FRET between CdSe Quantum Dots in Lipid Vesicles and Water- and Lipid-soluble Dyes

Because of the coatings needed to solubilize and passivate quantum dots for biological applications, their use
in fluorescent resonance energy transfer (FRET) has been limited. However, hydrophobic particles without
polymer coatings may be embedded into lipid membranes, as demonstrated here with biomimetic vesicles.
FRET is seen to a lipid-soluble dye (DiD) and a water-soluble dye (Cy3.5) in which the vesicles are suspended.
The degree of energy transfer to each dye suggests that most of the QDs are located deep within the lipid, as
confirmed by electron microscopy of whole mounts and thin sections of vesicles. Energy transfer is also seen
to a voltage-sensitive, lipid-soluble dye (di-4-ANEPPS) only when the potassium ionophore valinomycin is
present in the membrane. The effect is dependent upon potassium ion concentration rather than absolute
membrane potential.

由于用于生物应用的量子点（quantum dots）需通过表面包被实现增溶与钝化，其在荧光共振能量转移（FRET）中的应用一直受到限制。本研究证实，未经过聚合物包被的疏水颗粒可嵌入脂质膜中，该结论通过仿生囊泡体系得到验证。研究观察到，该体系可向囊泡悬浮液中的脂溶性染料（DiD）与水溶性染料（Cy3.5）发生荧光共振能量转移。两种染料对应的能量转移效率表明，绝大多数量子点均位于脂质膜的深层区域，这一结论通过完整标本与囊泡超薄切片的电子显微镜观察得到了证实。此外，仅当脂质膜中存在钾离子载体缬氨霉素时，该体系才可向电压敏感型脂溶性染料（di-4-ANEPPS）发生能量转移。该效应依赖于钾离子浓度，而非绝对膜电位。