In the present work, we show how amphipathic diblock copolymers affect the physicochemical properties of the lipid bilayer of DPPC liposome. Diblock copolymers proposed for this study are focused in the difference between PLA and PCL hydrophobic block, because PLA and PCL differ in their glass transition temperature, where a higher ratio of PLA, lowers the flexibility of the diblock copolymer. On the contrary, a greater proportion of PCL makes the diblock copolymer more flexible. This flexibility difference between hydrophobic block would affect the physicochemical properties of lipid bilayer of DPPC. The difference of rigidity or flexibility of hydrophobic block and their interaction with DPPC large unilamellar vesicles (LUVs) was evaluated at low and high copolymers concentration. The copolymer concentrations used were chosen based on their respective cmc. We measure (a) Thermotropic behavior from GP of Laurdan and fluorescence anisotropy of DPH; (b) Relation between wavelength excitation and generalized polarization of Laurdan; (c) Time-resolved fluorescence anisotropy of DPH; (d) Water outflow through the lipid bilayer and (e) calcein release from DPPC LUVs. Furthermore, large unilamellar vesicles in the absence and in the presence of different copolymers were characterized by size and zeta-potential. The results show that the diblock copolymer at high PLA/PCL ratio, that is, greater rigidity of hydrophobic block produces an increase of the phase transition temperature (Tm). For DPPC LUVs, Tm increase 3.5 °C at low and about 4.5 °C at high copolymers concentration, sensed by Laurdan and DPH fluorescent probes, although the DPPC/copolymers molar ratio for Cop4 is higher than Cop3, Cop2 and Cop1. In addition, we observed a decrease in the polarity of microenvironments in the bilayer and an increase in the order of the acyl chains in the bilayer to a high proportion of PLA. Furthermore, the presence of diblock copolymer with high proportion of PLA, decreases water outflow from DPPC liposome and water efflux is slower; leading to a decrease in calcein release from DPPC liposomes. Our results clearly show that the greater the stiffness of the hydrophobic block, greater degree of packaging of the lipid bilayer, greater the order of the acyl chains, and greater retention of water and calcein inside the liposome. Therefore, the presence of AB-type diblock copolymers with a more rigid hydrophobic block, stabilizes the lipid bilayer and would allow a more controlled release of water, and encapsulated molecules inside of the DPPC liposome.

在目前的工作中，我们表明两亲性二嵌段共聚物如何影响DPPC脂质体脂质双层的理化性质。这项研究提出的二嵌段共聚物集中在PLA和PCL疏水嵌段之间的差异，因为PLA和PCL的玻璃化转变温度不同，其中PLA的比例越高，二嵌段共聚物的柔韧性就越低。相反，较大比例的PCL使二嵌段共聚物更具挠性。疏水性嵌段之间的这种柔性差异将影响DPPC的脂质双层的理化性质。在低和高共聚物浓度下，评估了疏水性嵌段的刚性或柔性的差异以及它们与DPPC大单层囊泡（LUV）的相互作用。基于它们各自的cmc选择所使用的共聚物浓度。我们测量（a）Laurdan GP的热致行为和DPH的荧光各向异性；（b）波长激发与劳尔丹广义偏振之间的关系；（c）DPH的时间分辨荧光各向异性；（d）通过脂质双层流出的水和（e）钙黄绿素从DPPC LUV中释放出来。此外，在不存在和存在不同共聚物的情况下，大的单层囊泡的特征在于大小和ζ电位。结果表明，在高PLA / PCL比的情况下，二嵌段共聚物，即疏水嵌段的更大刚性，导致相变温度（Tm）的增加。对于DPPC LUV，通过Laurdan和DPH荧光探针检测到，Tm在低温下升高3.5°C，在高共聚物浓度下升高约4.5°C，尽管Cop4的DPPC /共聚物摩尔比高于Cop3，Cop2和Cop1。此外，我们观察到双层中微环境的极性降低，并且双层中酰基链的顺序增加，这对PLA的比例很高。此外，具有高比例PLA的二嵌段共聚物的存在，减少了从DPPC脂质体流出的水，水的流出较慢。导致钙黄绿素从DPPC脂质体释放的减少。我们的结果清楚地表明，疏水性嵌段的刚性越大，脂质双层的包装程度越高，酰基链的顺序越大，水和钙黄绿素在脂质体内的保留越大。因此，存在具有更刚性的疏水性嵌段的AB型二嵌段共聚物，