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By using the specifically designed multigap nanoelectrodes, we demonstrated an effective approach for the simultaneous dielectrophoretic separation and assembly of metallic and semiconducting single-walled carbon nanotubes (SWNTs). An approximate metallic—semiconductingߞmetallic multiarray structure was created by an inward-propagative sequential assembly of SWNTs under ac electric field. Such kinds of SWNT multiarray structures exhibited ultra-low-power consumption and excellent thermal sensing performances with the sensitivity being dependent on the number of gaps: the more gaps, the higher sensitivity. The effective separation of metallic and semiconducting tubes in different gaps is believed to be responsible for the improved sensitivity to temperature. [ABSTRACT FROM AUTHOR]

Fluorescence catalytic beacons have emerged as a general platform for sensing applications. However, almost all such sensing systems need covalent modification of the DNAzymes with fluorophore-quencher pairs, which may require elaborate design of the synthetic routes and many heavy and complicated synthetic steps and result in increased cost and lower synthesis yield. Here we report the construction of fluorescent cascadic catalytic beacons. With separation of the molecular recognition module from the signal reporter, this new design both avoids DNAzyme modifications and improves sensitivity through an endonuclease-based cascadic enzymatic signal amplification. This allows detection of l-histidine with high sensitivity (LOD = 200 nM) and excellent specificity. The proposed sensing system has also been used for detection of l-histidine in cellular homogenate with satisfactory results. [ABSTRACT FROM AUTHOR]

Various interferences from measurement conditions and substrate inhomogeneity are well-known confounding factors for poor reproducibility, which is a challenge in surface-enhanced Raman scattering (SERS) quantification. To address these issues, novel substrates and versatile internal standards have been designed and the repeatability is improved to some degree. However, these internal standards are either complex or unstable enough to resist harsh environments such as acid and oxidation. Graphene-isolated-Au-nanocrystal (GLAN) has unique properties and been applied for cell multimodal imaging and chemotherapy but not for SERS quantification analysis yet. Herein, we chose GLANs to improve the accuracy of SERS analysis. GIAN integrates the SERS effect and internal standard into a simple nanoparticle and is proved to be an ideal platform for SERS analysis given its superior properties: (l) chemical stability, it remains stable in strong acid and oxidation, even mimic bioenvironment; (2) a simple core--shell structure, with a thin graphitic shell which is not only a protector that avoiding inner Au catalysis unnecessary reaction but also an internal standard to eliminate the interference during the Raman detections; (3) the big-IT structure can absorb target molecule thus achieve an enrichment effect and quench background fluorescence. Laser power, focus, and substrate fluctuations as well as coexist substance interferences were investigated and the accuracy was improved greatly with the introduction of 2D band internal standard in Raman silent region with less background. Moreover, GIAN was applied for crystal violet determination directly on fish muscle and scale, which was rapid and convenient without complex extraction process. All these results indicate GIAN is an optimum choice for SERS analysis in complex systems. [ABSTRACT FROM AUTHOR]

With their unique optical properties and distinct Raman signatures, graphitic nanomaterials can serve as substrates for surface-enhanced Raman spectroscopy (SERS) or provide signal amplification for bioanalysis and detection. However, a relatively weak Raman signal has limited further biomedical applications. This has been addressed by encapsulating gold nanorods (AuNRs) in a thin graphitic shell to form gold graphitic nanocapsules. This step improves plasmon resonance, which enhances Raman intensity, and has the potential for integrating two-photon luminescence (TPL) imaging capability. However, changing the morphology of gold graphitic nanocapsules such that high quality and stability are achieved remains a challenge. To address this task, we herein report a confinement chemical vapor deposition (CVD) method to prepare the construction of AuNR-encapsulated graphitic nanocapsules with these properties. Specifically, through morphological modulation, we (1) achieved higher plasmon resonance with near-IR incident light, thus achieving greater Raman intensity, and (2) successfully integrated two-photon luminescence dual-modal (Raman/TPL) bioimaging capabilities. Cancer-cell-specific aptamers were further modified on the AuNR@G graphitic surface through simple, but strong, π-π interactions to achieve imaging selectivity through differential cancer cell recognition. [ABSTRACT FROM AUTHOR]

Sulfhydryl-containing proteins play critical roles in various physiological and biological processes, and the activities of those proteins have been reported to be susceptible to thiol oxidation. Therefore, the development of protein thiol target fluorescent probe is highly desirable. In the present work, a biotinylated coumarin fluorescence "off-on" probe SQ for selectively detecting protein thiols in biotin receptor-positive cancer cells was designed with a 2,4-dinitrobenzenesulfony as the thiol receptor. The probe exhibited dramatic fluorescence responses toward sulfhydryl-containing proteins (ovalbumin (OVA), bovine serum albumin (BSA)): up to 170-fold fluorescence enhancement with 70 nm blue-shift was observed with the addition of OVA. However, low molecular weight thiols (Cys, glutathione (GSH), Hey) caused negligible fluorescence changes of SQ In addition, biotin receptor-positive Hela cells displayed strong red and green fluorescence after incubation of SQfor 1 h; neither red nor green fluorescence signal could be visualized in biotin-negative normal lung Wi38 cells. These results imply that the probe has potential application in fluorescent imaging protein thiols on the surface of Hela cells. [ABSTRACT FROM AUTHOR]

Photoactivatable probe-based fluorescent imaging has become an efficient and attractive technique for spatiotemporal microscopic studies of biological events. However, almost all previously reported photoactivatable organic probes have been based on hydrosoluble precursors, which have produced water-soluble active fluorophores able to readily diffuse away from the photocleavage site, thereby dramatically reducing spatial resolution. Hydroxyphenylquinazolinone (HPQ), a small organic dye known for its classic luminescence mechanism through excited-state intramolecular proton transfer (ESIPT), shows strong light emission in the solid state, but no emission in solution. In this work, HPQ was employed as a precursor to develop a localizable, photoactivatable two-photon probe (PHPQ) for spatiotemporal bioimaging applications. After photocleavage, PHPQ releases a precipitating HPQ fluorophore which shows both one-photon and two-photon excited yellow-green fluorescence, thereby producing a localizable fluorescence signal that affords high spatial resolution for bioimaging, with more than 200-fold one-photon and 150-fold two-photon fluorescence enhancement. [ABSTRACT FROM AUTHOR]

Many one-photon fluorescence-based theranostic nanosystems have been developed for simultaneous therapeutic intervention/monitoring for various types of cancers. However, for early diagnosis of cancer, two-photon fluorescence microscopy (TPFM) can realize deep-tissue imaging with higher spatial resolution. In this study, we first report a multiple functional nanoprobe for contrast-enhanced bimodal cellular imaging and targeted therapy. Components of the nanoprobe include (1) two-photon dye-doped mesoporous silica nanoparticles (TPD-MSNs); (2) MnO2 nanosheets that act as a (i) gatekeeper for TPD-MSNs, (ii) quencher for TP fluorescence, and (iii) contrast agent for MRlj (3) cancer cell-targeting aptamers. Guided by aptamers, TPDMSNs are rapidly internalized into the target cells. Next, intracellular glutathione reduces Mn2 to Mn2+ ions, resulting in contrast-enhanced TP fluorescence and magnetic resonance signal for cellular imaging. Meanwhile, preloaded doxorubicin and Chlorin e6 are released for chemotherapy and photodynamic therapy, respectively, with a synergistic effect and significantly enhanced therapeutic efficacy. [ABSTRACT FROM AUTHOR]