@misc{CywińskiNonoCharbonniereetal.2014, author = {Cywiński, Piotr J. and Nono, Katia Nchimi and Charbonni{\`e}re, Lo{\"i}c J. and Hammann, Tommy and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-95390}, pages = {6060 -- 6067}, year = {2014}, abstract = {A new functional luminescent lanthanide complex (LLC) has been synthesized with terbium as a central lanthanide ion and biotin as a functional moiety. Unlike in typical lanthanide complexes assembled via carboxylic moieties, in the presented complex, four phosphate groups are chelating the central lanthanide ion. This special chemical assembly enhances the complex stability in phosphate buffers conventionally used in biochemistry. The complex synthesis strategy and photophysical properties are described as well as the performance in time-resolved F{\"o}rster Resonance Energy Transfer (FRET) assays. In those assays, this biotin-LLC transferred energy either to acceptor organic dyes (Cy5 or AF680) labelled on streptavidin or to quantum dots (QD655 or QD705) surface-functionalised with streptavidins. The permanent spatial donor-acceptor proximity is assured through strong and stable biotin-streptavidin binding. The energy transfer is evidenced from the quenching observed in donor emission and from a decrease in donor luminescence decay, both associated with simultaneous increase in acceptor intensity and in the decay time. The dye-based assays are realised in TRIS and in PBS, whereas QD-based systems are studied in borate buffer. The delayed emission analysis allows for quantifying the recognition process and for auto-fluorescence-free detection, which is particularly relevant for application in bioanalysis. In accordance with F{\"o}rster theory, F{\"o}rster-radii (R0) were found to be around 60 {\AA} for organic dyes and around 105 {\AA} for QDs. The FRET efficiency (η) reached 80\% and 25\% for dye and QD acceptors, respectively. Physical donor-acceptor distances (r) have been determined in the range 45-60 {\AA} for organic dye acceptors, while for acceptor QDs between 120 {\AA} and 145 {\AA}. This newly synthesised biotin-LLC extends the class of highly sensitive analytical tools to be applied in the bioanalytical methods such as time-resolved fluoroimmunoassays (TR-FIA), luminescent imaging and biosensing.}, language = {en} } @article{MeilingCywinskiLoehmannsroeben2018, author = {Meiling, Till Thomas and Cywinski, Piotr J. and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Two-Photon excitation fluorescence spectroscopy of quantum dots}, series = {The journal of physical chemistry : C, Nanomaterials and interfaces}, volume = {122}, journal = {The journal of physical chemistry : C, Nanomaterials and interfaces}, number = {17}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.7b12345}, pages = {9641 -- 9647}, year = {2018}, abstract = {The applications of quantum dots (QDs) in two-photon (2P) excitation applications demand reliable data about their 2P absorption (2PA) cross sections (sigma(2PA)). In the present study, sigma(2PA) values have been determined for a series of commercial colloidal CdSe/ZnS QDs and CdSeTe/ZnS QDs in aqueous media. For the first time for these QDs, the sigma(2PA) values have been determined over a wide spectral range, that is, between 720 and 900 nm, and are compared to the extinction coefficient (epsilon) values obtained under one-photon (1P) excitation. Furthermore, we present a QD in combination with an organic dye in a biotin-streptavidin Forster resonance energy transfer bioassay under 1P and 2P excitation. The results for the bioassay under 2P excitation are compared to those obtained under 1P excitation. The results demonstrate that in the case of the 2P excitation, higher sensitivity can be achieved because of an improved signal-to-noise ratio.}, language = {en} } @article{MorgnerBennemannCywińskietal.2017, author = {Morgner, Frank and Bennemann, Mark and Cywiński, Piotr J. and Kollosche, Matthias and G{\´o}rski, Krzysztof and Pietraszkiewicz, Marek and Geßner, Andr{\´e} and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Elastic FRET sensors for contactless pressure measurement}, series = {RSC Advances : an international journal to further the chemical sciences}, volume = {7}, journal = {RSC Advances : an international journal to further the chemical sciences}, publisher = {RSC Publishing}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c7ra06379b}, pages = {50578 -- 50583}, year = {2017}, abstract = {Contactless pressure monitoring based on Forster resonance energy transfer between donor/acceptor pairs immobilized within elastomers is demonstrated. The donor/acceptor energy transfer is employed by dispersing terbium(III) tris[(2-hydroxybenzoyl)-2-aminoethyl] amine complex (LLC, donor) and CdSe/ZnS quantum dots (QD655, acceptor) in styrene-ethylene/buthylene-styrene (SEBS) and poly(dimethylsiloxane) (PDMS). The continuous monitoring of QD luminescence showed a reversible intensity change as the pressure signal is alternated between two stable states indicating a pressure sensitivity of 6350 cps kPa(-1). Time-resolved measurements show the pressure impact on the FRET signal due to an increase of decay time (270 ms up to 420 ms) for the donor signal and parallel drop of decay time (170 mu s to 155 mu s) for the acceptor signal as the net pressure applied. The LLC/QD655 sensors enable a contactless readout as well as space resolved monitoring to enable miniaturization towards smaller integrated stretchable opto-electronics. Elastic FRET sensors can potentially lead to developing profitable analysis systems capable to outdo conventional wired electronic systems (inductive, capacitive, ultrasonic and photoelectric sensors) especially for point-of-care diagnostics, biological monitoring required for wearable electronics.}, language = {en} } @article{HarmaPihlasaloCywinskietal.2013, author = {Harma, Harri and Pihlasalo, Sari and Cywinski, Piotr J. and Mikkonen, Piia and Hammann, Tommy and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Hanninen, Pekka}, title = {Protein quantification using resonance energy transfer between donor nanoparticles and acceptor quantum dots}, series = {Analytical chemistry}, volume = {85}, journal = {Analytical chemistry}, number = {5}, publisher = {American Chemical Society}, address = {Washington}, issn = {0003-2700}, doi = {10.1021/ac303586n}, pages = {2921 -- 2926}, year = {2013}, abstract = {A homogeneous time-resolved luminescence resonance energy transfer (TR-LRET) assay has been developed to quantify proteins. The competitive assay is based on resonance energy transfer (RET) between two luminescent nanosized particles. Polystyrene nanoparticles loaded with Eu3+ chelates (EuNPs) act as donors, while protein-coated quantum dots (QDs), either CdSe/ZnS emitting at 655 nm (QD655-strep) or CdSeTe/ZnS with emission wavelength at 705 nm (QD705-strep), are acceptors. In the absence of analyte protein, in our case bovine serum albumin (BSA), the protein-coated QDs bind nonspecifically to the EuNPs, leading to RET. In the presence of analyte proteins, the binding of the QDs to the EuNPs is prevented and the RET signal decreases. RET from the EuNPs to the QDs was confirmed and characterized with steady-state and time-resolved luminescence spectroscopy. In accordance with the Forster theory, the approximate average donor acceptor distance is around 15 nm at RET efficiencies, equal to 15\% for QD655 and 13\% for QD705 acceptor, respectively. The limits of detection are below 10 ng of BSA with less than a 10\% average coefficient of variation. The assay sensitivity is improved, when compared to the most sensitive commercial methods. The presented mix-and-measure method has potential to be implemented into routine protein quantification in biological laboratories.}, language = {en} } @article{CywinskiNonoCharbonniereetal.2014, author = {Cywinski, Piotr J. and Nono, Katia Nchimi and Charbonniere, Loic J. and Hammann, Tommy and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {13}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c3cp54883j}, pages = {6060 -- 6067}, year = {2014}, abstract = {A new functional luminescent lanthanide complex (LLC) has been synthesized with terbium as a central lanthanide ion and biotin as a functional moiety. Unlike in typical lanthanide complexes assembled via carboxylic moieties, in the presented complex, four phosphate groups are chelating the central lanthanide ion. This special chemical assembly enhances the complex stability in phosphate buffers conventionally used in biochemistry. The complex synthesis strategy and photophysical properties are described as well as the performance in time-resolved Forster Resonance Energy Transfer (FRET) assays. In those assays, this biotin-LLC transferred energy either to acceptor organic dyes (Cy5 or AF680) labelled on streptavidin or to quantum dots (QD655 or QD705) surfacefunctionalised with streptavidins. The permanent spatial donor-acceptor proximity is assured through strong and stable biotin-streptavidin binding. The energy transfer is evidenced from the quenching observed in donor emission and from a decrease in donor luminescence decay, both associated with simultaneous increase in acceptor intensity and in the decay time. The dye-based assays are realised in TRIS and in PBS, whereas QD-based systems are studied in borate buffer. The delayed emission analysis allows for quantifying the recognition process and for auto-fluorescence-free detection, which is particularly relevant for application in bioanalysis. In accordance with Forster theory, Forsterradii (R0) were found to be around 60 angstrom for organic dyes and around 105 angstrom for QDs. The FRET efficiency (Z) reached 80\% and 25\% for dye and QD acceptors, respectively. Physical donor-acceptor distances (r) have been determined in the range 45-60 angstrom for organic dye acceptors, while for acceptor QDs between 120 angstrom and 145 angstrom. This newly synthesised biotin-LLC extends the class of highly sensitive analytical tools to be applied in the bioanalytical methods such as time-resolved fluoroimmunoassays (TR-FIA), luminescent imaging and biosensing.}, language = {en} } @article{CywinskiHammannHuehnetal.2014, author = {Cywinski, Piotr J. and Hammann, Tommy and Huehn, Dominik and Parak, Wolfgang J. and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Europium-quantum dot nanobioconjugates as luminescent probes for time-gated biosensing}, series = {Journal of biomedical optics}, volume = {19}, journal = {Journal of biomedical optics}, number = {10}, publisher = {SPIE}, address = {Bellingham}, issn = {1083-3668}, doi = {10.1117/1.JBO.19.10.101506}, pages = {8}, year = {2014}, abstract = {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)}, language = {en} } @article{CywinskiMoroLoehmannsroeben2014, author = {Cywinski, Piotr J. and Moro, Artur J. and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Cyclic GMP recognition using ratiometric QD-fluorophore conjugate nanosensors}, series = {Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics}, volume = {52}, journal = {Biosensors and bioelectronics : the principal international journal devoted to research, design development and application of biosensors and bioelectronics}, publisher = {Elsevier}, address = {Oxford}, issn = {0956-5663}, doi = {10.1016/j.bios.2013.09.002}, pages = {288 -- 292}, year = {2014}, language = {en} } @article{CywinskiOlejkoLoehmannsroeben2015, author = {Cywinski, Piotr J. and Olejko, Lydia and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {A time-resolved luminescent competitive assay to detect L-selectin using aptamers as recognition elements}, series = {Analytica chimica acta : an international journal devoted to all branches of analytical chemistry}, volume = {887}, journal = {Analytica chimica acta : an international journal devoted to all branches of analytical chemistry}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0003-2670}, doi = {10.1016/j.aca.2015.06.045}, pages = {209 -- 215}, year = {2015}, abstract = {L-selectin is a protein with potential importance for numerous diseases and clinical disorders. In this paper, we present a new aptamer-based luminescent assay developed to detect L-selectin. The sensing system working principle is based on Forster Resonance Energy Transfer (FRET) from a donor terbium complex (TbC) to an acceptor cyanine dye (Cy5). In the present approach, the biotinylated aptamer is combined with Cy5-labelled streptavidin (Cy5-Strep) to yield an aptamer-based acceptor construct (Apta-Cy5-Strep), while L-selectin is conjugated using luminescent TbC. Upon aptamer binding to the TbC-labelled L-selectin (L-selectin-TbC), permanent donor-acceptor proximity is established which allows for radiationless energy transfer to occur. However, when unlabelled L-selectin is added, it competes with the L-selectin-TbC and the FRET signal decreases as the L-selectin concentration increases. FRET from the TbC to Cy5 was observed with time-gated time-resolved luminescence spectroscopy. A significant change in the corrected luminescence signal was observed in the dynamic range of 10 -500 ng/mL L-selectin, the concentration range relevant for accelerated cognitive decline of Alzheimer's disease, with a limit of detection (LOD) equal to 10 ng/mL. The aptasensor-based assay is homogeneous and can be realized within one hour. Therefore, this method has the potential to become an alternative to tedious heterogeneous analytical methods, e.g. based on enzyme-linked immunosorbent assay (ELISA). (C) 2015 Elsevier B.V. All rights reserved.}, language = {en} } @article{CywinskiMoroRitscheletal.2011, author = {Cywinski, Piotr J. and Moro, Artur J. and Ritschel, Thomas and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Sensitive and selective fluorescence detection of guanosine nucleotides by nanoparticles conjugated with a naphthyridine receptor}, series = {Analytical \& bioanalytical chemistry}, volume = {399}, journal = {Analytical \& bioanalytical chemistry}, number = {3}, publisher = {Springer}, address = {Heidelberg}, issn = {1618-2642}, doi = {10.1007/s00216-010-4420-2}, pages = {1215 -- 1222}, year = {2011}, abstract = {Novel fluorescent nanosensors, based on a naphthyridine receptor, have been developed for the detection of guanosine nucleotides, and both their sensitivity and selectivity to various nucleotides were evaluated. The nanosensors were constructed from polystyrene nanoparticles functionalized by (N-(7-((3-aminophenyl) ethynyl)-1,8-naphthyridin- 2-yl) acetamide) via carbodiimide ester activation. We show that this naphthyridine nanosensor binds guanosine nucleotides preferentially over adenine, cytosine, and thymidine nucleotides. Upon interaction with nucleotides, the fluorescence of the nanosensor is gradually quenched yielding Stern-Volmer constants in the range of 2.1 to 35.9mM(-1). For all the studied quenchers, limits of detection (LOD) and tolerance levels for the nanosensors were also determined. The lowest (3 sigma) LOD was found for guanosine 3',5'-cyclic monophosphate (cGMP) and it was as low as 150 ng/ml. In addition, we demonstrated that the spatial arrangement of bound analytes on the nanosensors' surfaces is what is responsible for their selectivity to different guanosine nucleotides. We found a correlation between the changes of the fluorescence signal and the number of phosphate groups of a nucleotide. Results of molecular modeling and zeta-potential measurements confirm that the arrangement of analytes on the surface provides for the selectivity of the nanosensors. These fluorescent nanosensors have the potential to be applied in multi-analyte, array-based detection platforms, as well as in multiplexed microfluidic systems.}, language = {en} } @article{CywinskiPietraszkiewiczMaciejczyketal.2016, author = {Cywinski, Piotr J. and Pietraszkiewicz, Marek and Maciejczyk, Michal and Gorski, Krzysztof and Hammann, Tommy and Liermann, Konstanze and Paulke, Bernd-Reiner and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Total protein concentration quantification using nanobeads with a new highly luminescent terbium(III) complex}, series = {RSC Advances}, volume = {6}, journal = {RSC Advances}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2046-2069}, doi = {10.1039/c6ra23207h}, pages = {115068 -- 115073}, year = {2016}, abstract = {Total protein concentration (TPC) is a key parameter in many biochemical experiments and its quantification is often necessary for isolation, separation, and analysis of proteins. A sensitive and rapid nanobead-based TPC quantification assay based on Forster Resonance Energy Transfer (FRET) has been developed. A new, highly luminescent Tb(III) complex has been synthesised and applied as donor in this FRET assay with an organic dye (Cy5) as acceptor. FRET-induced changes in luminescence have been investigated both at donor and acceptor emission wavelength using time-resolved luminescence spectroscopy with time-gated detection. In the assay, the Tb(III) complex and fine-tuned polyglycidyl methacrylate (PGMA) nanobeads ensure that an improvement in sensitivity and background reduction is achieved. Using 40 nm large PGMA nanobeads loaded with the Tb(III) complex, it is possible to determine TPC down to 50 ng mL(-1) in just 10 minutes. Through specific assay components the sensitivity has been improved when compared to existing nanobead-based assays and to currently known commercial methods. Additionally, the assay is relatively insensitive to the presence of contaminants, such as non-ionic detergents commonly found in biological samples. Due to no need for any centrifugal steps, this mix-and-measure bioassay can easily be implemented into routine TPC quantification protocols in biochemical laboratories.}, language = {en} }