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.

鉴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）中的应用受到了限制。不过，无需聚合物包被的疏水颗粒可嵌入脂质膜，本研究通过仿生囊泡（biomimetic vesicles）验证了这一策略的可行性。实验观察到，该体系可与囊泡悬浮液中的脂溶性染料DiD以及水溶性染料Cy3.5发生FRET，向两种染料的能量转移效率表明，多数QDs位于脂质膜深层，这一结论通过囊泡整装标本与超薄切片的电子显微镜（electron microscopy）观察得到了证实。此外，仅当膜内存在钾离子载体缬氨霉素（potassium ionophore valinomycin）时，该体系才可与电压敏感性脂溶性染料di-4-ANEPPS发生能量转移，且该效应取决于钾离子浓度而非膜电位绝对值。