Coordination chemistry of Ca sites at the surface of nanosized hydroxyapatite: interaction with H₂O and CO

The affinity towards water of a selection of well-defined, nanostructured hydroxyapatite (HA) samples was investigated by H(2)O vapour adsorption microcalorimetry and infrared (IR) spectroscopy. A large hydrophilicity of all investigated materials was confirmed. The surface features of hydrated HA were investigated on the as-synthesized samples pre-treated in mild conditions at T=303 K, whereas dehydrated HA features were characterized on samples activated at T=573 K. The relatively large hydrophilicity of the hydrated surface (-Δ(ads)H~100-50 kJ mol(-1)) was due to the interaction of water with the highly polarized H(2)O molecules strongly coordinated to the surface Ca(2+) cations. At the dehydrated surface, exposing coordinatively unsaturated (cus) Ca(2+) cations, H(2)O was still molecularly adsorbed but more strongly (-Δ(ads)H~120-90 kJ mol(-1)). The use of CO adsorption to quantify the Lewis acidic strength of HA surface sites revealed only a moderate strength of cus Ca(2+) cations, as confirmed by both microcalorimetric and IR spectroscopic measurements and ab initio calculations. This result implies that the large HA/H(2)O interaction energy is due to the interplay between cus Ca(2+) sites and nearby hydrophilic PO(4) groups, not revealed by the CO probe. The lower density of cus Ca(2+) cations at the 573 K activated HA surface with respect to the pristine one did not affect the whole hydrophilicity of the surface, as the polarizing effect of Ca sites is so strong to extend up to the fourth hydrated layer, as confirmed by both high-coverage microcalorimetric and IR spectroscopic data. No specific effects due to the investigated specimen preparation method and/or different morphology were observed.     

Evaluating enzymes that generate genotoxic benzo[a]pyrene metabolites using sensor arrays

Arrays with individually addressable, demountable electrodes coated with ultrathin DNA/enzyme films were evaluated to estimate relative rates of genotoxic bioactivation of benzo[a]pyrene (BP) for several different enzymes simultaneously. Specifically, cytochrome (cyt) P450cam, cyt P40 1A2, and myoglobin in the array were activated with H2O2 to metabolize BP to genotoxic metabolites. DNA damage by the metabolites was detected by increases in square wave voltammetric oxidation peaks using Ru(bpy)3(2+) as catalyst. Cyt P450cam and cyt P450 1A2 showed 3-fold higher activity for genotoxic bioactivation of BP than myoglobin. The ability of the arrays to generate and detect metabolite-based DNA damage simultaneously for several enzymes is a rapid and promising approach to identify and characterize enzymes involved in genotoxicity of drugs and pollutants.     

Controlled release of Fe3O4 nanoparticles in encapsulated microbubbles to tumor cells via sonoporation and associated cellular bioeffects

Fe(3)O(4) nanoparticles embedded in the shells of encapsulated microbubbles could be used therapeutically as in situ drug-delivery vehicles. Bioeffects on liver tumor cells SMMC-7721 due to the excitation of Fe(3)O(4) nanoparticles attached to microbubbles generated by ultrasound (US) are studied in an in vitro setting. The corresponding release phenomenon of Fe(3)O(4) nanoparticles from the shells of the microbubbles into the cells via sonoporation and related phenomena, including nanoparticle delivery efficiency, cell trafficking, cell apoptosis, cell cycle, and disturbed flow of intracellular calcium ions during this process, are also studied. Experimental observations show that Fe(3)O(4) nanoparticles embedded in the shells of microbubbles can be delivered into the tumor cells; the delivery rate can be controlled by adjusting the acoustic intensity. The living status or behavior of Fe(3)O(4) -tagged tumor cells can then be noninvasively tracked by magnetic resonance imaging (MRI). It is further demonstrated that the concentration of intracellular Ca(2+) in situ increases as a result of sonoporation. The elevated Ca(2+) is found to respond to the disrupted site in the cell membrane generated by sonoporation for the purpose of cell self-resealing. However, the excessive Ca(2+) accumulation on the membrane results in disruption of cellular Ca(2+) cycling that may be one of the reasons for the death of the cells at the G1 phase. The results also show that the Fe(3)O(4) -nanoparticle-embedded microbubbles have a lower effect on cell bioeffects compared with the non-Fe(3)O(4) -nanoparticle-embedded microbubbles under the same US intensity, which is beneficial for the delivery of nanoparticles and simultaneously maintains the cellular viability.     

Evaluation of electrochemiluminescent metabolic toxicity screening arrays using a multiple compound set

Arrays for screening metabolite-generated toxicity utilizing spots containing DNA, enzyme, and electroluminescent (ECL) polymer ([Ru(bpy)(2)PVP(10)](2+)) were extended to include a fully representative set of metabolic enzymes from human and rat liver microsomes, human and rat liver cytosol, and mouse liver S9 fractions. Array use involves two steps: (1) enzyme activation of the test chemical and metabolite reaction with DNA, and then, (2) capture of ECL resulting from DNA damage using a charge coupled device (CCD) camera. Plots of ECL increase vs enzyme reaction time monitor relative rates of DNA damage and were converted into turnover rates for enzymic production of DNA-reactive metabolites. ECL turnover rates were defined by R, the initial slope of ECL increase versus enzyme reaction time normalized for amounts of enzyme and test chemical. R-values were used to establish correlations for 11 toxic compounds with the standard toxicity metrics rodent liver TD(50) and lethal dose (LD(50)), Ames tests, and Comet assays for in vitro DNA damage. Results support the value of the ECL genotoxicity arrays together with toxicity bioassays for early screening of new chemicals and drug candidates.     

Preparation of magnetic and bioactive calcium zinc iron silicon oxide composite for hyperthermia treatment of bone cancer and repair of bone defects

In this paper, a calcium zinc iron silicon oxide composite (CZIS) was prepared using the sol-gel method. X-ray diffraction (XRD) was then employed to test the CZIS composite. The results from the test showed that the CZIS had three prominent crystalline phases: Ca(2)Fe(1.7)Zn(0.15)Si(0.15)O(5), Ca(2)SiO(4), and ZnFe(2)O(4). Calorimetric measurements were then performed using a magnetic induction furnace. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis were conducted to confirm the growth of a precipitated hydroxyapatite phase after immersion in simulated body fluid (SBF). Cell culture experiments were also carried out, showing that the CZIS composite more visibly promoted osteoblast proliferation than ZnFe(2)O(4) glass ceramic and HA, and osteoblasts adhered and spread well on the surfaces of composite samples.     

Electrochemiluminescent arrays for cytochrome P450-activated genotoxicity screening. DNA damage from benzo[a]pyrene metabolites

Arrays suitable for genotoxicity screening are reported that generate metabolites from cytochrome P450 enzymes (CYPs) in thin-film spots. Array spots containing DNA, various human cyt P450s, and electrochemiluminescence (ECL) generating metallopolymer [Ru(bpy)2PVP10]2+ were exposed to H2O2 to activate the enzymes. ECL from all spots was visualized simultaneously using a CCD camera. Using benzo[a]pyrene as a test substrate, enzyme activity for producing DNA damage in the arrays was found in the order CYP1B1 > CYP1A2 > CYP1A1 > CYP2E1 > myoglobin, the same as the order of their metabolic activity. Thus, these arrays estimate the relative propensity of different enzymes to produce genotoxic metabolites. This is the first demonstration of ECL arrays for high-throughput in vitro genotoxicity screening.     

Online electrochemical measurements of Ca2+ and Mg2+ in rat brain based on divalent cation enhancement toward electrocatalytic NADH oxidation

This study describes a novel electrochemical approach to effective online monitoring of electroinactive Ca(2+) and Mg(2+) in the rat brain based on the current enhancement of divalent cations toward electrocatalytic oxidation of NADH. Cyclic voltammetry for NADH oxidation at the electrodes modified with the polymerized film of toluidine blue O (TBO) reveals that the current of such an electrocatalytic oxidation process is remarkably enhanced by divalent cations such as Ca(2+) and Mg(2+). The current enhancement is thus used to constitute an electrochemical method for the measurements of Ca(2+) and Mg(2+) in a continuous-flow system with the polyTBO-modified electrode as the detector. Upon being integrated with in vivo microdialysis, the electrochemical method is successfully applied in investigating on cerebral Ca(2+) and Mg(2+) of living animals in two aspects: (1) online simultaneous measurements of the basal levels of Ca(2+) and Mg(2+) in the brain of the freely moving rats by using ethyleneglcol-bis(2-aminoethylether) tetraacetic acid (EGTA) as the selective masking agent for Ca(2+) to differentiate the net current responses selectively for Ca(2+) and Mg(2+); and (2) online continuous monitoring of the cerebral Mg(2+) following the global ischemia by using Ca(2+)-masking agent (i.e., EGTA) to completely eliminate the interference from Ca(2+). Compared with the existing methods for the measurements of cerebral Ca(2+) and Mg(2+), the method demonstrated here is advantageous in terms of its simplicity both in instrumentation and in the experimental procedures and near real-time nature, and is thus highly anticipated to find wide applications in understanding of chemical events involved in some physiological and pathological processes.     

Preparation of hydroxyapatite ceramics by hydrothermal hot-pressing method at 300 °C

Hydroxyapatite (HA) ceramics were prepared by a hydrothermal hot-pressing (HHP) method at a low temperature (300 °C). DCPD (CaHPO₄·2H₂O) + Ca(OH)₂, OCP (Ca₈H₂(PO₄)₆·5H₂O) + Ca(OH)₂, DCPD + NH₃·H₂O, OCP + NH₃·H₂O or α-TCP (Ca₃(PO₄)₂) + NH₃·H₂O were used as the precursors. The mixture was treated by HHP under a condition of 300 °C/40 MPa. In sample DCPD + Ca(OH)₂ and OCP + Ca(OH)₂, the HA ceramics obtained showed a porous and homogenous microstructure, and the bending strength were 9.9 MPa and 10.9 MPa, respectively. In sample α-TCP+NH₃·H₂O, rod-like HA crystals produced. When the starting materials were DCPD + NH₃·H₂O, OCP + NH₃·H₂O, the HA particles produced exhibited plate-like features. It appeared that the plate-like HA particles stacked into a lamellar structure. The formation of the lamellar structure leads to a noticeable improvement in fracture property of the HA ceramic. The bending strength and the fracture toughness of the sample prepared from OCP and ammonia water reach 90 MPa and 2.3 MPam^1/2, respectively.     

Genotoxic evaluation of the non-halogenated disinfection by-products nitrosodimethylamine and nitrosodiethylamine

Disinfection by-products (DBPs) are chemicals that are produced as a result of chlorine being added to water for disinfection. As well as the halogenated DBPs, N-nitrosamines have recently been identified as DBPs, especially when amines and ammonia ions are present in raw water. In this work, the genotoxicity of two nitrosamines, namely nitrosodimethylamine (NDMA) and nitrosodiethylamine (NDEA), has been studied in cultured human cells. To evaluate their genotoxic potential two assays were used, the comet assay and the micronucleus test. The comet assay measures the induction of single and double-strand breaks, and also reveals the induced oxidative DNA damage by using endoIII and FPG enzymes. Chromosomal damage was evaluated by means of the cytokinesis-blocked micronucleus test. The results of the comet assay show that both compounds are slightly genotoxic but only at high concentrations, NDEA being more effective than NDMA. Enzyme treatments revealed that only NDEA was able to produce increased levels of oxidized bases, mainly in purine sites. The results obtained in the micronucleus assay, which measures the capacity of the tested agents to induce clastogenic and/or aneugenic effects, are negative for both of the nitrosamines evaluated, either using TK6 cells or human peripheral blood lymphocytes. Taking into account the very high concentrations needed to produce DNA damage, our data suggest a low, if existent, genotoxic risk associated with the presence of these compounds in drinking water.     

Bioeffects of CdTe quantum dots on human umbilical vein endothelial cells

Quantum dots (QDs) hold great potential for applications in nanomedicine, however, their health effects are largely unknown. In the present study, the cytotoxicity and genotoxicity of CdTe QDs were examined in human umbilical vein endothelial cells (HUVECs). The QDs exhibited a dose-dependent inhibitory effect on cell growth. It was shown that after a 12 h treatment QDs at 1, 10, and 50 microg x ml(-1) induced formation of yH2AX foci, indicative of DNA damage, in a dose-dependent manner. Moreover, QD treatment clearly induced the generation of reactive oxygen species (ROS). Pre-treatment with N-acetyl-cysteine (NAC), a ROS scavenger, could inhibit the induction of ROS by QDs, as well as the formation of yH2AX foci. Taken together, our data indicate that CdTe QDs have cytotoxic and genotoxic effects on HUVECs, and that ROS generation may be involved in QD induced DNA damage.     

A simple and rapid method to graft hydroxyapatite on carbon nanotubes

Herein a simple and effective approach is introduced to functionalize single walled carbon nanotubes (SWCNTs) by in-situ grafting of hydroxyapatite (HA). The pristine SWCNTs were chemically activated through introduction of carboxylic groups on their surfaces by refluxing in the mixture of H(2)SO(4) and HNO(3). The resulting carboxylated SWCNTs were further utilized for grafting of HA. The Fourier transform infrared and Raman spectroscopic studies demonstrated the formation of HA and its grafting over SWCNTs. The phase composition of HA and existence Ca(2+) and PO(4) (3-) ions were studied using X-ray diffraction and energy dispersive X-ray analyses, respectively. The surface morphology of functionalized SWCNTs was analyzed using scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis confirmed the existence of HA on SWCNTs by exhibiting different thermogram for pure HA and functionalized SWCNTs. Overall this method produced uniform grafting of low crystalline HA on carboxylated SWCNTs with strong interfacial bonding.     

磁性羟基磷灰石复合物的制备与表征

为探索磁性颗粒在治疗因缺乏骨骼应有的应力刺激而导致骨质疏松方面的潜在应用,研究制备了兼具良好生物活性和超顺磁性的羟基磷灰石(HA)/Fe3O4复合物。以化学沉积法合成的纳米Fe3O4浆料为底物,在Ca、P溶液中通过尿素酶催化水解尿素缓慢升高pH值,从而使HA逐渐在Fe3O4上沉积,形成具有一定核壳结构的磁性HA复合物。利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线能量色散谱仪(EDX)、振动样品磁强计(VSM)和磁铁对底物及试样进行了表征。结果表明,以纳米Fe3O4浆料为底物,一定浓度含氯化钠的Ca、P溶液(Ca、P原子比为5∶3,Ca、Fe原子比为5∶3)为媒介,在37℃水浴中,反应48h,可制得具有较好磁性能的HA复合物,其饱和磁化强度可达7.23A.m2/kg,剩磁为0.073A.m2/kg,矫顽力为261.08A/m。     

Effect of NaOH on the vitrification process of waste Ni-Cr sludge

This study investigated the effect of NaOH on the vitrification of electroplating sludge. Ni, the major metal in the electroplating sludge, is the target for recovery in the vitrification. Sludge and encapsulation materials (dolomite, limestone, and cullet) were mixed and various amounts of NaOH were added to serve as a glass modifier and a flux. A vitrification process at 1450 °C separated the molten specimens into slag and ingot. The composition, crystalline characteristics, and leaching characteristics of samples were measured. The results indicate that the recovery of Ni is optimal with a 10% NaOH mass ratio; the recoveries of Fe, Cr, Zn, Cu, and Mn all exhibited similar trends. The results of the toxicity characteristic leaching procedure (TCLP) show that leaching characteristics of the slag meet the requirements of regulation in Taiwan. In addition, a semi-quantitative X-ray diffraction analysis revealed that the main crystalline phase of slag changed from Ca(3)(Si(3)O(9)) to Na(4)Ca(4)(Si(6)O(18)) with a NaOH mass ratio of over 15%, because the Ca(2+) ions were replaced with Na(+) ions during the vitrification process. Na(4)Ca(4)(Si(6)O(18)), a complex mineral which hinders the mobility of metals, accounts for the decrease of metal recovery.     

Sulfide removal in petroleum refinery wastewater by chemical precipitation

Sulfide removal by chemical precipitation from petroleum refinery wastewater was investigated. The wastewater samples were taken from the flocculation pond influent of TUPRAS Kirikkale Middle Anatolia Petroleum Refinery Wastewater Treatment Plant (WWTP) and physicochemical treatments using conventional coagulants which were partial precipitant [FeCl(3) . 6H(2)O and FeSO(4) . 7H(2)O] and coagulant-aids [Ca(OH)(2) and CaCO(3)] were applied to both raw and sulfide added wastewater. Sulfide and chemical oxygen demand (COD) removal efficiencies of Fe(3+) ions alone for sulfide added wastewaters having different pH values varied between 62-95 and 45-75%, respectively. In addition, removal efficiencies of sulfide (96-99%) and COD (50-80%) were obtained by using Fe(2+) ions together with Ca(OH)(2) as precipitant-aid under the same conditions. In experiments performed with raw wastewater which had different pH values, COD removal efficiencies of Fe(3+) and Fe(2+) ions together with Ca(OH)(2), were 50-80 and 32-50%, respectively.     

Single-cell microarray for analyzing cellular response

Detection of cellular response by measuring intracellular calcium, (Ca2+)i with Ca2+-dependent fluorescent dye are standard approaches to detect ligand-stimulated cells and to study signaling through ligand/receptor interaction. We describe a single-cell microarray system to analyze cellular response of individual cells such as lymphocytes using microchamber array chips. The single-cell microarray chip is made from polystyrene with over 30,000 microchambers, which can accommodate only single cells. Lymphocytes derived from mouse spleen or human blood were spread on the microarray, and over 80% of the microchambers achieved single-cell status. Stimulation of B-cells through antigen receptors on the microarray allowed us to detect activated B-cells by comparing the states of single B-cells before and after stimulation with antigen, which is disabled for flow cytometry. In addition, this novel method demonstrated retrieval of positive single B-cells from microchambers by a micromanipulator and achieved antibody DNA analysis. The system is suitable for high-throughput analysis of intracellular Ca2+ response at the single-cell level and is applicable to screen antigen-specific lymphocytes for making specific monoclonal antibody.     

Plasma spraying of zirconia-reinforced hydroxyapatite composite coatings on titanium: Part I Phase, microstructure and bonding strength

Plasma-sprayed hydroxyapatite (HA) coatings applied to metal substrates can induce a direct chemical bond with bone and hence achieve biological fixation of the implant. However, the poor bonding strength between HA and substrate has been of concern to orthopaedists. In this study, two submicrometre ZrO2 powders stabilized with both 3 and 8 mol% Y2O3 (TZ3Y and TZ8Y, respectively) were incorporated in a plasma-sprayed HA coating on Ti-6Al-4V substrate to investigate the change in phase, microstructure and bonding strength. The results show that ZrO2 composite coatings contain more unmelted particles and greater porosity. During plasma spraying, ZrO2 reacts with the CaO in HA to form CaZrO3 and accelerates HA decomposition to -TCP and Ca4P2O9. Nevertheless, bonding strength increases with increase of ZrO2 content in the range 0 to 10 wt% studied. The higher Y2O3-containing TZ8Y apparently exerts a greater strengthening effect than the lower Y2O3-containing TZ3Y.     

Fluorometric detection of ca(2+) based on an induced change in the conformation of sol-gel entrapped parvalbumin

We report the development of a fluorometric detection strategy for Ca(2+) based on induced changes in the conformation of cod III parvalbumin entrapped within a sol-gel processed glass. The detection scheme utilizes a fluorescent allosteric signal transduction (FAST) strategy wherein conformational changes induced by Ca(2+) binding result in alterations in the intrinsic fluorescence from the single tryptophan residue at position 102. Intrinsic fluorescence was also used to examine chemically induced changes in protein structure to ascertain the effects of entrapment on the conformational motions and stability of the protein. Fluorescence analysis indicated that the behavior of the protein depended on the entrapment protocols used. The entrapped protein retained conformational flexibility similar to that observed in solution and remained accessible to analytes such as Ca(2+). Entrapment also caused improvements in protein stability against chemical denaturants. However, entrapment caused the apparent affinity constant for binding of Ca(2+) to decrease substantially with aging time. Even so, in optimum cases, fluorometric detection of Ca(2+) could be done over a 600 μM range with a limit of detection of 3 μM and with no interference from divalent ions such as Mg(2+), Sr(2+), or Cd(2+), indicating the viability of using sol-gel entrapped FAST proteins for the detection of Ca(2+).     

Characterisation of products of tricalcium silicate hydration in the presence of heavy metals

The hydration of tricalcium silicate (C(3)S) in the presence of heavy metal is very important to cement-based solidification/stabilisation (s/s) of waste. In this work, tricalcium silicate pastes and aqueous suspensions doped with nitrate salts of Zn(2+), Pb(2+), Cu(2+) and Cr(3+) were examined at different ages by X-ray powder diffraction (XRD), thermal analysis (DTA/TG) and (29)Si solid-state magic angle spinning/nuclear magnetic resonance (MAS/NMR). It was found that heavy metal doping accelerated C(3)S hydration, even though Zn(2+) doping exhibited a severe retardation effect at an early period of time of C(3)S hydration. Heavy metals retarded the precipitation of portlandite due to the reduction of pH resulted from the hydrolysis of heavy metal ions during C(3)S hydration. The contents of portlandite in the control, Cr(3+)-doped, Cu(2+)-doped, Pb(2+)-doped and Zn(2+)-doped C(3)S pastes aged 28 days were 16.7, 5.5, 5.5, 5.5, and <0.7%, respectively. Heavy metals co-precipitated with calcium as double hydroxides such as (Ca(2)Cr(OH)(7).3H(2)O, Ca(2)(OH)(4)4Cu(OH)(2).2H(2)O and CaZn(2)(OH)(6).2H(2)O). These compounds were identified as crystalline phases in heavy metal doping C(3)S suspensions and amorphous phases in heavy metal doping C(3)S pastes. (29)Si NMR data confirmed that heavy metals promoted the polymerisation of C-S-H gel in 1-year-old of C(3)S pastes. The average numbers of Si in C-S-H gel for the Zn(2+)-doped, Cu(2+)-doped, Cr(3+)-doped, control, and Pb(2+)-doped C(3)S pastes were 5.86, 5.11, 3.66, 3.62, and 3.52. And the corresponding Ca/Si ratios were 1.36, 1.41, 1.56, 1.57 and 1.56, respectively. This study also revealed that the presence of heavy metal facilitated the formation of calcium carbonate during C(3)S hydration process in the presence of carbon dioxide.     

Comparative study of differently treated animal bones for Co(2+) removal

The objective of the present study was the evaluation of differently treated bovine bones for Co(2+) removal from aqueous media. Powdered bones (B), as well as samples prepared by H(2)O(2) oxidation (BH(2)O(2)) and annealing at 400-1000 degrees C (B400-B1000), were tested as sorbent materials. A combination of XRD, FTIR spectroscopies, DTA/TGA analyses, specific surface area (S(p)) and point of zero charge (pH(PZC)) measurements was utilized for physicochemical characterization of sorbents. Sorption of Co(2+) was studied in batch conditions as a function of pH, contact time and Co(2+) concentration. Initial pH values in the range 4-8 were found optimal for sorption experiments. Equilibrium time of 24h was required in all investigated systems. The maximum sorption capacities differ significantly from 0.078 to 0.495mmol/g, whereas the affinity towards Co(2+) decreased in the order: B400>BH(2)O(2)>B600>B>B800>B1000. The pseudo-second-order model and Langmuir theoretical equation were used for fitting the kinetic and equilibrium data, respectively. Ion-exchange with Ca(2+) and specific cation sorption were identified as main removal mechanisms. The amounts of Co(2+) desorbed from loaded bone sorbents increased with the decrease of pH as well as with the increase of Ca(2+) concentration. Heating at 400 degrees C was found to be an optimal treatment for the production of the Co(2+) removal agent.     

Impedimetric immobilized DNA-based sensor for simultaneous detection of Pb2+, Ag+, and Hg2+

An unlabeled immobilized DNA-based sensor was reported for simultaneous detection of Pb(2+), Ag(+), and Hg(2+) by electrochemical impedance spectroscopy (EIS) with [Fe(CN)(6)](4-/3-) as redox probe, which consisted of three interaction sections: Pb(2+) interaction with G-rich DNA strands to form G-quadruplex, Ag(+) interaction with C-C mismatch to form C-Ag(+)-C complex, and Hg(2+) interaction with T-T mismatch to form T-Hg(2+)-T complex. Circular dichroism (CD) and UV-vis spectra indicated that the interactions between DNA and Pb(2+), Ag(+), or Hg(2+) occurred. Upon DNA interaction with Pb(2+), Ag(+), and Hg(2+), respectively, a decreased charge transfer resistance (R(CT)) was obtained. Taking advantage of the R(CT) difference (ΔR(CT)), Pb(2+), Ag(+), and Hg(2+) were selectively detected with the detection limit of 10 pM, 10 nM, and 0.1 nM, respectively. To simultaneously (or parallel) detect the three metal ions coexisting in a sample, EDTA was applied to mask Pb(2+) and Hg(2+) for detecting Ag(+); cysteine was applied to mask Ag(+) and Hg(2+) for detecting Pb(2+), and the mixture of G-rich and C-rich DNA strands were applied to mask Pb(2+) and Ag(+) for detecting Hg(2+). Finally, the simple and cost-effective sensor could be successfully applied for simultaneously detecting Pb(2+), Ag(+), and Hg(2+) in calf serum and lake water.