title: The Role of Negative Charge in the Delivery of Quantum Dots to Neurons.
abstract: Despite our extensive knowledge of the structure of negatively charged cell surface proteoglycans and sialoglycoconjugates in the brain, we have little understanding of how their negative charge contributes to brain function. We have previously shown that intensely photoluminescent 9-nm diameter quantum dots (QDs) with a CdSe core, a ZnS shell, and a negatively charged compact molecular ligand coating (CL4) selectively target neurons rather than glia. We now provide an explanation for this selective neuronal delivery. In this study, we compared three zwitterionic QD coatings differing only in their regions of positive or negative charge, as well as a positively charged (NH2) polyethylene glycol (PEG) coat, for their ability to deliver the cell-membrane-penetrating chaperone lipopeptide JB577 (WG(Palmitoyl)VKIKKP9G2H6) to individual cells in neonatal rat hippocampal slices. We confirm both that preferential uptake in neurons, and the lack of uptake in glia, is strongly associated with having a region of greater negative charge on the QD coating. In addition, the role of negatively charged chondroitin sulfate of the extracellular matrix (ECM) in restricting uptake was further suggested by digesting neonatal rat hippocampal slices with chondroitinase ABC and showing increased uptake of QDs by oligodendrocytes. Treatment still did not affect uptake in astrocytes or microglia. Finally, the future potential of using QDs as vehicles for trafficking proteins into cells continues to show promise, as we show that by administering a histidine-tagged green fluorescent protein (eGFP-His6) to hippocampal slices, we can observe neuronal uptake of GFP.
authors.affiliation: Committee on Neurobiology, University of Chicago, IL, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Walters
authors.affiliation: Center for Bio/Molecular Science and Engineering, Code 6900, U.S. Naval Research Laboratory, Washington, DC, USA.
authors.forename: Igor L
authors.initials: IL
authors.lastname: Medintz
authors.affiliation: Center for Bio/Molecular Science and Engineering, Code 6900, U.S. Naval Research Laboratory, Washington, DC, USA.
authors.forename: James B
authors.initials: JB
authors.lastname: Delehanty
authors.affiliation: Optical Sciences Division, Code 5611, U.S. Naval Research Laboratory, Washington, DC, USA.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Stewart
authors.affiliation: Optical Sciences Division, Code 5611, U.S. Naval Research Laboratory, Washington, DC, USA.
authors.forename: Kimihiro
authors.initials: K
authors.lastname: Susumu
authors.affiliation: Optical Sciences Division, Code 5611, U.S. Naval Research Laboratory, Washington, DC, USA.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Huston
authors.affiliation: Scripps Research Institute, La Jolla, CA, USA.
authors.forename: Philip E
authors.initials: PE
authors.lastname: Dawson
authors.affiliation: Committee on Neurobiology, University of Chicago, IL, USA Departments of Pediatrics, Biochemistry and Molecular Biology, University of Chicago, IL, USA dawg@uchicago.edu.
authors.forename: Glyn
authors.initials: G
authors.lastname: Dawson
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D016503:Drug Delivery Systems; D055590:Electromagnetic Phenomena; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D057927:Hydrophobic and Hydrophilic Interactions; D066298:In Vitro Techniques; D008247:Lysosomes; D009474:Neurons / Q000378:metabolism*; D009836:Oligodendroglia; D009924:Organ Culture Techniques; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D045663:Quantum Dots / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013499:Surface Properties
chemical_list: D049452:Green Fluorescent Proteins; D011092:Polyethylene Glycols
keywords: charge; chondroitin sulfate; endosomal uptake; neuron; oligodendrocyte; quantum dot