TY  - JOUR
A1  - Cywinski, Piotr J.
A1  - Hammann, Tommy
A1  - Huehn, Dominik
A1  - Parak, Wolfgang J.
A1  - Hildebrandt, Niko
A1  - Löhmannsröben, Hans-Gerd
T1  - Europium-quantum dot nanobioconjugates as luminescent probes for time-gated biosensing
JF  - Journal of biomedical optics
N2  - Nanobioconjugates have been synthesized using cadmium selenide quantum dots (QDs), europium complexes (EuCs), and biotin. In those conjugates, long-lived photoluminescence (PL) is provided by the europium complexes, which efficiently transfer energy via Forster resonance energy transfer (FRET) to the QDs in close spatial proximity. As a result, the conjugates have a PL emission spectrum characteristic for QDs combined with the long PL decay time characteristic for EuCs. The nanobioconjugates synthesis strategy and photo-physical properties are described as well as their performance in a time-resolved streptavidin-biotin PL assay. In order to prepare the QD-EuC-biotin conjugates, first an amphiphilic polymer has been functionalized with the EuC and biotin. Then, the polymer has been brought onto the surface of the QDs (either QD655 or QD705) to provide functionality and to make the QDs water dispersible. Due to a short distance between EuC and QD, an efficient FRET can be observed. Additionally, the QD-EuC-biotin conjugates' functionality has been demonstrated in a PL assay yielding good signal discrimination, both from autofluorescence and directly excited QDs. These newly designed QD-EuC-biotin conjugates expand the class of highly sensitive tools for bioanalytical optical detection methods for diagnostic and imaging applications. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)
KW  - quantum dots
KW  - europium complex
KW  - amphiphilic polymer assembly
KW  - nanobioconjugate
KW  - biosensor
KW  - time-resolved fluorescence
Y1  - 2014
U6  - https://doi.org/10.1117/1.JBO.19.10.101506
SN  - 1083-3668
SN  - 1560-2281
VL  - 19
IS  - 10
PB  - SPIE
CY  - Bellingham
ER  - 
TY  - JOUR
A1  - Riedel, M.
A1  - Sabir, N.
A1  - Scheller, Frieder W.
A1  - Parak, Wolfgang J.
A1  - Lisdat, Fred
T1  - Connecting quantum dots with enzymes
BT  - mediator-based approaches for the light-directed read-out of glucose and fructose oxidation
JF  - Nanoscale
N2  - The combination of the biocatalytic features of enzymes with the unique physical properties of nanoparticles in a biohybrid system provides a promising approach for the development of advanced bioelectrocatalytic devices. This study describes the construction of photoelectrochemical signal chains based on CdSe/ZnS quantum dot (QD) modified gold electrodes as light switchable elements, and low molecular weight redox molecules for the combination with different biocatalysts. Photoelectrochemical and photoluminescence experiments verify that electron transfer can be achieved between the redox molecules hexacyanoferrate and ferrocene, and the QDs under illumination. Since for both redox mediators a concentration dependent photocurrent change has been found, light switchable enzymatic signal chains are built up with fructose dehydrogenase (FDH) and pyrroloquinoline quinone-dependent glucose dehydrogenase ((PQQ) GDH) for the detection of sugars. After immobilization of the enzymes at the QD electrode the biocatalytic oxidation of the substrates can be followed by conversion of the redox mediator in solution and subsequent detection at the QD electrode. Furthermore, (PQQ) GDH has been assembled together with ferrocenecarboxylic acid on top of the QD electrode for the construction of a funtional biohybrid architecture, showing that electron transfer can be realized from the enzyme over the redox mediator to the QDs and subsequently to the electrode in a completely immobilized fashion. The results obtained here do not only provide the basis for light-switchable biosensing and bioelectrocatalytic applications, but may also open the way for self-driven point-of-care systems by combination with solar cell approaches (power generation at the QD electrode by enzymatic substrate consumption).
Y1  - 2017
U6  - https://doi.org/10.1039/c7nr00091j
SN  - 2040-3364
SN  - 2040-3372
VL  - 9
SP  - 2814
EP  - 2823
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -