE-PEG and hydration with 9% sucrose solution, as compared with 13 microg/mg lipid without DSPE-PEG. The encapsulated amount increased with increasing amount of DSPE-PEG used and plateaued at 6 mol% of DSPE-PEG. The optimum molecular weight of PEG in DSPE-PEG was 2000 and a larger molecular weight resulted in lower encapsulation. The incorporation of CH affected the self-association of nystatin with lipid membranes, which was detected by fluorescence measurement. The molecular interaction between an amino group in nystatin and a phosphate group in DSPE-PEG plays an important role in efficient encapsulation of nystatin. Finally, the encapsulation characteristics of nystatin were compared with those of amphotericin B (AmB). Nystatin more readily associated with CH-free lipid membranes, but, AmB more readily interacted with DSPE-PEG. The results indicated that the differences in the molecular association of AmB or nystatin with lipids or DSPE-PEG are reflected in the encapsulation characteristics in liposomes.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Cholesterol; Drug Compounding; Fluorescence; Liposomes; Magnetic Resonance Spectroscopy; Nystatin; Phosphatidylethanolamines; Polyethylene Glycols