Responsive or smart magnetic resonance imaging (MRI) contrast agents are molecular sensors that alter the MRI signal upon changes in a particular parameter in their microenvironment. Consequently, they could be exploited for visualization of various biochemical events that take place at molecular and cellular levels. In this study, a set of dual‐frequency calcium‐responsive MRI agents are reported. These are paramagnetic, fluorine‐containing complexes that produce remarkably high MRI signal changes at the 1H and 19F frequencies at varying Ca2+ concentrations. The nature of the processes triggered by Ca2+ was revealed, allowing a better understanding of these complex systems and their further improvement. The findings indicate that these double‐frequency tracers hold great promise for development of novel functional MRI methods. 相似文献
Single‐molecule fluorescence super‐resolution imaging and tracking provide nanometer‐scale information about subcellular protein positions and dynamics. These single‐molecule imaging experiments can be very powerful, but they are best suited to high‐copy number proteins where many measurements can be made sequentially in each cell. We describe artifacts associated with the challenge of imaging a protein expressed in only a few copies per cell. We image live Bacillus subtilis in a fluorescence microscope, and demonstrate that under standard single‐molecule imaging conditions, unlabeled B. subtilis cells display punctate red fluorescent spots indistinguishable from the few PAmCherry fluorescent protein single molecules under investigation. All Bacillus species investigated were strongly affected by this artifact, whereas we did not find a significant number of these background sources in two other species we investigated, Enterococcus faecalis and Escherichia coli. With single‐molecule resolution, we characterize the number, spatial distribution, and intensities of these impurity spots. 相似文献
Cancer‐cell‐targeted gene silencing was observed with a magnetic‐nanoparticle platform (MEIO, magnetism‐engineered iron oxide) on which a fluorescent dye, siRNA, and a RGD‐peptide targeting moiety were attached (see picture). The different functionalities enable the macroscopic (magnetic resonance) and microscopic (fluorescence) imaging of target cells. This system may be suitable for concurrent diagnostic and therapeutic applications.
Phosphorylation is a post‐translational modification that is involved in many basic cellular processes and diseases, but is difficult to detect in real time with existing technologies. A label‐free detection of phosphorylation is reported in real time with self‐assembled nano‐oscillators. Each nano‐oscillator consists of a gold nanoparticle tethered to a gold surface with a molecular linker. When the nanoparticle is charged, the nano‐oscillator can be driven into oscillation with an electric field and detected with a plasmonic imaging approach. The nano‐oscillators measure charge change associated with phosphorylation of peptides attached onto a single nanoparticle, allowing us to study the dynamic process of phosphorylation in real time without antibodies down to a few molecules, from which Michaelis and catalytic rate constants are determined. 相似文献
Water‐dispersible and luminescent gadolinium oxide (GO) nanoparticles (NPs) were designed and synthesized for potential dual‐modal biological imaging. They were obtained by capping gadolinium oxide nanoparticles with a fluorescent glycol‐based conjugated carboxylate (H L ). The obtained nanoparticles (GO‐ L ) show long‐term colloidal stability and intense blue fluorescence. In addition, L can sensitize the luminescence of europium(III) through the so‐called antenna effect. Thus, to extend the spectral ranges of emission, europium was introduced into L‐ modified gadolinium oxide nanoparticles. The obtained EuIII‐doped particles (Eu:GO‐ L ) can provide visible red emission, which is more intensive than that without L capping. The average diameter of the monodisperse modified oxide cores is about 4 nm. The average hydrodynamic diameter of the L ‐modified nanoparticles was estimated to be about 13 nm. The nanoparticles show effective longitudinal water proton relaxivity. The relaxivity values obtained for GO‐ L and Eu:GO‐ L were r1=6.4 and 6.3 s?1 mM ?1 with r2/r1 ratios close to unity at 1.4 T. Longitudinal proton relaxivities of these nanoparticles are higher than those of positive contrast agents based on gadolinium complexes such as Gd‐DOTA, which are commonly used for clinical magnetic resonance imaging. Moreover, these particles are suitable for cellular imaging and show good biocompatibility. 相似文献
Intrinsically integrating precise diagnosis, effective therapy, and self‐anti‐inflammatory action into a single nanoparticle is attractive for tumor treatment and future clinical application, but still remains a great challenge. In this study, bovine serum albumin–iridium oxide nanoparticles (BSA‐IrO2 NPs) with extraordinary photothermal conversion efficiency, good photocatalytic activity, and a high X‐ray absorption coefficient were prepared through one‐step biomineralization. The nanoparticles allow tumor phototherapy and simultaneous photoacoustic/thermal imaging and computed tomography. More importantly, BSA‐IrO2 NPs can also act as a catalase to protect normal cells against H2O2‐induced reactive oxygen pressure and inflammation while significantly enhancing photoacoustic imaging through microbubble‐based inertial cavitation. These remarkable features may open up the exploration iridium‐based nanomaterials in theranostics. 相似文献
The redox microenvironment within a cell graft can be considered as an indicator to assess whether the graft is metabolically active or hypoxic. We present a redox‐responsive MRI probe based on porous silica microparticles whose surface has been decorated with a Gd‐chelate through a disulphide bridge. Such microparticles are designed to be interspersed with therapeutic cells within a biocompatible hydrogel. The onset of reducing conditions within the hydrogel is paralleled by an increased clearance of Gd, that can be detected by MRI. 相似文献
Real‐time imaging of cell‐surface‐associated proteolytic enzymes is critical to better understand their performances in both physiological and pathological processes. However, most current approaches are limited by their complexity and poor membrane‐anchoring properties. Herein, we have designed and synthesized a unique small‐molecule fluorescent probe, which combines the principles of passive exogenous membrane insertion and Förster resonance energy transfer (FRET) to image cell‐surface‐localized furin‐like convertase activities. The membrane‐associated furin‐like enzymatic cleavage of the peptide probe leads to an increased fluorescence intensity which was mainly localized on the plasma membrane of the furin‐expressed cells. This small‐molecule fluorescent probe may serve as a unique and reliable reporter for real‐time visualization of endogenous cell‐surfaceassociated proteolytic furin‐like enzyme functions in live cells and tissues using one‐photon and two‐photon microscopy. 相似文献
A polymeric thermosensor composed of the thermo‐responsive block copolymer Pluronic F127 (PF127) and the near‐infrared (NIR) dye Cy5.5 can simply monitor, image, and analyze temperature changes. The thermoprobe exhibited linear NIR fluorescent emission changes (see figure) over a broad temperature range (0–80 °C).