DOPE–oleic acid–Ca2+ as DNA condensing agent

Phospholipid-based non-viral carriers composed of neutral phospholipid dioleoylphosphatidylethanolamine (DOPE) and the binary mixture DOPE-oleic acid (OA) are examined as potential DNA delivery vectors. The process of DNA condensation in the presence of Ca2+ions has been monitored through changes in emmision intensity of fluorescent probe ethidium bromide. The decline in fluorescence intensity with increasing Ca2+concentration at two different time intervals was correlated with the binding capacity of complexes and possible release of DNA from the complex. The microstructure of DOPE-OA mixtures at different OA/DOPE molar ratios and that of DOPE-OA-DNA-Ca2+complexes were determined using synchrotron small angle X-ray diffraction (SAXD). We identified inverted hexagonal phase HIIas the dominant structure. OA affects the lattice parameter of HIIformed by DOPE. With the increasing OA/DOPE molar ratio, the lattice parameter decreases, which results in significantly lower fraction of DNA bound to the OA-enriched complexes

A DSC and XPS characterization of Core-shell Morphology of Block Copolymer Nanoparticles

Self-assembly of amphiphilic block copolymer chains is known to produce core–shell nanoparticles, but imaging techniques have generally failed to provide clear evidence about the multiphase structure. We report herein the advantages and limitations of modulated temperature differential scanning calorimetry (MDSC) and X-ray photoelectron spectroscopy (XPS) for the morphology study of spherical poly(hydroxyethyl acrylate)-b-polystyrene diblock copolymer nanoparticles with an intensity-average diameter of 40 nm. Using lyophilized particles, MDSC is more informative than XPS since it allows the three morphological features of composite latex particles to be distinguished: polystyrene core, poly(hydroxyethyl acrylate) shell, and interface. In MDSC, phase separation is evidenced by two distinct increments of heat capacity (ΔCp) in the glass transition regions of the two blocks. By measuring ΔCp values, an interface weight fraction of 70% is measured that gradually decreases to 50% with annealing time (150 °C, 2 h), indicating a higher extent of phase separation