Minimizing the Hydrodynamic Size of Quantum Dots with Multifunctional Multidentate Polymer Ligands

摘要

Semiconductor quantum dots (QDs) are light-emitting nanocrystals with unique optical and electronic properties that are not available from organic dyes or fluorescent proteins. In the near term, one of the most promising applications of these particles is for use as fluorescent probes for molecular, cellular, and in vivo imaging. However, a major problem is the large size of conventional QD probes, which adversely affects their molecular binding and in vivo biodistribution. This bulkiness is not an intrinsic problem of QD nanocrystals, but arises mainly from organic surface coatings used for encapsulation and stabilization. In fact, small 4-7 nrn QDs have been shown to have hydrodynamic sizes (diameters) of 20-40 nm when coated with amphiphilic polymers. Small hydrophilic and cross-linked ligands such as thioglycerol and dihydrolipoic acid have been used to reduce the coating layer thickness, but the resulting dots often suffer from low colloidal stability, photobleaching, or low quantum yield. Consequently, these size-reduced QDs have found only limited utility in live cell and in vivo applications.