Search

The tendency of boron-dipyrromethene (BODIPY) dyes to associate in water is well known, and usually a cause for inferior fluorescence properties. Synthetic efforts to chemically improve BODIPYs’ water solubility and minimize this problem have been numerous in the past. However, a deeper understanding of the phenomena responsible for fluorescence quenching is still required. Commonly, the spectroscopic behaviour in aqueous media has been attributed to aggregate or excimer formation, with such works often centring on a single BODIPY family. Herein, we provide an integrating discussion including very diverse types of BODIPY dyes. Our studies revealed that even subtle structural changes can distinctly affect the association behaviour of the fluorophores in water, involving different photophysical processes. The palette of behaviour found ranges from unperturbed emission, to the formation of H or J aggregates and excimers, to the involvement of tightly bound, pre-formed excimers. These results are a first step to a more generalized understanding of spectroscopic properties vs. structure, facilitating future molecular design of BODIPYs, especially as probes for biological applications., Spanish Ministry of Science and Innovation (Ramón y Cajal Program), Alexander von Humboldt Foundation, Depto. de Química Orgánica, Fac. de Ciencias Químicas, TRUE, pub

In vitro cultured 3D models of CRC have been demonstrated to hold considerable worth in drug discovery, drug resistance analysis, and in studying cell-cell and cell-matrix interactions that occur in the tumor microenvironment. The 3D models resemble the in vivo physiological microenvironment by replicating the cell type composition and tissue architecture. Molecularly imprinted polymers (MIPs) have been investigated for use instead of antibodies against small non-immunogenic structures, such as sialic acid (SA). Glyco-conjugates including SA are present on all cells, and often deregulated on cancer cells. Here, we present a novel approach for targeting and detecting colorectal cancer cells (CRC) by using in vitro cultured HT29 3D spheroids co-cultured in vitro with either fluorescent MIPs targeting SA, SA-MIPs, or the two lectins targeting SA, MAL I, and SNA. Both formaldehyde-fixed and viable HT29 3D spheroids with or without SA-MIPs were imaged in 3D by confocal microscopy. The results revealed a preserved cell morphology and viability of the HT29 3D spheroids co-cultured in vitro with SA-MIPs. However, the lectins MAL I and SNA targeting the a-2,3 or a-2,6 SA glycosidic linkages, respectively, affected the cell viability when co-cultured with the viable HT29 3D spheroids, and no living cells could be detected. Here, we have shown that the SA-MIPs could be used as a safe and low-cost diagnostic tool for targeting and detecting cancer cells in a physiologically relevant 3D cancer model in vitro.

Glycoproteins are abundant on the cell surface of mammals, providing structural support, modulating cell membrane properties, and acting as signaling agents. Variation of glycosylation patterns has been found to indicate various disease states, including cell malignancy. Sialic acid (SA) is present as a terminating group on cell-surface glycans, and its overexpression has been linked to several types of cancer. Detection of SA on the cell surface is therefore critical for detection of cancer in its early stages. In this work, a fluorescent molecularly imprinted polymer layer targeting SA was synthesized on the surface of silica-coated polystyrene (PS) particles. Compared to previous works, a PS core supplies a lighter, lower-density support for improved suspension stability and scattering properties. Moreover, their smaller size provides a higher surface-area-to-volume ratio for binding. The incorporation of a fluorescent monomer in the MIP shell allowed for simple and rapid determination of binding specificity in polar media due to a deprotonation-reprotonation interaction mechanism between the fluorescent monomer and SA, which led to spectral changes. Upon titration of the MIP particles with SA in suspension, an increase in fluorescence emission of the particles was observed, with the MIP particles binding SA more selectively compared to the nonimprinted polymer (NIP) control particles. In cell staining experiments performed by flow cytometry, the binding behavior of the MIP particles compared favorably with that of SA-binding lectins. NIPs prepared with a "dummy" template served as a better negative control in cell binding assays due to the favorable inward orientation of template-binding functional groups in the polymer shell, which reduced nonspecific binding. The results show that fluorescent MIPs targeting SA are a promising tool for in vitro fluorescence staining of cancerous cells and for future diagnosis of cancer at early stages.

[EN] New hybrid oligonucleotide-capped mesoporous silica nanoparticles able to detect genomic DNA were designed.

The design of comparatively simple and modularly configurable artificial systems able to communicate through the exchange of chemical messengers is, to the best of our knowledge, an unexplored field. As a proof-of-concept, we present here a family of nanoparticles that have been designed to communicate with one another in a hierarchical manner. The concept involves the use of capped mesoporous silica supports in which the messenger delivered by a first type of gated nanoparticle is used to open a second type of nanoparticle, which delivers another messenger that opens a third group of gated nanoobjects.We believe that the conceptual idea that nanodevices can be designed to communicate with one another may result in novel applications and will boost further advances towards cooperative systems with complex behavior as a result of the communication between simple abiotic individual components.

Das Design von vergleichsweise einfachen und modular konfigurierbaren k nstlichen Systemen, die ber den Austausch von chemischen Botenstoffen miteinander kommunizieren kçnnen, ist unseres Wissens ein bislang unerforschtes Gebiet. In einer grundlegenden Arbeit pr sentieren wir hier eine Serie von Nanopartikeln, die in hierarchischer Art und Weise miteinander kommunizieren kçnnen. Das Konzept beruht auf gedeckelten mesoporçsen Silikat-Tr gern, bei denen der aus einem ersten Typ von gesteuerten Nanopartikeln freigesetzte chemische Botenstoff einen zweiten Typ von gedeckelten Nanopartikeln çffnet, welche wiederum einen anderen Botenstoff freisetzen, die eine dritte Gruppe von gesteuerten Nanoobjekten çffnen. Dieses Konzept, das nanoskopische Objekte so aufgebaut werden kçnnen, dass sie miteinander Informationen austauschen, kann unserer Meinung nach zu einer Reihe neuartiger Anwendungen f hren und wird Fortschritte im Bereich kooperativer Systeme mit komplexen Eigenschaften, die auf der Kommunikation einfacher individueller abiotischer Komponenten basieren, befçrdern.

A heteroditopic BODIPY dye that performs all basic Boolean operations with a cation (K+) and an anion (F-) as inputs and absorption, transmission and fluorescence as outputs is described. The molecular logic gate can also act as a digital comparator between the inputs.

[DE] Mit DNA verschlossene und mit Farbstoff beladene mesoporöse Siliciumdioxid-Nanopartikel wurden zum Nachweis von Mycoplasma bis zu einer Nachweisgrenze von ca. 70 genomischen DNA-Kopien pro mu-L in real kontaminierten Zellkulturmedien ohne die Hilfe von PCR-Techniken eingesetzt.

The coupling of gated-indicator delivery with highly specific biochemical recognition is an innovative strategy for the detection of DNA sequences, able to compete with classical methods which need PCR amplification, in important areas such as point-of-care diagnostics or detection of specific biological contaminations with pathogens. Such comparatively simple and cheap yet highly selective and sensitive assays hold promise for use in less-developed areas of the world.

Hybrid nanoparticles with a large specific surface area are a particularly exciting vehicle for delivery applications. Such highly porous or container-like structures, usually prepared from silica and frequently from gold, can incorporate a large number of chemical substances such as drug and/or indicator molecules. When equipped with a chemically or physically addressable gating function at the openings of the voids, the release of the cargo can be controlled at will. Because many more molecules can be stored as cargo in the pores of the support than there are functional groups as anchoring sites for the gating entities attached to the outer surface (for efficient pore capping), the systems possess inherent features of (signal) amplification. The present article will introduce various design strategies for different types of physical (light, temperature, magnetism) and chemical (pH, metal ions, anion, small organic molecules, enzymes) stimuli in connection with drug and indicator release. We will highlight exciting aspects of combining both features in theranostic applications and will stress which requirements still have to be met by many of the systems to be readily applicable in a sensory context.

[EN] Antibodygated MSNs that are loaded with a rhodamine dye and that can be used for the determination of the presence of peroxide-based explosive TATP with a lateral-flow fluorescence reader have been designed and prepared, thereby allowing for detection limits in the lower ppb range. The mechanism of the detection relies on a displacement of the antibody from the surface of the hybrid material because of highly affine antibody-TATP interactions, which release a much larger number of entrapped dye molecules from the pores than antibodies are displaced. The high selectivity of the antibody is retained in the gated material, thus allowing for a remarkable discrimination against H2O2. System design and optimization led to straightforward integration into a lateral-flow assay without further treatment or conditioning of the test strips while guaranteeing fast overall assay times of minus or equal 10 min. Moreover, besides showing a remarkable robustness, the inherent architecture of the assay relies on a single-step immunochemical reaction, that is, it can dispense with secondary (labeled) antibodies and enables ratiometric signal assessment in the presence of the analyte by simple comparison of the fluorescence signals in two zones. Because of the modularity of the approach, the concept is easily generalizable and applicable for many small-molecule analytes. For instance, assays can be imagined that contain various hybrids of S1-AB(n) type, for which each material capped with a certain antibody is loaded with a different dye, thus envisioning multiplexed analysis with such simple assays.

Design strategies for (bio)chemical systems that are inspired by nature's accomplishments in system design and operation on various levels of complexity are increasingly gaining in importance. Within the broad field of biomimetic chemistry, this article highlights various attempts toward improved and sophisticated sensory materials that rely on the combination of supramolecular (bio)chemical recognition principles and nanoscopic solid structures. Examples range from more established concepts such as hybrid sensing ensembles with improved sensitivity and selectivity or for target analytes for which selectivity is hard to achieve by conventional methods, which were often inspired by protein binding pockets or ion channels in membranes, to very recent approaches relying on target-gated amplified signalling with functionalised mesoporous inorganic supports and the integration of native biological sensory species such as transmembrane proteins in spherically supported bilayer membranes. Besides obvious mimicry of recognition-based processes, selected approaches toward chemical transduction junctions utilizing artificially organized synapses, hybrid ensembles for improved antibody generation and uniquely colour changing systems are discussed. All of these strategies open up exciting new prospects for the development of sensing concepts and sensory devices at the interface of nanotechnology, smart materials and supramolecular (bio)chemistry. © 2011 The Royal Society of Chemistry.

In conjunction with quenching metal ions, silica nanoparticles carrying terpyridine coordination sites and sulforhodamine B signalling units were employed for the differential fluorometric recognition of anions. © 2011 The Royal Society of Chemistry.

[EN] This review highlights how the combination of supramolecular principles and nanoscopic solid structures enables the design of new hybrid sensing ensembles with improved sensitivity and/or selectivity and for the targeting of analytes for which selectivity is hard to achieve by conventional methods. Such ideas are bridging the gap between molecules, materials sciences and nanotechnology. Relevant examples will be detailed, taking into account functional aspects such as (1) enhanced coordination of functionalized solids, (2) enhanced signalling through preorganization, (3) signalling by assembly-disassembly of nanoscopic objects, (4) biomimetic probes utilizing discrimination by polarity and size and (5) distinct switching and gating protocols. These strategies are opening new prospects for sensor research and signalling paradigms at the frontier between nanotechnology, smart materials and supramolecular chemistry. © 2010 Springer-Verlag.

[EN] The inclusion of squaraine (SQ) dye I into the supercages of zeolite Y (structure code FAU) with a SiO(2)/Al(2)O(3) ratio of 30 (Z30) through a two-step ship-in-the-bottle approach is reported, resulting in the squaraine-containing hybrid material Z30-SQ. Attempts to use the same synthetic procedure on sodium and ammonium Y zeolites were unsuccessful, stressing the importance of the presence of Bronsted acid centres in the Z30 zeolite. The reflectance spectra of Z30-SQ show a maximum in the typical squaraine monomer region at 618 nm and a shoulder at 570 nm. Spectral analyses revealed that the major species are SQ dimers and (tightly adsorbed) SQ monomers and SQ aggregates are only formed to a minor degree. The emission spectrum of Z30-SQ shows a single band at 669 nm. The sensory performance of this material was tested in the presence of volatile propylamine and propylthiol and other volatile organic compounds (acetone, ethanol, dichloromethane, hexane, acetonitrile, ethyl acetate, ethyl ether and acetic acid). The blue Z30-SQ material reacts with the thiol and amine derivatives, resulting in the bleaching of the solid and disappearance of the absorption band in the visible region, but does not undergo spectroscopic changes in the presence of other volatile organic compounds (VOCs). Whereas the reaction with propylamine is irreversible, a partial reversibility was found in the presence of the thiol. Theoretical investigations of the reactivity of I with several VOC molecules at the semi-empirical level reproduced well the experimentally observed reactivity.