1,721,014 research outputs found
Protein aggregation detection with fluorescent macromolecular and nanostructured probes: challenges and opportunities
No full textProtein aggregation is a phenomenon widespread in all organisms, that responds to a variety of external stimuli and is involved in complex functions such as storage and recycling of protein residues in crowded environments. In some cases, aggregation of proteins is related to serious human diseases. Understanding, monitoring and, eventually, intervening in the process of aggregation – in particular at its early stage – is a topic of high relevance and urgency. Recently, nanostructured materials have allowed for an unmet versatility and modularity in the field of sensing and inhibition of aggregation. Fluorescent oligomers and polymers, via controlled tuning of chemical functionalities, are yielding detailed comprehension of the interactions between probe candidates and protein aggregates; AIEgens are rapidly addressing many open challenges on sensitivity and signal enhancement; nanomaterials are increasingly serving as theranostic platforms, with multiple functionalities stemming from the assembly of components with complementary abilities. Here we review the most recent achievements in protein aggregation sensing based on macromolecular or nanostructured probes, highlighting the general experimental and computational findings that may serve as guidelines for the next generation of theranostic probes
Fluorogenic hyaluronan nanogels for detection of micro- and nanoplastics in water
Full text linkEnvironmental pollution from plastics is exponentially increasing due to human activities. While larger microplastics can be detected with various methods, retrieving micron-sized fragments and nanoplastics remains challenging. Yet, these smaller-sized plastics have been raising considerable toxicological concern. Here, we show that a poorly emissive hyaluronan functionalized with rhodamine B (HA–RB) adheres with high affinity to various microplastic surfaces, becoming brightly emissive. Micro- and nanoplastics (MNPs) can be successfully detected with size as small as the diffraction limit of confocal microscopy (ca. 250 nm). FLIM images show that the fluorescence lifetime of the dye moieties changes according to the plastics, making possible a discrimination of the nature of MNPs based on lifetime. HA–RB, compared to previous reports, eliminates false-positive results caused by formation of dye aggregates, resulting in a higher S/N ratio which allows the unequivocal detection of nano-sized fragments
Photo-tunable multicolour fluorescence imaging based on self-assembled fluorogenic nanoparticles
No full textNon-fluorescent nanoparticles resulting from the self-assembly of a new perylene diimide behave as fluorogenic probes for biological cells under physiological conditions giving a dosage-dependent green or red fluorescence and showing very low cytotoxicity. The emission colour can be tuned by photo-irradiation to achieve multicolour labelling
Static quenching upon adduct formation: a treatment without shortcuts and approximations
Full text linkLuminescence quenching is a process exploited in transversal applications in science and technology and it has been studied for a long time. The luminescence quenching mechanisms are typically distinguished in dynamic (collisional) and static, which can require different quantitative treatments. This is particularly important – and finds broad and interdisciplinary application – when the static quenching is caused by the formation of an adduct between the luminophore – at the ground state – and the quencher. Due to its nature, this case should be treated starting from the well-known law of mass action although, in specific conditions, general equations can be conveniently reduced to simpler ones. A proper application of simplified equations, though, can be tricky, with frequent oversimplifications taking to severe errors in the interpretation of the photophysical data. This tutorial review aims to (i) identify the precise working conditions for the application of the simplified equations of static quenching and to (ii) provide general equations for broadest versatility and applicability. The latter equations can be used even beyond the sole case of pure quenching, i.e., in the cases of partial quenching and even luminescence turn-on. Finally, we illustrate different applications of the equations via a critical discussion of examples in the field of sensing, supramolecular chemistry and nanotechnology
NIR-fluorescent dye doped silica nanoparticles for in vivo imaging, sensing and theranostic
No full textThe development of nanostructures devoted to in vivo imaging and theranostic applications is one of the frontier fields of research worldwide. In this context, silica nanoparticles (SiO2-NPs) offer unquestionable positive properties: silica is intrinsically non-toxic, several versatile and accessible synthetic methods are available and many variations are possible, both in terms of porosity and functionalization for delivery and targeting purposes, respectively. Moreover, the accumulation of several dyes within a single nanostructure offers remarkable possibilities to produce very bright and photostable luminescent nanosystems. Advancements in imaging technology, bioassay, fluorescent molecular probes have boosted the efforts to develop dye doped fluorescent SiO2-NPs, but despite this, only a quite limited set of systems are applicable in vivo. Herein we discuss selected examples that appeared in the literature between 2013-17, with imaging capabilities in vivo and characterized by a significant near infrared (NIR) fluorescence emission. We present here very promising strategies to develop SiO2-NPs for diagnostic and therapeutic applications - some of which are already in clinical trials - and the possibility to develop bio-erodable SiO2-NPs. We are convinced that all these findings will be the basis for the spread of SiO2-NPs into clinical use in the near future
Collective Properties Extend Resistance to Photobleaching of Highly Doped PluS NPs
No full textDye-doped nanoparticles (NPs) are intriguing fluorescent systems in which collective properties can arise, which are ascribable to the ensemble of dyes rather than to individual ones. Collective properties can be tailored to increase brightness and introduce photophysical versatility. In this context, self-quenching has long been regarded as the phenomenon to avoid. Here we report on the possibility to profit from a property stemming from self-quenching: nanoparticles with a high number of dyes per NP (including self-quenched dyes) display much slower photobleaching compared to nanoparticles with a lower doping degree. In this way, their emission intensity can be kept almost constant for ten times longer. This extended duration of luminescence is due to preferential photobleaching of self-quenched fluorophores. These observations can shine new light on the use of highly dye-doped nanoparticles as long-lasting, super-photostable probes under strong excitation conditions
Electrochemical and Surface Characterization of Dense Monolayers Grafted on ITO and Si/SiO2 Surfaces via Tetra (tert‐Butoxy) Tin Linker
No full textIndium tin oxide (ITO) and silicon with a thermally grown SiO2 layer (Si/SiO2) substrates have been functionalized by ferrocene bound through Sn(O)x (x=2 or 3) linkers preliminarly grafted on the surface by reaction of the terminal hydroxyl groups with tetra(tert-butoxy)tin. The two steps modification of the surface was carried out by chemical vapour deposition metathesis reaction producing a self-assembled monolayer of ferrocene. The ITO and Si/SiO2 thus functionalized have been characterized by voltammetric, amperometric, electrochemical impedance spectroscopy and scanning probe microscopy techniques which assessed the formation of a stable and rather compact covalently bound ferrocenyl monolayer with improved electron transfer properties
Fluorescence methods to probe mass transport and sensing in solid-state nanoporous membranes
No full textSingle- and multi-nanoporous (1-100 nm pore size) solid-state membranes (SSNMs) receive significant attention in various fields, spanning from biosensing to water purification. Their finely tunable nanopore geometry and chemistry, combined with the large selection of materials that they can be made of, such as polymers, inorganic materials (e.g., silicon, silica, and alumina), and hydrogels, provide an excellent platform to control their mass transport and sensing capabilities for different cargoes from Å scale ions up to macromolecular biomaterials. The critical requirement to merge these nanoporous membranes’ advanced structural and chemical features with their applications is to find the most suitable analytical techniques that permit macro- and micro-scale and real-time probing of different nanopore activities. Luminescence-based detection of various physico-chemical processes in nanoporous membranes has recently received great attention: it permits rapid, non-invasive, and dynamic probing of nanoporous materials, yielding information on mass transport and sensing both (i) macroscopically, such as from an array of nanopores, and (ii) micro-nanoscopically, with ultra-high (e.g., single molecule) sensitivity and high resolution in time and space. Quantitative information arising from luminescence experiments on membrane-analyte interactions has uncovered the effects of nanoconfinement, membrane stability, and performance. This review article aims to provide the reader with a handbook of fluorescent methods-from the simplest to implement to the most advanced-helpful in studying different kinds of SSNMs for a specific application or function. To this end, we include examples from the literature published in the last ten years. At the end of our article, we also discuss limitations of the current state of fluorescence probing techniques and their future prospects
Mapping heterogeneous polarity in multicompartment nanoparticles
No full textUnderstanding polarity gradients inside nanomaterials is essential to capture their potential as nanoreactors, catalysts or in drug delivery applications. We propose here a method to obtain detailed, quantitative information on heterogeneous polarity in multicompartment nanostructures. The method is based on a 2-steps procedure, (i) deconvolution of complex emission spectra of two solvatochromic probes followed by (ii) spectrally resolved analysis of FRET between the same solvatochromic dyes. While the first step yields a list of polarities probed in the nanomaterial suspension, the second step correlates the polarities in space. Colocalization of polarities falling within few nanometer radius is obtained via FRET, a process called here nanopolarity mapping. Here, Prodan and Nile Red are tested to map the polarity of a water-dispersable, multicompartment nanostructure, named PluS nanoparticle (NPs). PluS NPs are uniform core-shell nanoparticles with silica cores (diameter ~10 nm) and Pluronic F127 shell (thickness ~7 nm). The probes report on a wide range of nanopolarities among which the dyes efficiently exchange energy via FRET, demonstrating the coexistence of a rich variety of environments within nanometer distance. Their use as a FRET couple highlights the proximity of strongly hydrophobic sites and hydrated layers, and quantitatively accounts for the emission component related to external water, which remains unaffected by FRET processes. This method is general and applicable to map nanopolarity in a large variety of nanomaterials
Improving the Electrical Percolating Network of Carbonaceous Slurries by Superconcentrated Electrolytes: An Electrochemical Impedance Spectroscopy Study
Full text linkSemisolid redox flow batteries simultaneously address the need for high energy density and design flexibility. The electrical percolating network and electrochemical stability of the flowable electrodes are key features that are required to fully exploit the chemistry of the semisolid slurries. Superconcentrated electrolytes are getting much attention for their wide electrochemical stability window that can be exploited to design high-voltage batteries. Here, we report on the effect of the ion concentration of superconcentrated electrolytes on the electronic percolating network of carbonaceous slurries. Slurries based on different concentrations of lithium bis(trifluoromethane)sulfonamide in tetraethylene glycol dimethyl ether (0.5, 3, and 5 mol/kg) at different content of Pureblack carbon (from 2 up to 12 wt %) have been investigated. The study was carried out by coupling electrochemical impedance spectroscopy (EIS), optical fluorescence microscopy, and rheological measurements. A model that describes the complexity and heterogeneity of the semisolid fluids by multiple conductive branches is also proposed. For the first time, to the best of our knowledge, we demonstrate that besides their recognized high electrochemical stability, superconcentrated electrolytes enable more stable and electronically conductive slurry. Indeed, the high ionic strength of the superconcentrated solution shields interparticle interactions and enables better carbon dispersion and connections
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