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Ubiquinone-quantum dot bioconjugates for in vitro and intracellular complex I sensing.

ABSTRACT: Quantum dots (QDs) have attracted increasing interest in bioimaging and sensing. Here, we report a biosensor of complex I using ubiquinone-terminated disulphides with different alkyl spacers (QnNS, n = 2, 5 and 10) as surface-capping ligands to functionalise CdSe/ZnS QDs. The enhancement or quenching of the QD bioconjugates fluorescence changes as a function of the redox state of QnNS, since QDs are highly sensitive to the electron-transfer processes. The bioconjugated QnNS-QDs emission could be modulated by complex I in the presence of NADH, which simulates an electron-transfer system part of the mitochondrial respiratory chain, providing an in vitro and intracellular complex I sensor. Epidemiological studies suggest that Parkinson's patients have the impaired activity of complex I in the electron-transfer chain of mitochondria. We have demonstrated that the QnNS-QDs system could aid in early stage Parkinson's disease diagnosis and progression monitoring by following different complex I levels in SH-SY5Y cells.

SUBMITTER: Ma W

PROVIDER: S-EPMC3607194 | biostudies-other | 2013

REPOSITORIES: biostudies-other

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Ubiquinone-quantum dot bioconjugates for in vitro and intracellular complex I sensing.

Ma Wei W Qin Li-Xia LX Liu Feng-Tao FT Gu Zhen Z Wang Jian J Pan Zhi Gang ZG James Tony D TD Long Yi-Tao YT

Scientific reports 20130101

Quantum dots (QDs) have attracted increasing interest in bioimaging and sensing. Here, we report a biosensor of complex I using ubiquinone-terminated disulphides with different alkyl spacers (QnNS, n = 2, 5 and 10) as surface-capping ligands to functionalise CdSe/ZnS QDs. The enhancement or quenching of the QD bioconjugates fluorescence changes as a function of the redox state of QnNS, since QDs are highly sensitive to the electron-transfer processes. The bioconjugated QnNS-QDs emission could be ...[more]

PMID: 23524384

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Project description:We report the development of a quantum dot (QD)-peptide-fullerene (C60) electron transfer (ET)-based nanobioconjugate for the visualization of membrane potential in living cells. The bioconjugate is composed of (1) a central QD electron donor, (2) a membrane-inserting peptidyl linker, and (3) a C60 electron acceptor. The photoexcited QD donor engages in ET with the C60 acceptor, resulting in quenching of QD photoluminescence (PL) that tracks positively with the number of C60 moieties arrayed around the QD. The nature of the QD-capping ligand also modulates the quenching efficiency; a neutral ligand coating facilitates greater QD quenching than a negatively charged carboxylated ligand. Steady-state photophysical characterization confirms an ET-driven process between the donor-acceptor pair. When introduced to cells, the amphiphilic QD-peptide-C60 bioconjugate labels the plasma membrane by insertion of the peptide-C60 portion into the hydrophobic bilayer, while the hydrophilic QD sits on the exofacial side of the membrane. Depolarization of cellular membrane potential augments the ET process, which is manifested as further quenching of QD PL. We demonstrate in HeLa cells, PC12 cells, and primary cortical neurons significant QD PL quenching (ΔF/F0 of 2-20% depending on the QD-C60 separation distance) in response to membrane depolarization with KCl. Further, we show the ability to use the QD-peptide-C60 probe in combination with conventional voltage-sensitive dyes (VSDs) for simultaneous two-channel imaging of membrane potential. In in vivo imaging of cortical electrical stimulation, the optical response of the optimal QD-peptide-C60 configuration exhibits temporal responsivity to electrical stimulation similar to that of VSDs. Notably, however, the QD-peptide-C60 construct displays 20- to 40-fold greater ΔF/F0 than VSDs. The tractable nature of the QD-peptide-C60 system offers the advantages of ease of assembly, large ΔF/F0, enhanced photostability, and high throughput without the need for complicated organic synthesis or genetic engineering, respectively, that is required of traditional VSDs and fluorescent protein constructs.

Dataset Information

Ubiquinone-quantum dot bioconjugates for in vitro and intracellular complex I sensing.

Publications

Ubiquinone-quantum dot bioconjugates for in vitro and intracellular complex I sensing.

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