Table 1.

Selected strategies for the intracellular delivery of QDs.

Strategy	Mechanism	Examples	Targeted Cells	References
Passive uptake	Electrostatic interactions	-	HeLa	[15]
			Human macrophages	[27,72]
			Breast cancer (MDA-MB-231)	[73,74]
			Human melanoma cells (LU1205)	[75]
Facilitated delivery	Peptide-mediated	TAT	Human embryonic kidney	[76]
			HeLa	[77]
			Mesenchymal stem cells	[53]
			Jurkat cells	[28]
		Pep-1 (Chariot)	Osteoblast	[78]
			Vascular endothelial cells	[78]
		RGD motify	Fibroblast (NIH 3T3)	[79]
			Epidermoid carcinoma	[80]
	Protein-mediated	Neuropeptide	HeLa	[17]
		Transferrin	Human pancreatic cancer	[2,81,82]
		Antibody	Breast cancer (MCF-7)	[11]
		EGF	Mesenchymal stem cells	[83]
			Chinese hamster ovary	[84–86]
			Medulloblastoma tumors	[87]
			Glioma tumors	[87]
		Cholera toxin B	Fibroblast	[88,89]
		NGF	PC12 neural cells	[90,91]
	Polymer/lipid-mediated	Lipid polymers	Mouse lymphoma	[92]
			HeLa	[93]
			A549 epithelial lung HeLa	[94]
		Polyethyleneimine	HeLa	[95]
	Drug-mediated	Tiopronin	Fibroblast	[96]
	Small molecule	Glucose/sugar	S. cerevisiae (Baker’s yeast)	[97,98]
		Folate	Epidermal carcinoma	[99]
		Adenine/AMP	Bacteria (Bacillus subtilis, E. coli)	[100,101]
		Dopamin	A9 mouse fibroblast with transfected dopamine receptor	[102]
Active Delivery	Electroporation	-	HeLa	[71]
			Mouse neural stem progenitor cells	[9]
	Microinjection	-		[71]
			Xenopus embryo	[103]
			HeLa	[104]
			Human embryonic kidney