Crystallization, Luminescence and Cytocompatibility of Hexagonal Calcium Doped Terbium Phosphate Hydrate Nanoparticles

Luminescent lanthanide-containing biocompatible nanosystems represent promising candidates as nanoplatforms for bioimaging applications. Herein, citrate-functionalized calcium-doped terbium phosphate hydrate nanophosphors of the rhabdophane type were prepared at different synthesis times and different Ca2+/Tb3+ ratios by a bioinspired crystallization method consisting of thermal decomplexing of Ca2+/Tb3+/citrate/phosphate/carbonate solutions. Nanoparticles were characterized by XRD, TEM, SEM, HR-TEM, FTIR, Raman, Thermogravimetry, inductively coupled plasma spectroscopy, thermoanalysis, dynamic light scattering, electrophoretic mobility, and fluorescence spectroscopy. They displayed ill-defined isometric morphologies with sizes ≤50 nm, hydration number n ~ 0.9, tailored Ca2+ content (0.42-8.11 wt%), and long luminescent lifetimes (800-2600 µs). Their relative luminescence intensities in solid state are neither affected by Ca2+, citrate content, nor by maturation time for Ca2+ doping concentration in solution below 0.07 M Ca2+. Only at this doping concentration does the maturation time strongly affect this property, decreasing it. In aqueous suspensions, neither pH nor ionic strength nor temperature affect their luminescence properties. All the nanoparticles displayed high cytocompatibility on two human carcinoma cell lines and cell viability correlated positively with the amount of doping Ca2+. Thus, these nanocrystals represent promising new luminescent nanoprobes for potential biomedical applications and, if coupled with targeting and therapeutic moieties, they could be effective tools for theranostics.

Self-Assembled Type I Collagen-Apatite Fibers with Varying Mineralization Extent and Luminescent Terbium Promote Osteogenic Differentiation of Mesenchymal Stem Cells

This work explores in depth the simultaneous self-assembly and mineralization of type I collagen by a base-acid neutralization technique to prepare biomimetic collagen-apatite fibrils with varying mineralization extent and doped with luminescent bactericidal Tb³⁺ ions. Two variants of the method are tested: base-acid titration, a solution of Ca(OH)₂ is added dropwise to a stirred solution containing type I collagen dispersed in H₃ PO₄ ; and direct mixing, the Ca(OH)₂ solution is added by fast dripping onto the acidic solution. Only the direct mixing variant yielded an effective control of calcium phosphate polymorphism. Luminescence spectroscopy reveals the long luminescence lifetime and high relative luminescence intensity of the Tb³⁺ -doped materials, while two-photon confocal fluorescence microscopy shows the characteristic green fluorescence light when using excitation wavelength of 458 nm, which is not harmful to bone tissue. Cytotoxicity/viability tests reveal that direct mixing samples show higher cell proliferation than titration samples. Additionally, osteogenic differentiation essays show that all mineralized fibrils promote the osteogenic differentiation, but the effect is more pronounced when using samples prepared by direct mixing, and more notably when using the Tb³⁺ -doped mineralized fibrils. Based on these findings it is concluded that the new nanocomposite is an ideal candidate for bone regenerative therapy.

Luminescent biomimetic citrate-coated europium-doped carbonated apatite nanoparticles for use in bioimaging: physico-chemistry and cytocompatibility

Nanomedicine covers the application of nanotechnologies in medicine. Of particular interest is the setup of highly-cytocompatible nanoparticles for use as drug carriers and/or for medical imaging. In this context, luminescent nanoparticles are appealing nanodevices with great potential for imaging of tumor or other targetable cells, and several strategies are under investigation. Biomimetic apatite nanoparticles represent candidates of choice in nanomedicine due to their high intrinsic biocompatibility and to the highly accommodative properties of the apatite structure, allowing many ionic substitutions. In this work, the preparation of biomimetic (bone-like) citrate-coated carbonated apatite nanoparticles doped with europium ions is explored using the citrate-based thermal decomplexing approach. The technique allows the preparation of the single apatitic phase with nanosized dimensions only at Eu³⁺ doping concentrations ≤0.01 M at some timepoints. The presence of the citrate coating on the particle surface (as found in bone nanoapatites) and Eu³⁺ substituting Ca²⁺ is beneficial for the preparation of stable suspensions at physiological pH, as witnessed by the ζ-potential versus pH characterizations. The sensitized luminescence features of the solid particles, as a function of the Eu³⁺ doping concentrations and the maturation times, have been thoroughly investigated, while those of particles in suspensions have been investigated at different pHs, ionic strengths and temperatures. Their cytocompatibility is illustrated in vitro on two selected cell types, the GTL-16 human carcinoma cells and the m17.ASC murine mesenchymal stem cells. This contribution shows the potentiality of the thermal decomplexing method for the setup of luminescent biomimetic apatite nanoprobes with controlled features for use in bioimaging.

Biomimetic citrate-coated europium doped carbonated apatite nanoparticles show a high luminescence intensity and cytocompatibility for uses in cell/tissue imaging.

A novel tridentate bis(phosphinic acid)phosphine oxide based europium(III)-selective Nafion membrane luminescent sensor

A new europium(III) membrane luminescent sensor based on a new tridentate bis(phosphinic acid)phosphine oxide (3) system has been developed. The synthesis of this new ligand is described and its full characterization by NMR, IR and elemental analyses is provided. The luminescent complex formed between europium(III) chloride and ligand 3 was evaluated in solution, observing that its spectroscopic and chemical characteristics are excellent for measuring in polymer inclusion membranes. Included in a Nafion membrane, all the parameters (ligand and ionic additives) that can affect the sensitivity and selectivity of the sensing membrane as well as the instrumental conditions were carefully optimized. The best luminescence signal (λexc = 229.06 nm and λem = 616.02 nm) was exhibited by the sensing film having a Nafion : ligand composition of 262.3 : 0.6 mg mL(-1). The membrane sensor showed a short response time (t95 = 5.0 ± 0.2 min) and an optimum working pH of 5.0 (25 mM acetate buffer solution). The membrane sensor manifested a good selectivity toward europium(III) ions with respect to other trivalent metals (iron, chromium and aluminium) and lanthanide(III) ions (lanthanum, samarium, terbium and ytterbium), although a small positive interference of terbium(III) ions was observed. It provided a linear range from 1.9 × 10(-8) to 5.0 × 10(-6) M with a very low detection limit (5.8 × 10(-9) M) and sensitivity (8.57 × 10(-7) a.u. per M). The applicability of this sensing film has been demonstrated by analyzing different kinds of spiked water samples obtaining recovery percentages of 95-97%.

Direct observation of reversible electronic energy transfer involving an iridium center

A cyclometalated iridium complex is reported where the core complex comprises naphthylpyridine as the main ligand and the ancillary 2,2'-bipyridine ligand is attached to a pyrene unit by a short alkyl bridge. To obtain the complex with satisfactory purity, it was necessary to modify the standard synthesis (direct reaction of the ancillary ligand with the chloro-bridged iridium dimer) to a method harnessing an intermediate tetramethylheptanolate-based complex, which was subjected to acid-promoted removal of the ancillary ligand and subsequent complexation. The photophysical behavior of the bichromophoric complex and a model complex without the pendant pyrene were studied using steady-state and time-resolved spectroscopies. Reversible electronic energy transfer (REET) is demonstrated, uniquely with an emissive cyclometalated iridium center and an adjacent organic chromophore. After excited-state equilibration is established (5 ns) as a result of REET, extremely long luminescence lifetimes of up to 225 μs result, compared to 8.3 μs for the model complex, without diminishing the emission quantum yield. As a result, remarkably high oxygen sensitivity is observed in both solution and polymeric matrices.

A rapid, sensitive screening test for polycyclic aromatic hydrocarbons applied to Antarctic water

We describe a rapid, sensitive, fluorescence screening test for polycyclic aromatic hydrocarbons in water samples that avoids more costly time-consuming methods. The screening test works by detecting benzo[a]pyrene. It runs without the need for any pre-concentration step, thus rendering it suitable for routine use in water-quality-control laboratories. The test recognizes contaminated samples rapidly (150 s) and inexpensively with a cut-off level of 10 ng l(-1), which is the value that the European Union and World Health Organization (WHO) have laid down in its assessment of the quality of water for human consumption. This was first ascertained by analysing tap and waste-water samples before studying environmental water samples from the Antarctic region. The reliability of the screening test was 2% false positives and 4% false negatives in 200 samples of tap and waste-water. The applicability was confirmed by the fact that the predictions of the screening test coincided exactly with results obtained with gas chromatography-mass spectrometry assays. We also discuss the polluted Antarctic samples and the possible sources of the contamination involved.

A fluorescence optosensor for analyzing naphazoline in pharmaceutical preparations

We have developed an optical sensor for determining and quantifying naphazoline (NPZ) based on its inherent fluorescence property. We have placed a non-ionic-exchanger solid support (Amberlite XAD-7) in a flow cell in the light path of the excitation beam and the fluorescence signal for NPZ is continuously monitored at lambda(exc/nm)=294/306 nm. The response time for this sensor is acceptably fast, 80s, obtaining a detection limit of 2.6 ng mL(-1) with standard deviations of 2.0% at 125 ng mL(-1). This device has been satisfactorily applied to two commercial formulations and its selectivity has been demonstrated with an interference study. The advantages have been compared with the only published sensor for determining NPZ in pharmaceutical preparations and with other analytical methods in the literature.

Fluorescence optosensors based on different transducers for the determination of polycyclic aromatic hydrocarbons in water

This paper presents the development of two optosensors for the determination of four polycyclic aromatic hydrocarbons (anthracene, benzo[a]pyrene, fluoranthene and benzo[b]fluoranthene) using a photomultiplier device and an intensified coupled charge device (ICCD) as optical transducers, respectively. These optosensors are based on the on-line immobilization of the analytes onto a non-ionic resin solid support (Amberlite XAD-4) in a continuous flow system, followed by the measurement of their native fluorescence. The determinations were performed using 15 mM H(2)PO(4)(-)/HPO(4)(2-) buffer solution at pH 7 and 25% 1,4-dioxane. Detection limits were 6.4 and 9.3 for ANT, 3.3 and 2.5 for BbF, 1.4 and 13.2 for FLT, and 1.7 and 7.8 for BaP using optosensor 1 or 2, respectively. Relative standard deviations were 7.9 and 6.7 for ANT at 50 ng mL(-1), 3.5 and 7.4 for BbF at 60 ng mL(-1), 3.6 and 8.9 for FLT at 50 ng mL(-1), and 6.7 and 11.6 for BaP at 50 ng mL(-1) using optosensor 1 or 2, respectively. Finally, a critical comparison between the two configurations based on different transducers (photomultiplier and ICCD) for resolving and simultaneously determining mixtures of the polycyclic aromatic hydrocarbons under study in water samples (tap and mineral waters) were carried out.

A sensitive fluorescence optosensor for analysing propranolol in pharmaceutical preparations and a test for its control in urine in sport

We describe a simple and selective method for analysing propranolol and a sensitive test for its control in urine. A flow-through fluorescence optosensor based on on-line immobilization in a non-ionic-exchanger (Amberlite XAD-7) solid support in a continuous flow was used in both cases. Determination was made in 5 mM H(2)PO(4)(-)/HPO(4)(2-) buffer solution at pH 6 at a working temperature of 20 degrees C. Fluorescence intensities were measured at lambda(ex/em) = 300/338 nm with a response time of 80 s, thus obtaining a linear concentration range of between 0 and 250.0 ng ml(-1) with a detection limit of 1.3 ng ml(-1), an analytical sensitivity of 6.0 ng ml(-1) and a standard deviation of 2.40% at a 150 ng ml(-1) concentration level for propranolol. We also propose a test to detect propranolol in urine with a linear concentration range between 0 and 100.0 ng ml(-1), a detection limit of 0.2 ng ml(-1), an analytical sensitivity of 1.0 ng ml(-1), and a standard deviation of 0.84% at a 75 ng ml(-1) concentration level. The effect of proteins presents in urine samples were evaluated. The two proposed methods were satisfactorily applied to commercial formulations and urine samples respectively.

HAI-RTP determination of carbaryl pesticide in different irrigation water samples of south Spain

In this work, a widely used pesticide named carbaryl, present in numerous water supplies, has been determined by the so-called heavy atom induced room-temperature phosphorescence (HAI-RTP) methodology. A detailed study of numerous instrumental variables such as sensitivity, slits, decay time, and gate time, and those of experimental type such as heavy atoms, oxygen scavenger, temperature, buffer solutions, and organic solvents, have been carried out. The detection limit was 2.8 ng mL(-)(1) with a relative standard deviation of 2.12% at the 150 ng mL(-)(1) level. Spiked irrigation water samples taken from different places near agricultural fields gave mean percentage recoveries of 95.7%. The results obtained in this study indicate that the proposed method is suitable for the determination of residues of carbaryl pesticide in water samples with good reproducibility and sensitivity for the analysis of this compound being rapid and very simple for routine analysis.