Evaluation of monoxide film-based dosimeters for surface dose detection in electron therapy.

Generally, electron therapy is applied to tumors on or close to the skin surface. However, this causes a variety of skin-related side effects. To alleviate the risk of these side effects, clinical treatment uses skin dosimeters to verify the therapeutic dose. However, dosimeters suffer from poor accuracy, because their attachment sites are approximated with the help of naked eyes. Therefore, a dosimeter based on a flexible material that can adjust to the contours of the human body is required. In this study, the reproducibility, linearity, dose-rate dependence, and percentage depth ionization (PDI) of PbO and HgO film-based dosimeters are evaluated to explore their potential as large-scale flexible dosimeters. The results demonstrate that both dosimeters deliver impressive reproducibility (within 1.5%) and linearity (≥ 0.9990). The relative standard deviations of the dose-rate dependence of the PbO and HgO dosimeters were 0.94% and 1.16% at 6 MeV, respectively, and 1.08% and 1.25% at 9 MeV, respectively, with the PbO dosimeter outperforming the 1.1% of existing diodes. The PDI analysis of the PbO and HgO dosimeters returned values of 0.014 cm (-0.074 cm) and 0.051 cm (-0.016 cm), respectively at 6 MeV (9 MeV) compared to the thimble chamber and R50. Therefore, the maximum error of each dosimeter is within the allowable range of 0.1 cm. In short, the analysis reveals that the PbO dosimeter delivers a superior performance relative to its HgO counterpart and has strong potential for use as a surface dosimeter. Thus, flexible monoxide materials have the necessary qualities to be used for dosimeters that meet the requisite quality assurance standards and can satisfy a variety of radiation-related applications as flexible functional materials.

Ayurvedic processing of α-HgS gives novel physicochemistry and distinct toxicokinetics in zebrafish.

Rasasindura (RS) is an Ayurvedic medicine, which contains ∼99% α-HgS. It is used as a rejuvenating agent and commonly used to treat diseases such as syphilis, insomnia, high fever, and nervous disorders. Cinnabar ore (α-HgS) is a well-known mineral, which is readily available. Despite it, Ayurvedic practitioners adopted an involved and tedious procedure for the preparation of RS. In this study, three samples, one was Ayurvedic (RS), the second one was the commercial (HGS), and the third one was cinnabar ore (CN), were physiochemically examined. Zebrafish model was employed for toxicity study with an oral dose of 100 mg/kg/day for the three samples for 10 days. We found that RS conferred novel physicochemical properties, which were not seen in HGS and CN. Significantly, the average crystallite size of RS was lowest (26 nm) as compared to HGS (31 nm) and CN (34 nm), and the rate of increase of crystallite size with temperature was lowest in RS. RS did not show any significant behavioral toxicity in zebrafish, which was seen with the HGS-and CN-treated zebrafish. HGS-and CN-treated zebrafish showed a significantly high (∗∗∗p < 0.001) decrease (77 ± 7.6% and 51 ± 6.5%, respectively) of glutathione (GSH) levels in the brain, however, for RS-treated zebrafish, the change of GSH was insignificant (26 ± 2.5%, p > 0.05). Interestingly, HGS significantly altered the γ-aminobutyric acid (GABA) in brain tissue. Therefore, among all three samples, RS exhibited the lowest toxicity, which can be credited to the distinct toxicokinetics by these samples.

Chiral ß-HgS quantum dots: Aqueous synthesis, optical properties and cytocompatibility.

ß-HgS quantum dots (QDs) have drawn enormous attention due to the size-tunable bandgap and the lowest quantum state in conduction band which have been applied to semiconductor transistor and photodetector. Though ß-HgS is the essential component of Tibetan medicine, the potential toxicity of ß-HgS limits its applications, especially in bio-application. Herein, chiral biomolecule enantiomers N-isobutyryl-L(D)-cysteine (L(D)-NIBC) and L(D)-cysteine (L(D)-Cys) were introduced into HgCl2 and Na2S aqueous solution to synthesize chiral ß-HgS QDs in one-pot, which significantly improved their water-solubility and cytocompatibility. Notably, all chiral ß-HgS QDs showed none cytotoxicity even at high concentration (20 mg·L-1), and the cytocompatibility of D-ß-HgS QDs was better than corresponding L-ß-HgS QDs at the concentration of 20 mg·L-1. This cytotoxicity discrimination was associated with the chirality inversion of chiral ß-HgS QDs compared with the corresponding chiral ligands. In-situ real-time circular dichroism (CD) monitoring indicated that the chirality of ß-HgS QDs originated from the asymmetrical arrangement of chiral ligands on the achiral core surface. Their chiroptical activity, near-infrared optical absorption (800 nm), fluorescence emission (900-1000 nm), high-performance photothermal conversion and good cytocompatibility, implied chiral ß-HgS QDs could be used as a candidate material for photothermal therapy or a near-infrared fluorescent probe in organism, which brings a novel insight for bio-application of ß-HgS QDs.

Hg Compound-Specific Isotope Analysis at Ultratrace Levels Using an on Line Gas Chromatographic Preconcentration and Separation Strategy Coupled to Multicollector-Inductively Coupled Plasma Mass Spectrometry.

Stable Hg isotope analyses are nowadays widely employed to discriminate Hg sources and understand its biogeochemical cycle. Until now, total Hg isotopic compositions have been mainly used but Hg compound-specific isotopic analysis (CSIA) methodologies are emerging. Online Hg-CSIA were limited to samples containing high concentrations, but in this work we overcome this limitation for the measurement of inorganic (IHg) and monomethylmercury (MMHg) by gas chromatography hyphenated to multicollector-inductively coupled plasma mass spectrometry (GC/MC-ICPMS) through the use of an automated online preconcentration strategy, allowing injection volumes up to 100 times larger than usual. The preconcentration of Hg species and subsequent transfer to the column were achieved by a programmed temperature vaporization (PTV) injector fitted with a packed liner. The PTV parameters were first optimized using a quadrupole ICPMS, and then its suitability for Hg-CSIA was evaluated with long-term replicate analysis of various standards and reference materials (RMs). The large preconcentration capability enables analyses with Hg concentrations in the organic solvent 2 orders of magnitude lower than the previous conventional GC/MC-ICPMS method, but a compound specific standard bracketing procedure was required for MMHg in order to correct for the differential behavior of Hg species in the liner. The external reproducibility of the method ranged from 0.19 to 0.39 ‰ for Δ199Hg and δ202Hg (as 2 SD, n = 143-167) depending on the species. The analysis of various RMs demonstrated the applicability to environmental samples with species concentrations down to about 150 ng g-1. This new methodology opens the way for a much wider range of online Hg-CSIA measurements that will improve our understanding of the Hg biogeochemical cycle.

Inactivation dynamics of 222 nm krypton-chlorine excilamp irradiation on Gram-positive and Gram-negative foodborne pathogenic bacteria.

The object of this study was to elucidate the bactericidal mechanism of a 222 nm Krypton Chlorine (KrCl) excilamp compared with that of a 254 nm Low Pressure mercury (LP Hg) lamp. The KrCl excilamp had higher bactericidal capacity against Gram-positive pathogenic bacteria (Staphylococcus aureus and L. monocytogenes) and Gram-negative pathogenic bacteria (S. Typhimurium and E. coli O157:H7) than did the LP Hg lamp when cell suspensions in PBS were irradiated with each type of UV lamp. It was found out that the KrCl excilamp induced cell membrane damage as a form of depolarization. From the study of respiratory chain dehydrogenase activity and the lipid peroxidation assay, it was revealed that cell membrane damage was attributed to inactivation of enzymes related to generation of membrane potential and occurrence of lipid peroxidation. Direct absorption of UV radiation which led to photoreaction through formation of an excited state was one of the causes inducing cell damage. Additionally, generation of ROS and thus occurrence of secondary damage can be another cause. The LP Hg lamp only induced damage to DNA but not to other components such as lipids or proteins. This difference was derived from differences of UV radiation absorption by cellular materials.

pH-Dependent Effects of L-Cysteine on Mercury Dissolution of α-HgS and ß-HgS.

Mercury sulfide is an insoluble inorganic mercury compound, and it is the main chemical form in traditional oral mercury-containing medicines. Hg2+ has a high affinity for thiols, and small molecule thiols in the gastrointestinal tract may promote mercury dissolution of mercury sulfide by binding to Hg2+. L-cysteine is the only amino acid that possesses a reducing sulfhydryl group (-SH), out of the 20 amino acids. This study investigates the effect of L-cysteine on mercury dissolution of mercury sulfide at pHs ranging from 1.2 to 7.2. The results showed that L-cysteine had different pH-dependent effects on the mercury dissolution of α-HgS and ß-HgS. For α-HgS, the dissolved mercury concentration increased from 5.47 ± 0.97 ng/mL to 12.49 ± 0.54 ng/mL when the pH rose from 1.2 to 4.2, and decreased to 3.37 ± 0.70 ng/mL at pH 6.0 and then increased to 9.36 ± 0.79 ng/mL at pH 7.2. For ß-HgS, the dissolved mercury concentration increased from 151.09 ± 2.25 ng/mL to 2346.71 ± 62.62 ng/mL when the pH increased from 1.2 to 7.2. In conclusion, L-Cys was distinctly enhanced upon mercury dissolution of α-HgS and ß-HgS with increasing pH. These results may contribute to our understanding of the mercury absorption mechanism of traditional oral mercury-containing medicines.

Effect of Cys, GSH, and pH on Mercury Release from Tibetan Medicine Zuotai, ß-HgS, and α-HgS in Artificial Gastrointestinal Juices.

Zuotai, also named as "gTso thal", a known Tibetan medicinal mixture containing insoluble cubic crystal mercuric sulfide (ß-HgS), has been used to treat diseases with long history. The mercury release ratio from Zuotai in gastrointestinal environment is one determinant factor for its bioavailability and biological effect. However, the information is still scarce now. Therefore, the study was designed to investigate the effect of sulfhydryl biomolecules [L-cysteine (Cys) and glutathione (GSH)] and pH on mercury dissociation from Zuotai, ß-HgS, and hexagonal crystal mercuric sulfide (α-HgS) in artificial gastrointestinal juices or pure water with a 1:100 solid-liquid ratio. And, the digestion and peristalsis of gastrointestinal tract were simulated in vitro. The results showed the following trend for the mercury release ratio of Zuotai, artificial gastric juice > artificial intestinal juice > pure water, whereas the trend for ß-HgS and α-HgS was as follows, artificial intestinal fluid > artificial gastric fluid > pure water. The mercury release ratios of Zuotai, ß-HgS, and α-HgS significantly increased in artificial intestinal juice containing L-Cys or GSH compared to those without sulfhydryl biomolecules in the juice. However, in contrast to the results observed for ß-HgS and α-HgS, the mercury release ratio of Zuotai was reduced remarkably in pure water and artificial gastric juice with Cys or GSH. And, we found that strong acidic or strong alkaline environments promoted the dissociation of mercury from Zuotai, ß-HgS, and α-HgS. Taken together, current findings may contribute to other studies regarding clinical safety and bioavailability of the traditional drug Zuotai containing ß-HgS.

Ion-pairing reversed-phase chromatography coupled to inductively coupled plasma mass spectrometry as a tool to determine mercurial species in freshwater fish.

Most of analytical community is focused on reversed phase high performance liquid chromatography (RP-HPLC) for mercury speciation by employing mobile phases comprising of high salts and moderate amounts of organic solvents. This study aims at rapid mercury speciation analysis by ion-pairing RP-HPLC with inductively coupled plasma mass spectrometry (ICP-MS) detection only using low salts for the sake of green analytical chemistry. Two ion-pairing HPLC methods were developed on individual usage of positively and negatively charged ion-pairing reagents (tetrabutylammonium hydroxide -TBAH and sodium dodecylbenzene sulfonate -SDBS), where sodium 3-mercapto-1-propysulfonate (MPS) and l-cysteine (Cys) were individually added in mobile phases to transform mercury species into negative and positive Hg-complexes for good resolution. Addition of phenylalanine was also utilized for rapid baseline separation in combination of short C18 guard columns. Optimum mobile phases of 2.0mM SDBS+2.0mM Cys+1.0mM Phe (pH 3.0) and 4.0mM TBAH+2.0mM MPS+2.0mM Phe (pH 6.0) both achieved baseline separation of inorganic mercury (Hg2+), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) on two consecutive 12.5-mm C18 columns. The former mobile phase was selected for mercury speciation in freshwater fish because of short separation time (3.0min). Detection limits of 0.015 for Hg2+, 0.014 for MeHg, 0.028 for EtHg and 0.042µgL-1 for PhHg were obtained along with satisfactory precisions of peak height and area (1.0-2.8% for 5.0µgL-1 Hg-mixture standard). Good accordance of determined values of MeHg and total mercury in certified reference materials of fish tissue (GBW 10029) and tuna fish (BCR-463) with certified values as well as good recoveries (91-106%) proved good accuracy of the proposed method. An example application to freshwater fish indicated its potential in routine analysis, where MeHg was presented at 3.7-20.3µgkg-1 as the dominate species.

Transport and transformation of mercury during wet flue gas cleaning process of nonferrous metal smelting.

Reducing mercury emission is hot topic for international society. The first step for controlling mercury in fuel gas is to investigate mercury distribution and during the flue gas treatment process. The mercury transport and transformation in wet flue gas cleaning process of nonferrous smelting industry was studied in the paper with critical important parameters, such as the solution temperature, Hg0 concentration, SO2 concentration, and Hg2+ concentration at the laboratory scale. The mass ratio of the mercury distribution in the solution, flue gas, sludge, and acid fog from the simulated flue gas containing Hg2+ and Hg0 was 49.12~65.54, 18.34~35.42, 11.89~14.47, and 1.74~3.54%, respectively. The primary mercury species in the flue gas and acid fog were gaseous Hg0 and dissolved Hg2+. The mercury species in the cleaning solution were dissolved Hg2+ and colloidal mercury, which accounted for 56.56 and 7.34% of the total mercury, respectively. Various mercury compounds, including Hg2Cl2, HgS, HgCl2, HgSO4, and HgO, existed in the sludge. These results for mercury distribution and speciation are highly useful in understanding mercury transport and transformation during the wet flue gas cleaning process. This research is conducive for controlling mercury emissions from nonferrous smelting flue gas and by-products.

Removal and speciation of mercury compounds in flue gas from a waste incinerator.

The management and control of mercury emissions from waste incinerators have become more significant, because waste incinerators are sinks to treat mercury-containing consumer products. This study investigated the effects of mercury concentrations and waste incineration temperatures on mercury speciation using a lab-scale experimental instrument. The removal characteristics of different mercury species were also investigated using an apparatus to simulate the fabric filter with a thin layer of additives such as Ca(OH)2 and NaHCO3, activated carbon (AC), and fly ash. HgCl2 generation rates peaked at 800°C for initial Hg(0) concentrations of 0.08-3.61 mg/Nm(3) in the presence of 400 ppm HCl. A linear relationship was established between the generation rate of HgCl2 and the logarithmic value of initial mercury concentration. Fly ash proved highly efficient in mercury removal, being equal or superior to AC. On the other hand, Ca(OH)2 and NaHCO3 were shown to have no effects on mercury removal. In the dry-scrubbing process, alkali agent is often sprayed in amounts beyond those stoichiometrically required to aid acidic gas removal. The research suggests, however, that this may hinder mercury removal from the flue gas of solid waste incinerators.

A Study of the Complexation of Mercury(II) with Dicysteinyl Tetrapeptides by Electrospray Ionization Mass Spectrometry.

In this study we evaluated a method for the characterization of complexes, formed in different relative ratios of mercury(II) to dicysteinyl tetrapeptide, by electrospray ionization orbitrap mass spectrometry. This strategy is based on previous successful characterization of mercury-dicysteinyl complexes involving tripeptides by utilizing mass spectrometry among other techniques. Mercury(II) chloride and a dicysteinyl tetrapeptide were incubated in a degassed buffered medium at varying stoichiometric ratios. The complexes formed were subsequently analyzed on an electrospray mass spectrometer consisting of a hybrid linear ion- and orbi- trap mass analyzer. The electrospray ionization mass spectrometry (ESI-MS) spectra were acquired in the positive mode and the observed peaks were then analyzed for distinct mercury isotopic distribution patterns and associated monoisotopic peak. This work demonstrates that an accurate stoichiometry of mercury and peptide in the complexes formed under specified electrospray ionization conditions can be determined by using high resolution ESI MS based on distinct mercury isotopic distribution patterns.

Phenylthiourea alters toxicity of mercury compounds in zebrafish larvae.

In recent years larval stage zebrafish have been emerging as a standard vertebrate model in a number of fields, ranging from developmental biology to pharmacology and toxicology. The tyrosinase inhibitor 1-phenyl-2-thiourea (PTU) is used very widely with larval zebrafish to generate essentially transparent organisms through inhibition of melanogenesis, which has enabled many elegant studies in areas ranging from neurological development to cancer research. Here we show that PTU can have dramatic synergistic and antagonistic effects on the chemical toxicology of different mercury compounds. Our results indicate that extreme caution should be used when employing PTU in toxicological studies, particularly when studying toxic metal ions.

Understanding natural semiquinone radicals--multifrequency EPR and relativistic DFT studies of the structure of Hg(II) complexes.

Multifrequency EPR spectroscopy and DFT calculations were used to investigate Hg(II) complexes with semiquinone radical ligands formed in a direct reaction between the metal ions and tannic acid (a polyphenol closely related to tannins). Because of the intricate structure of tannic acid a vast array of substituted phenolic compounds were tested to find a structural model mimicking its ability to react with Hg(II) ions. The components of the g matrix (the g tensor) determined from the high field (208 GHz) EPR spectra of the Hg(II) complexes with the radical ligands derived from tannic acid and from the model compounds were analogous, indicating a similar coordination mode in all the studied Hg(II) complexes. Since catechol (1,2-dihydroxybenzene) was the simplest compound undergoing the reaction with Hg(II) it was selected for DFT studies which were aimed at providing an insight into the structural properties of the investigated complexes. Various coordination numbers and different conformations and protonation states of the ligands were included in the theoretical analyses. g Matrices were computed for all the DFT optimized geometries. A good agreement between the theoretical and experimental values was observed only for the model with the Hg(II) ion tetracoordinated by two ligands, one of the ligands being monoprotonated with the unpaired electron mainly localized on it.

Facile synthesis of N-acetyl-L-cysteine capped CdHgSe quantum dots and selective determination of hemoglobin.

Using N-acetyl-L-cysteine (NAC) as a stabilizer, well water-dispersed, high-quality and stable CdHgSe quantum dots were facilely synthesized via a simple aqueous phase method. The as-prepared NAC capped CdHgSe quantum dots were thoroughly characterized by fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. A novel method for the selective determination of hemoglobin (Hb) was developed based on fluorescence quenching of the NAC capped CdHgSe quantum dots. A number of key factors including pH value of phosphate buffer solution, quantum dots concentration, the adding sequence of reagents and reaction time that influence the analytical performance of the NAC capped CdHgSe quantum dots in Hb determination were investigated. Under the optimal experimental conditions, the change of fluorescence intensity (ΔI) was linearly proportional to the concentration of Hb in the range of 4.0×10(-9)-4.4×10(-7) mol L(-1) with a detection limit of 2.0×10(-9) mol L(-1). The developed method has been successfully employed to determine Hb in human urine samples.

One-pot synthesis of glycopolymer-porphyrin conjugate as photosensitizer for targeted cancer imaging and photodynamic therapy.

One-pot system combining multi-reactions is used to synthesize novel porphyrin-glycopolymer conjugates. Sodium mercury amalgam is used to catalyze the reactions: 1) reduction of RAFT polymerized poly(2-(methacrylamido) glucopyranose) (PMAG), 2) converting protoporphyrin to protoporphyrinogen, 3) thiol-ene coupling reaction of PMAG and protoporphyrinogen. The product is oxidized in the same pot to generate the final porphyrin-PMAG conjugates. The resulting conjugates are characterized by NMR, GPC, UV-Vis, and fluorescence spectroscopy. Glycoparticles (≈ 200 nm) bearing glucose units are formed by dissolving the conjugates in water. Glycoparticles show enhanced binding ability toward Con A, bind K562 cells efficiently and kill these cells under light irradiation in dose and light treatment length dependent manners, illustrating the potential biological applications of the conjugates as photosensitizer for cancer imaging and photodynamic therapy.

Large scale production of the active human ASCT2 (SLC1A5) transporter in Pichia pastoris--functional and kinetic asymmetry revealed in proteoliposomes.

The human glutamine/neutral amino acid transporter ASCT2 (hASCT2) was over-expressed in Pichia pastoris and purified by Ni(2+)-chelating and gel filtration chromatography. The purified protein was reconstituted in liposomes by detergent removal with a batch-wise procedure. Time dependent [(3)H]glutamine/glutamine antiport was measured in proteoliposomes which was active only in the presence of external Na(+). Internal Na(+) slightly stimulated the antiport. Optimal activity was found at pH7.0. A substantial inhibition of the transport was observed by Cys, Thr, Ser, Ala, Asn and Met (≥70%) and by mercurials and methanethiosulfonates (≥80%). Heterologous antiport of [(3)H]glutamine with other neutral amino acids was also studied. The transporter showed asymmetric specificity for amino acids: Ala, Cys, Val, Met were only inwardly transported, while Gln, Ser, Asn, and Thr were transported bi-directionally. From kinetic analysis of [(3)H]glutamine/glutamine antiport Km values of 0.097 and 1.8mM were measured on the external and internal sides of proteoliposomes, respectively. The Km for Na(+) on the external side was 32mM. The homology structural model of the hASCT2 protein was built using the GltPh of Pyrococcus horikoshii as template. Cys395 was the only Cys residue externally exposed, thus being the potential target of SH reagents inhibition and, hence, potentially involved in the transport mechanism.

Development of active matrix flat panel imagers incorporating thin layers of polycrystalline HgI(2) for mammographic x-ray imaging.

Active matrix flat-panel imagers (AMFPIs) offer many advantages and have become ubiquitous across a wide variety of medical x-ray imaging applications. However, for mammography, the imaging performance of conventional AMFPIs incorporating CsI:Tl scintillators or a-Se photoconductors is limited by their relatively modest signal-to-noise ratio (SNR), particularly at low x-ray exposures or high spatial resolution. One strategy for overcoming this limitation involves the use of a high gain photoconductor such as mercuric iodide (HgI(2)) which has the potential to improve the SNR by virtue of its low effective work function (W(EFF)). In this study, the performance of direct-detection AMFPI prototypes employing relatively thin layers of polycrystalline HgI(2) operated under mammographic irradiation conditions over a range of 0.5 to 16.0 mR is presented. High x-ray sensitivity (corresponding to W(EFF) values of ∼19 eV), low dark current (<0.1 pA mm(-2)) and good spatial resolution, largely limited by the size of the pixel pitch, were observed. For one prototype, a detective quantum efficiency of ∼70% was observed at an x-ray exposure of ∼0.5 mR at 26 kVp.

Aqueous synthesis and characterization of glutathione-stabilized ß-HgS nanocrystals with near-infrared photoluminescence.

A simple, rapid and green aqueous approach to near-infrared (NIR)-emitting ß-HgS nanocrystals (NCs) was demonstrated for the first time by using glutathione (GSH) as the stabilizer at room temperature. The resulting HgS NCs with zinc blend structure exhibited strong quantum size effect, and the emission peak could be tuned in a wide NIR region from ca. 775 to 1041 nm. As compared with early achievements, the emission intensity of GSH-stabilized HgS NCs enhanced, with the maximum quantum yield reaching ~2.8%. It was also found that the stability of the GSH-HgS NCs was improved noticeably, the PL peak red-shifting only 9 nm and 23 nm after stored at 4°C for 4 months and 25°C for 7 days, respectively. The better stability of the HgS NCs was elucidated by FT-IR due to the multiple coordination of GSH molecule to surface Hg of the NCs. The emission range of GSH-stabilized HgS NCs was located between the visible region (500-800 nm) and IR region (1000-1600 nm) of HgS NCs as reported previously, extending the emission region of HgS nanomaterial. Therefore, the continuous emission from visible to IR spectral ranges provided HgS material more potential applications.

Competitive aptamer bioassay for selective detection of adenosine triphosphate based on metal-paired molecular conformational switch and fluorescent gold nanoclusters.

A competitive aptamer bioassay was developed for the selective detection of adenosine triphosphate (ATP). The proposed bioassay employed the T-Hg-T induced hairpin-structure as the molecule conformational switch (MCS), aptamer as a specific recognizer, and mercaptoundecanoic acid modified gold nanoclusters (MUA-AuNCs) as a sensitive signal reporter. The T-rich MCS ssDNA with the sequence complementary with that for the aptamer of ATP was bound with Hg(2+) to form the metal-paired hairpin-structure. Addition of the aptamer and its target biomolecule ATP resulted in a competitive aptamer bioassay. The aptamer competed with Hg(2+) to hybridize with T-rich MCS ssDNA, thereby destroyed the hairpin-structure. As a result, the Hg(2+) was released and the signal transduction was achieved. The ATP affected the interaction between aptamer and hairpin-structure, thus mediated the release of Hg(2+), which was sensitively quantified by fluorescent MUA-AuNCs. Under selected conditions, the developed method allowed sensitive and selective detection of ATP with a linear range of 100-2000 nM and a detection limit (3s) of 48 nM. The relative standard deviation for sixty replicate detections of 200 nM ATP was 2.1%, and the recoveries of the spiked ATP in urine samples ranged from 89% to 105%. The developed metal-paired MCS can be easily extended to the sensitive and selective detection of other biomolecules by changing the base sequence of hairpin structure and choosing the corresponding aptamer for the target biomolecule.

Au:CdHgTe quantum dots for in vivo tumor-targeted multispectral fluorescence imaging.

Near-infrared gold-doped CdHgTe quantum dots (QDs) with improved photoluminescence and biocompatibility were developed using an aqueous solution route with L-glutathione and L-cysteine as stabilizers. As-prepared Au:CdHgTe QDs were covalently linked to arginine-glycine-aspartic acid (RGD) peptide, anti-epidermal growth factor receptor (EGFR) monoclonal antibody (MAb), and anti- carcinoembryonic antigen-related cell adhesion molecule-1 (CEACAM1) MAb separately. Three Au:CdHgTe QD bioconjugates (QD800-RGD, QD820-anti-CEACAM1, and QD840-anti-EGFR) were successfully used as probes for in vivo tumor-targeted multispectral fluorescence imaging of xenografts. Fluorescence signals from the QD bioconjugates used to detect three tumor markers were spectrally unmixed, and their co-localization was analyzed. The results indicate that multiple tumor markers could be simultaneously detected by multispectral fluorescence imaging in vivo using QD bioconjugates as probes. This approach has excellent potential as an imaging method for the noninvasive exploration and detection of multiple tumor markers in vivo, thereby substantially aiding the diagnosis of cancer.