The use of zero-valent iron for groundwater remediation and wastewater treatment: a review

Recent industrial and urban activities have led to elevated concentrations of a wide range of contaminants in groundwater and wastewater, which affect the health of millions of people worldwide. In recent years, the use of zero-valent iron (ZVI) for the treatment of toxic contaminants in groundwater and wastewater has received wide attention and encouraging treatment efficiencies have been documented. This paper gives an overview of the recent advances of ZVI and progress obtained during the groundwater remediation and wastewater treatment utilizing ZVI (including nanoscale zero-valent iron (nZVI)) for the removal of: (a) chlorinated organic compounds, (b) nitroaromatic compounds, (c) arsenic, (d) heavy metals, (e) nitrate, (f) dyes, and (g) phenol. Reaction mechanisms and removal efficiencies were studied and evaluated. It was found that ZVI materials with wide availability have appreciable removal efficiency for several types of contaminants. Concerning ZVI for future research, some suggestions are proposed and conclusions have been drawn.

A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters

Textile industry is one of the most chemically intensive industries on the earth and the major polluter of potable water. It generates huge quantities of complex chemical substances as a part of unused materials including dyes in the form of wastewater during various stages of textile processing. The direct discharge of this wastewater into environment affects its ecological status by causing various undesirable changes. As environmental protection becomes a global concern, industries are finding novel solutions for developing technologies that can diminish the environmental damage. However, colour removal from textile wastewater by means of cheaper and environmental friendly technologies is still a major challenge. In this manuscript, several options of decolourisation of textile wastewater by chemical means have been reviewed. Based on the present review, some novel pre-hydrolysed coagulants such as Polyaluminium chloride (PACl), Polyaluminium ferric chloride (PAFCl), Polyferrous sulphate (PFS) and Polyferric chloride (PFCl) have been found to be more effective and suggested for decolourisation of the textile wastewater. Moreover, use of natural coagulants for textile wastewater treatment has also been emphasised and encouraged as the viable alternative because of their eco-friendly nature.

Small-sized microplastics and pigmented particles in bottled mineral water

Up to now, only a few studies about microparticle contamination of bottled mineral water have been published. The smallest analysed particle size was 5 μm. However, due to toxicological reasons, especially microparticles smaller than 1.5 μm are critically discussed. Therefore, in the present study, 32 samples of bottled mineral water were investigated for contamination by microplastics, pigment and additive particles. Due to the application of aluminium coated polycarbonate membrane filters and micro-Raman spectroscopy, a lowest analysed particle size of 1 μm was achieved. Microplastics were found in water from all bottle types: in single use and reusable bottles made of poly(ethylene terephthalate) (PET) as well as in glass bottles. The amount of microplastics in mineral water varied from 2649 ± 2857 per litre in single use PET bottles up to 6292 ± 10521 per litre in glass bottles. While in plastic bottles, the predominant polymer type was PET; in glass bottles various polymers such as polyethylene or styrene-butadiene-copolymer were found. Hence, besides the packaging itself, other contamination sources have to be considered. Pigment particles were detected in high amounts in reusable, paper labelled bottles (195047 ± 330810 pigment particles per litre in glass and 23594 ± 25518 pigment particles per litre in reusable paper labelled PET bottles). Pigment types found in water samples were the same as used for label printing, indicating the bottle cleaning process as possible contamination route. Furthermore, on average 708 ± 1024 particles per litre of the additive Tris(2,4-di-tert-butylphenyl)phosphite were found in reusable PET bottles. This additive might be leached out from the bottle material itself. Over 90% of the detected microplastics and pigment particles were smaller than 5 μm and thus not covered by previous studies. In summary, this is the first study reporting about microplastics, pigment and additive particles found in bottled mineral water samples with a smallest analysed particle size of 1 μm.

Recent advances for dyes removal using novel adsorbents: A review

Dyeing wastewaters are toxic and carcinogenic to both aquatic life and human beings. Adsorption technology, as a facile and effective method, has been extensively used for removing dyes from aqueous solutions for decades. Numerous researchers have attempted to seek or design alternative materials for dye adsorption. However, using various novel adsorbents to remove dyes has not been extensively reviewed before. In this review, the key advancement on the preparation and modification of novel adsorbents and their adsorption capacities for dyes removal under various conditions have been highlighted and discussed. Specific adsorption mechanisms and functionalization methods, particularly for increasing adsorption capacities are discussed for each adsorbent. This review article mainly includes (1) the categorization, side effects and removal technologies of dyes; (2) the characteristics, advantages and limitations of each sort of adsorbents; (3) the functionalization and modification methods and controlling mechanisms; and (4) discussion on the problems and future perspectives about adsorption technology from adsorbents aspects and practical application aspects.

An overview on the removal of synthetic dyes from water by electrochemical advanced oxidation processes

Wastewater containing dyes are one of the major threats to our environment. Conventional methods are insufficient for the removal of these persistent organic pollutants. Recently much attention has been received for the oxidative removal of various organic pollutants by electrochemically generated hydroxyl radical. This review article aims to provide the recent trends in the field of various Electrochemical Advanced Oxidation Processes (EAOPs) used for removing dyes from water medium. The characteristics, fundamentals and recent advances in each processes namely anodic oxidation, electro-Fenton, peroxicoagulation, fered Fenton, anodic Fenton, photoelectro-Fenton, sonoelectro-Fenton, bioelectro-Fenton etc. have been examined in detail. These processes have great potential to destroy persistent organic pollutants in aqueous medium and most of the studies reported complete removal of dyes from water. The great capacity of these processes indicates that EAOPs constitute a promising technology for the treatment of the dye contaminated effluents.

In situ measurement of collagen synthesis by human bone cells with a sirius red-based colorimetric microassay: effects of transforming growth factor beta2 and ascorbic acid 2-phosphate

Staining of collagens by Sirius Red, a standard histological procedure, was applied to quantify collagen synthesis in human osteoblast-like cell cultures in situ. After morphological analysis of the deposited material, the stain was dissolved and its optical density determined spectrophotometrically using a microtiter plate assay system. The method was sensitive with a detection limit for collagen synthesized by 3000 normal human periosteal cells. The assay is easy to perform and specific with respect to different extracellular materials, for example, collagen types I and III were well stained, collagen type IV and laminin exhibited only low staining, and fibronectin, chondroitin sulfate, dermatan sulfate, and amyloid beta were negative. A major advantage of the method is the combination of identification of collagen-producing cells in situ with subsequent spectrophotometric quantification of the dissolved stain. Thus it is possible to obtain information on cell morphology, active sites of collagen deposition in a cell culture, microscopic detection of high-and low-producer cells prior to dissolution and quantification of the deposited material. In this regard the assay is superior to either radioactive labeling, hydroxyproline determination, or Sirius Red-based colorimetric assays with cell lysates. Since the quantification is based on microtiter plate reading, the method can be recommended for the screening of large quantities of samples.

Recent advances based on the synergetic effect of adsorption for removal of dyes from waste water using photocatalytic process

The problem of textile dye pollution has been addressed by various methods, mainly physical, chemical, biological, and acoustical. These methods mainly separate and/or remove the dye present in water. Recently, advanced oxidation processes (AOP) have been focused for removal of dye from waste water due to their advantages such as ecofriendly, economic and capable to degrade many dyes or organic pollutant present in water. Photocatalysis is one of the advance oxidation processes, mainly carried out under irradiation of light and suitable photocatalytic materials. The photocatalytic activity of the photocatalytic materials mainly depends on the band gap, surface area, and generation of electron-hole pair for degradation dyes present in water. It has been observed that the surface area plays a major role in photocatalytic degradation of dyes, by providing higher surface area, which leads to the higher adsorption of dye molecule on the surface of photocatalyst and enhances the photocatalytic activity. This present review discusses the synergic effect of adsorption of dyes on the photocatalytic efficiency of various nanostructured high surface area photocatalysts. In addition, it also provides the properties of the water polluting dyes, their mechanism and various photocatalytic materials; and their morphology used for the dye degradation under irradiation of light along with the future prospects of highly adsorptive photocatalytic material and their application in photocatalytic removal of dye from waste water.

Quantifying amyloid beta-peptide (Abeta) aggregation using the Congo red-Abeta (CR-abeta) spectrophotometric assay

Congo red (CR) is a histologic dye that binds to many amyloid proteins because of their extensive beta-sheet structure. The absorbance spectrum of the dye changes upon binding to amyloid. This spectral change has previously been exploited to develop a method to study the interaction of CR with fibrillar beta-sheet insulin fibrils, a model amyloid protein. The amyloid beta-peptide (Abeta) is an amyloid protein which is deposited in the brains of Alzheimer's disease victims. Abeta is toxic to neurons in vitro in a manner that is highly dependent on the assembly of this peptide into beta-sheet fibrils. The CR-insulin assay has been applied as a means of studying the aggregation of Abeta, despite the fact that the CR-insulin procedure was never adequately developed for this purpose. In this study, we modify our original CR-insulin assay specifically for the purpose of quantifying Abeta aggregation and discuss the reasons why application of the CR-insulin method is not valid for this purpose. The CR-Abeta method is equally simple and retains the advantages of speed and lack of necessity for specialized instrumentation or expensive/radioactive reagents. Furthermore, this method can directly provide quantitation of aggregated Abeta in absolute terms (i.e., microg/ml).

Evans Blue Dye as an in vivo marker of myofibre damage: optimising parameters for detecting initial myofibre membrane permeability

Evans Blue Dye (EBD) is widely used to study cellular membrane permeability and has recently been utilised in mdx mice to identify permeable skeletal myofibres that have become damaged as a result of muscular dystrophy. EBD has the potential to be a useful vital stain of myofibre permeability in other models of skeletal muscle injury and membrane-associated fragility. The parameters for its use for such purposes were optimised in the present study, of particular interest is the use of EBD to identify the onset of muscle damage. This study compared intravenous vs. intraperitoneal injection; tissue fixation; volume of EBD; time of availability in tissue; and persistence after injection in mdx mice (with endogenous muscle damage) and control mice. Satisfactory labelling of permeable myofibres was seen in frozen sections viewed with fluorescence microscopy when intraperitoneal injection of a 1% EBD solution injected at 1% volume relative to body mass was administered between 16 and 24 h prior to tissue sampling. EBD labelling was then assessed in three mouse models of experimental injury and repair-cut injury, whole muscle grafts, and exercise-induced muscle damage. These experiments demonstrated that (i) following a cut injury across myofibres, EBD penetrated up to 150 microm from the injury site over a 20-h period; (ii) EBD was present throughout myofibres of avascular whole muscle graft by one day after transplantation; and (iii) damaged myofibres were detected within 20 min after controlled lengthening-contraction exercise. This simple and inexpensive technique has sensitivity for the detection of increased myofibre permeability and/or sublethal damage that has advantages over other traditional histological techniques at the light microscopy level.

Optimization of the tetrazolium dye (MTT) colorimetric assay for cellular growth and viability

The MTT colorimetric assay is an established method of determining viable cell number in proliferation and cytotoxicity studies. This assay is based on the cleavage of the yellow tetrazolium salt, MTT, to form a soluble blue formazan product by mitochondrial enzymes, and the amount of formazan produced is directly proportional to the number of living, not dead cells, present during MTT exposure. Since the MTT assay is rapid, convenient, and economical, it has become a very popular technique for quantification of viable cells in culture. However, various parameters have been identified that can affect cellular metabolism and other factors, which significantly modify MTT-specific activity and can result in calculated false high or false low cell counts. Therefore, it is essential to establish assay parameters with the proper controls for each cell line and/or drug treatment in order to optimize assay conditions and minimize confounding effects. These parameters should include determining appropriate cell densities, culture medium, optimal concentrations and exposure times for MTT, fresh culture medium at the time of assay to avoid nutrient depletion, and controlling for drug treatment effects that may influence cellular metabolism. By controlling these important parameters, the MTT colorimetric assay provides accurate and reliable quantification of viable cell number.

Chemical aspects of santalin as a histological stain

Recent research on the chemical nature of the red dyes isolated from Pterocarpus santalinus and certain West African plants, viz., Baphia nitida, Pterocarpus osun and Pterocarpus soyauxii, have been reviewed. P. santalinus contains santalins A, B and C, but no santarubin. Santalins and santarubins have been found in P. osun, P. soyauxii and B. nitida. The structural formulae of the santalins are presented and their differences from santarubins indicated. Santalins A and B have some similarities in structure with hematein. This is probably responsible for their staining properties; the possible mechanism of staining is discussed.

Assessment of water contamination caused by a mutagenic textile effluent/dyehouse effluent bearing disperse dyes

High performance liquid chromatography coupled to a diode array detector method was developed to detect disperse dyes in water samples over the range 0.50-35 ng, with detection limits of 0.09 ng, 0.84 ng and 0.08 ng, respectively, with good repeatability and accuracy. This study identifies the disperse azo dyes C.I. Disperse Blue 373, C.I. Disperse Orange 37 and Disperse Violet 93 as components of a commercial dye formulation assigned as Dispersol Black Dye (CVS) used in the textile industry for dyeing synthetic fibers that are contributing to the mutagenicity found in the Cristais River, São Paulo, Brazil. High performance liquid chromatography coupled to a diode array detector was applied to monitor the occurrence of these dyes in: (1) the treated industrial effluent, (2) raw river water, (3) treated river water, and (4) the sludge produced by a Drinking Water Treatment Plant (DWTP) which is located 6 km downstream from the textile industrial discharge, where dyes' concentrations changed from 1.65 ng L(-1) to 316 microL(-1).

Adsorption isotherm models for dye removal by cationized starch-based material in a single component system: error analysis

This article describes the adsorption of an anionic dye, namely C.I. Acid Blue 25 (AB 25), from aqueous solutions onto a cationized starch-based adsorbent. Temperature was varied to investigate its effect on the adsorption capacity. Equilibrium adsorption isotherms were measured for the single component system and the experimental data were analyzed by using Langmuir, Freundlich, Tempkin, Generalized, Redlich-Peterson, and Toth isotherm equations. Five error functions were used to determine the alternative single component parameters by non-linear regression due to the bias in using the correlation coefficient resulting from linearization. The error analysis showed that, compared with other models, the Langmuir model described best the dye adsorption data. Both linear regression method and non-linear error functions provided the best-fit to experimental data with the Langmuir model.

Fibroblasts can be genetically modified to produce excitable cells capable of electrical coupling

BACKGROUND

Cardiac conduction occurs in an electrical syncytium of excitable cells connected by gap junctions. Disruption of these electrophysiological properties causes conduction slowing or block. Depending on the location of affected cells within the heart, this has the potential to result in clinical syndromes such as atrioventricular block. With a view to developing gene therapy strategies for repairing cardiac conduction defects, we sought to establish whether the phenotype of fibroblasts can be modified by gene transfer to produce cells capable of electrical excitation and coupling.

METHODS AND RESULTS

High-titer lentiviral vectors encoding MyoD, a myogenic transcription factor, and connexin43, a gap junction protein, were produced by established methods. Human dermal fibroblasts (HDFs) were efficiently (>80%) transduced at a multiplicity of infection of 50. HDFs transduced with the MyoD-encoding vector underwent myogenic conversion, as evidenced by myotube formation and detection of muscle-specific proteins. Importantly, calcium transients indicative of membrane excitability were observed in MyoD-induced myotubes after loading with a calcium-sensitive dye and electrical stimulation. Transients from adjacent myotubes displayed different excitation thresholds, indicating an absence of coupling between cells, consistent with skeletal muscle biology. In contrast, simultaneous transduction of HDFs with MyoD and connexin43-encoding vectors resulted in the appearance of transients in adjacent myotubes with identical thresholds, indicative of electrical coupling. Notably, dye transfer studies confirmed gap junctional intercellular communication.

CONCLUSIONS

Fibroblasts can be genetically modified to produce excitable cells capable of electrical coupling. These observations strengthen the prospect of developing gene-based strategies for repairing cardiac conduction defects.

A comparative study of fat storage quantitation in nematode Caenorhabditis elegans using label and label-free methods

The nematode Caenorhabditis elegans has been employed as a model organism to study human obesity due to the conservation of the pathways that regulate energy metabolism. To assay for fat storage in C. elegans, a number of fat-soluble dyes have been employed including BODIPY, Nile Red, Oil Red O, and Sudan Black. However, dye-labeled assays produce results that often do not correlate with fat stores in C. elegans. An alternative label-free approach to analyze fat storage in C. elegans has recently been described with coherent anti-Stokes Raman scattering (CARS) microscopy. Here, we compare the performance of CARS microscopy with standard dye-labeled techniques and biochemical quantification to analyze fat storage in wild type C. elegans and with genetic mutations in the insulin/IGF-1 signaling pathway including the genes daf-2 (insulin/IGF-1 receptor), rict-1 (rictor) and sgk-1 (serum glucocorticoid kinase). CARS imaging provides a direct measure of fat storage with unprecedented details including total fat stores as well as the size, number, and lipid-chain unsaturation of individual lipid droplets. In addition, CARS/TPEF imaging reveals a neutral lipid species that resides in both the hypodermis and the intestinal cells and an autofluorescent organelle that resides exclusively in the intestinal cells. Importantly, coherent addition of the CARS fields from the C-H abundant neutral lipid permits selective CARS imaging of the fat store, and further coupling of spontaneous Raman analysis provides unprecedented details including lipid-chain unsaturation of individual lipid droplets. We observe that although daf-2, rict-1, and sgk-1 mutants affect insulin/IGF-1 signaling, they exhibit vastly different phenotypes in terms of neutral lipid and autofluorescent species. We find that CARS imaging gives quantification similar to standard biochemical triglyceride quantification. Further, we independently confirm that feeding worms with vital dyes does not lead to the staining of fat stores, but rather the sequestration of dyes in lysosome-related organelles. In contrast, fixative staining methods provide reproducible data but are prone to errors due to the interference of autofluorescent species and the non-specific staining of cellular structures other than fat stores. Importantly, both growth conditions and developmental stage should be considered when comparing methods of C. elegans lipid storage. Taken together, we confirm that CARS microscopy provides a direct, non-invasive, and label-free means to quantitatively analyze fat storage in living C. elegans.

Nucleation-dependent polymerization is an essential component of amyloid-mediated neuronal cell death

Accumulating evidence suggests that amyloid protein aggregation is pathogenic in many diseases, including Alzheimer's disease. However, the mechanisms by which protein aggregation mediates cellular dysfunction and overt cell death are unknown. Recent reports have focused on the potential role of amyloid oligomers or protofibrils as a neurotoxic form of amyloid-beta (Abeta) and related amyloid aggregates. Here we describe studies indicating that overt neuronal cell death mediated by Abeta(1-40) is critically dependent on ongoing Abeta(1-40) polymerization and is not mediated by a single stable species of neurotoxic aggregate. The extent and rate of neuronal cell death can be controlled by conditions that alter the rate of Abeta polymerization. The results presented here indicate that protofibrils and oligomeric forms of Abeta most likely generate neuronal cell death through a nucleation-dependent process rather than acting as direct neurotoxic ligands. These findings bring into question the use of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide formazan assay (MTT assay) as a reporter of Abeta-mediated neuronal cell death and suggest that diffusible Abeta protofibrils and oligomers more likely mediate subtle alterations of synaptic function and long-term potentiation rather than overt neuronal cell death. These results have been extended to Abeta(1-42), the non-Abeta component of Alzheimer's disease amyloid plaques, and human amylin, suggesting that nucleation-dependent polymerization is a common mechanism of amyloid-mediated neuronal cell death. Our findings indicate that ongoing amyloid fibrillogenesis may be an essential mechanistic process underlying the pathogenesis associated with protein aggregation in amyloid disorders.

Removal of an anionic dye by adsorption/precipitation processes using alkaline white mud

Alkaline white mud (AWM) has been investigated as a low-cost material for removal of an anionic dye, acid blue 80. The effects of contact time, initial pH of dye solution, AWM dosage, and the presence of inorganic anion sulphate or phosphate ion on removal of the dye were evaluated. The results show that AWM could be used as an effective material for removal of acid blue 80 in a pre or main process, particularly at high dye concentration (>300 mgL(-1)), reaching maximum removal efficiency of 95%. At low dye concentration, surface adsorption is mainly responsible for the dye removal, while chemical precipitation of the dye anions with soluble Ca(2+) and Mg(2+) may play a dominant role for the dye removal at high concentration, producing much less sludge than conventional adsorption method. Solution pH has only a limited effect on the dye removal due to high alkalinity and large pH buffer capacity of AWM suspension and thereby pH is not a limiting factor in pursuing high dye removal. The presence of SO(4)(2-) could reduce the dye removal by AWM only when SO(4)(2-) concentration is beyond 0.7 mmolL(-1). The dye removal may be significantly suppressed by the presence of phosphate with increasing concentration, and the reduction in the dye removal is much larger at high dye concentrations than at low ones.

Environmental fate of Triclosan in the River Aire Basin, UK

The concentrations and removal rate of Triclosan, an antibacterial ingredient in consumer products, were measured at advanced trickling filter (TF) and activated sludge (AS) wastewater treatment plants (WWTPs) in the River Aire basin in the UK in September 2000. Additionally, the in-stream removal of Triclosan was measured directly in Mag Brook, the stream receiving the treated effluent from the TF plant, using a fluorescent dye tracer to determine the water plug travel times. The in-stream removal of the dissolved and un-ionized (i.e. bioavailable) fraction of the compound was measured using semipermeable membrane devices (SPMDs) deployed at various distances downstream from the WWTP discharge point. The estimated removal rates were used in the GREAT-ER (Geography-Referenced Regional Exposure Assessment Tool for European Rivers) model to predict the site-specific distribution of Triclosan concentrations in the Aire basin as well as to calculate regional concentrations. High WWTP (approximately 95%) and in-stream (0.21-0.33 h-1) removal rates of Triclosan in Mag Brook confirm that this chemical is rapidly eliminated from the aquatic environment.

Aqueous adsorption and removal of organic contaminants by carbon nanotubes

Organic contaminants have become one of the most serious environmental problems, and the removal of organic contaminants (e.g., dyes, pesticides, and pharmaceuticals/drugs) and common industrial organic wastes (e.g., phenols and aromatic amines) from aqueous solutions is of special concern because they are recalcitrant and persistent in the environment. In recent years, carbon nanotubes (CNTs) have been gradually applied to the removal of organic contaminants from wastewater through adsorption processes. This paper reviews recent progress (145 studies published from 2010 to 2013) in the application of CNTs and their composites for the removal of toxic organic pollutants from contaminated water. The paper discusses removal efficiencies and adsorption mechanisms as well as thermodynamics and reaction kinetics. CNTs are predicted to have considerable prospects for wider application to wastewater treatment in the future.

Remediation of textile effluents by membrane based treatment techniques: a state of the art review

The textile industries hold an important position in the global industrial arena because of their undeniable contributions to basic human needs satisfaction and to the world economy. These industries are however major consumers of water, dyes and other toxic chemicals. The effluents generated from each processing step comprise substantial quantities of unutilized resources. The effluents if discharged without prior treatment become potential sources of pollution due to their several deleterious effects on the environment. The treatment of heterogeneous textile effluents therefore demands the application of environmentally benign technology with appreciable quality water reclamation potential. These features can be observed in various innovative membrane based techniques. The present review paper thus elucidates the contributions of membrane technology towards textile effluent treatment and unexhausted raw materials recovery. The reuse possibilities of water recovered through membrane based techniques, such as ultrafiltration and nanofiltration in primary dye houses or auxiliary rinse vats have also been explored. Advantages and bottlenecks, such as membrane fouling associated with each of these techniques have also been highlighted. Additionally, several pragmatic models simulating transport mechanism across membranes have been documented. Finally, various accounts dealing with techno-economic evaluation of these membrane based textile wastewater treatment processes have been provided.

Resin composite monomers alter MTT and LDH activity of human gingival fibroblasts in vitro

OBJECTIVES

Substances such as monomers may be released from composite resin systems and may induce adverse effects in biological tissues. The aim of this study is to investigate the cytotoxic concentrations of resin composite monomers on cultures of human gingival fibroblasts.

METHODS

A range of dilutions of five resin composite monomers (HEMA, HPMA, DMAEMA, TEGDMA, and Bis-GMA) were added to the culture medium of human gingival fibroblasts for 24 h. Their cytotoxic effects were measured by using two colorimetric functional assays, mitochondrial dehydrogenase activity (MTT) and lactate dehydrogenase activity (LDH) assay. The logP values (water/octanol partition) of test monomers were also calculated computationally.

RESULTS

Mitochondrial reducing activity assessed with the MTT test was inhibited by all monomers and all the monomers increased the LDH release in a reproducible dose dependent manner. A wide range of TC 50 values (concentrations altering MTT and LDH activity by 50%) (0.32-5.8 mM by MTT assay and 0.36-6.7 mM by LDH assay) was observed. Ranking of composite resin monomer cytotoxicities (TC 50) were similar for both the MTT and LDH assays, (Bis-GMA>TEGDMA>DMAEMA>HPMA >HEMA). However, the MTT assay was found to be more sensitive than the LDH assay, particularly when lower doses of the tested monomers were determined. The ranking of TC 50 concentrations correlated with the calculated logP values.

SIGNIFICANCE

Monomers used in dental restorative materials show a variety of toxic effects on gingival fibroblasts. A combination approach using MTT and LDH assays provides valuable information about their toxic effects.

RNA-selective, live cell imaging probes for studying nuclear structure and function

The higher-order structural organization of the cell nucleus reflects the underlying genome-wide transcriptional activity and macromolecular transport processes. To study the microscopic organization of RNA distribution within the nucleus, a combinatorial library of fluorescent styryl molecules was synthesized and screened for an in vitro RNA response and live cell nuclear imaging. Four different cell lines (HeLa, A549, 3T3, and 3T3-L1) were analyzed in terms of higher-order nuclear organization. We identified RNA-selective dyes with better imaging properties relative to commercially available SYTORNASelect dye; the selected dyes were also cell permeant, photostable, and well tolerated by the cells. Our dyes also had very good counterstain compatibility with Hoechst and DAPI, which could help to image the DNA distribution in relation to RNA distribution in live cells and therefore reveal different patterns of RNA-DNA colocalization.

Photostability and thermal stability of indocyanine green

The photo-fading of the S0-S1 absorption band of the infrared dye indocyanine green sodium iodide (ICG-NaI) has been studied by cw laser excitation to the S1 band. Monomeric solutions in water, heavy water, aqueous sodium azide, human plasma, methanol and dimethyl sulfoxide (DMSO) as well as J-aggregated solutions in H2O and D2O have been investigated. A leucoform of indocyanine green seems to be formed by photodegradation. The degradation slows down with exposure time. The initial degradation yield, phi D,0, is determined. In monomeric and dimeric water, heavy water and sodium azide solutions the initial photostability is of the order of phi D.0 approximately 10(-3), in the organic solvents methanol and DMSO it is of the order of phi D.0 approximately 10(-5), and in human plasma it is phi D.0 approximately 2 x 10(-6). J-aggregates at high concentration are very stable. The thermal stability of the ICG-NaI solutions at room temperature in the dark is compared with their photostability. The thermal degradation time of monomeric and dimeric ICG-NaI in water, heavy water and sodium azide solutions is t(th) approximately 10 days, while no thermal degradation is observed for ICG-NaI J-aggregates and ICG-NaI in methanol, DMSO and human plasma.