TY - CONF A1 - Schäferling, Michael A1 - Deguchi, T. A1 - Christ, S. A1 - Peltomaa, R. A1 - Prabhakar, N. A1 - Rosenholm, J. A1 - Arppe, Riika A1 - Soukka, T. A1 - Näreoja, T. T1 - Nanoprobes for sensing and imaging of intracellular pH based on polyethyleneimide-coated photon upconversion nanoparticles conjugated to a pH sensitive rhodamine dye N2 - Lanthanide-doped photon upconversion nanoparticles (UCNPs) exhibit many advantages compared to Stokes-shifted luminescent probes (organic dyes, quantum dots). Due to the upconversion process, the limitations of photobleaching, autofluorescence and low penetration depths in tissue shown by classical fluorescent probes are avoided. This makes UCNPs particularly useful for applications in complex biological samples. Sensing of intracellular pH is of particular interest in biomedical research since structure and function of biomolecules strongly depend on the concentration of protons in their environment. T2 - UPCON 2016 CY - Wroclaw, Poland DA - 23.05.2016 KW - upconversion KW - nanoprobes KW - chemical sensing PY - 2016 AN - OPUS4-37282 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schäferling, Michael A1 - Deguchi, T. A1 - Christ, S. A1 - Peltomaa, R. A1 - Prabhakar, N. A1 - Rosenholm, J. A1 - Arppe, Riika A1 - Soukka, T. A1 - Näreoja, T. T1 - Sensing and Imaging of Intracellular pH Using Polyethyleneimine-coated Photon Upconversion Based Nanoprobes N2 - Lanthanide-doped photon upconversion nanoparticles (UCNPs) exhibit many advantages compared to conventional Stokes-shifted luminescent probes such as organic dyes and quantum dots. Due to the upconversion (UC) process, which describes the conversion of NIR light into shorter wavelength radiation, the limitations of photobleaching, autofluorescence and low penetration depths in tissue shown by classical fluorescent probes absorbing in the UV/vis range are avoided. This makes UCNPs particularly useful for applications in complex samples occurring in bioanalysis, biomedicine and imaging. Sensing of intracellular pH is of particular interest in biomedical research since structure and function of biomolecules strongly depend on the concentration of protons in their environment. We described previously a UCNP nanosensor for pH based on a resonance energy transfer from hexagonal nanocrystals of NaYF4: Yb3+,Er3+ to a pH-sensitive fluorophore (pHrodoTM Red).[1] The nanocrystals were coated with a thin shell of aminosilane with several nanometer layer thickness for coupling of the pH indicator. In this contribution we present a new generation of UC nanoprobes that are coated with a layer of highly branched polyethylenimine (PEI). The PEI coating enables a higher coupling of indicator molecules on the particle surface, better signal to reference ratios in ratiometric readout and an improved cellular uptake compared to the aminosilane coated particles due to a more positive zeta potential. Again, pHrodoTM Red is used as pH indicator, sensitized by the 550 nm emission of the UCNPs. The nanoprobes are calibrated by ratiometric dual wavelength readout at 550 nm (reference signal) and 590 nm (sensor signal) and visualized using a scanning confocal fluorescence microscope with 980 nm excitation wavelength. We studied the cellular uptake efficacy of the nanoprobes and determined to which type of compartment, lysosomes, endosomes or cytosol, the probes are targeted to by measuring the pH of their microenvironment. An in situ control was performed in live cells by a treatment with nigericin, whereby the pH of all intracellular compartments is set at extracellular level. Our results suggest that the PEI coating facilitated endosomal escape of the nanoprobes. T2 - Europtrode XIII CY - Graz, Austria DA - 20.03.2016 KW - upconversion KW - chemical sensing KW - nanoprobes PY - 2016 AN - OPUS4-37283 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schäferling, Michael T1 - Nanoparticle-based luminescent probes for intracellular sensing and imaging of pH N2 - Fluorescence imaging microscopy is an essential tool in biomedical research. Meanwhile, various fluorescent probes are available for the staining of cells, cell membranes, and organelles. Though, to monitor intracellular processes and dysfunctions, probes that respond to ubiquitous chemical parameters determining the cellular function such as pH, pO2, and Ca2+ are required. This review is focused on the progress in the design, fabrication, and application of photoluminescent nanoprobes for sensing and imaging of pH in living cells. The advantages of using nanoprobes carrying fluorescent pHindicators compared to single molecule probes are discussed as well as their limitations due to the mostly lysosomal uptake by cells. Particular attention is paid to ratiometric dual wavelength nanosensors that enable intrinsic referenced measurements. Referencing and proper calibration procedures are basic prerequisites to carry out reliable quantitative pH determinations in complex samples such as living cells. A variety of examples will be presented that highlight the diverseness of nanocarrier materials (polymers, micelles, silica, quantum dots, carbon dots, gold, photon upconversion nanocrystals, or bacteriophages), fluorescent pH indicators for the weak acidic range, and referenced sensing mechanisms, that have been applied intracellularly up to now. KW - pH sensing KW - Luminescent probes KW - Imaging PY - 2016 DO - https://doi.org/10.1002/wnan.1366 SN - 1939-0041 SN - 1939-5116 VL - 8 IS - 3 SP - 378 EP - 413 PB - Wiley-Blackwell CY - Hoboken, New Jersey, USA AN - OPUS4-36367 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, X.-D. A1 - Meier, R.J. A1 - Schmittlein, C. A1 - Schreml, S. A1 - Schäferling, Michael A1 - Wolfbeis, Otto S. T1 - A water-sprayable, thermogelating and biocompatible polymer host for use in fluorescent chemical sensing and imaging of oxygen, pH values and temperature N2 - We report on the use of a sprayable and thermogelating biomaterial (Poloxamer™; a.k.a. Pluronic™) in optical imaging of pH values, local oxygen and temperature. The material is highly biocompatible and easy to handle. We also show that the material is well permeable to oxygen (thus making it a good choice for use in oxygen sensors), and is stable in liquid solution and at elevated temperature. We demonstrate its applicability in optical sensors for oxygen, pH and temperature. This was accomplished by incorporating appropriate luminescent probes in various kinds of microparticles (which act as hosts for the probes and prevent dye leaching and aggregation), and then dispersing the microparticles in the thermogelating polymer. The resulting sensor gels were deposited on the surface of interest via spraying at temperatures of <20 °C. At these temperatures, the gels adhere well to the target, even on uneven surfaces such as skin, wounds, and bacterial cultures. If temperature is risen to above 25 °C, the gels form a thin and soft but solid sensing layer which, however, can be simply removed from surface of interest by cooling and wiping it off, or by washing with water. Sprayable thermogelating sensors present obvious advantages over other sensors by not causing damage to the surface of interest. In our perception, the sensing materials also have wide further applicability in sensors for other species including clinically relevant gases, enzyme substrates (such as glucose or lactate) and ions. KW - Chemical sensing KW - Imaging KW - Biocompatible polymer KW - Sprayable sensor KW - Fluorescence KW - Poloxamer KW - Pluronic KW - Oxygen sensor KW - pH sensor KW - Temperature sensor PY - 2015 DO - https://doi.org/10.1016/j.snb.2015.05.082 SN - 0925-4005 SN - 1873-3077 VL - 221 SP - 37 EP - 44 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-33855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ondrus, V. A1 - Meier, R.J. A1 - Klein, C. A1 - Henne, U. A1 - Schäferling, Michael A1 - Beifuss, U. T1 - Europium 1,3-di(thienyl)propane-1,3-diones with outstanding properties for temperature sensing N2 - The synthesis of novel Eu complexes with 1,3-di(thienyl)propane-1,3-diones as ligands as well as their luminescence properties in different polymers are reported. The new temperature sensitive paints (TSPs) exhibit not only exceptional high temperature sensitivity over a wide range of temperatures but are also characterized by negligible pressure sensitivity and marked photostability. This is why they are outstandingly suitable for applications, e.g. in aerodynamics and hydrodynamics. KW - Temperature sensitive paint KW - Eu diketonate KW - Luminescence KW - Intensity method KW - Lifetime method PY - 2015 DO - https://doi.org/10.1016/j.sna.2015.07.023 SN - 0924-4247 VL - 233 SP - 434 EP - 441 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-33856 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Christ, S. A1 - Schäferling, Michael T1 - Chemical sensing and imaging based on photon upconverting nano- and microcrystals: a review N2 - The demand for photostable luminescent reporters that absorb and emit light in the red to near-infrared (NIR) spectral region continues in biomedical research and bioanalysis. In recent years, classical organic fluorophores have increasingly been displaced by luminescent nanoparticles. These consist of either polymer or silica based beads that are loaded with luminescent dyes, conjugated polymers, or inorganic nanomaterials such as semiconductor nanocrystals (quantum dots), colloidal clusters of silver and gold, or carbon dots. Among the inorganic materials, photon upconversion nanocrystals exhibit a high potential for application to bioimaging or biomolecular assays. They offer an exceptionally high photostability, can be excited in the NIR, and their anti-Stokes emission enables luminescence detection free of background and perturbing scatter effects even in complex biological samples. These lanthanide doped inorganic crystals have multiple emission lines that can be tuned by the selection of the dopants. This review article is focused on the applications of functionalized photon upconversion nanoparticles (UCNPs) to chemical sensing. This is a comparatively new field of research activity and mainly directed at the sensing and imaging of ubiquitous chemical analytes in biological samples, particularly in living cells. For this purpose, the particles have to be functionalized with suitable indicator dyes or recognition elements, as they do not show an intrinsic or specific luminescence response to most of these analytes (e.g. pH, oxygen, metal ions). We describe the strategies for the design of such responsive nanocomposites utilizing either luminescence resonance energy transfer or emission–reabsorption (inner filter effect) mechanisms and also highlight examples for their use either immobilized in sensor layers or directly as nanoprobes for intracellular sensing and imaging. KW - Photon upconversion KW - Nanoprobes KW - Chemical sensors KW - Imaging PY - 2015 DO - https://doi.org/10.1088/2050-6120/3/3/034004 SN - 2050-6120 VL - 3 IS - 3 SP - 034004-1 EP - 034004-22 PB - IOP Publ. CY - Bristol AN - OPUS4-33857 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meier, R.J. A1 - Simbürger, J.M.B. A1 - Soukka, T. A1 - Schäferling, Michael T1 - A FRET based pH probe with broad working range applicable to referenced ratiometric dual wavelength and luminescence lifetime read out N2 - A luminescent probe for determination of pH was designed based on a Förster resonance energy transfer (FRET) system, combining a europium chelate as the donor and carboxynaphtho-fluorescein as a pH sensitive acceptor. The FRET system enables referenced pH detection in an exceptional broad dynamic range from pH 3 to 9. PY - 2015 DO - https://doi.org/10.1039/c5cc00144g SN - 0022-4936 SN - 0009-241x SN - 1359-7345 SN - 1364-548x VL - 51 IS - 28 SP - 6145 EP - 6148 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-33858 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Arppe, Riika A1 - Hyppänen, I. A1 - Perälä, N. A1 - Peltomaa, R. A1 - Kaiser, Martin A1 - Würth, Christian A1 - Christ, S. A1 - Resch-Genger, Ute A1 - Schäferling, Michael A1 - Soukka, T. T1 - Quenching of the upconversion luminescence of NaYF4:Yb3+,Er3+ and NaYF4:Yb3+,Tm3+ nanophosphors by water: the role of the sensitizer Yb3+ in non-radiative relaxation N2 - We have studied the mechanisms of water-based quenching of the upconversion photoluminescence of upconverting nanophosphors (UCNPs) via luminescence decay measurements for a better understanding of the non-radiative deactivation pathways responsible for the relatively low upconversion luminescence efficiency in aqueous solutions. This included both upconversion luminescence measurements and the direct excitation of emissive energy states of Er3+ and Yb3+ dopants in NaYF4:Yb3+,Er3+ UCNPs by measuring the decays at 550 and 655 nm upon 380 nm excitation and at 980 nm upon 930 nm excitation, respectively. The luminescence intensities and decays were measured from both bare and silanized NaYF4:Yb3+,Er3+ and NaYF4:Yb3+,Tm3+ UCNPs in H2O and D2O. The measurements revealed up to 99.9% quenching of the upconversion photoluminescence intensity of both Er3+ and Tm3+ doped bare nanophosphors by water. Instead of the multiphonon relaxation of excited energy levels of the activators, the main mechanism of quenching was found to be the multiphonon deactivation of the Yb3+ sensitizer ion caused by OH-vibrations on the surface of the nanophosphor. Due to the nonlinear nature of upconversion, the quenching of Yb3+ has a higher order effect on the upconversion emission intensity with the efficient Yb–Yb energy migration in the ~35 nm nanocrystals making the whole nanophosphor volume susceptible to surface quenching effects. The study underlines the need of efficient surface passivation for the use of UCNPs as labels in bioanalytical applications performed in aqueous solutions. PY - 2015 DO - https://doi.org/10.1039/c5nr02100f SN - 2040-3364 SN - 2040-3372 VL - 7 IS - 27 SP - 11746 EP - 11757 PB - RSC Publ. CY - Cambridge AN - OPUS4-33815 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Schäferling, Michael ED - Meyers, R.A. T1 - Fluorescence-based biosensors N2 - Biosensors, as defined by Pure and Applied Chemistry, are ‘chemical sensors in which the recognition System utilizes a biochemical mechanism. The biological recognition system translates information from the biochemical domain, usually an analyte concentration, into a chemical or physical output signal with a defined sensitivity’.(1) It is also appointed that chemical or biological sensors contain two basic components connected in series: a chemical or biomolecular recognition System (receptor) and a physicochemical transducer. According to this prerequisite, this overlook is confined to sensor devices that combine a biomolecular recognition element with an optical signal transducer. Homogeneous or intracellular assays using fluorescent molecular probes or nanoparticles are not considered, although they are frequently termed as molecular sensors or nanosensors in the literature. Fluorescence-based biosensors are generalized as those devices that derive an analytical signal from a photoluminescent (either fluorescence or phosphorescence) emission process. Chemi- or bioluminescent detection systems are only briefly discussed in this review. Biosensors are used for a wide variety of tasks, including detection of compounds of biomedical, environmental or defense interest; on-line monitoring for process control; quality control of foodstuffs; selective detection of compounds undergoing a chemical separation; and screening of drug compounds. Advantages of such devices include high selectivity, rapid response times, reusability, amenability to remote analysis, and immunity to electrical interferences. The selective nature of complexation between biomolecule and analyte and the small size of sensor devices can be combined with advanced detection techiques such as total internal reflection (TIR) spectroscopy. This results in an ability to measure analytes in complex matrices with unsurpassed sensitivity. Such samples may include highly scattering components such as milk or whole blood,(11) or relatively inaccessible locations such as groundwater wells, or even intracellular environments. The key limitation of such devices mainly centers on the poor stability of biological compounds, which can lead to a substantial drift in instrumental response over time. The so-called Cambridge Definition appoints another characteristic property of sensors. Therein, they are defined as ‘miniaturized devices which can deliver real-time and on-line information on the presence of specific compounds or ions in even complex samples’. Accordingly, a sensor is expected to respond reversibly and continuously. With the exception of some enzymatic sensors, these conditions are not fulfilled in case of most biosensors. Particularly, in devices where immunological reagents or DNA are used as recognition elements, they show a lack of reversibility and operate only as a ‘one-shot’ screen, without the potential for continuous, quantitative analysis. Nevertheless, the designations immunosensors or DNA sensors became accepted for such analytical or diagnostic tools. KW - Biosensor KW - Fluorescence KW - Immunoassay KW - Enzyme sensor KW - DNA sensor PY - 2016 UR - http://onlinelibrary.wiley.com/doi/10.1002/9780470027318.a0206.pub3/abstract SN - 9780470027318 DO - https://doi.org/10.1002/9780470027318.a0206.pub3 SP - 1 EP - 51 PB - John Wiley & Sons AN - OPUS4-38741 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, X.-d. A1 - Meier, R.J. A1 - Schäferling, Michael A1 - Bange, S. A1 - Lupton, J.M. A1 - Sperber, M. A1 - Wegener, J. A1 - Ondrus, V. A1 - Beifuss, U. A1 - Henne, U. A1 - Klein, C. A1 - Wolfbeis, Otto S. T1 - Two-photon excitation temperature nanosensors based on a conjugated fluorescent polymer doped with an Europium probe N2 - A strongly fluorescent organic semiconducting polymer doped with a highly temperature dependent fluorescent europium(III) complex is converted into a nanosized material that is capable of optically sensing temperature (T) in the range from 0 to 50 °C via two-photon excitation at 720 nm. The nanosensors are prepared from a blue-fluorescent polyfluorene that acts as both a lightharvesting antenna (to capture two-photon energy) and an energy donor in a fluorescence resonance energy transfer (FRET) system. The photonic energy absorbed by the polymer is transferred to the T-sensitive red-luminescent europium complex contained in the nanoparticles. The close spatial proximity of the donor and the acceptor warrants efficient FRET. A poly(ethylene glycol)- co-poly(propylene oxide) block copolymer is also added to render the particles biocompatible. It is shown that T can be calculated from a) the intensity of the luminescence of the europium complex, b) the ratio of the intensities of the red and blue luminescence, or c) the T-dependent luminescence lifetime of the Eu(III) complex. KW - Optical sensor KW - Temperature sensor KW - Nanosensor KW - FRET system PY - 2016 UR - http://onlinelibrary.wiley.com/doi/10.1002/adom.201600601/abstract DO - https://doi.org/10.1002/adom.201600601 SN - 2195-1071 VL - 4 IS - 11 SP - 1854 EP - 1859 PB - Wiley-VCH CY - Weinheim AN - OPUS4-38737 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -