Stabilization of polymer lipid complexes prepared with lipids of lactic acid bacteria upon preservation and internalization into eukaryotic cells

ALVES, P.A; HUGO, A. A.; SZYMANOWSKI, F; TYMCZYSZYN,E.E; PÉREZ, P.F; COHELO,J.F.J; SIMOES, P.N; GÓMEZ-ZAVAGLIA, A

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 123 p. 446 - 451

0927-7765

The physicochemical characterization of polymer liposome complexes (PLCs) prepared with lactic acid bacteria lipids and cholesterol covalently bound to poly(N,N-dimethylaminoethyl methacrylate) (CHO-PDMAEMA) was carried out in an integrated approach, including their stability upon preservation and incorporation into eukaryotic cells. PLCs were prepared with different polymer:lipid molar ratios (0, 5 and 10). Zeta potential, particle size distribution and polydispersity index were determined. The optimal polymer:lipid ratio and the stability of both bare liposomes and PLCs were evaluated at 37°C and at different pHs, as well as after preservation at 4°C, ?80°C and freeze-drying in the presence or absence of trehalose 250 mM. Endocytosis of PLCs by eukaryotic cells was assessed to give a complete picture of the system. Incorporation of CHO-PDMAEMA onto bacterial lipids (ratio 5 and 10) led to stabilization at 37°C and pH 7. A slight decrease in pH strongly destabilized them. Bacteria PLCs showed to be more stable than lecithin (LEC) PLCs (used for comparison) upon preservation at 4 and ?80°C. The harmful nature of the preservation processes led to a strong decrease in the stability of PLCs, bacterial formulations being more stable than LEC PLCs. The addition of trehalose stabilized LEC PLC and did not have effect on bacterial PLCs. In vitro studies on Raw 264.7 and Caco-2/TC7 cells demonstrated an efficient incorporation of PLCs into the cells. Preparations with higher stability were the ones that showed better cell-uptake. The nature of lipid composition is determinant for the stability of PLCs. Lipids from lactic acid bacteria are composed of glycolipids and phospholipids like cardiolipin and phosphatidylglycerol. The presence of negatively charged lipids strongly improves the interaction with the positively charged CHO-PDMAEMA, thus stabilizing liposomes. In addition, glycolipids and phosphatidylglycerol act as intrinsic protectants of PLCs upon preservation. This particular lipid composition of lactic acid bacteria makes them natural formulations potentially useful as drug delivery systems.