Relationship between Membrane Properties and Biological Function

C.F. TEMPRANA, M.C. TAIRA, SILVIA DEL VALLE ALONSO.

Long Beach, California, USA

Congreso; Biophysical Society 52nd Annual Meeting. 16th IUPAB International Biophysics Congress.; 2008

Biophysical Society USA

Our research is related to studies elucidating the molecular properties of membranes including stability in vitro and in vivo; influence of cholesterol and the role of proteins in sequestering design-targeted carrier systems leading to time circulating efficacy and drug delivery. The diacetylenic moiety  (DC8,9PC) can form highly conjugated polymers within the hydrocarbon region of the bilayer. The polymerization efficiency was found to be dependent on the number of UV polymerization cycles, and the DC8,9PC and DXPC molar ratio.  DC8,9PC presents a very sharp, cooperative, thermal transition around 43.5ºC. DSC of samples that went through 20 cycles of UV irradiation, presented a band, showing that not all the DC8,9PC molecules were polymerized. Both DSC and ESR spectra indicate the presence of domains rich in DXPC and non-polymerized DC8,9PC. When cholesterol is added ternary polymerized or non polymerized mixtures (DXPC/DC8,9PC/Chol), with DXPC corresponding to DMPC, DPPC or DSPC, were studied using probe MC540, vesicle size  was determined by dynamic light scattering (DLS) and citotoxicity was performed on L-929 cell line. From DSC analysis, cholesterol favors lipid miscibility independently of the saturated lipid present in the formulation. For polymerized formulations cholesterol addition is related to a slight tendency of increasing cell toxicity at 5 mM lipid concentration, without a clear relationship with saturated lipid carbon chain length. In the case of non polymerized samples, DSPC:Chol and DMPC:Chol showed the higher toxicity. When DC8,9PC was added, toxicity was significantly reduced. Cholesterol addition seems to have an influence in reducing size except for DMPC:DC8,9PC .