Application of Quantum Dots-Based Biotechnology in Cancer Diagnosis: Current Status and Future Perspectives

Table 1

Application of QDs in molecular, cell, tissue, animal model cancer imaging (since 2007).

Authors	QDs used	Major findings	Advantages	Problems
Molecular imaging
Yezhelyev et al. [25], 2007	QD-HER2 (525 nm), QD-ER (565 nm), QD-PR (605 nm), QD-EGFR (655 nm), QD-mTOR (705 nm)	QDs can be used for multiplexed and quantitative detection of tumor biomarkers.	High sensitivity; Increased resolution; Decreased autofluorescence.	Better conjugation chemistry for well-controlled bio-ligand are needed;
Mulder et al. [26], 2009	RGD-conjugated QDs	QDs readily reveal the angiogenic tumor vasculature, with the highest angiogenic activity occurring in the periphery of the tumor.		The number of bio-ligands per nanoparticle needs to be characterized
Cancer cell imaging
Tada et al. [27], 2007	Trastuzumab-QDs (800 nm)	Single breast cancer cell can be observed with QDs.	High brightness; Resistance to photobleachings;	The methods current used for delivery into cells are not highly efficient.
Shah et al. [28], 2007	Bio-conjugated QDs	Stem cells can be effectively labeled by QDs during both proliferation and multilineage differentiation for long term.	InP/ZnS QDs are nontoxic.	It is difficult to prepare InP/ZnS QDs because of the sensitivity of
Yong et al. [29], 2009	Bio-conjugated InP/ZnS QDs	InP/ZnS QDs can be used as non-cadmium-based safe and efficient optical imaging nanoprobes.		precursors and surfactants toward the reaction environment in obtaining good InP QDs
Cancer tissue imaging
Chen et al. [30], 2009	HER2-QDs	The expression of Her2 of human breast cancer tissue was detected.	Highly efficient, nontoxic, quantitative, sensitive, convenient.	Data from clinical trials about QDs comparing with “Gold standard” is required.
Animal model imaging
Smith et al. [31], 2008	RGD-QDs	For the first time, authors have demonstrated the ability to directly follow the specific binding of nanoparticles to biomolecules expressed on tumor neovascular endothelium in mouse model.	Portends the promise of studying nanoscale structures interacting with microscale entities in living subjects at the cellular-to-subcellular level.	The kinetic and toxicity of QDs in animal model are still controversial limiting the clinical use of QDs.
Parungo et al. [32], 2007	NIR QDs (840 nm)	The purpose was to determin whether the peritoneal space has a predictable lymph node drainage pattern. Bowel lymphatics are a key determinant of peritoneal lymph flow, because bowel resection shifts lymph flow directly to the intrathoracic lymph nodes via chest wall lymphatics.	QDs can be excellently visualized in vivo using IVM.

QDs: quantum dots; Her2: human epidermal growth factor receptor 2; ER: estrogen receptor, PR: progestogen receptor; EGFR: epithelial growth factor receptor; mTOR: mammalian target of rapamycin; RGD: argine-glycine-aspartic aci; NIR: near infrared; IVM: in vivo metric systems.