Effect of the lipid chain melting transition on the stability of DSPE-PEG(2000) micelles.
Effect of the lipid chain melting transition on the stability of DSPE-PEG(2000) micelles.
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DOI：
10.1021/la900310k
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发表时间：
2009-07-07
期刊：
影响因子：
--
通讯作者：
Tirrell M
中科院分区：
文献类型：
--
作者：
Kastantin M;Ananthanarayanan B;Karmali P;Ruoslahti E;Tirrell M
胶束纳米粒子作为诊断和治疗生物功能的载体显示出很好的前景，导致人们对它们的性质和行为，特别是它们的大小、形状和稳定性产生了越来越大的兴趣。这项工作研究了DSPE-PEG(2000)单体形成的胶束的物理化学，因为它与这些性质有关。在差示扫描量热图中观察到球形DSPE-PEG(2000)胶束在加热时在12.8℃出现一个吸热峰，其脂核发生熔融转变。体积庞大的聚乙二醇(2000)头组阻止了低温玻璃态和高温流体相中脂类的规则结晶堆积，广角X射线散射证明了这一点。平衡胶束几何形状在转变温度上下都是球形的，这表明迫使聚乙二醇刷进入平坦几何形状的熵惩罚大于填充在扩展配置中的玻璃芯的热效应。玻璃相的胶束稳定性增强，单体的解吸率明显低于液体相。玻璃相和液体相的单体脱附活化能分别为156±6.7和79±5.0kJ/mol。观察到的玻璃化转变增加了胶束的稳定性，但不会扰乱胶束的几何形状，这对于设计更有效的生物功能胶束是有用的。
Micellar nanoparticles are showing promise as carriers of diagnostic and therapeutic biofunctionality, leading to increased interest in their properties and behavior, particularly their size, shape, and stability. This work investigates the physical chemistry of micelles formed from DSPE-PEG(2000) monomers as it pertains to these properties. A melting transition in the lipid core of spheroidal DSPE-PEG(2000) micelles is observed as an endothermic peak at 12.8°C upon heating in differential scanning calorimetry thermograms. Bulky PEG(2000) head groups prevent regular crystalline packing of lipids in both the low-temperature glassy and high-temperature fluid phases, as evidenced by wide-angle x-ray scattering. Equilibrium micelle geometry is spheroidal above and below the transition temperature indicating that the entropic penalty to force the PEG brush into flat geometry is greater than the enthalpic benefit to the glassy core to pack in an extended configuration. Increased micelle stability is seen in the glassy phase with monomer desorption rates significantly lower than in the fluid phase. Activation energies for monomer desorption are 156 ± 6.7 and 79 ± 5.0 kJ/mol for the glassy and fluid phases, respectively. The observation of a glass transition that increases micelle stability but does not perturb micelle geometry is useful for the design of more effective biofunctional micelles.
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