Polarization-based oxygen sensor

A new approach to oxygen sensing based on the luminescence polarization observed from a novel type of sensor is described. The oxygen sensor consists of an oxygen-sensitive silicone film containing tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) chloride [Ru(dpp)3Cl2] and an oxygen-insensitive film of Styryl 7 in poly(vinyl alcohol). Polarizers are used to select orthogonally polarized emission components from Ru(dpp)3Cl2 and Styryl 7. The polarization of the combined emission was found to be highly sensitive to the partial pressure of oxygen. This method of polarization sensing is generic and can be used with any fluorophore which displays an analyte-dependent change in intensity.     

基于钌配合物荧光猝灭原理的新型氟化有机改性溶胶-凝胶氧传感膜的研究

选用3,3,3-三氟丙基三甲氧基硅烷为前驱体,制备氧光化学传感膜材料.利用4,7-二苯基-1,10-邻菲咯啉钌(Ⅱ)([Ru(dpp)3(ClO4)2])为氧荧光猝灭指示剂,通过优化制备条件获得对氧浓度变化具有敏感响应的传感膜.研究结果表明:所制备的氧传感膜对水体中的溶解氧的线性响应范围为0.5～16.0 mg/L,最...     

Direct observation of triplet state emission of single molecules: single molecule phosphorescence quenching of metalloporphyrin and organometallic complexes by molecular oxygen and their quenching rate distributions

Single molecules are detected through the phosphorescence emission of their triplet states. Emission of the triplet states of single molecules of Pt octabutoxycarbonyl porphyrin (PtOBCP) and ruthenium(II)-tris-4,7-diphenyl-1,10-phenanthroline dichloride (Ru(dpp)(3)Cl(2)) is reported. The single molecule phosphorescence is very sensitive to molecular oxygen. Each molecule has its own characteristic quenching rate by oxygen, and the distribution of these rates is measured for (Ru(dpp)(3)Cl(2)) on a quartz surface. The large variance of this distribution is presumed to be caused by fluctuations in the pseudobimolecular rate coefficient and the local oxygen concentration. The possibility of creating a quantitative single oxygen molecule sensor is suggested.     

Fluorescent Metal Nanoshells: Lifetime-Tunable Molecular Probes in Fluorescent Cell Imaging

We reported the preparation of lifetime-tunable fluorescent metal nanoshells and used them as lifetime imaging agents for potential detection of multiple target molecules by a single cell imaging scan. These metal nanoshells were generated to have 40 nm silica cores and 10 nm silver shells. Three kinds of metal-ligand complexes tris(5-amino-1,10-phenanthroline)ruthenium(II) (Ru(NH(2)-Phen)(3) (2+)), tris(2,2'-bipyridine) ruthenium(II) (Ru(bpy)(3) (2+)), and tris(2,3-bis(2-pyridyl)pyrazine))ruthenium(II) (Ru(dpp)(3) (2+)) that have similar excitation and emission wavelengths but different lifetimes were respectively encapsulated in the cores of metal nanoshells for the purpose of fluorescence. Compared with the metal-free silica spheres, these metal nanoshells were found to display enhanced emission intensities and shortened lifetimes due to near-field interactions of Ru(II) complexes with the metal shells. The shortened lifetimes of these metal nanoshells were definitely unique relevant to the Ru(II) complexes: 10 ns for the Ru(Phen-NH(2))(3) (2+)-Ag nanoshells, 45 ns for the Ru(bpy)(3) (2+)-Ag nanoshells, and 200 ns for the Ru(dpp)(3) (2+)-Ag nanoshells. These lifetimes were longer than the lifetime of cellular autofluorescence (2 - 5 ns), so the emission signals of these metal nanoshells could be distinctly isolated from the cellular background on the lifetime cell images. Moreover, these lifetimes were also different from one another, resulting in the emission signals of three metal nanoshells could be distinguished from one another on the cell images. This feature may offer an opportunity to detect multiple target molecules in a single cell imaging scan when the metal nanoshells are bound with various targets in the cells.     

Chemosensors and biosensors based on polyelectrolyte microcapsules containing fluorescent dyes and enzymes

The concept of enzyme-assisted substrate sensing based on use of fluorescent markers to detect the products of enzymatic reaction has been investigated by fabrication of micron-scale polyelectrolyte capsules containing enzymes and dyes in one entity. Microcapsules approximately 5 μm in size entrap glucose oxidase or lactate oxidase, with peroxidase, together with the corresponding markers Tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride (Ru(dpp)) complex and dihydrorhodamine 123 (DHR123), which are sensitive to oxygen and hydrogen peroxide, respectively. These capsules are produced by co-precipitation of calcium carbonate particles with the enzyme followed by layer-by-layer assembly of polyelectrolytes over the surface of the particles and incorporation of the dye in the capsule interior or in the multilayer shell. After dissolution of the calcium carbonate the enzymes and dyes remain in the multilayer capsules. In this study we produced enzyme-containing microcapsules sensitive to glucose and lactate. Calibration curves based on fluorescence intensity of Ru(dpp) and DHR123 were linearly dependent on substrate concentration, enabling reliable sensing in the millimolar range. The main advantages of using these capsules with optical recording is the possibility of building single capsule-based sensors. The response from individual capsules was observed by confocal microscopy as increasing fluorescence intensity of the capsule on addition of lactate at millimolar concentrations. Because internalization of the micron-sized multi-component capsules was feasible, they could be further optimized for in-situ intracellular sensing and metabolite monitoring on the basis of fluorescence reporting.     

改性SiO2载体对邻菲咯啉钌荧光特性及氧敏感荧光膜性能的影响

为提高极性荧光指示剂Ru(dpp)₃Cl₂在非极性硅橡胶中的分散性,以沉淀白炭黑、气相白炭黑和甲基MQ树脂,载负荧光指示剂Ru(dpp)₃Cl₂,再填充到二甲基硅橡胶(PDMS)中,制备氧敏感荧光膜.以分光光度计和荧光光谱仪,研究载体种类对Ru(dpp)₃Cl₂的吸附性、荧光特性及氧敏感荧光膜性能的影响.白炭黑载负Ru(dpp)₃Cl₂的荧光发射光谱相对其稀溶液约红移20 nm.载体表面的甲基可减弱SiO₂载体对Ru(dpp)₃Cl₂分子的吸附性和相互作用,减少荧光发射光谱的红移12 nm,提高荧光强度近10倍.白炭黑有助改善Ru(dpp)₃Cl₂在PDMS中的分散性和氧敏感荧光膜的荧光输出和猝灭比,尤以MQ树脂的效果最为显著.     

胺基邻菲咯啉-钌(Ⅱ)反应性荧光指示剂的合成与化学固定的研究

为减少荧光指示剂被水萃取流失,提高荧光膜的使用寿命,将5-氨基-邻菲咯啉与二(4,7-二苯基-邻菲咯啉)二氯化钌(Ⅱ)络合,合成带氨基的荧光指示剂[Ru(dpp)₂(phen-NH₂)]Cl₂,并经氨基键合到有机玻璃表面。以核磁、质谱、红外验证合成荧光指示剂的结构,研究键合条件对染色有机玻璃荧光发射的影响,监测荧光强度随水浸泡时间的变化。合成荧光指示剂的荧光发射峰值波长为570 nm,键合到有机玻璃后发射光谱红移20 nm,荧光强度受溶解氧影响,响应时间约为10 s,氧猝灭比达4。染色有机玻璃的荧光稳定性好,在50 ℃水中浸泡7个月,荧光强度下降小于1%。     

Ruthenium(II)-polyazine light absorbers bridged to reactive cis-dichlororhodium(III) centers in a bimetallic molecular architecture

Bimetallic complexes of the form [(bpy)(2)Ru(BL)RhCl(2)(phen)](PF(6))(3), where bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, and BL = 2,3-bis(2-pyridyl)pyrazine (dpp) or 2,2'-bipyrimidine (bpm), were synthesized, characterized, and compared to the [{(bpy)(2)Ru(BL)}(2)RhCl(2)](PF(6))(5) trimetallic analogues. The new complexes were synthesized via the building block method, exploiting the known coordination chemistry of Rh(III) polyazine complexes. In contrast to [{(bpy)(2)Ru(dpp)}(2)RhCl(2)](PF(6))(5) and [{(bpy)(2)Ru(bpm)}(2)RhCl(2)](PF(6))(5), [(bpy)(2)Ru(dpp)RhCl(2)(phen)](PF(6))(3) and [(bpy)(2)Ru(bpm)RhCl(2)(phen)](PF(6))(3) have a single visible light absorber subunit coupled to the cis-Rh(III)Cl(2) moiety, an unexplored molecular architecture. The electrochemistry of [(bpy)(2)Ru(dpp)RhCl(2)(phen)](PF(6))(3) showed a reversible oxidation at 1.61 V (vs Ag/AgCl) (Ru(III/II)), quasi-reversible reductions at -0.39 V, -0.74, and -0.98 V. The first two reductive couples corresponded to two electrons, consistent with Rh reduction. The electrochemistry of [(bpy)(2)Ru(bpm)RhCl(2)(phen)](PF(6))(3) exhibited a reversible oxidation at 1.76 V (Ru(III/II)). A reversible reduction at -0.14 V (bpm(0/-)), and quasi-reversible reductions at -0.77 and -0.91 V each corresponded to a one electron process, bpm(0/-), Rh(III/II), and Rh(II/I). The dpp bridged bimetallic and trimetallic display Ru(dpi)-->dpp(pi*) metal-to-ligand charge transfer (MLCT) transitions at 509 nm (14,700 M(-1) cm(-1)) and 518 nm (26,100 M(-1) cm(-1)), respectively. The bpm bridged bimetallic and trimetallic display Ru(dpi)-->bpm(pi*) charge transfer (CT) transitions at 581 nm (4,000 M(-1) cm(-1)) and 594 nm (9,900 M(-1) cm(-1)), respectively. The heteronuclear complexes [(bpy)(2)Ru(dpp)RhCl(2)(phen)](PF(6))(3) and [{(bpy)(2)Ru(dpp)}(2)RhCl(2)](PF(6))(5) had (3)MLCT emissions that are Ru(dpi)-->dpp(pi*) CT in nature but were red-shifted and lower intensity than [(bpy)(2)Ru(dpp)Ru(bpy)(2)](PF(6))(4). The lifetimes of the (3)MLCT state of [(bpy)(2)Ru(dpp)RhCl(2)(phen)](PF(6))(3) at room temperature (30 ns) was shorter than [(bpy)(2)Ru(dpp)Ru(bpy)(2)](PF(6))(4), consistent with favorable electron transfer to Rh(III) to generate a metal-to-metal charge-transfer ((3)MMCT) state. The reported synthetic methods provide means to a new molecular architecture coupling a single Ru light absorber to the Rh(III) center while retaining the interesting cis-Rh(III)Cl(2) moiety.     

Mixed-metal supramolecular complexes coupling phosphine-containing Ru(II) light absorbers to a reactive Pt(II) through polyazine bridging ligands

Supramolecular bimetallic Ru(II)/Pt(II) complexes [(tpy)Ru(PEt(2)Ph)(BL)PtCl(2)](2+) and their synthons [(tpy)Ru(L)(BL)](n)()(+) (where L = Cl(-), CH(3)CN, or PEt(2)Ph; tpy = 2,2':6',2'-terpyridine; and BL = 2,2'-bipyrimidine (bpm) or 2,3-bis(2-pyridyl)pyrazine (dpp)) have been synthesized and studied by cyclic voltammetry, electronic absorption spectroscopy, mass spectral analysis, and (31)P NMR. The mixed-metal bimetallic complexes couple phosphine-containing Ru chromophores to a reactive Pt site. These complexes show how substitution of the monodentate ligand on the [(tpy)RuCl(BL)](+) synthons can tune the properties of these light absorbers (LA) and incorporate a (31)P NMR tag by addition of the PEt(2)Ph ligand. The redox potentials for the Ru(III/II) couples occur at values greater than 1.00 V versus the Ag/AgCl reference electrode and can be tuned to more positive potentials on going from Cl(-) to CH(3)CN or PEt(2)Ph (E(1/2) = 1.01, 1.55, and 1.56 V, respectively, for BL = bpm). The BL(0/-) couple at -1.03 (bpm) and -1.05 V (dpp) for [(tpy)Ru(PEt(2)Ph)(BL)](2+) shifts dramatically to more positive potentials upon the addition of the PtCl(2) moiety to -0.34 (bpm) and -0.50 V (dpp) for the [(tpy)Ru(PEt(2)Ph)(BL)PtCl(2)](2+) bridged complex. The lowest energy electronic absorption for these complexes is assigned as the Ru(d pi) --> BL(pi*) metal-to-ligand charge transfer (MLCT) transition. These MLCT transitions are tuned to higher energy in the monometallic synthons when Cl(-) is replaced by CH(3)CN or PEt(2)Ph (516, 452, and 450 nm, for BL = bpm, respectively) and to lower energy when Pt(II)Cl(2) is coordinated to the bridging ligand (560 and 506 nm for BL = bpm or dpp). This MLCT state displays a broad emission at room temperature for all the dpp systems with the [(tpy)Ru(PEt(2)Ph)(dpp)PtCl(2)](2+) system exhibiting an emission centered at 750 nm with a lifetime of 56 ns. These supramolecular complexes [(tpy)Ru(PEt(2)Ph)(BL)PtCl(2)](2+) represent the covalent linkage of TAG-LA-BL-RM assembly (TAG = NMR active tag, RM = Pt(II) reactive metal).     

Electrochemical and luminescent properties of new mononuclear ruthenium(II) and binuclear iridium(III)-ruthenium(II) terpyridine complexes.

Hexafluorophosphate salts of mononuclear complexes [Ru(II)Cl(L)(terpy)]+ (L = dmbpy (1); dpbpy (2), sambpy (3), and dpp (7), and binuclear complexes [Ru(II)2Cl2(dpp)(terpy)2]2+ (8) and [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+ (9) were prepared and characterized. Abbreviations of the ligands are bpy = 2,2'-bipyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, dpbpy = 4,4'-diphenyl-2,2'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, sambpy = 4,4'-bis((S)-(+)-alpha-1-phenylethylamido)-2,2'-bipyridine, and terpy = 2,2':6',2'-terpyridine. The absorption spectra of 8 and 9 are dominated by ligand-centered bands in the UV region and by metal-to-ligand charge-transfer bands in the visible region. The details of their spectroscopic and electrochemical properties were investigated. In both binuclear complexes, it has been found that the HOMO is based on the Ru metal, and LUMO is dpp-based. [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+, indicating intense emission at room temperature, and a lifetime of 154 ns. The long lifetime of this bimetallic chromophore makes it a useful component in the design of supramolecular complexes.     

Characteristics and properties of metal-to-ligand charge-transfer excited states in 2,3-bis(2-pyridyl)pyrazine and 2,2'-bypyridine ruthenium complexes. Perturbation-theory-based correlations of optical absorption and emission parameters with electrochemistry and thermal kinetics and related Ab initio calculations

The absorption, emission, and infrared spectra, metal (Ru) and ligand (PP) half-wave potentials, and ab initio calculations on the ligands (PP) are compared for several [L(n)()Ru(PP)](2+) and [[L(n)Ru]dpp[RuL'(n)]](4+) complexes, where L(n) and L'(n) = (bpy)(2) or (NH(3))(4) and PP = 2,2'-bipyridine (bpy), 2,3-bis(2-pyridyl)pyrazine (dpp), 2,3-bis(2-pyridyl)quinoxaline (dpq), or 2,3-bis(2pyridyl)benzoquinoxaline (dpb). The energy of the metal-to-ligand charge-transfer (MLCT) absorption maximum (hnu(max)) varies in nearly direct proportion to the difference between Ru(III)/Ru(II) and (PP)/(PP)(-) half-wave potentials, DeltaE(1/2), for the monometallic complexes but not for the bimetallic complexes. The MLCT spectra of [(NH(3))(4)Ru(dpp)](2+) exhibit three prominent visible-near-UV absorptions, compared to two for [(NH(3))(4)Ru(bpy)](2+), and are not easily reconciled with the MLCT spectra of [[(NH(3))(4)Ru]dpp[RuL(n)]](4+). The ab initio calculations indicate that the two lowest energy pi orbitals are not much different in energy in the PP ligands (they correlate with the degenerate pi orbitals of benzene) and that both contribute to the observed MLCT transitions. The LUMO energies calculated for the monometallic complexes correlate strongly with the observed hnu(max) (corrected for variations in metal contribution). The LUMO computed for dpp correlates with LUMO + 1 of pyrazine. This inversion of the order of the two lowest energy pi orbitals is unique to dpp in this series of ligands. Configurational mixing of the ground and MLCT excited states is treated as a small perturbation of the overall energies of the metal complexes, resulting in a contribution epsilon(s) to the ground-state energy. The fraction of charge delocalized, alpha(DA)(2), is expected to attenuate the reorganizational energy, chi(reorg), by a factor of approximately (1 - 4alpha(DA)(2) + alpha(DA)(4)), relative to the limit where there is no charge delocalization. This appears to be a substantial effect for these complexes (alpha(DA)(2) congruent with 0.1 for Ru(II)/bpy), and it leads to smaller reorganizational energies for emission than for absorption. Reorganizational energies are inferred from the bandwidths found in Gaussian analyses of the emission and/or absorption spectra. Exchange energies are estimated from the Stokes shifts combined with perturbation--theory-based relationship between the reorganizational energies for absorption and emission values. The results indicate that epsilon(s) is dominated by terms that contribute to electron delocalization between metal and PP ligand. This inference is supported by the large shifts in the N-H stretching frequency of coordinated NH(3) as the number of PP ligands is increased. The measured properties of the bpy and dpp ligands seem to be very similar, but electron delocalization appears to be slightly larger (10-40%) and the exchange energy contributions appear to be comparable (e.g., approximately 1.7 x 10(3) cm(-1) in [Ru(bpy)(2)dpp](2+) compared to approximately 1.3 x 10(3) cm(-1) in the bpy analogue).     

Electrochemical, spectroscopic, and photophysical properties of structurally diverse polyazine-bridged Ru(II),Pt(II) and Os(II),Ru(II),Pt(II) supramolecular motifs

Five new tetrametallic supramolecules of the motif [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) and three new trimetallic light absorbers [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) (TL = bpy = 2,2'-bipyridine or phen = 1,10-phenanthroline; M = Ru(II) or Os(II); BL = dpp = 2,3-bis(2-pyridyl)pyrazine, dpq = 2,3-bis(2-pyridyl)quinoxaline, or bpm = 2,2'-bipyrimidine) were synthesized and their redox, spectroscopic, and photophysical properties investigated. The tetrametallic complexes couple a Pt(II)-based reactive metal center to Ru and/or Os light absorbers through two different polyazine BL to provide structural diversity and interesting resultant properties. The redox potential of the M(II/III) couple is modulated by M variation, with the terminal Ru(II/III) occurring at 1.58-1.61 V and terminal Os(II/III) couples at 1.07-1.18 V versus Ag/AgCl. [{(TL)(2)M(dpp)}(2)Ru(BL)](PF(6))(6) display terminal M(dπ)-based highest occupied molecular orbitals (HOMOs) with the dpp(π*)-based lowest unoccupied molecular orbital (LUMO) energy relatively unaffected by the nature of BL. The coupling of Pt to the BL results in orbital inversion with localization of the LUMO on the remote BL in the tetrametallic complexes, providing a lowest energy charge separated (CS) state with an oxidized terminal Ru or Os and spatially separated reduced BL. The complexes [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) and [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) efficiently absorb light throughout the UV and visible regions with intense metal-to-ligand charge transfer (MLCT) transitions in the visible at about 540 nm (M = Ru) and 560 nm (M = Os) (ε ≈ 33,000-42,000 M(-1) cm(-1)) and direct excitation to the spin-forbidden (3)MLCT excited state in the Os complexes about 720 nm. All the trimetallic and tetrametallic Ru-based supramolecular systems emit from the terminal Ru(dπ)→dpp(π*) (3)MLCT state, λ(max)(em) ≈ 750 nm. The tetrametallic systems display complex excited state dynamics with quenching of the (3)MLCT emission at room temperature to populate the lowest-lying (3)CS state population of the emissive (3)MLCT state.     

On-line fluorescent monitoring of the degradation of polymeric scaffolds for tissue engineering

Tissue engineering involves culturing, growing and assembling cells and newly generated matrix in polymeric scaffolds. To achieve a functional tissue in vitro, the cell-scaffold constructs are subjected to various stimulations during an incubation phase, which mimics the in vivo environment. In order to monitor the progression of tissue formation, there is a need for on-line and non-destructive methods of monitoring at the cellular and biomolecular level, for example, the assessment of scaffold degradation alongside the measure of matrix production. This study presents a proof of concept for monitoring scaffold degradation on-line within a culture environment. Using a mesoporous silica based approach, a pH sensitive fluorescent probe, fluorescein isothiocyanate (FITC), was incorporated into degradable polymeric scaffolds made from poly(L-lactic acid) which has a slow degradation rate, and poly(lactide-co-glycolide) which has a rapid degradation rate. The fluorescent probe was incorporated into thin films and three dimensional porous scaffolds demonstrating the capabilities of monitoring on-line. Following incubation, the intensity of fluorescence in the rapidly degrading scaffolds reduced with culture time in comparison to slow degrading polymeric scaffolds when observed qualitatively using fluorescent microscopy. The relationship between pH and fluorescent intensity was assessed, and the use of this technique for monitoring by-products via the solid scaffold by microscopy or through culture medium by a luminescence spectrometer is discussed. This study demonstrates that endowing scaffolds with a sensing element could provide an on-line and non-destructive monitoring method for tissue engineering.     

Surface confinement and its effects on the luminescence quenching of a ruthenium-containing metallopolymer

Luminescence quenching of the metallopolymers [Ru(bpy)(2)(PVP)(10)](2+) and [Ru(bpy)(2)(PVP)(10)Os(bpy)(2)](4+), both in solution and as thin films, is reported, where bpy is 2,2'-bipyridyl and PVP is poly(4-vinylpyridine). When the metallopolymer is dissolved in ethanol, quenching of the ruthenium excited state, Ru(2+*), within [Ru(bpy)(2)(PVP)(10)](2+) by [Os(bpy)(3)](2+) proceeds by a dynamic quenching mechanism and the rate constant is (1.1 +/- 0.1) x 10(11) M(-1) s(-1). This quenching rate is nearly two orders of magnitude larger than that found for quenching of monomeric [Ru(bpy)(3)](2+) under the same conditions. This observation is interpreted in terms of an energy transfer quenching mechanism in which the high local concentration of ruthenium luminophores leads to a single [Os(bpy)(3)](2+) centre quenching the emission of several ruthenium luminophores. Amplifications of this kind will lead to the development of more sensitive sensors based on emission quenching. Quenching by both [Os(bpy)(3)](2+) and molecular oxygen is significantly reduced within a thin film of the metallopolymer. Significantly, in both optically driven emission and electrogenerated chemiluminescence, emission is observed from both ruthenium and osmium centres within [Ru(bpy)(2)(PVP)(10)Os(bpy)(2)](4+) films, i.e. the ruthenium emission is not quenched by the coordinated [Os(bpy)(2)](2+) units. This observation opens up new possibilities in multi-analyte sensing since each luminophore can be used to detect separate analytes, e.g. guanine and oxoguanine.     

Glucose sensing by electrogenerated chemiluminescence of glucose-dehydrogenase produced NADH on electrodeposited redox hydrogel

In this work, we report a new sensing approach based on electrogenerated chemiluminescence (ECL) in an electrodeposited redox hydrogel using glucose dehydrogenase as a model system. The ECL-hydrogel films were electrodeposited by potential cycling of a PBS solution containing [poly(4-vinylpyridine)Ru(2,2'-bipyridine)(2)Cl(-)](+/2+). The film was easily prepared in a rapid, reproducible and well-controlled one-step procedure. The deposited hydrogel film is permeable to water-soluble chemicals and biochemicals, like enzyme substrates and coenzymes. Electrochemistry and ECL of NADH were studied at the level of the hydrogel film. Results indicate that ECL emission occurs at a relatively low anodic potential compared to the classical Ru(bipy)(3)(2+) complex. This is an important advantage since the measurements performed with the ECL hydrogel are thus less sensitive to interfering species. An ECL oxidative-reductive mechanism is presented for the ECL-hydrogel. Then we showed that the intensity of the ECL of NADH produced by the enzymatic activity varies with the enzyme substrate concentration. Such sensing approach combines enzymatic selectivity with the ECL advantages at low oxidation potential.     

A Water-Soluble Luminescence Oxygen Sensor

We developed a water-soluble luminescent probe for dissolved oxygen. This probe is based on (Ru[dpp(SO₃Na)₂]₃) Cl₂, which is a sulfonated analogue of the well-known oxygen probe (Ru[dpp]₃)Cl₂. The compound dpp is 4,7-diphenyl-1,10-phenanthroline and dpp(SO₃Na)₂ is a disulfonated derivative of the same ligand. In aqueous solution in the absence of oxygen (Ru[dpp(SO₃Na)₂]₃)Cl₂ displays a lifetime of 3.7 μs that decreases to 930 ns on equilibrium with air and 227 ns on equilibrium with 100% oxygen. The Stern–Vohner quenching constant is 11330 M⁻¹. This high oxygen-quenching constant means that the photoluminescence of Ru(dpp[SO₃Na]₂)₃Cl₂ is 10% quenched at an oxygen concentration of 8.8 x 10⁻⁶ M , or equilibration with 5.4 torr of oxygen. The oxygen probe dissolved in water displays minimal interactions with lipid vesicles composed of dipalmityl-L-α-phosphatidyl glycerol but does appear to interact with human serum albumin. The absorption maximum near 480 nm, long lifetime and large Stokes'shift allow this probe to be used with simple instrumentation based on a light-emitting diode light source, allowing low-cost oxygen sensing in aqueous solutions. To the best of our knowledge this is the first practical water-soluble oxygen sensor.     

Electrochemiluminescence analysis of folate receptors on cell membrane with on-chip bipolar electrode

In this paper we report a transparent bipolar electrode based microfluidic chip-electrochemiluminescence (ECL) system for sensitive detection of folate receptors (FR) on cell membranes. This integrated system consists of a poly(dimethylsiloxane) (PDMS) layer containing a microchannel and a glass bottom sheet with indium tin oxide (ITO) strips as bipolar detectors. The ITO strips are fabricated using a PDMS micromold with carbon ink as a protective layer in place of traditional photoresist. The configuration of the bipolar electrode has great influence on the ECL intensity of Ru(bpy)(3)(2+)/tripropylamine(TPA) system. Further studies show that folic acid (FA) can strongly inhibit the ECL of the Ru(bpy)(3)(2+)/TPA system. Based on specific recognition between FA and FR on cell membrane, this microfluidic chip-ECL system is successfully applied for detecting the level of FR on human cervical tumor (HL-60) cells and MEF cells. It is found that the ECL intensity increases with the number of HL-60 cells in the range of 21 to 3.28 × 10(4) cells/mL. The average level of FR on HL-60 cells is calculated to be 8.05 ± 0.75 × 10(-18) mol/cell. While for MEF cells, it shows a much slower ECL increment than HL-60 cells due to the much lower FR level on MEF cells (5.30 ± 0.61 × 10(-19) mol/cell). Moreover, exocytosis of FA after FR mediated endocytosis was observed according to the change of the ECL signal with the incubation time of HL-60 cells in the FA- Ru(bpy)(3)(2+)/TPA system.     

trans-[Ru(II)(dpp)Cl2]: a convenient reagent for the preparation of heteroleptic Ru(dpp) complexes, where dpp is 2,9-di(pyrid-2'-yl)-1,10-phenanthroline

The reaction of 2,9-di(pyrid-2'-yl)-1,10-phenanthroline (dpp) with [RuCl(3)·3H(2)O] or [Ru(DMSO)(4)Cl(2)] provides the reagent trans-[Ru(II)(dpp)Cl(2)] in yields of 98 and 89%, respectively. This reagent reacts with monodentate ligands L to replace the two axial chlorides, affording reasonable yields of a ruthenium(II) complex with dpp bound tetradentate in the equatorial plane. The photophysical and electrochemical properties of the tetradentate complexes are strongly influenced by the axial ligands with electron-donating character to stabilize the ruthenium(III) state, shifting the metal-to-ligand charge-transfer absorption to lower energy and decreasing the oxidation potential. When the precursor trans-[Ru(II)(dpp)Cl(2)] reacts with a bidentate (2,2'-bipyridine), tridentate (2,2';6,2'-terpyridine), or tetradentate (itself) ligand, a peripheral pyridine on dpp is displaced such that dpp binds as a tridentate. This situation is illustrated by an X-ray analysis of [Ru(dpp)(bpy)Cl](PF(6)).     

Temperature Responsive Shape‐Memory Scaffolds with Circumferentially Aligned Nanofibers for Guiding Smooth Muscle Cell Behavior

Structural simulation of the smooth muscle layer plays an important role in tissue engineering of blood vessels for the replacement of damaged arteries. However, it is difficult to construct small‐diameter tubular scaffolds to homogenously locate and align smooth muscle cells (SMCs). In this work, novel temperature responsive shape‐memory scaffolds are designed for SMC culturing. The scaffolds are composed of an outer layer of poly(lactide–glycolide–trimethylene carbonate) (PLGATMC) for programming the deformation from planar to small‐diameter tubular shape and an inner layer of aligned nanofibrous membrane of poly(lactide–glycolide)/chitosan (PLGA/CS) to regulate cell adhesion, proliferation, and morphology. The SMC behaviors and functions are dependent on the PLGA/CS ratios of membranes, and the scaffold with PLGA/CS 7:3 membrane exhibits the most suitable ability to regulate SMC behavior. The PLGA/CS@PLGATMC scaffold can be deformed into a temporary planar at 20 °C for convenient seeding and attachment of SMCs and then immediately self‐rolled into 3D tube at 37 °C. The proposed strategy offers a practical approach for the development of small‐diameter vascular scaffolds from 2D planar into 3D tubular shape by self‐rolling.     

Interaction of oxygen-sensitive luminescent probes Ru(phen)(3)(2+) and Ru(bipy)(3)(2+) with animal and plant cells in vitro. Mechanism of phototoxicity and conditions for non-invasive oxygen measurements.

Understanding the role of oxygen in the physiology, pathophysiology and radio- and chemosensitivity of animal cells requires accurate and non-invasive measurements of oxygen concentrations in the range of 0-2x10(-4) M, in cells in vitro or in vivo. High resolution 3D imaging techniques could be particularly useful in investigating tissue oxygenation in vivo and in model tissues (multicellular spheroids) in vitro. The goals of this work were to develop microscopy techniques and (i) to define conditions under which two oxygen-sensitive luminescent dyes, Ru(bipy)(3)(2+) (tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate) and Ru(phen)(3)(2+) (tris(1,10-phenanthroline)ruthenium(II) chloride hydrate) can be used to probe oxygen concentrations within viable cells in vitro, when no phototoxic effects are evident, and (ii) to investigate the mechanism of phototoxicity once cell damage occurs. This report demonstrates that Ru(bipy)(3)(2+) and Ru(phen)(3)(2+) do not pass through intact biological membranes, do not cause measurable photodamage to plasma membranes at a concentration of 0.2 mM and, when loaded into endosomes, yield a strong luminescent signal. However, at an extracellular concentration of 1 mM, in the presence of 457-nm light, detectable amounts of both complexes accumulate at the plasma membrane and cause a loss of membrane integrity via a mechanism which may involve the generation of singlet oxygen.