Quantum dot/antibody conjugates for in vivo cytometric imaging in mice

Abstract

Multiplexed, phenotypic, intravital cytometric imaging requires novel fluorophore conjugates that have an appropriate size for long circulation and diffusion and show virtually no nonspecific binding to cells/serum while binding to cells of interest with high specificity. In addition, these conjugates must be stable and maintain a high quantum yield in the in vivo environments. Here, we show that this can be achieved using compact (∼15 nm in hydrodynamic diameter) and biocompatible quantum dot (QD) -Ab conjugates. We developed these conjugates by coupling whole mAbs to QDs coated with norbornene-displaying polyimidazole ligands using tetrazine–norbornene cycloaddition. Our QD immunoconstructs were used for in vivo single-cell labeling in bone marrow. The intravital imaging studies using a chronic calvarial bone window showed that our QD-Ab conjugates diffuse into the entire bone marrow and efficiently label single cells belonging to rare populations of hematopoietic stem and progenitor cells (Sca1+c-Kit+ cells). This in vivo cytometric technique may be useful in a wide range of structural and functional imaging to study the interactions between cells and between a cell and its environment in intact and diseased tissues.

Quantum dots in imaging, drug delivery and sensor applications

“…By employing this method, the disadvantages associated with fluorescently labeled antibodies such as low photo-stability, small multiphoton action cross-section and asymmetric emission are no longer an issue. 17 In order to achieve superior biomedical properties, Osifeko and Nyokong have proposed hybrid nanoparticles with phthalocyanines in combination with QDs, magnetic nanoparticles and gold nanoparticles (GNPs). Their results showed an increase in triplet quantum yields for phthalocyanines in the presence of QDs and GNPs, while a general decrease in fluorescence quantum yields for them was observed in the presence of all the nanoparticles investigated (QDs, GNPs and magnetic nanoparticles).…”

Quantum dots in nanomedicine: recent trends, advances and unresolved issues

“…These multiplexed probes were applied for intravital cytometric in vivo imaging and single-cell labelling in bone marrow. Using a calvarial bone window system, the authors showed that the QD conjugates efficiently diffused into the bone marrow and labelled single cells of rare populations of hematopoietic stem and progenitor cells [85]. Shi et al have designed the multifunctional graphene oxide QDsdecorated magnetic nanoplatform enabling the challenging task of capturing rare Glypican-3-expressing Hep G2 circulating liver cancer tumour cells in tumour cell-enriched blood preparations containing as few as 10 cancer cells in 15 mL [86].…”

Nanotechnologies for biomedical science and translational medicine

“…4 illustrates two in vivo live-animal imaging applications of highly fluorescent semiconductor QDs (Fig. 4A) (89) and near-IR fluorescing SWNTs (Fig. 4B) (90).…”