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The present article delineates the formation of green fluorescent organic nanoparticle through supramolecular aggregation of naphthalene diimide (NDI)-based, carboxybenzyl-protected, l-phenylalanine-appended bola-amphiphile, NDI-1. The amphiphilic molecule is soluble in DMSO, and, with gradual addition of water within the DMSO solution, the amphiphile starts to self-assemble via H-type aggregation to form spherical nanoparticles. These self-assembly of NDI-1 in the presence of a high amount of water exhibited aggregation-induced emission (AIE) through excimer formation. Notably, in the presence of 99% water content, the amphiphile forms spherical aggregated nanoparticles as confirmed from microscopic investigations and dynamic light scattering study. Interestingly, the emission maxima of molecularly dissolved NDI-1 (weak blue fluorescence) red-shifted upon aggregation with increase in water concentration and led to the formation of green-emitting fluorescent organic nanoparticles (FONPs) at 99% water content. These green-emitting FONPs were utilized in cell imaging as well as for efficient transportation of anticancer drug curcumin inside mammalian cells. [ABSTRACT FROM AUTHOR]

A robustreusable fluoride sensor comprised of a receptor in charge of thechemical recognition and a fluorophore responsible for signal recognitionhas been designed. Highly fluorescent carbon quantum dot (CD) andmagnetically separable nickel ethylenediaminetetraaceticacid (EDTA) complex bound-silica coated magnetite nanoparticle (Fe3O4@SiO2–EDTA–Ni) havebeen used as fluorophore and fluoride ion receptor, respectively.The assay is based on the exchange reaction between the CD and F–, which persuades the binding of fluoride to magneticreceptor. This method is highly sensitive, fast, and selective forfluoride ion in aqueous solution. The linear response range of fluoride(R2= 0.992) was found to be 1–20μM with a minimum detection limit of 0.06 μM. Excellentmagnetic property and superparamagnetic nature of the receptor areadvantageous for the removal and well quantification of fluoride ion.The practical utility of the method is well tested with tap water.Because of high sensitivity, reusability, effectivity, and biocompatibility,it exhibits great promise as a fluorescent probe for intracellulardetection of fluoride. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) andscanning ion conductance microscopy(SICM) are excellent and commonly used techniques for imaging thetopography of living cells with high resolution. We present a directcomparison of AFM and SICM for imaging microvilli, which are smallfeatures on the surface of living cells, and for imaging the shapeof whole cells. The imaging quality on microvilli increased significantlyafter cell fixation for AFM, whereas for SICM it remained constant.The apparent shape of whole cells in the case of AFM depended on theimaging force, which deformed the cell. In the case of SICM, celldeformations were avoided, owing to the contact-free imaging mechanism.We estimated that the lateral resolution on living cells is limitedby the cell’s elastic modulus for AFM, while it is not forSICM. By long-term, time-lapse imaging of microvilli dynamics, weshowed that the imaging quality decreased with time for AFM, whileit remained constant for SICM. [ABSTRACT FROM AUTHOR]

Inthis article, ionic liquid-functionalized carbon nanodots (IL-CDs)were produced in a simple manner by electrochemical exfoliation ofgraphite rods in the presence of an amino-terminated ionic liquid,and their preliminary applications were exploited. TEM and AFM resultsshowed that these IL-CDs are about 2.6 nm in diameter. The small-sizedIL-CDs have strong photoluminescence, with a quantum yield of about11.3%, and could be used for cell imaging. Moreover, the IL-CDs exhibitgood electron transfer properties and catalytic activities for O2and H2O2reduction. Additionally, theas-prepared IL-CDs can be applied as a matrix for immobilizing enzymes(glucose oxidase) to construct biosensors. Due to these favorableproperties, IL-CDs will find promising practical applications in electrocatalysis,biosensing, and bioimaging. [ABSTRACT FROM AUTHOR]

In in vitro live-cell imaging, itwould be beneficial to grow andassess human embryonic stem cell-derived retinal pigment epithelial(hESC-RPE) cells on thin, transparent, rigid surfaces such as coverglasses. In this study, we assessed how the silanization of glasswith 3-aminopropyltriethoxysilane (APTES), 3-(trimethoxysilyl)propylmethacrylate (MAPTMS), or polymer–ceramic material Ormocompaffects the surface properties, protein binding, and maturation ofhESC-RPE cells. The surface properties were studied by contact anglemeasurements, X-ray photoelectron spectroscopy (XPS), atomic forcemicroscopy (AFM), and a protein binding assay. The cell adherenceand proliferation were evaluated by culturing hESCRPE cells on collagenIV-coated untreated or silanized surfaces for 42 days. The Ormocomptreatment significantly increased the hydrophobicity and roughnessof glass surfaces compared to the APTES and MAPTMS treatments. TheXPS results indicated that the Ormocomp treatment changes the chemicalcomposition of the glass surface by increasing the carbon contentand the number of C–O/O bonds. The protein-bindingtest confirmed that the Ormocomp-treated surfaces bound more collagenIV than did APTES- or MAPTMS-treated surfaces. All of the silane treatmentsincreased the number of cells: after 42 days of culture, Ormocomphad 0.38, APTES had 0.16, MAPTMS had 0.19, and untreated glass hadonly 0.062, all presented as million cells cm–2.There were no differences in cell numbers compared to smoother torougher Ormocomp surfaces, suggesting that the surface chemistry and,more specifically, the collagen binding in combination with Ormocompare beneficial to hESC-RPE cell culture. This study clearly demonstratesthat Ormocomp treatment combined with collagen coating significantlyincreases hESC-RPE cell attachment compared to commonly used silanizingagents APTES and MAPTMS. Ormocomp silanization could thus enable theuse of microscopic live cell imaging methods for hESC-RPE cells. [ABSTRACT FROM AUTHOR]

Wereport on a europium-complex-grafted polymer for preparing stablenanoparticle probes with high luminescence brightness, narrow emissionbandwidth, and long luminescence lifetimes. A Eu complex bearing anamino group was used to react with a functional copolymer poly(styrene-co-maleic anhydride) by the spontaneous amidation reaction,producing the polymer grafted with Eu complexes in the side chains.The Eu-complex-grafted polymer was further used to prepare Eu-complex-graftedpolymer dots (Pdots) and Eu-complex-blended poly(9-vinylcarbazole)composite Pdots, which showed improved colloidal stability as comparedto those directly doped with Eu-complex molecules. Both types of Pdotscan be efficiently quenched by a nile blue dye, exhibiting much lowerdetection limit and higher quenching sensitivity as compared to freeEu-complex molecules. Steady-state spectroscopy and time-resolveddecay dynamics suggest the quenching mechanism is via efficient fluorescenceresonance energy transfer from the Eu complex inside a Pdot to surfacedye molecules. The amplified quenching in Eu-complex Pdots, togetherwith efficient cell uptake and specific cell surface labeling observedin mammalian cells, suggests their potential applications in time-resolvedbioassays and cellular imaging. [ABSTRACT FROM AUTHOR]

Two-photonfluorescence microscopy is a widely used noninvasivebioimaging technique because of unique advantages such as a largepenetration depth and 3D mapping capability. Ideal two-photon fluorophoresrequire large two-photon absorption cross sections and red emissionwith high quantum yields. Here we report red-emitting-dye-doped conjugatedpolymer nanoparticles that display high two-photon excitation brightness.In these nanoparticles, conjugated polymer (PFV) was chosen as a two-photonlight-harvesting material, and red-emitting dyes (MgPc and Nile red)were chosen as the energy acceptors and red-emitting materials. Two-photonexcitation fluorescence of MgPc and Nile red was enhanced by up to∼53 and ∼240 times, respectively. We have successfullydemonstrated the application of these conjugated polymer-based nanoparticlesin two-photon excitation cancer cell imaging with an excellent contrastratio. This concept could become a general approach to the preparationof two-photon excitation red-emitting materials for deep-tissue live-cellimaging with high contrast. [ABSTRACT FROM AUTHOR]

In this study, we describe a solutionprocedure for the preparationand surface modification of photostable colloidal silicon quantumdots (SiQDs) for imaging of cancer cells. Photoluminescent SiQDs weresynthesized by reduction of halogenated silane precursors using amicroemulsion process. It was shown that 1,8-nonadiyne molecules couldbe grafted onto the surface of hydrogen-terminated SiQDs via ultraviolet(UV)-promoted hydrosilylation, demonstrated by Fourier transform infraredspectroscopy (FTIR) measurements. In addition, various azide moleculeswere coupled onto nonadiyne-functionalized particles, rendering particlesdispersible in selected polar and nonpolar solvents. The photoluminescenceof functionalized SiQDs was stable against photobleaching and didnot vary appreciably within biologically applicable pH and temperatureranges. To demonstrate compatibility with biological systems, water-solubleSiQDs were used for fluorescent imaging of HeLa cells. In addition,the SiQDs were shown to be non-cytotoxic at concentrations up to 240μg/mL. The results presented herein provide good evidence forthe versatility of functionalized SiQDs for fluorescent bioimagingapplication. [ABSTRACT FROM AUTHOR]