Person:
Gerke, Christoph

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First Name
Christoph
Last Name
Gerke
URI
https://hdl.handle.net/20.500.14352/87045
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Farmacia
Department
Química en Ciencias Farmacéuticas
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2020 - 20223
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Item Type: Publication × Subject: 539.2:620.1 ×

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Now showing 1 - 3 of 3
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    Upconverting Nanoparticles in Aqueous Media: Not a Dead-End Road. Avoiding Degradation by Using Hydrophobic Polymer Shells
    (Small, 2021) Méndez González, Diego; Torres Vera, Vivian Andrea; Zabala Gutiérrez, Irene; Gerke, Christoph; Cascales Sedano, Concepción; Rubio Retama, Jorge; Gómez Calderón, Óscar; Melle Hernández, Sonia; Laurenti, Marco
    The stunning optical properties of upconverting nanoparticles (UCNPs) have inspired promising biomedical technologies. Nevertheless, their transfer to aqueous media is often accompanied by intense luminescence quenching, partial dissolution by water, and even complete degradation by molecules such as phosphates. Currently, these are major issues hampering the translation of UCNPs to the clinic. In this work, a strategy is developed to coat and protect β-NaYF4 UCNPs against these effects, by growing a hydrophobic polymer shell (HPS) through miniemulsion polymerization of styrene (St), or St and methyl methacrylate mixtures. This allows one to obtain single core@shell UCNPs@HPS with a final diameter of ≈60–70 nm. Stability studies reveal that these HPSs serve as a very effective barrier, impeding polar molecules to affect UCNPs optical properties. Even more, it allows UCNPs to withstand aggressive conditions such as high dilutions (5 μg mL−1), high phosphate concentrations (100 mm), and high temperatures (70 °C). The physicochemical characterizations prove the potential of HPSs to overcome the current limitations of UCNPs. This strategy, which can be applied to other nanomaterials with similar limitations, paves the way toward more stable and reliable UCNPs with applications in life sciences.
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    Boosting the Near-Infrared Emission of Ag2S Nanoparticles by a Controllable Surface Treatment for Bioimaging Applications
    (ACS Applied Materials & Interfaces, 2022) Zabala Gutiérrez, Irene; Gerke, Christoph; Shen, Yingli; Ximendes, Erving Clayton; Manso Silvan, Miguel; Marin, Riccardo; Jaque García, Daniel; Gómez Calderón, Óscar; Melle Hernández, Sonia; Rubio Retama, Benito Jorge
    Ag2S nanoparticles are the staple for high-resolution preclinical imaging and sensing owing to their photochemical stability, low toxicity, and photoluminescence (PL) in the second near-infrared biological window. Unfortunately, Ag2S nanoparticles exhibit a low PL efficiency attributed to their defective surface chemistry, which curbs their translation into the clinics. To address this shortcoming, we present a simple methodology that allows to improve the PL quantum yield from 2 to 10%, which is accompanied by a PL lifetime lengthening from 0.7 to 3.8 μs. Elemental mapping and X-ray photoelectron spectroscopy indicate that the PL enhancement is related to the partial removal of sulfur atoms from the nanoparticle’s surface, reducing surface traps responsible for nonradiative de-excitation processes. This interpretation is further backed by theoretical modeling. The acquired knowledge about the nanoparticles’ surface chemistry is used to optimize the procedure to transfer the nanoparticles into aqueous media, obtaining water-dispersible Ag2S nanoparticles that maintain excellent PL properties. Finally, we compare the performance of these nanoparticles with other near-infrared luminescent probes in a set of in vitro and in vivo experiments, which demonstrates not only their cytocompatibility but also their superb optical properties when they are used in vivo, affording higher resolution images.
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    10-Fold Quantum Yield Improvement of Ag2S Nanoparticles by Fine Compositional Tuning
    (ACS Applied materials and interfaces, 2020) Ortega Rodríguez, Alicia; Shen, Yingli; Zabala Gutiérrez, Irene; Santos, Harrison D. A.; Torres Vera, Vivian Andrea; Ximedes, Erving; Villaverde Cantizano, Gonzalo; Lifante, José; Gerke, Christoph; Fernández Monsalve, Nuria; Gómez Calderón, Óscar; Melle Hernández, Sonia; Marqués Hueso, José; Méndez González, Diego; Laurenti, Marco; Jones, Callum M. S.; López Romero, Juan Manuel; Contreras Cáceres, Rafael; Jaque García, Daniel; Rubio Retama, Benito Jorge; Garma Pons, Santiago
    Ag2S semiconductor nanoparticles (NPs) are near-infrared luminescent probes with outstanding properties (good biocompatibility, optimum spectral operation range, and easy biofunctionalization) that make them ideal probes for in vivo imaging. Ag2S NPs have, indeed, made possible amazing challenges including in vivo brain imaging and advanced diagnosis of the cardiovascular system. Despite the continuous redesign of synthesis routes, the emission quantum yield (QY) of Ag2S NPs is typically below 0.2%. This leads to a low luminescent brightness that avoids their translation into the clinics. In this work, an innovative synthetic methodology that permits a 10-fold increment in the absolute QY from 0.2 up to 2.3% is presented. Such an increment in the QY is accompanied by an enlargement of photoluminescence lifetimes from 184 to 1200 ns. The optimized synthetic route presented here is based on a fine control over both the Ag core and the Ag/S ratio within the NPs. Such control reduces the density of structural defects and decreases the nonradiative pathways. In addition, we demonstrate that the superior performance of the Ag2S NPs allows for high-contrast in vivo bioimaging. .