Kim Sook Heun, Park Yoonjee, Matalon Sadis, Franses Elias I
School of Chemical Engineering, Purdue University, West Lafayette, IN 47907-2100, USA.
Colloids Surf B Biointerfaces. 2008 Dec 1;67(2):253-60. doi: 10.1016/j.colsurfb.2008.09.003. Epub 2008 Sep 16.
The effect of the buffer composition and the preparation protocol on the dynamic surface tension (DST) and vesicle sizes of aqueous dipalmitoylphosphatidylcholine (DPPC) dispersions was studied. Four isotonic buffers were used in preparing DPPC dispersions at physiological conditions for possible biological applications: (1) a standard PBS solution; (2) the above PBS with 1mM CaCl(2); (3) PBS with one tenth the previous standard phosphate salt concentrations and 2.5 mM CaCl(2); and (4) 150 mM NaCl with 2.5 mM CaCl(2) and 10mM HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid). Two protocols, with a new method and an old method (Bangham method), were used in preparing the DPPC dispersions. The DPPC dispersions prepared with the new method contained mostly vesicles and were quite stable at 25 or 37 degrees C. Dynamic light scattering (DLS) and spectroturbidimetry (ST) results showed that the DPPC vesicle sizes in buffer (4) were much smaller than those in the other buffers. When the DPPC dispersions were prepared with the new method, the diameter of the DPPC particles was smaller than those with the old method. The DPPC vesicles with the new method were more stable than those with the other method. The DPPC dispersions of 1000 ppm at 37 degrees C with the new method produced, at pulsating area conditions at 20 cycles per minute, low tension minima (gamma(min)), lower than 10 mN/m, in buffers (1), (2), and (4). With buffer (4) the DSTs were lower and were achieved faster than with the other buffers. A minimum concentration of 1000 or 250 ppm DPPC was needed to produce DSTs lower than 10 mN/m within 10 min or less, with buffer (2) or (4), respectively. IRRAS results suggest that DPPC in buffer (2) or (4) forms a close-packed monolayer at the interface. These results have implications for designing efficient protocols of lipid dispersion preparation and lung surfactant replacement formulations in treating respiratory disease.
研究了缓冲液组成和制备方案对二棕榈酰磷脂酰胆碱（DPPC）水分散体的动态表面张力（DST）和囊泡大小的影响。在生理条件下制备可能用于生物应用的DPPC分散体时使用了四种等渗缓冲液：（1）标准PBS溶液；（2）上述含1 mM CaCl₂的PBS；（3）磷酸盐盐浓度为先前标准浓度十分之一且含2.5 mM CaCl₂的PBS；以及（4）含2.5 mM CaCl₂和10 mM 4-（2-羟乙基）-1-哌嗪乙磺酸（HEPES）的150 mM NaCl。制备DPPC分散体时使用了两种方案，一种新方法和一种旧方法（Bangham法）。用新方法制备的DPPC分散体主要包含囊泡，并且在25或37℃下相当稳定。动态光散射（DLS）和分光比浊法（ST）结果表明，缓冲液（4）中的DPPC囊泡大小比其他缓冲液中的小得多。用新方法制备DPPC分散体时，DPPC颗粒的直径比用旧方法制备的小。用新方法制备的DPPC囊泡比用其他方法制备的更稳定。在37℃下，采用新方法制备的1000 ppm的DPPC分散体，在每分钟20次循环的脉动面积条件下，在缓冲液（1）、（2）和（4）中产生的最低张力最小值（γ(min)）低于10 mN/m。对于缓冲液（4），DST更低，且比其他缓冲液更快达到。分别用缓冲液（2）或（4）时，需要1000 ppm或250 ppm的最低DPPC浓度才能在10分钟或更短时间内产生低于10 mN/m的DST。红外反射吸收光谱（IRRAS）结果表明，缓冲液（2）或（4）中的DPPC在界面处形成紧密堆积的单分子层。这些结果对于设计脂质分散体制备的有效方案以及治疗呼吸系统疾病的肺表面活性剂替代制剂具有重要意义。
