Méndez González, Diego

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First Name
Last Name
Méndez González
Universidad Complutense de Madrid
Faculty / Institute
Química en Ciencias Farmacéuticas
Química Física
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Now showing 1 - 10 of 13
  • Publication
    The effects of dopant concentration and excitation intensity on the upconversion and downconversion emission processes of β-NaYF4:Yb3+,Er3+nanoparticles
    (Royal Soc. Chemistry, 2021-06-04) Torres Vera, Vivian; Méndez González, Diego; Ramos Ramos, D.J.; Igalla El Youssfi, Asmae; Laurenti, Marco; Contreras Cáceres, Rafael; López Cabarcos, Enrique; Díaz García, Elena; Rubio Retama, Jorge; Melle Hernández, Sonia; Gómez Calderón, Oscar
    The dopant concentration of lanthanide ions in photon upconversion nanoparticles (UCNPs) remains one of the key points to boost the brightness of these nanomaterials and, therefore, their application developments. Here, we analyzed the effect of Er3+ and Yb3+ dopant concentrations of b-NaYF4:Yb3+,Er3+ nanoparticles on the visible upconversion and near-infrared downconversion luminescence intensities. Our approach carefully excluded all other factors whose variation affects luminescence properties such as the size, morphology, crystal structure, ion distribution, ligand, and surrounding medium, allowing us to exactly infer the influence of the ratio of Yb3+ to Er3+ ions on the nanoparticle luminescence. To maintain the size and morphological properties of nanoparticles, we used a total dopant concentration of 22% while varying the ratio of Yb3+ to Er3+ ions from 0 to 10. A huge increase in luminescence takes place as the Yb/Er ratio increases following a power-law behavior, and this luminescence enhancement is greater at low excitation intensities. Above a Yb/Er ratio of around two, saturation occurs with a slight peak when this ratio is around four. Simulations using a rate equation model showed that upconversion luminescence (UCL) is mainly produced by the energy transfer between neighboring Er3+ ions at low Yb/Er ratios, while at high ratios, the energy transfer from Yb3+ to Er3+ ions dominates. However, downconversion luminescence (DCL) is produced at all analyzed ratios, except 0, by the previous mechanism.
  • Publication
    Control of upconversion luminescence by gold nanoparticle size: from quenching to enhancement
    (RSC, 2019-08-07) Méndez González, Diego; Melle Hernández, Sonia; Gómez Calderón, Óscar; Laurenti, Marco; Cabrera Granado, Eduardo; Egatz-Gómez, Ana; López Cabarcos, Enrique; Rubio Retama, Jorge; Díaz García, Elena
    Metallic nanostructures have the potential to modify the anti-Stokes emission of upconverting nanoparticles (UCNPs) by coupling their plasmon resonance with either the excitation or the emission wavelength of the UCNPs. In this regard gold nanoparticles (AuNPs) have often been used in sensors for UCNP luminescence quenching or enhancement, although systematic studies are still needed in order to design optimal UCNP–AuNP based biosensors. Amidst mixed experimental evidence of quenching or enhancement, two key factors arise: the nanoparticle distance and nanoparticle size. In this work, we synthesize AuNPs of different sizes to assess their influence on the luminescence of UCNPs. We find that strong luminescence quenching due to resonance energy transfer is preferentially achieved for small AuNPs, peaking at an optimal size. A further increase in the AuNP size is accompanied by a reduction of luminescence quenching due to an incipient plasmonic enhancement effect. This enhancement counterbalances the luminescence quenching effect at the biggest tested AuNP size. The experimental findings are theoretically validated by studying the decay rate of the UCNP emitters near a gold nanoparticle using both a classical phenomenological model and the finite-difference time-domain method. Results from this study establish general guidelines to consider when designing sensors based on UCNPs–AuNPs as donor–quencher pairs, and suggest the potential of plasmon-induced luminescence enhancement as a sensing strategy.
  • Publication
    Oligonucleotide Sensor Based on Selective Capture of Upconversion Nanoparticles Triggered by Target Induced DNA Inter-Strand Ligand Reaction
    (Amer Chemical Soc., 2017-03-23) Méndez González, Diego; Laurenti, Marco; Latorre, Alfonso; Somoza, Álvaro; Vázquez, Ana; Negredo, Ana Isabel; López Cabarcos, Enrique; Calderón, Oscar Gómez; Melle Hernández, Sonia; Rubio Retama, Jorge
    We present a sensor that exploits the phenomenon of upconversion luminescence to detect the presence of specific sequences of small oligonucleotides like miRNAs among others. The sensor is based on NaYF4:Yb,Er@SiO2 nanoparticles functionalized with ssDNA that contain azide groups on the 3' ends. In the presence of a target sequence, inter-strand ligation is possible via click-reaction between one azide of the upconversion probe and a DBCO-ssDNA-biotin probe present in the solution. As result of this specific and selective process, biotin is covalently attached to the surface of the upconversion nanoparticles. The presence of biotin on the surface of the nanoparticles allows their selective capture on a streptavidin-coated support, giving a luminescent signal proportional to the amount of target present in the test samples. With the aim of studying the analytical properties of the sensor, total RNA samples were extracted from healthy mosquitoes and spiked-in with a specific target sequence at different concentrations. The result of these experiments revealed that the sensor was able to detect 10-17 moles (100 fM) of the target sequence in mixtures containing 100 ng of total RNA per well. Similar limit of detection was found for spiked human serum samples, demonstrating its suitability for detecting specific sequences of small oligonucleotides under real conditions. By contrast, under the presence of non-complementary sequences or sequences having mismatches, the luminescent signal was negligible or conspicuously reduced.
  • Publication
    FRET distance dependence from upconverting nanoparticles to quantum dots
    (Amer Chemical Soc, 2018-05) Melle Hernández, Sonia; Gómez Calderón, Óscar; Laurenti, Marco; Méndez González, Diego; Egatz-Gómez, Ana; López Cabarcos, Enrique; Cabrera Granado, Eduardo; Díaz García, Elena; Rubio Retama, Jorge
    Förster resonant energy transfer (FRET) with upconverting nanoparticles (UCNPs) as donors and quantum dots (QDs) as acceptors has been regarded as a promising tool for biosensing applications. In this work, we use time-resolved fluorescence spectroscopy to analyze the UCNP-to-QD FRET and we focus on the most relevant parameter of the FRET phenomenon, UCNP-QD distance. This distance is controlled by a nanometric silica shell around the UCNP surface. We theoretically reproduce the experimental results applying FRET theory to the distribution of emitting erbium ions in the UCNP. This simple model allows us to estimate the contribution of every erbium ion to the final FRET response and to explore different strategies to improve FRET efficiency.
  • Publication
    Oligonucleotide sensor based on magnetic capture and photoligation of upconverting nanoparticles in solid surfaces
    (Elsevier, 2021-03-11) Méndez González, Diego; Silva Ibáñez, Pedro Pablo; Valiente Dies, Fernando; Gómez Calderón, Óscar; Mendez González, Juan Luis; Laurenti, Marco; Egatz-Gómez, Ana; Díaz García, Elena; Rubio Retama, Jorge; Melle Hernández, Sonia
    In this work, we present a luminescence platform that can be used as point of care system for determining the presence and concentration of specific oligonucleotide sequences. This sensor exhibited a limit of detection as low as 50 fM by means of: i) the use of single-stranded DNA (ssDNA) functionalized magnetic microparticles that captured and concentrated ssDNA-upconverting nanoparticles (ssDNA-UCNPs) on a solid support, when the target sequence (miR-21-5p DNA-analogue) was in the sample, and ii) a photoligation reaction that covalently linked the ssDNA-UCNPs and the ssDNA magnetic microparticles, allowing stringent washes. The presented sensor showed a similar limit of detection when the assays were conducted in samples containing total miRNA extracted from human serum, demonstrating its suitability for detecting small specific oligonucleotide sequences under real-like conditions. The strategy of combining UCNPs, magnetic microparticles, and photoligation reaction provides new insight into low-cost, rapid, and ultra-sensitive detection of oligonucleotide sequences.
  • Publication
    Upconverting Nanoparticles in Aqueous Media: Not a Dead-End Road. Avoiding Degradation by Using Hydrophobic Polymer Shells
    (Wiley, 2021-12-13) 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.
  • Publication
    Clickable albumin nanoparticles for pretargeted drug deliv-ery towards PD-L1 overexpressing tumors in combination immunotherapy
    (American Chemical Society (ACS), ) Gerke, Christoph; Zabala Gutiérrez, Irene; Méndez González, Diego; Iglesias de la Cruz, María del Carmen; Mulero, Francisca; Jaque García, Daniel; Rubio Retama, Jorge
    We present a simple methodology to design a pretargeted drug delivery system, based on clickable anti-PD-L1 antibodies and clickable BSA nanoparticles (NPs). In this work, BSA NPs were produced using the solvent pre-cipitation methodology that renders colloidally stable NPs which were subsequently functionalized with a clickable moiety based on chlorosydnone (Cl-Syd). Those reactive groups are able to specifically react with dibenzocyclooctyne (DBCO) groups in a click-type fashion, reaching second order reaction rate constants as high as 1.9 M-1·s-1 which makes this reaction highly suitable for in vivo applications. The presence of reactive Cl-Syd was demonstrated by re-acting the functionalized NPs with a DBCO modified sulfo-cyanine-5 dye (sCy5). With this reaction, it was possible to infer the number of reactive moieties per NPs. Finally, and with the aim of demonstrating the suitability of this system to be used in pretargeted strategies, functionalized fluorescent NPs were used to label H358 cells with a clickable anti-PD-L1 antibody, applying the reaction between Cl-Syd and DBCO as corresponding clickable groups. The results of these experiments demonstrate the biorthogonality of the system to perform the reaction in vitro, in a period as short as 15 minutes.
  • Publication
    10-Fold Quantum Yield Improvement of Ag2S Nanoparticles by Fine Compositional Tuning
    (ACS, 2020-02-18) Ortega Rodríguez, Alicia; Shen, Yingli; Zabala Gutiérrez, Irene; Santos, Harrison D. A.; Torres Vera, Vivian; 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, Jorge
    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. .
  • Publication
    Ultrafast photochemistry produces superbright short-wave infrared dots for low-dose in vivo imaging
    (Nature Publishing Group, 2020-06-10) Santos, Harrison D. A.; Zabala Gutiérrez, Irene; Shen, Yingli; Lifante, José; Ximendes, Erving; Laurenti, Marco; Méndez González, Diego; Melle Hernández, Sonia; Gómez Calderón, Óscar; López Cabarcos, Enrique; Fernández Monsalve, Nuria; Chavez Coria, Irene; Lucena Agell, Daniel; Monge, Luis; Mackenzie, Mark D.; Marqués Hueso, José; Jones, Callum M. S.; Jacinto, Carlos; Rosal, Blanca, del; Kar, Ajoy K.; Rubio Retama, Jorge; Jaque García, Daniel
    Optical probes operating in the second near-infrared window (NIR-II, 1,000-1,700 nm), where tissues are highly transparent, have expanded the applicability of fluorescence in the biomedical field. NIR-II fluorescence enables deep-tissue imaging with micrometric resolution in animal models, but is limited by the low brightness of NIR-II probes, which prevents imaging at low excitation intensities and fluorophore concentrations. Here, we present a new generation of probes (Ag2S superdots) derived from chemically synthesized Ag2S dots, on which a protective shell is grown by femtosecond laser irradiation. This shell reduces the structural defects, causing an 80-fold enhancement of the quantum yield. PEGylated Ag2S superdots enable deep-tissue in vivo imaging at low excitation intensities (<10 mW cm−2) and doses (<0.5 mg kg−1), emerging as unrivaled contrast agents for NIR-II preclinical bioimaging. These results establish an approach for developing superbright NIR-II contrast agents based on the synergy between chemical synthesis and ultrafast laser processing.
  • Publication
    Contribution of resonance energy transfer to the luminescence quenching of upconversion nanoparticles with graphene oxide
    (Academic Press Inc Elsevier Science, 2020-04-20) Méndez González, Diego; Gómez Calderón, Óscar; Melle Hernández, Sonia; González Izquierdo, Jesús; Bañares Morcillo, Luis; López Díaz, David; Velazquez Salicio, M. Mercedes; López Cabarcos, Enrique; Rubio Retama, Jorge; Laurenti, Marco
    Upconversion nanoparticles (UCNP) are increasingly used due to their advantages over conventional fluorophores, and their use as resonance energy transfer (RET) donors has permitted their application as biosensors when they are combined with appropriate RET acceptors such as graphene oxide (GO). However, there is a lack of knowledge about the design and influence that GO composition produces over the quenching of these nanoparticles that in turn will define their performance as sensors. In this work, we have analysed the total quenching efficiency, as well as the actual values corresponding to the RET process between UCNPs and GO sheets with three different chemical compositions. Our findings indicate that excitation and emission absorption by GO sheets are the major contributor to the observed luminescence quenching in these systems. This challenges the general assumption that UCNPs luminescence deactivation by GO is caused by RET. Furthermore, RET efficiency has been theoretically calculated by means of a semiclassical model considering the different nonradiative energy transfer rates from each Er3+ ion to the GO thin film. These theoretical results highlight the relevance of the relative positions of the Er3+ ions inside the UCNP with respect to the GO sheet in order to explain the RET-induced efficiency measurements.