1
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Scholtz L, Eckert JG, Graf RT, Kunst A, Wegner KD, Bigall NC, Resch-Genger U. Correlating semiconductor nanoparticle architecture and applicability for the controlled encoding of luminescent polymer microparticles. Sci Rep 2024; 14:11904. [PMID: 38789603 PMCID: PMC11126414 DOI: 10.1038/s41598-024-62591-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 05/20/2024] [Indexed: 05/26/2024] Open
Abstract
Luminophore stained micro- and nanobeads made from organic polymers like polystyrene (PS) are broadly used in the life and material sciences as luminescent reporters, for bead-based assays, sensor arrays, printable barcodes, security inks, and the calibration of fluorescence microscopes and flow cytometers. Initially mostly prepared with organic dyes, meanwhile luminescent core/shell nanoparticles (NPs) like spherical semiconductor quantum dots (QDs) are increasingly employed for bead encoding. This is related to their narrower emission spectra, tuneability of emission color, broad wavelength excitability, and better photostability. However, correlations between particle architecture, morphology, and photoluminescence (PL) of the luminescent nanocrystals used for encoding and the optical properties of the NP-stained beads have been rarely explored. This encouraged us to perform a screening study on the incorporation of different types of luminescent core/shell semiconductor nanocrystals into polymer microparticles (PMPs) by a radical-induced polymerization reaction. Nanocrystals explored include CdSe/CdS QDs of varying CdS shell thickness, a CdSe/ZnS core/shell QD, CdSe/CdS quantum rods (QRs), and CdSe/CdS nanoplatelets (NPLs). Thereby, we focused on the applicability of these NPs for the polymerization synthesis approach used and quantified the preservation of the initial NP luminescence. The spectroscopic characterization of the resulting PMPs revealed the successful staining of the PMPs with luminescent CdSe/CdS QDs and CdSe/CdS NPLs. In contrast, usage of CdSe/CdS QRs and CdSe QDs with a ZnS shell did not yield luminescent PMPs. The results of this study provide new insights into structure-property relationships between NP stained PMPs and the initial luminescent NPs applied for staining and underline the importance of such studies for the performance optimization of NP-stained beads.
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Affiliation(s)
- Lena Scholtz
- Federal Institute for Materials Research and Testing (BAM), Division 1.2 Biophotonics, Richard-Willstätter-Str. 11, 12489, Berlin, Germany
- Institute for Chemistry and Biochemistry, Free University Berlin, Takustraße 3, 14195, Berlin, Germany
| | - J Gerrit Eckert
- Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstraße 3A, 30167, Hannover, Germany
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering - Innovation Across Disciplines), 30167, Hannover, Germany
| | - Rebecca T Graf
- Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstraße 3A, 30167, Hannover, Germany
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering - Innovation Across Disciplines), 30167, Hannover, Germany
- Laboratory of Nano- and Quantum Engineering, Leibniz University Hannover, Schneiderberg 39, 30167, Hanover, Germany
| | - Alexandra Kunst
- Federal Institute for Materials Research and Testing (BAM), Division 1.2 Biophotonics, Richard-Willstätter-Str. 11, 12489, Berlin, Germany
- Institute for Chemistry and Biochemistry, Free University Berlin, Takustraße 3, 14195, Berlin, Germany
| | - K David Wegner
- Federal Institute for Materials Research and Testing (BAM), Division 1.2 Biophotonics, Richard-Willstätter-Str. 11, 12489, Berlin, Germany
| | - Nadja C Bigall
- Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstraße 3A, 30167, Hannover, Germany
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering - Innovation Across Disciplines), 30167, Hannover, Germany
- Laboratory of Nano- and Quantum Engineering, Leibniz University Hannover, Schneiderberg 39, 30167, Hanover, Germany
- Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany
| | - Ute Resch-Genger
- Federal Institute for Materials Research and Testing (BAM), Division 1.2 Biophotonics, Richard-Willstätter-Str. 11, 12489, Berlin, Germany.
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2
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Geißler D, Wegner KD, Fischer C, Resch-Genger U. Exploring Simple Particle-Based Signal Amplification Strategies in a Heterogeneous Sandwich Immunoassay with Optical Detection. Anal Chem 2024; 96:5078-5085. [PMID: 38498677 PMCID: PMC10993196 DOI: 10.1021/acs.analchem.3c03691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 02/28/2024] [Accepted: 02/28/2024] [Indexed: 03/20/2024]
Abstract
Heterogeneous sandwich immunoassays are widely used for biomarker detection in bioanalysis and medical diagnostics. The high analyte sensitivity of the current "gold standard" enzyme-linked immunosorbent assay (ELISA) originates from the signal-generating enzymatic amplification step, yielding a high number of optically detectable reporter molecules. For future point-of-care testing (POCT) and point-of-need applications, there is an increasing interest in more simple detection strategies that circumvent time-consuming and temperature-dependent enzymatic reactions. A common concept to aim for detection limits comparable to those of enzymatic amplification reactions is the usage of polymer nanoparticles (NP) stained with a large number of chromophores. We explored different simple NP-based signal amplification strategies for heterogeneous sandwich immunoassays that rely on an extraction-triggered release step of different types of optically detectable reporters. Therefore, streptavidin-functionalized polystyrene particles (PSP) are utilized as carriers for (i) the fluorescent dye coumarin 153 (C153) and (ii) hemin (hem) molecules catalyzing the luminol reaction enabling chemiluminescence (CL) detection. Additionally, (iii) NP labeling with hemin-based microperoxidase MP11 was assessed. For each amplification approach, the PSP was first systematically optimized regarding size, loading concentration, and surface chemistry. Then, for an immunoassay for the inflammation marker C-reactive protein (CRP), the analyte sensitivity achievable with optimized PSP systems was compared with the established ELISA concept for photometric and CL detection. Careful optimization led to a limit of detection (LOD) of 0.1 ng/mL for MP11-labeled PSP and CL detection, performing similarly well to a photometric ELISA (0.13 ng/mL), which demonstrates the huge potential of our novel assay concept.
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Affiliation(s)
| | | | | | - Ute Resch-Genger
- Division Biophotonics, Federal Institute for Materials Research and Testing
(BAM), Richard-Willstaetter-Str. 11, 12489 Berlin, Germany
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3
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Scholtz L, Tavernaro I, Eckert JG, Lutowski M, Geißler D, Hertwig A, Hidde G, Bigall NC, Resch-Genger U. Influence of nanoparticle encapsulation and encoding on the surface chemistry of polymer carrier beads. Sci Rep 2023; 13:11957. [PMID: 37488159 PMCID: PMC10366211 DOI: 10.1038/s41598-023-38518-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 07/10/2023] [Indexed: 07/26/2023] Open
Abstract
Surface-functionalized polymer beads encoded with molecular luminophores and nanocrystalline emitters such as semiconductor nanocrystals, often referred to as quantum dots (QDs), or magnetic nanoparticles are broadly used in the life sciences as reporters and carrier beads. Many of these applications require a profound knowledge of the chemical nature and total number of their surface functional groups (FGs), that control bead charge, colloidal stability, hydrophobicity, and the interaction with the environment and biological systems. For bioanalytical applications, also the number of groups accessible for the subsequent functionalization with, e.g., biomolecules or targeting ligands is relevant. In this study, we explore the influence of QD encoding on the amount of carboxylic acid (COOH) surface FGs of 2 µm polystyrene microparticles (PSMPs). This is done for frequently employed oleic acid and oleylamine stabilized, luminescent core/shell CdSe QDs and two commonly used encoding procedures. This included QD addition during bead formation by a thermally induced polymerization reaction and a post synthetic swelling procedure. The accessible number of COOH groups on the surface of QD-encoded and pristine beads was quantified by two colorimetric assays, utilizing differently sized reporters and electrostatic and covalent interactions. The results were compared to the total number of FGs obtained by a conductometric titration and Fourier transform infrared spectroscopy (FTIR). In addition, a comparison of the impact of QD and dye encoding on the bead surface chemistry was performed. Our results demonstrate the influence of QD encoding and the QD-encoding strategy on the number of surface FG that is ascribed to an interaction of the QDs with the carboxylic acid groups on the bead surface. These findings are of considerable relevance for applications of nanoparticle-encoded beads and safe-by-design concepts for nanomaterials.
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Affiliation(s)
- Lena Scholtz
- Division 1.2 Biophotonics, Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, 12489, Berlin, Germany
- Institute for Chemistry and Biochemistry, Free University Berlin, Takustraße 3, 14195, Berlin, Germany
| | - Isabella Tavernaro
- Division 1.2 Biophotonics, Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, 12489, Berlin, Germany
| | - J Gerrit Eckert
- Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstraße 3A, 30167, Hannover, Germany
| | - Marc Lutowski
- Division 1.2 Biophotonics, Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, 12489, Berlin, Germany
| | - Daniel Geißler
- Division 1.2 Biophotonics, Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, 12489, Berlin, Germany
- PolyAn GmbH, Schkopauer Ring 6, 12681, Berlin, Germany
| | - Andreas Hertwig
- Division 6.1 Surface Analysis and Interfacial Chemistry, Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205, Berlin, Germany
| | - Gundula Hidde
- Division 6.1 Surface Analysis and Interfacial Chemistry, Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205, Berlin, Germany
| | - Nadja C Bigall
- Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstraße 3A, 30167, Hannover, Germany
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering - Innovation Across Disciplines), 30167, Hannover, Germany
| | - Ute Resch-Genger
- Division 1.2 Biophotonics, Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, 12489, Berlin, Germany.
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4
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Würth C, Behnke T, Gienger J, Resch-Genger U. Efficiency scale for scattering luminescent particles linked to fundamental and measurable spectroscopic properties. Sci Rep 2023; 13:6254. [PMID: 37069220 PMCID: PMC10110600 DOI: 10.1038/s41598-023-32933-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 04/04/2023] [Indexed: 04/19/2023] Open
Abstract
Comparing the performance of molecular and nanoscale luminophores and luminescent micro- and nanoparticles and estimating achievable signal amplitudes and limits of detection requires a standardizable intensity scale. This initiated the development of the relative MESF (number of molecules of equivalent soluble fluorochromes) and ERF (equivalent reference fluorophores) scales for flow cytometry and fluorescence microscopy. Both intensity scales rely on fluorescence intensity values assigned to fluorescent calibration beads by an intensity comparison to spectrally closely matching fluorophore solutions of known concentration using a spectrofluorometer. Alternatively, the luminophore or bead brightness (B) can be determined that equals the product of the absorption cross section (σa) at the excitation wavelength (σa(λex)) and the photoluminescence quantum yield (Φpl). Thereby, an absolute scale based on fundamental and measurable spectroscopic properties can be realized which is independent of particle size, material, and luminophore staining or labeling density and considers the sensitivity of the optical properties of luminophores to their environment. Aiming for establishing such a brightness scale for light-scattering dispersions of luminescent particles with sizes exceeding a few ten nanometers, we demonstrate how the brightness of quasi-monodisperse 25 nm, 100 nm, and 1 µm sized polystyrene particles (PSP), loaded with two different dyes in varying concentrations, can be obtained with a single custom-designed integrating sphere setup that enables the absolute determination of Φpl and transmittance and diffuse reflectance measurements. The resulting Φpl, σa(λex), imaginary parts of the refractive index, and calculated B values of these samples are given in dependence of the number of incorporated dye molecule per particle. Finally, a unitless luminescence efficiency (LE) is defined allowing for the direct comparison of luminescence efficiencies of particles with different sizes.
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Affiliation(s)
- Christian Würth
- Division Biophotonics, Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstaetter Str. 11, 12489, Berlin, Germany.
| | - Thomas Behnke
- Division Biophotonics, Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstaetter Str. 11, 12489, Berlin, Germany
| | - Jonas Gienger
- Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
| | - Ute Resch-Genger
- Division Biophotonics, Bundesanstalt für Materialforschung und -prüfung (BAM), Richard-Willstaetter Str. 11, 12489, Berlin, Germany.
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5
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Luminescence encoding of polymer microbeads with organic dyes and semiconductor quantum dots during polymerization. Sci Rep 2022; 12:12061. [PMID: 35835808 PMCID: PMC9283474 DOI: 10.1038/s41598-022-16065-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 07/04/2022] [Indexed: 01/15/2023] Open
Abstract
Luminescence-encoded microbeads are important tools for many applications in the life and material sciences that utilize luminescence detection as well as multiplexing and barcoding strategies. The preparation of such beads often involves the staining of premanufactured beads with molecular luminophores using simple swelling procedures or surface functionalization with layer-by-layer (LbL) techniques. Alternatively, these luminophores are sterically incorporated during the polymerization reaction yielding the polymer beads. The favorable optical properties of semiconductor quantum dots (QDs), which present broadly excitable, size-tunable, narrow emission bands and low photobleaching sensitivity, triggered the preparation of beads stained with QDs. However, the colloidal nature and the surface chemistry of these QDs, which largely controls their luminescence properties, introduce new challenges to bead encoding that have been barely systematically assessed. To establish a straightforward approach for the bead encoding with QDs with minimized loss in luminescence, we systematically assessed the incorporation of oleic acid/oleylamine-stabilized CdSe/CdS-core/shell-QDs into 0.5-2.5 µm-sized polystyrene (PS) microspheres by a simple dispersion polymerization synthesis that was first optimized with the organic dye Nile Red. Parameters addressed for the preparation of luminophore-encoded beads include the use of a polymer-compatible ligand such as benzyldimethyloctadecylammonium chloride (OBDAC) for the QDs, and crosslinking to prevent luminophore leakage. The physico-chemical and optical properties of the resulting beads were investigated with electron microscopy, dynamic light scattering, optical spectroscopy, and fluorescence microscopy. Particle size distribution, fluorescence quantum yield of the encapsulated QDs, and QD leaking stability were used as measures for bead quality. The derived optimized bead encoding procedure enables the reproducible preparation of bright PS microbeads encoded with organic dyes as well as with CdSe/CdS-QDs. Although these beads show a reduced photoluminescence quantum yield compared to the initially very strongly luminescent QDs, with values of about 35%, their photoluminescence quantum yield is nevertheless still moderate.
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6
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Geißler D, Nirmalananthan-Budau N, Scholtz L, Tavernaro I, Resch-Genger U. Analyzing the surface of functional nanomaterials-how to quantify the total and derivatizable number of functional groups and ligands. Mikrochim Acta 2021; 188:321. [PMID: 34482449 PMCID: PMC8418596 DOI: 10.1007/s00604-021-04960-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 08/08/2021] [Indexed: 12/04/2022]
Abstract
Functional nanomaterials (NM) of different size, shape, chemical composition, and surface chemistry are of increasing relevance for many key technologies of the twenty-first century. This includes polymer and silica or silica-coated nanoparticles (NP) with covalently bound surface groups, semiconductor quantum dots (QD), metal and metal oxide NP, and lanthanide-based NP with coordinatively or electrostatically bound ligands, as well as surface-coated nanostructures like micellar encapsulated NP. The surface chemistry can significantly affect the physicochemical properties of NM, their charge, their processability and performance, as well as their impact on human health and the environment. Thus, analytical methods for the characterization of NM surface chemistry regarding chemical identification, quantification, and accessibility of functional groups (FG) and surface ligands bearing such FG are of increasing importance for quality control of NM synthesis up to nanosafety. Here, we provide an overview of analytical methods for FG analysis and quantification with special emphasis on bioanalytically relevant FG broadly utilized for the covalent attachment of biomolecules like proteins, peptides, and oligonucleotides and address method- and material-related challenges and limitations. Analytical techniques reviewed include electrochemical titration methods, optical assays, nuclear magnetic resonance and vibrational spectroscopy, as well as X-ray based and thermal analysis methods, covering the last 5-10 years. Criteria for method classification and evaluation include the need for a signal-generating label, provision of either the total or derivatizable number of FG, need for expensive instrumentation, and suitability for process and production control during NM synthesis and functionalization.
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Affiliation(s)
- Daniel Geißler
- Bundesanstalt für Materialforschung und -prüfung (BAM), Division Biophotonics (BAM-1.2), Richard-Willstätter-Str. 11, 12489, Berlin, Germany
| | - Nithiya Nirmalananthan-Budau
- Bundesanstalt für Materialforschung und -prüfung (BAM), Division Biophotonics (BAM-1.2), Richard-Willstätter-Str. 11, 12489, Berlin, Germany
| | - Lena Scholtz
- Bundesanstalt für Materialforschung und -prüfung (BAM), Division Biophotonics (BAM-1.2), Richard-Willstätter-Str. 11, 12489, Berlin, Germany
| | - Isabella Tavernaro
- Bundesanstalt für Materialforschung und -prüfung (BAM), Division Biophotonics (BAM-1.2), Richard-Willstätter-Str. 11, 12489, Berlin, Germany
| | - Ute Resch-Genger
- Bundesanstalt für Materialforschung und -prüfung (BAM), Division Biophotonics (BAM-1.2), Richard-Willstätter-Str. 11, 12489, Berlin, Germany.
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7
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Nirmalananthan-Budau N, Rühle B, Geißler D, Moser M, Kläber C, Schäfer A, Resch-Genger U. Multimodal Cleavable Reporters for Quantifying Carboxy and Amino Groups on Organic and Inorganic Nanoparticles. Sci Rep 2019; 9:17577. [PMID: 31772213 PMCID: PMC6879591 DOI: 10.1038/s41598-019-53773-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/25/2019] [Indexed: 02/06/2023] Open
Abstract
Organic and inorganic nanoparticles (NPs) are increasingly used as drug carriers, fluorescent sensors, and multimodal labels in the life and material sciences. These applications require knowledge of the chemical nature, total number of surface groups, and the number of groups accessible for subsequent coupling of e.g., antifouling ligands, targeting bioligands, or sensor molecules. To establish the concept of catch-and-release assays, cleavable probes were rationally designed from a quantitatively cleavable disulfide moiety and the optically detectable reporter 2-thiopyridone (2-TP). For quantifying surface groups on nanomaterials, first, a set of monodisperse carboxy-and amino-functionalized, 100 nm-sized polymer and silica NPs with different surface group densities was synthesized. Subsequently, the accessible functional groups (FGs) were quantified via optical spectroscopy of the cleaved off reporter after its release in solution. Method validation was done with inductively coupled plasma optical emission spectroscopy (ICP-OES) utilizing the sulfur atom of the cleavable probe. This comparison underlined the reliability and versatility of our probes, which can be used for surface group quantification on all types of transparent, scattering, absorbing and/or fluorescent particles. The correlation between the total and accessible number of FGs quantified by conductometric titration, qNMR, and with our cleavable probes, together with the comparison to results of conjugation studies with differently sized biomolecules reveal the potential of catch-and-release reporters for surface analysis. Our findings also underline the importance of quantifying particularly the accessible amount of FGs for many applications of NPs in the life sciences.
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Affiliation(s)
- Nithiya Nirmalananthan-Budau
- Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, D-12489, Berlin, Germany
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195, Berlin, Germany
| | - Bastian Rühle
- Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, D-12489, Berlin, Germany
| | - Daniel Geißler
- Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, D-12489, Berlin, Germany
| | - Marko Moser
- Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, D-12489, Berlin, Germany
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195, Berlin, Germany
| | - Christopher Kläber
- Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, D-12489, Berlin, Germany
| | - Andreas Schäfer
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195, Berlin, Germany
| | - Ute Resch-Genger
- Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, D-12489, Berlin, Germany.
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8
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Roloff A, Nirmalananthan-Budau N, Rühle B, Borcherding H, Thiele T, Schedler U, Resch-Genger U. Quantification of Aldehydes on Polymeric Microbead Surfaces via Catch and Release of Reporter Chromophores. Anal Chem 2019; 91:8827-8834. [PMID: 31188569 DOI: 10.1021/acs.analchem.8b05515] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Aldehyde moieties on 2D-supports or micro- and nanoparticles can function as anchor groups for the attachment of biomolecules or as reversible binding sites for proteins on cell surfaces. The use of aldehyde-based materials in bioanalytical and medical settings calls for reliable methods to detect and quantify this functionality. We report here on a versatile concept to quantify the accessible aldehyde moieties on particle surfaces through the specific binding and subsequent release of small reporter molecules such as fluorescent dyes and nonfluorescent chromophores utilizing acylhydrazone formation as a reversible covalent labeling strategy. This is representatively demonstrated for a set of polymer microparticles with different aldehyde labeling densities. Excess reporter molecules can be easily removed by washing, eliminating inaccuracies caused by unspecific adsorption to hydrophobic surfaces. Cleavage of hydrazones at acidic pH assisted by a carbonyl trap releases the fluorescent reporters rapidly and quasi-quantitatively and allows for their fluorometric detection at low concentration. Importantly, this strategy separates the signal-generating molecules from the bead surface. This circumvents common issues associated with light scattering and signal distortions that are caused by binding-induced changes in reporter fluorescence as well as quenching dye-dye interactions on crowded particle surfaces. In addition, we demonstrate that the release of a nonfluorescent chromophore via disulfide cleavage and subsequent quantification by absorption spectroscopy gives comparable results, verifying that both assays are capable of rapid and sensitive quantification of aldehydes on microbead surfaces. These strategies enable a quantitative comparison of bead batches with different functionalization densities, and a qualitative prediction of their coupling efficiencies in bioconjugations, as demonstrated in reductive amination reactions with Streptavidin.
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Affiliation(s)
- Alexander Roloff
- Federal Institute for Materials Research and Testing (BAM) , Richard-Willstätter-Straße 11 , D-12489 Berlin , Germany
| | - Nithiya Nirmalananthan-Budau
- Federal Institute for Materials Research and Testing (BAM) , Richard-Willstätter-Straße 11 , D-12489 Berlin , Germany.,Institut für Chemie und Biochemie , Freie Universität Berlin , Takustrasse 3 , D-14195 Berlin , Germany
| | - Bastian Rühle
- Federal Institute for Materials Research and Testing (BAM) , Richard-Willstätter-Straße 11 , D-12489 Berlin , Germany
| | | | - Thomas Thiele
- PolyAn GmbH , Rudolf-Baschant-Straße 2 , D-13086 Berlin , Germany
| | - Uwe Schedler
- PolyAn GmbH , Rudolf-Baschant-Straße 2 , D-13086 Berlin , Germany
| | - Ute Resch-Genger
- Federal Institute for Materials Research and Testing (BAM) , Richard-Willstätter-Straße 11 , D-12489 Berlin , Germany
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9
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Sun Y, Kunc F, Balhara V, Coleman B, Kodra O, Raza M, Chen M, Brinkmann A, Lopinski GP, Johnston LJ. Quantification of amine functional groups on silica nanoparticles: a multi-method approach. NANOSCALE ADVANCES 2019; 1:1598-1607. [PMID: 36132607 PMCID: PMC9417554 DOI: 10.1039/c9na00016j] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 02/21/2019] [Indexed: 05/08/2023]
Abstract
Surface chemistry is an important factor for quality control during production of nanomaterials and for controlling their behavior in applications and when released into the environment. Here we report a comparison of four methods for quantifying amine functional groups on silica nanoparticles (NPs). Two colorimetric assays are examined, ninhydrin and 4-nitrobenzaldehyde, which are convenient for routine analysis and report on reagent accessible amines. Results from the study of a range of commercial NPs with different sizes and surface loadings show that the assays account for 50-100% of the total amine content, as determined by dissolution of NPs under basic conditions and quantification by solution-state 1H NMR. To validate the surface quantification by the colorimetric assays, the NPs are modified with a trifluoromethylated benzaldehyde probe to enhance sensitivity for quantitative 19F solid state NMR and X-ray photoelectron spectroscopy (XPS). Good agreement between the assays and the determination from solid-state NMR is reinforced by elemental ratios from XPS, which indicate that in most cases the difference between total and accessible amine content reflects amines that are outside the depth probed by XPS. Overall the combined results serve to validate the relatively simple colorimetric assays and indicate that the reactions are efficient at quantifying surface amines, by contrast to some other covalent modifications that have been employed for functional group quantification.
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Affiliation(s)
- Ying Sun
- National Research Council Canada Ottawa ON Canada K1A 0R6
| | - Filip Kunc
- National Research Council Canada Ottawa ON Canada K1A 0R6
| | - Vinod Balhara
- National Research Council Canada Ottawa ON Canada K1A 0R6
| | - Brian Coleman
- National Research Council Canada Ottawa ON Canada K1A 0R6
| | - Oltion Kodra
- National Research Council Canada Ottawa ON Canada K1A 0R6
| | - Mohammad Raza
- National Research Council Canada Ottawa ON Canada K1A 0R6
| | - Maohui Chen
- National Research Council Canada Ottawa ON Canada K1A 0R6
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10
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Martinić I, Eliseeva SV, Collet G, Luo TY, Rosi N, Petoud S. One Approach for Two: Toward the Creation of Near-Infrared Imaging Agents and Rapid Screening of Lanthanide(III) Ion Sensitizers Using Polystyrene Nanobeads. ACS APPLIED BIO MATERIALS 2019; 2:1667-1675. [DOI: 10.1021/acsabm.9b00053] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ivana Martinić
- Centre de Biophysique Moléculaire CNRS UPR4301, Rue Charles Sadron, 45071 Orléans, France
| | - Svetlana V. Eliseeva
- Centre de Biophysique Moléculaire CNRS UPR4301, Rue Charles Sadron, 45071 Orléans, France
| | - Guillaume Collet
- Centre de Biophysique Moléculaire CNRS UPR4301, Rue Charles Sadron, 45071 Orléans, France
| | - Tian-Yi Luo
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Nathaniel Rosi
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Stéphane Petoud
- Centre de Biophysique Moléculaire CNRS UPR4301, Rue Charles Sadron, 45071 Orléans, France
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11
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Kunc F, Balhara V, Brinkmann A, Sun Y, Leek DM, Johnston LJ. Quantification and Stability Determination of Surface Amine Groups on Silica Nanoparticles Using Solution NMR. Anal Chem 2018; 90:13322-13330. [DOI: 10.1021/acs.analchem.8b02803] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Filip Kunc
- National Research Council Canada, Metrology Research Centre, Ottawa, Ontario K1A 0R6, Canada
| | - Vinod Balhara
- National Research Council Canada, Metrology Research Centre, Ottawa, Ontario K1A 0R6, Canada
| | - Andreas Brinkmann
- National Research Council Canada, Metrology Research Centre, Ottawa, Ontario K1A 0R6, Canada
| | - Ying Sun
- National Research Council Canada, Metrology Research Centre, Ottawa, Ontario K1A 0R6, Canada
| | - Donald M. Leek
- National Research Council Canada, Metrology Research Centre, Ottawa, Ontario K1A 0R6, Canada
| | - Linda J. Johnston
- National Research Council Canada, Metrology Research Centre, Ottawa, Ontario K1A 0R6, Canada
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12
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Bouzas-Ramos D, Trapiella-Alfonso L, Pons K, Encinar JR, Costa-Fernández JM, Tsatsaris V, Gagey-Eilstein N. Controlling Ligand Surface Density on Streptavidin-Magnetic Particles by a Simple, Rapid, and Reliable Chemiluminescent Test. Bioconjug Chem 2018; 29:2646-2653. [DOI: 10.1021/acs.bioconjchem.8b00347] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Diego Bouzas-Ramos
- UMR 8638 CNRS, Université Paris Descartes, Faculté des Sciences Pharmaceutiques et Biologiques, Sorbonne Paris Cité. 4 avenue de l’observatoire, 75006 Paris, France
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Avda. Julián Clavería, 8, 33006 Oviedo, Spain
| | - Laura Trapiella-Alfonso
- UMR 8638 CNRS, Université Paris Descartes, Faculté des Sciences Pharmaceutiques et Biologiques, Sorbonne Paris Cité. 4 avenue de l’observatoire, 75006 Paris, France
- Cochin Hospital, Assistance Publique-Hôpital de Paris, DHU Risques et Grossesse, Paris Descartes University, INSERM UMR 1139, PremUP Foundation, 53 Avenue de l’Observatoire, 75014 Paris, France
| | - Kelly Pons
- UMR 8638 CNRS, Université Paris Descartes, Faculté des Sciences Pharmaceutiques et Biologiques, Sorbonne Paris Cité. 4 avenue de l’observatoire, 75006 Paris, France
- Cochin Hospital, Assistance Publique-Hôpital de Paris, DHU Risques et Grossesse, Paris Descartes University, INSERM UMR 1139, PremUP Foundation, 53 Avenue de l’Observatoire, 75014 Paris, France
| | - Jorge Ruiz Encinar
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Avda. Julián Clavería, 8, 33006 Oviedo, Spain
| | - José M. Costa-Fernández
- Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Avda. Julián Clavería, 8, 33006 Oviedo, Spain
| | - Vassilis Tsatsaris
- Cochin Hospital, Assistance Publique-Hôpital de Paris, DHU Risques et Grossesse, Paris Descartes University, INSERM UMR 1139, PremUP Foundation, 53 Avenue de l’Observatoire, 75014 Paris, France
| | - Nathalie Gagey-Eilstein
- UMR 8638 CNRS, Université Paris Descartes, Faculté des Sciences Pharmaceutiques et Biologiques, Sorbonne Paris Cité. 4 avenue de l’observatoire, 75006 Paris, France
- Cochin Hospital, Assistance Publique-Hôpital de Paris, DHU Risques et Grossesse, Paris Descartes University, INSERM UMR 1139, PremUP Foundation, 53 Avenue de l’Observatoire, 75014 Paris, France
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13
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Abstract
Upconverting nanoparticles (UCNPs) are inorganic crystalline nanomaterials that can convert near-infrared (NIR) excitation light into visible and ultraviolet emission light. Excitation with NIR light minimizes autofluorescence background and enables deeper penetration into biological samples due to reduced light scattering. Although these optical features make UCNPs promising candidates for bioanalytical and biomedical applications, the performance of UCNPs is compromised by their low optical brightness. Research in the field of UCNP technology focuses on strategies to boost upconversion luminescence brightness and efficiencies. In this Perspective, I discuss challenges associated with the use of UCNPs and provide a 10-year proposed strategic plan to enable translation of UCNP technology from the academic stage into real world products and applications.
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Affiliation(s)
- Stefan Wilhelm
- Stephenson School of Biomedical Engineering, University of Oklahoma , 101 David L. Boren Boulevard, Norman, Oklahoma 73072, United States
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14
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Resch-Genger U, Gorris HH. Perspectives and challenges of photon-upconversion nanoparticles - Part I: routes to brighter particles and quantitative spectroscopic studies. Anal Bioanal Chem 2017; 409:5855-5874. [DOI: 10.1007/s00216-017-0499-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/29/2017] [Accepted: 06/27/2017] [Indexed: 12/31/2022]
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15
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16
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Kantner K, Ashraf S, Carregal-Romero S, Carrillo-Carrion C, Collot M, Del Pino P, Heimbrodt W, De Aberasturi DJ, Kaiser U, Kazakova LI, Lelle M, de Baroja NM, Montenegro JM, Nazarenus M, Pelaz B, Peneva K, Gil PR, Sabir N, Schneider LM, Shabarchina LI, Sukhorukov GB, Vazquez M, Yang F, Parak WJ. Particle-based optical sensing of intracellular ions at the example of calcium - what are the experimental pitfalls? SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2015; 11:896-904. [PMID: 25504784 DOI: 10.1002/smll.201402110] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 09/24/2014] [Indexed: 06/04/2023]
Abstract
Colloidal particles with fluorescence read-out are commonly used as sensors for the quantitative determination of ions. Calcium, for example, is a biologically highly relevant ion in signaling, and thus knowledge of its spatio-temporal distribution inside cells would offer important experimental data. However, the use of particle-based intracellular sensors for ion detection is not straightforward. Important associated problems involve delivery and intracellular location of particle-based fluorophores, crosstalk of the fluorescence read-out with pH, and spectral overlap of the emission spectra of different fluorophores. These potential problems are outlined and discussed here with selected experimental examples. Potential solutions are discussed and form a guideline for particle-based intracellular imaging of ions.
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Affiliation(s)
- Karsten Kantner
- Fachbereich Physik, Philipps- Universität Marburg, Marburg, Germany
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17
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Hennig A, Dietrich PM, Hemmann F, Thiele T, Borcherding H, Hoffmann A, Schedler U, Jäger C, Resch-Genger U, Unger WES. En route to traceable reference standards for surface group quantifications by XPS, NMR and fluorescence spectroscopy. Analyst 2015; 140:1804-8. [DOI: 10.1039/c4an02248c] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A strategy is outlined, which will provide reference materials for surface functional group quantifications by XPS, NMR and fluorescence.
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Affiliation(s)
- Andreas Hennig
- BAM Federal Institute for Materials Research and Testing
- 12203 Berlin
- Germany
- Jacobs University Bremen
- School of Engineering and Science
| | - Paul M. Dietrich
- BAM Federal Institute for Materials Research and Testing
- 12203 Berlin
- Germany
| | - Felix Hemmann
- BAM Federal Institute for Materials Research and Testing
- 12203 Berlin
- Germany
| | | | | | - Angelika Hoffmann
- BAM Federal Institute for Materials Research and Testing
- 12203 Berlin
- Germany
| | | | - Christian Jäger
- BAM Federal Institute for Materials Research and Testing
- 12203 Berlin
- Germany
| | - Ute Resch-Genger
- BAM Federal Institute for Materials Research and Testing
- 12203 Berlin
- Germany
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18
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Würth C, Geißler D, Behnke T, Kaiser M, Resch-Genger U. Critical review of the determination of photoluminescence quantum yields of luminescent reporters. Anal Bioanal Chem 2014; 407:59-78. [DOI: 10.1007/s00216-014-8130-z] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/15/2014] [Accepted: 08/22/2014] [Indexed: 12/13/2022]
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19
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Rödiger S, Liebsch C, Schmidt C, Lehmann W, Resch-Genger U, Schedler U, Schierack P. Nucleic acid detection based on the use of microbeads: a review. Mikrochim Acta 2014. [DOI: 10.1007/s00604-014-1243-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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20
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Dai X, Wu QH, Wang PC, Tian J, Xu Y, Wang SQ, Miao JY, Zhao BX. A simple and effective coumarin-based fluorescent probe for cysteine. Biosens Bioelectron 2014; 59:35-9. [PMID: 24690559 DOI: 10.1016/j.bios.2014.03.018] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 03/05/2014] [Accepted: 03/06/2014] [Indexed: 01/01/2023]
Abstract
Acrylic acid 3-acetyl-2-oxo-2 H-chromen-7-yl ester (ACA) was rationally designed and synthesized as a simple and effective fluorescent probe for sensing cysteine with high selectivity and naked-eye detection. The probe can detect cysteine by fluorescence spectrometry with a detection limit of 0.657 μM and can be used with calf serum and in live cell imaging. The conjugate addition/cyclization sequence mechanism of the reaction between ACA and cysteine was confirmed by ESI-MS and fluorescence spectra.
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Affiliation(s)
- Xi Dai
- Institute of Organic Chemistry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P.R. China
| | - Qing-Hua Wu
- Institute of Developmental Biology, School of Life Science, Shandong University, Jinan 250100, P.R. China
| | - Peng-Chong Wang
- Institute of Developmental Biology, School of Life Science, Shandong University, Jinan 250100, P.R. China
| | - Jie Tian
- Institute of Organic Chemistry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P.R. China
| | - Yu Xu
- Institute of Organic Chemistry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P.R. China
| | - Sheng-Qing Wang
- Institute of Organic Chemistry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P.R. China
| | - Jun-Ying Miao
- Institute of Developmental Biology, School of Life Science, Shandong University, Jinan 250100, P.R. China.
| | - Bao-Xiang Zhao
- Institute of Organic Chemistry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P.R. China.
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21
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Resch-Genger U, Rurack K. Determination of the photoluminescence quantum yield of dilute dye solutions (IUPAC Technical Report). PURE APPL CHEM 2013. [DOI: 10.1351/pac-rep-12-03-03] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Procedures for the determination of photoluminescence quantum yields with optical
methods are addressed, and challenges associated with these measurements are
discussed. Special emphasis is dedicated to relative measurements of fluorescent
(i.e., short excited-state lifetime), transparent, dilute dye solutions in
conventional cuvettes in a 0°/90° measurement geometry.
Recommendations on the selection of suitable quantum yield standards are
presented, and requirements for the documentation of photoluminescence quantum
yields are derived.
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22
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Würth C, Grabolle M, Pauli J, Spieles M, Resch-Genger U. Relative and absolute determination of fluorescence quantum yields of transparent samples. Nat Protoc 2013; 8:1535-50. [DOI: 10.1038/nprot.2013.087] [Citation(s) in RCA: 670] [Impact Index Per Article: 60.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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23
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Hennig A, Hatami S, Spieles M, Resch-Genger U. Excitation energy migration and trapping on the surface of fluorescent poly(acrylic acid)-grafted polymer particles. Photochem Photobiol Sci 2013; 12:729-37. [DOI: 10.1039/c2pp25364j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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24
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Fleige E, Ziem B, Grabolle M, Haag R, Resch-Genger U. Aggregation Phenomena of Host and Guest upon the Loading of Dendritic Core-Multishell Nanoparticles with Solvatochromic Dyes. Macromolecules 2012. [DOI: 10.1021/ma301977r] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Emanuel Fleige
- Institut für Organische
Chemie und Biochemie, Freie Universität Berlin, Takustraße
3, 14195 Berlin, Germany
| | - Benjamin Ziem
- Institut für Organische
Chemie und Biochemie, Freie Universität Berlin, Takustraße
3, 14195 Berlin, Germany
| | - Markus Grabolle
- Division 1.10, BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Straße 11, 12489
Berlin, Germany
| | - Rainer Haag
- Institut für Organische
Chemie und Biochemie, Freie Universität Berlin, Takustraße
3, 14195 Berlin, Germany
| | - Ute Resch-Genger
- Division 1.10, BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Straße 11, 12489
Berlin, Germany
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25
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Behnke T, Mathejczyk JE, Brehm R, Würth C, Gomes FR, Dullin C, Napp J, Alves F, Resch-Genger U. Target-specific nanoparticles containing a broad band emissive NIR dye for the sensitive detection and characterization of tumor development. Biomaterials 2012; 34:160-70. [PMID: 23072943 DOI: 10.1016/j.biomaterials.2012.09.028] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 09/15/2012] [Indexed: 02/08/2023]
Abstract
Current optical probes including engineered nanoparticles (NPs) are constructed from near infrared (NIR)-emissive organic dyes with narrow absorption and emission bands and small Stokes shifts prone to aggregation-induced self-quenching. Here, we present the new asymmetric cyanine Itrybe with broad, almost environment-insensitive absorption and emission bands in the diagnostic window, offering a unique flexibility of the choice of excitation and detection wavelengths compared to common NIR dyes. This strongly emissive dye was spectroscopically studied in different solvents and encapsulated into differently sized (15, 25, 100 nm) amino-modified polystyrene NPs (PSNPs) via a one-step staining procedure. As proof-of-concept for its potential for pre-/clinical imaging applications, Itrybe-loaded NPs were surface-functionalized with polyethylene glycol (PEG) and the tumor-targeting antibody Herceptin and their binding specificity to the tumor-specific biomarker HER2 was systematically assessed. Itrybe-loaded NPs display strong fluorescence signals in vitro and in vivo and Herceptin-conjugated NPs bind specifically to HER2 as demonstrated in immunoassays as well as on tumor cells and sections from mouse tumor xenografts in vitro. This demonstrates that our design strategy exploiting broad band-absorbing and -emitting dyes yields versatile and bright NIR probes with a high potential for e.g. the sensitive detection and characterization of tumor development and progression.
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Affiliation(s)
- Thomas Behnke
- BAM Federal Institute for Materials Research and Testing, 1.10, Richard-Willstätter-Str. 11, 12489 Berlin, Germany
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26
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Hennig A, Borcherding H, Jaeger C, Hatami S, Würth C, Hoffmann A, Hoffmann K, Thiele T, Schedler U, Resch-Genger U. Scope and Limitations of Surface Functional Group Quantification Methods: Exploratory Study with Poly(acrylic acid)-Grafted Micro- and Nanoparticles. J Am Chem Soc 2012; 134:8268-76. [DOI: 10.1021/ja302649g] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Andreas Hennig
- BAM Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse
11, D-12489 Berlin, Germany
| | | | - Christian Jaeger
- BAM Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse
11, D-12489 Berlin, Germany
| | - Soheil Hatami
- BAM Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse
11, D-12489 Berlin, Germany
| | - Christian Würth
- BAM Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse
11, D-12489 Berlin, Germany
| | - Angelika Hoffmann
- BAM Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse
11, D-12489 Berlin, Germany
| | - Katrin Hoffmann
- BAM Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse
11, D-12489 Berlin, Germany
| | - Thomas Thiele
- PolyAn GmbH, Rudolf-Baschant-Strasse 2,
D-13086 Berlin, Germany
| | - Uwe Schedler
- PolyAn GmbH, Rudolf-Baschant-Strasse 2,
D-13086 Berlin, Germany
| | - Ute Resch-Genger
- BAM Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse
11, D-12489 Berlin, Germany
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