A Quantum Dot Conjugated Sugar Ball and Its Cellular Uptake. On the Size Effects of Endocytosis in the Subviral Region

TLDR

The lipophilic CdSe quantum dot coated with TOPO can be extracted from chloroform into water upon interaction with macrocyclic glycocluster amphiphile 1, forming a 15 nm highly fluorescent sugar ball (TOPOQD1) that readily invades HeLa cells via endocytosis. The study demonstrates a dramatic size effect on endocytic uptake (50 ≫ 15 ≫ 5 nm) in the subviral region, with an optimal size near 50 nm, indicating that size complementarity governs recognition and encapsulation by endocytic vesicles and underscoring the importance of size control for designing nanometric delivery systems.

Abstract

The lipophilic CdSe quantum dot (QD) coated with trioctylphosphine oxide (TOPOQD) can be extracted from chloroform into water upon interaction with macrocyclic glycocluster amphiphile 1. The QD-conjugated and highly fluorescent sugar ball of a size of 15 nm (TOPOQD1) thus solubilized in water readily invades Hela cells via endocytosis. The endocytic activity of TOPOQD1 (15 nm), in light of those of the micellar homoaggregate of 1 (5 nm) and the virus-like 1−DNA conjugate (50 nm) as references, reveals a dramatic size effect (50 ≫ 15 ≫ 5) in the subviral size region. The optimal size at ∼50 nm indicates that size complementarity which governs molecular recognition in small host−guest systems also plays key roles in the encapsulation of nanometric guest particles by the endocytic vesicles (≤100 nm) as a macrobiomolecular host. The work thus suggests an utmost importance of size control at the viral size when designing molecular (gene, drug, probe, etc.) delivery machines.