TY - JOUR A1 - Takeuchi, T. A1 - Montenegro, J. A1 - Hennig, Andreas A1 - Matile, S. T1 - Pattern generation with synthetic sensing systems in lipid bilayer membranes N2 - The objective of this study was to introduce differential sensing techniques to synthetic systems that act, like olfactory receptors, as transporters in lipid bilayer membranes. Routine with most alternative chemosensing ensembles, pattern generation has, quite ironically, remained inaccessible in lipid bilayers because the number of available crossresponsive sensor components has been insufficient. To address this challenge, we here report on the use of cationic hydrazides that can react in situ with hydrophobic analytes to produce cationic amphiphiles which in turn can act as countercation activators for polyanionic transporters in fluorogenic vesicles. To expand the dimension of signals generated by this system, a small collection of small peptides containing a positive charge (guanidinium, ammonium) and one to three reactive hydrazides are prepared. Odorants are used as examples for hydrophobic analytes, perfumes to probe compatibility with complex matrices, and counterion-activated calf-thymus DNA as representative polyion–counterion transport system. Principal component and hierarchical cluster analysis of the obtained multidimensional patterns are shown to differentiate at least 21 analytes in a single score plot, discriminating also closely related structures such as enantiomers, cis–trans isomers, single-atom homologs, as well as all tested perfumes. Inverse detection provides access to analytes as small as acetone. The general nature of the introduced methodology promises to find diverse applications in current topics in biomembrane research. KW - Liposome KW - DNA KW - Biosensor KW - Principal component analysis PY - 2011 U6 - https://doi.org/10.1039/c0sc00386g SN - 2041-6520 SN - 2041-6539 VL - 2 IS - 2 SP - 303 EP - 307 PB - RSC CY - Cambridge AN - OPUS4-24844 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sloniec, Jagoda A1 - Schnurr, M. A1 - Witte, C. A1 - Resch-Genger, Ute A1 - Schröder, L. A1 - Hennig, Andreas T1 - Biomembrane interactions of functionalized cryptophane-A: combined fluorescence and 129Xe NMR studies of a bimodal contrast agent N2 - Fluorescent derivatives of the 129Xe NMR contrast agent cryptophane-A were obtained by functionalization with near infrared fluorescent dyes DY680 and DY682. The resulting conjugates were spectrally characterized, and their interaction with giant and large unilamellar vesicles of varying phospholipid composition was analyzed by fluorescence and NMR spectroscopy. In the latter, a chemical exchange saturation transfer with hyperpolarized 129Xe (Hyper-CEST) was used to obtain sufficient sensitivity. To determine the partitioning coefficients, we developed a method based on fluorescence resonance energy transfer from Nile Red to the membrane-bound conjugates. This indicated that not only the hydrophobicity of the conjugates, but also the phospholipid composition, largely determines the membrane incorporation. Thereby, partitioning into the liquid-crystalline phase of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine was most efficient. Fluorescence depth quenching and flip-flop assays suggest a perpendicular orientation of the conjugates to the membrane surface with negligible transversal diffusion, and that the fluorescent dyes reside in the interfacial area. The results serve as a basis to differentiate biomembranes by analyzing the Hyper-CEST signatures that are related to membrane fluidity, and pave the way for dissecting different contributions to the Hyper-CEST signal. KW - Biosensors KW - Fluorescence KW - FRET KW - Hyperpolarization KW - Lipids KW - Xenon PY - 2013 U6 - https://doi.org/10.1002/chem.201203773 SN - 0947-6539 SN - 1521-3765 VL - 19 IS - 9 SP - 3110 EP - 3118 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-28980 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sloniec, Jagoda A1 - Resch-Genger, Ute A1 - Hennig, Andreas T1 - Photophysics and release kinetics of enzyme-activatable optical probes based on H-dimerized fluorophores on self-immolative linkers N2 - A series of activatable optical probes for the model enzyme penicillin G amidase based on intramolecular formation of non-fluorescent H-dimer between two identical dyes were synthesized. The probes are based on a self-immolative linker, which allows positioning both dyes in close spatial proximity to ensure efficient quenching of probes with absorption and fluorescence emission in the near-infrared (NIR) range. A detailed photophysical investigation of the novel optical probes led to a revision of a previously anticipated quenching mechanism and revealed their potential for optimizing the performance of activatable probes based on H-dimer formation. A kinetic analysis indicated that the fluorescence progress curves can be used to qualitatively extract enzyme kinetic parameters. PY - 2013 U6 - https://doi.org/10.1021/jp409388b SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 117 IS - 46 SP - 14336 EP - 14344 PB - Soc. CY - Washington, DC AN - OPUS4-30053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Resch-Genger, Ute A1 - Behnke, Thomas A1 - Brehm, Robert A1 - Grabolle, Markus A1 - Hennig, Andreas A1 - Hoffmann, Angelika A1 - Hoffmann, Katrin A1 - Linck, Lena A1 - Lochmann, Cornelia A1 - Pauli, Jutta A1 - Spieles, Monika A1 - Würth, Christian T1 - Funktionelle Chromophor-Systeme, innovative Validierungskonzepte und rückführbare Standards für die fluoreszenzbasierte multiparametrische Bioanalytik N2 - Unter dem Motto „Innovation und Qualitätssicherung in der (Bio)Analytik“ werden in der Arbeitsgruppe Fluoreszenzspektroskopie der BAM, Bundesanstalt für Materialforschung und -prüfung, funktionelle Chromophor-Systeme, einfache Signalverstärkungs- und Multiplexingstrategien sowie innovative Validierungs- und rückführbare Standardisierungskonzepte für verschiedene fluorometrische Messgrößen und Methoden entwickelt. Im Mittelpunkt stehen dabei molekulare Fluorophore, Nanokristalle mit größenabhängigen optischen Eigenschaften (sogenannte Quantenpunkte, QDs) und fluoreszierende Partikel variabler Größe sowie Sonden und Sensormoleküle für neutrale und ionische Analyte und für die Charakterisierung von funktionellen Gruppen. Dabei erfolgen auch methodische Entwicklungen für die Fluoreszenzspektroskopie, die Fluoreszenzmikroskopie, die Milcrofluorometrie, die Sensorik und die Mikroarraytechnologie. Ziele sind u. a. das Design und die Untersuchung von multiplexfähigen selektiven und sensitiven Sonden für die Biomarkeranalytik, die Entwicklung von Methoden zur Charakterisierung der signalrelevanten Eigenschaften dieser Chromophor-Systeme und zur Charakterisierung von funktionellen Gruppen an Oberflächen und ihre Validierung sowie die Entwicklung und Bereitstellung von formatadaptierbaren, flexibel ersetzbaren Standards für die fluoreszenzbasierte Multiparameteranalytik. T2 - 5. Senftenberger Innovationsforum Multiparameteranalytik CY - Senftenberg, Deutschland DA - 10.03.2011 KW - Multiparametric KW - Multiplexing KW - Fluorescence KW - Nanoparticles KW - NIR dyes KW - Surface analysis KW - Quantum yield KW - Quantum dot KW - Lifetime PY - 2011 SP - 86 EP - 108 CY - Senftenberg AN - OPUS4-23635 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mizaikoff, B. A1 - Lämmerhofer, M. A1 - Broekaert, J.A.C. A1 - Popp, J. A1 - Lendl, B. A1 - Leopold, K. A1 - Scheller, F.W. A1 - Yarman, A. A1 - Schumacher, S. A1 - Plumeré, N. A1 - Hennig, Andreas A1 - Nau, W. A1 - Kranz, C. A1 - Einax, J.W. T1 - Trendbericht - Analytische Chemie 2010/2011 N2 - Mit Nanoporen detektieren elektrochemische Biosensoren einzelne Moleküle, Nanopartikel aus molekular geprägten Polymeren erkennen Proteine und Nukleinsäuren, und Nanostrukturen verstärken die Signale in der Ramanspektroskopie. Kleiner wurden auch die Säulenmaterialien für die Flüssigkeits- chromatographie: Partikeldurchmesser liegen unterhalb von 3 µm, Porendurchmesser im 10-nm- Bereich. Nano ist aber nur ein Thema der Forschung in der analytischen Chemie. Der Trendbericht stellt in diesem Jahr auch Rastersondenmethoden und ihre Kombinationen vor, leistungsstarke Lichtquellen und neue Methoden in der Schwingungsspektroskopie, Alternativen zum induktiv gekoppelten Plasma und Atomabsorptionsspektroskopie in der Routineanalytik sowie Anwendungen in der Chemometrik. PY - 2012 U6 - https://doi.org/10.1002/nadc.201290145 SN - 1439-9598 SN - 1521-3854 VL - 60 IS - 4 SP - 406 EP - 420 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-27695 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hennig, Andreas A1 - Hoffmann, Angelika A1 - Borcherding, H. A1 - Thiele, T. A1 - Schedler, U. A1 - Resch-Genger, Ute T1 - Simple colorimetric method for quantification of surface carboxy groups on polymer particles N2 - We present a novel, simple, and fast colorimetric method to quantify the total number of carboxy groups on polymer microparticle and nanoparticle surfaces. This method exploits that small divalent transition metal cations (M2+ = Ni2+, Co2+, Cd2+) are efficiently bound to these surface functional groups, which allows their extraction by a single centrifugation step. Remaining M2+ in the supernatant is subsequently quantified spectrophotometrically after addition of the metal ion indicator pyrocatechol violet, for which Ni2+ was identified to be the most suitable transition metal cation. We demonstrate that the difference between added and detected M2+ is nicely correlated to the number of surface carboxy groups as determined by conductometry, thereby affording a validated measure for the trueness of this procedure. The variation coefficient of ~5% found in reproducibility studies underlines the potential of this novel method that can find conceivable applications for the characterization of different types of poly(carboxylic acid)-functionalized materials, e.g., for quality control by manufacturers of such materials. KW - Polymer surface KW - Complexometry KW - Quantification KW - Pyrocatechol violet PY - 2011 U6 - https://doi.org/10.1021/ac2007619 SN - 0003-2700 SN - 1520-6882 VL - 83 IS - 12 SP - 4970 EP - 4974 PB - American Chemical Society CY - Washington, DC AN - OPUS4-23892 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hennig, Andreas A1 - Hoffmann, Angelika A1 - Borcherding, H. A1 - Thiele, T. A1 - Schedler, U. A1 - Resch-Genger, Ute T1 - Quantification of surface functional groups on polymer microspheres by supramolecular host-guest interactions N2 - We introduce a method to determine the number of accessible functional groups on a polymer microsphere surface based on the interaction between the macrocyclic host cucurbit[7]uril (CB7) and a guest reacted to the microsphere surface. After centrifugation, CB7 in the supernatant is quantified by addition of a fluorescent dye. The difference between added and detected CB7 affords the number of accessible surface functional groups. KW - Cucurbituril KW - Acridine orange KW - Fluorescence KW - Polymer surface KW - Surface modification KW - Quantification PY - 2011 U6 - https://doi.org/10.1039/c1cc11692d SN - 0022-4936 SN - 0009-241x SN - 1359-7345 SN - 1364-548x VL - 47 IS - 27 SP - 7842 EP - 7844 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-24034 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hennig, Andreas A1 - Hatami, Soheil A1 - Spieles, Monika A1 - Resch-Genger, Ute T1 - Excitation energy migration and trapping on the surface of fluorescent poly(acrylic acid)-grafted polymer particles N2 - The surface of poly(methyl methacrylate) particles with different amounts of a grafted layer of poly(acrylic acid) was labeled with varying degrees of an amino derivative of fluorescein isothiocyanate. The resulting fluorescent polymer particles were analyzed by absorption spectroscopy and by steady-state and time-resolved fluorescence spectroscopy including measurements of the fluorescence anisotropy. The combined results indicate that the overall decrease in fluorescence intensity with increasing surface concentrations of the fluorophore can be traced back to the formation of non-fluorescent aggregates. A mechanism is proposed, in which the excitation energy migrates between identical fluorophores until it is transferred to non-fluorescent aggregates acting as an energy trap. Increases in the surface fluorophore concentration increase both the probability for energy transfer between identical fluorophores and the probability for energy transfer to non-fluorescent aggregates. Furthermore, we suggest that this mechanism also applies to fluorescent protein conjugates and rationalizes the nonlinear dependence of the fluorescence emission on the labeling density. PY - 2013 U6 - https://doi.org/10.1039/c2pp25364j SN - 1474-905X SN - 1474-9092 VL - 12 IS - 5 SP - 729 EP - 737 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-28522 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hennig, Andreas A1 - Dietrich, Paul A1 - Hemmann, Felix A1 - Thiele, T. A1 - Borcherding, H. A1 - Hoffmann, Angelika A1 - Schedler, U. A1 - Jäger, Christian A1 - Resch-Genger, Ute A1 - Unger, Wolfgang T1 - En route to traceable reference standards for surface group quantifications by XPS, NMR and fluorescence spectroscopy N2 - The fluorine content of polymer particles labelled with 2,2,2-trifluoroethylamine was reliably quantified with overlapping sensitivity ranges by XPS and solid-state NMR. This provides a first step towards reference materials for the metrological traceability of surface group quantifications. The extension of this concept to fluorescence spectroscopy is illustrated. KW - Polymer beads KW - Poly(acrylic acid)-grafted particles KW - XPS KW - SEM KW - Surface analysis KW - Fluorescent dye labeling KW - NMR PY - 2015 U6 - https://doi.org/10.1039/c4an02248c SN - 0003-2654 SN - 1364-5528 VL - 140 IS - 6 SP - 1804 EP - 1808 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-32794 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hennig, Andreas A1 - Borcherding, H. A1 - Jäger, Christian A1 - Hatami, Soheil A1 - Würth, Christian A1 - Hoffmann, Angelika A1 - Hoffmann, Katrin A1 - Thiele, T. A1 - Schedler, U. A1 - Resch-Genger, Ute T1 - Scope and limitations of surface functional quantification methods: exploratory study with poly(acrylic acid)-grafted micro- and nanoparticles N2 - The amount of grafted poly(acrylic acid) on poly(methyl methacrylate) micro- and nanoparticles was quantified by conductometry, 13C solid-state NMR, fluorophore labeling, a supramolecular assay based on high-affinity binding of cucurbit[7]uril, and two colorimetric assays based on toluidine blue and nickel complexation by pyrocatechol violet. The methods were thoroughly validated and compared with respect to reproducibility, sensitivity, and ease of use. The results demonstrate that only a small but constant fraction of the surface functional groups is accessible to covalent surface derivatization independently of the total number of surface functional groups, and different contributing factors are discussed that determine the number of probe molecules which can be bound to the polymer surface. The fluorophore labeling approach was modified to exclude artifacts due to fluorescence quenching, but absolute quantum yield measurements still indicate a major uncertainty in routine fluorescence-based surface group quantifications, which is directly relevant for biochemical assays and medical diagnostics. Comparison with results from protein labeling with streptavidin suggests a porous network of poly(acrylic acid) chains on the particle surface, which allows diffusion of small molecules (cutoff between 1.6 and 6.5 nm) into the network. KW - Polymers KW - Surface groups KW - Quantification KW - Fluorescence PY - 2012 U6 - https://doi.org/10.1021/ja302649g SN - 0002-7863 SN - 1520-5126 VL - 134 IS - 19 SP - 8268 EP - 8276 PB - American Chemical Society CY - Washington, DC AN - OPUS4-26002 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -