Materials Engineering of Violin Soundboards by Stradivari and Guarneri.

We investigated the material properties of Cremonese soundboards using a wide range of spectroscopic, microscopic, and chemical techniques. We found similar types of spruce in Cremonese soundboards as in modern instruments, but Cremonese spruces exhibit unnatural elemental compositions and oxidation patterns that suggest artificial manipulation. Combining analytical data and historical information, we may deduce the minerals being added and their potential functions-borax and metal sulfates for fungal suppression, table salt for moisture control, alum for molecular crosslinking, and potash or quicklime for alkaline treatment. The overall purpose may have been wood preservation or acoustic tuning. Hemicellulose fragmentation and altered cellulose nanostructures are observed in heavily treated Stradivari specimens, which show diminished second-harmonic generation signals. Guarneri's practice of crosslinking wood fibers via aluminum coordination may also affect mechanical and acoustic properties. Our data suggest that old masters undertook materials engineering experiments to produce soundboards with unique properties.

Biodistribution of Graphene Oxide Determined through Postadministration Labeling with DNA-Conjugated Gold Nanoparticles and ICPMS.

Recent research has revealed the use of graphene oxide (GO) and its derivatives as a potential biomaterial because of their attractive physicochemical characteristics and functional properties. However, if GO and related derivatives are to become useful materials for biomedical applications, it will be necessary to evaluate their biodistribution for health and safety considerations. To obtain a more accurate biodistribution for GO, we (i) developed a postadministration labeling strategy employing DNA-conjugated gold nanoparticles (DNA-AuNPs) to selectively label administered GO in Solvable-treated tissue samples and (ii) constructed an automatic sample pretreatment scheme (using a C18-packed minicolumn) to effectively separate the DNA-AuNP-labeled GO from the unbound DNA-AuNPs and the dissolved tissue matrices, thereby enabling ultrasensitive, interference-free quantification of GO through measurement (inductively coupled plasma mass spectrometry) of the Au signal intensities. The DNA-AuNPs can bind to GO in a concentration- and time-dependent manner. After optimizing the labeling conditions (DNA length, incubation pH, DNA-AuNP concentration, and incubation time) and the separation scheme (sample loading flow rate, rinsing volume, and eluent composition), we found that A20R20-AuNPs (R20: random DNA sequence including A, T, C, and G) had the strongest binding affinity for labeling of the administered GO (dissociation constant: 36.0 fM) and that the method's detection limit reached 9.3 ag L-1 with a calibration curve having a working range from 10-1 to 1010 fg L-1. Moreover, this approach revealed that the intravenously administered GO accumulated predominantly in the liver and spleen at 1 and 12 h post administration, with apparent discrepancies in the concentrations measured using pre- and postadministration labeling strategies.

Nanocomposite-Coated Microfluidic-Based Photocatalyst-Assisted Reduction Device To Couple High-Performance Liquid Chromatography and Inductively Coupled Plasma-Mass Spectrometry for Online Determination of Inorganic Arsenic Species in Natural Water.

To selectively and sensitively determine the trace inorganic As species, As(III) and As(V), we developed a nanocomposite-coated microfluidic-based photocatalyst-assisted reduction device (PCARD) as a vapor generation (VG) device to couple high-performance liquid chromatography (HPLC) separation and inductively coupled plasma-mass spectrometry (ICPMS) detection. Au nanoparticles were deposited on TiO2 nanoparticles to strengthen the conversion efficiency of the nanocomposite photocatalytic reduction. The sensitivity for As was significantly enhanced by employing the nanocomposite photocatalyst and using prereduction and signal-enhancement reagents. Under the optimal operating conditions, the analytical detection limits (based on 3σ) of the proposed online HPLC/nanocomposite-coated microfluidic-based PCARD/ICPMS system for As(III) and As(V) were 0.23 and 0.34 µg·L-1, respectively. The results were validated using a certified reference material (NIST SRM 1643e) and groundwater sample analysis, indicating the good reliability and applicability of our proposed system for the determination of inorganic As species in natural fresh water.

Vortex-assisted liquid-liquid microextraction of strontium from water samples using 4',4″(5″)-di-(tert-butylcyclohexano)-18-crown-6 and tetraphenylborate.

A vortex-assisted liquid-liquid microextraction method was developed for the chromatographic determination of strontium in aqueous samples. In the method, strontium was complexed with 4',4″(5″)-di-(tert-butylcyclohexano)-18-crown-6 in the presence of tetraphenylborate as the counter anion, which increased the hydrophobicity of the ion-association complex, resulting in its improved extraction into 1-octanol. Strontium from the organic phase was stripped with nitric acid back to aqueous solution and determined by ion chromatography. The optimum microextraction conditions were as follows: 2.0 mL aqueous samples with 3 mM tetraphenylborate; 150 µL of 1-octanol as the extractant phase with 10 mM DtBuCH18C6; vortex extraction time for 10 s; centrifugation at 6000 rpm for 4 min; stripping by 0.1 M nitric acid. Under the optimum conditions, the detection limit for strontium was 0.005 mg/L. The calibration curves showed good linearity over the range between 0.01 and 2.5 mg/L. Intra- and interday precisions of the present method were satisfactory with relative standard deviations of 1.7 and 2.1%, respectively.

Enzyme-Immobilized 3D-Printed Reactors for Online Monitoring of Rat Brain Extracellular Glucose and Lactate.

In this study we constructed a highly sensitive system for in vivo monitoring of the concentrations of rat brain extracellular glucose and lactate. This system involved microdialysis (MD) sampling and fluorescence determination in conjunction with a novel sample derivatization scheme in which glucose oxidase and lactate oxidase were immobilized in ABS flow bioreactors (manufactured through low-cost three-dimensional printing (3DP)), via fused deposition modeling, for online oxidization of sampled glucose and lactate, respectively, in rat brain microdialysate. After optimizing the experimental conditions for MD sampling, the manufacture of the designed flow reactors, the enzyme immobilization procedure, and the online derivatization scheme, the available sampling frequency was 15 h(-1) and the system's detection limits reached as low as 0.060 mM for glucose and 0.059 mM for lactate, based on a 20-µL conditioned microdialysate; these characteristics were sufficient to reliably determine the concentrations of extracellular glucose and lactate in the brains of living rats. To demonstrate the system's applicability, we performed (i) spike analyses of offline-collected rat brain microdialysate and (ii) in vivo dynamic monitoring of the extracellular glucose and lactate in living rat brains, in addition to triggering neuronal depolarization by perfusing a high-K(+) medium from the implanted MD probe. Our analytical results and demonstrations confirm that postprinting functionalization of analytical devices manufactured using 3DP technology can be a powerful strategy for extending the diversity and adaptability of currently existing analytical configurations.

Fully 3D-Printed Preconcentrator for Selective Extraction of Trace Elements in Seawater.

In this study, we used a stereolithographic 3D printing technique and polyacrylate polymers to manufacture a solid phase extraction preconcentrator for the selective extraction of trace elements and the removal of unwanted salt matrices, enabling accurate and rapid analyses of trace elements in seawater samples when combined with a quadrupole-based inductively coupled plasma mass spectrometer. To maximize the extraction efficiency, we evaluated the effect of filling the extraction channel with ordered cuboids to improve liquid mixing. Upon automation of the system and optimization of the method, the device allowed highly sensitive and interference-free determination of Mn, Ni, Zn, Cu, Cd, and Pb, with detection limits comparable with those of most conventional methods. The system's analytical reliability was further confirmed through analyses of reference materials and spike analyses of real seawater samples. This study suggests that 3D printing can be a powerful tool for building multilayer fluidic manipulation devices, simplifying the construction of complex experimental components, and facilitating the operation of sophisticated analytical procedures for most sample pretreatment applications.

A dipole-assisted solid-phase extraction microchip combined with inductively coupled plasma-mass spectrometry for online determination of trace heavy metals in natural water.

We employed a polymeric material, poly(methyl methacrylate) (PMMA), for fabricating a microdevice and then implanted the chlorine (Cl)-containing solid-phase extraction (SPE) functionality into the PMMA chip to develop an innovative on-chip dipole-assisted SPE technique. Instead of the ion-ion interactions utilized in on-chip SPE techniques, the dipole-ion interactions between the highly electronegative C-Cl moieties in the channel interior and the positively charged metal ions were employed to facilitate the on-chip SPE procedures. Furthermore, to avoid labor-intensive manual manipulation, a programmable valve manifold was designed as an interface combining the dipole-assisted SPE microchip and inductively coupled plasma-mass spectrometry (ICP-MS) to achieve the fully automated operation. Under the optimized operation conditions for the established system, the detection limits for each analyte ion were obtained based on three times the standard deviation of seven measurements of the blank eluent solution. The limits ranged from 3.48 to 20.68 ng L(-1), suggesting that this technique appears uniquely suited for determining the levels of heavy metal ions in natural water. Indeed, a series of validation procedures demonstrated that the developed method could be satisfactorily applied to the determination of trace heavy metals in natural water. Remarkably, the developed device was durable enough to be reused more than 160 times without any loss in its analytical performance. To the best of our knowledge, this is the first study reporting on the combination of a dipole-assisted SPE microchip and elemental analysis instrument for the online determination of trace heavy metal ions.

Quantitatively profiling the dissolution and redistribution of silver nanoparticles in living rats using a knotted reactor-based differentiation scheme.

Whether silver nanoparticles (AgNPs) degrade and release silver ions (Ag(+)) in vivo has remained an unresolved issue. To evaluate the biodistribution and dissolution behavior of intravenously administered AgNPs in living rats, we employed a knotted reactor (KR) device to construct a differentiation scheme for quantitative assessment of residual AgNPs and their released Ag(+) ions in complicated animal tissues; to do so, we adjusted the operating parameters of the KR, namely, the presence/absence of a rinse solution and the sample acidity. After optimization, our proposed differentiation system was confirmed to be tolerant to rat tissue and organ matrix and provide superior reliability of differentiating AgNPs/Ag(+) than the conventional centrifugal filtration method. We then applied this differentiation strategy to investigate the biodistribution and dissolution of AgNPs in rats 1, 3, and 5 days postadministration, and it was found that the administered AgNPs accumulated predominantly in the liver and spleen, then dissolved and released Ag(+) ions that were gradually excreted, resulting in almost all of the Ag(+) ions becoming deposited in the kidney, lung, and brain. Histopathological data also indicated that toxic responses were specifically located in the AgNP-rich liver, not in the Ag(+)-dominated tissues and organs. Thus, the full-scale chemical fate of AgNPs in vivo should be integrated into future assessments of the environmental health effects and utilization of AgNP-containing products.

In-vivo evaluation of the permeability of the blood-brain barrier to arsenicals, molybdate, and methylmercury by use of online microdialysis-packed minicolumn-inductively coupled plasma mass spectrometry.

To study the permeability of the blood-brain barrier (BBB) to arsenates, arsenite, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), molybdate, and methylmercury, and the transfer behavior of these species, we constructed an automatic online analytical system comprising a microdialysis sampling device, a minicolumn packed with nonfunctionalized poly(vinyl chloride) beads, and an inductively coupled plasma mass spectrometer for continuous in-vivo measurement of their dynamic variation in the extracellular space of the brains of living rats. By using ion-polymer interactions as a novel working mechanism for sample pretreatment of volume-limited microdialysate, we simplified the operating procedure of conventional solid-phase extraction and reduced the contribution to the blank of the chemicals used. After optimizing this hyphenated system, we measured its performance by analysis of NIST standard reference materials 1640a (trace elements in natural water) and 2672a (trace elements in human urine) and by in-vivo monitoring of the dynamic variation of the compounds tested in the extracellular fluid (ECF) of rat brain. We found that intraperitoneal administration led to observable BBB permeability of arsenates, arsenite, DMA, MMA, and molybdate. Nevertheless, the limited sensitivity of the system and the size of microdialysis samples meant that detection of MeHg in ECF remained problematic, even when we administered a dose of 20 mg MeHg kg(-1) body weight. On the basis of these practical demonstrations, we suggest that our analytical system could be used not only for dynamic monitoring of the transfer kinetics of the four arsenicals and molybdate in the rat brain but also to describe associated neurotoxicity in terms of exposure to toxic metals and their species.

Investigation of C-terminal domain of SARS nucleocapsid protein-Duplex DNA interaction using transistors and binding-site models.

AlGaN/GaN high electron mobility transistors (HEMTs) were used to sense the binding between double stranded DNA (dsDNA) and the severe acute respiratory syndrome coronavirus (SARS-CoV) nucleocapsid protein (N protein). The sensing signals were the drain current change of the HEMTs induced by the protein-dsDNA binding. Binding-site models using surface coverage ratios were utilized to analyze the signals from the HEMT-based sensors to extract the dissociation constants and predict the number of binding sites. Two dissociation constants, K D1 = 0.0955 nM, K D2 = 51.23 nM, were obtained by fitting the experimental results into the two-binding-site model. The result shows that this technique is more competitive than isotope-labeling electrophoretic mobility shift assay (EMSA). We demonstrated that AlGaN/GaN HEMTs were highly potential in constructing a semiconductor-based-sensor binding assay to extract the dissociation constants of nucleotide-protein interaction.

Development of a titanium dioxide-coated microfluidic-based photocatalyst-assisted reduction device to couple high-performance liquid chromatography with inductively coupled plasma-mass spectrometry for determination of inorganic selenium species.

We developed a selective and sensitive hyphenated system employing a microfluidic-based vapor generation (VG) system in conjunction with high-performance liquid chromatography (HPLC) separation and inductively coupled plasma-mass spectrometry (ICPMS) detection for the determination of trace inorganic selenium (Se) species. The VG system exploited poly(methyl methacrylate) (PMMA) substrates of high optical quality to fabricate a microfluidic-based photocatalyst-assisted reduction device (microfluidic-based PCARD). Moreover, to reduce the consumption of photocatalysts during analytical procedures, a microfluidic-based PCARD coated with titanium dioxide nanoparticles (nano-TiO2) was employed to avoid consecutive loading. Notably, to simplify the coating procedure and improve the stability of the coating materials, a dynamic coating method was utilized. Under the optimized conditions for the selenicals of interest, the online HPLC/TiO2-coated microfluidic-based PCARD/ICPMS system enabled us to achieve detection limits (based on 3σ) of 0.043 and 0.042 µg L(-1) for Se(IV) and Se(VI), respectively. Both Se(IV) and Se(VI) could be efficiently vaporized within 15 s, while a series of validation experiments indicated that our proposed method could be satisfactorily applied to the determination of inorganic Se species in the environmental water samples.

In vivo monitoring of distributional transport kinetics and extravasation of quantum dots in living rat liver.

Although the unique optical properties of surface-modified quantum dots (QDs) have attracted wide interest in molecular biology and bioengineering, there are very few reports of their in vivo biodistribution, due to a lack of analytical techniques for characterizing the dynamic variation of QDs in living animals. In this study, we used an in vivo online monitoring system and a batch-wise elemental analytical method to investigate the biodistribution/extravasation of various surface-modified CdTeSe/ZnS (QDs) in rat liver. It is found that the surface modification dictated not only the blood retention profile but also the degree of extravasation and the clearance of extracellular QDs, making it an important variable for regulating the transfer and exchange process of QDs among three physiological compartments-bloodstream, extracellular space and Kupffer cells/hepatocytes.

In vivo monitoring of the transfer kinetics of trace elements in animal brains with hyphenated inductively coupled plasma mass spectrometry techniques.

The roles of metal ions to sustain normal function and to cause dysfunction of neurological systems have been confirmed by various studies. However, because of the lack of adequate analytical method to monitor the transfer kinetics of metal ions in the brain of a living animal, research on the physiopathological roles of metal ions in the CNS remains in its early stages and more analytical efforts are still needed. To explicitly model the possible links between metal ions and physiopathological alterations, it is essential to develop in vivo monitoring techniques that can bridge the gap between metalloneurochemistry and neurophysiopathology. Although inductively coupled plasma mass spectrometry (ICP-MS) is a very powerful technique for multiple trace element analyses, when dealing with chemically complex microdialysis samples, the detection capability is largely limited by instrumental sensitivity, selectivity, and contamination that arise from the experimental procedure. As a result, in recent years several high efficient and clean on-line sample pretreatment systems have been developed and combined with microdialysis and ICP-MS for the continuous and in vivo determination of the concentration-time profiles of metal ions in the extracellular space of rat brain. This article reviews the research relevant to the development of analytical techniques for the in vivo determination of dynamic variation in the concentration levels of metal ions in a living animal.

NIR-cleavable drug adducts of gold nanostars for overcoming multidrug-resistant tumors.

An aptamer-conjugated gold nanostar (dsDDA-AuNS) has been developed for targeting nucleolin present in both tumor cells and tumor vasculature for conducting a drug-resistant cancer therapy. AuNS with its strong absorption in the near-infrared (NIR) region was assembled with a layer of the anti-nucleolin aptamer AS1411. An anticancer drug, namely doxorubicin (DOX), was specifically conjugated on deoxyguanosine residues employing heat and acid labile methylene linkages. In response to NIR irradiation, dsDDA-AuNS allowed on-demand therapeutics. AS1411 played an active role in drug cargo-nucleus interactions, enhancing drug accumulation in the nuclei of drug-resistant breast cancer cells. The intravenous injection of dsDDA-AuNS allowed higher drug accumulation in drug-resistant tumors over naked drugs, leading to greater therapeutic efficacy even at a 54-fold less equivalent drug dose. The in vivo triggered release of DOX from dsDDA-AuNS was achieved by NIR irradiation, resulting in simultaneous photothermal and chemotherapeutic actions, yielding superior tumor growth inhibition than those obtained from either type of monotherapy for overcoming drug resistance in cancers.

Development of a titanium dioxide-assisted preconcentration/on-site vapor-generation chip hyphenated with inductively coupled plasma-mass spectrometry for online determination of mercuric ions in urine samples.

In this study, a novel automatic analytical methodology using a titanium dioxide (TiO2)-assisted preconcentration/on-site vapor-generation (VG) chip hyphenated with inductively coupled plasma-mass spectrometry (ICP-MS) for online determination of mercuric ions (Hg2+) was developed. Interestingly, the TiO2 nanoparticle (nano-TiO2) coating on the channel surface acted not only as a sorbent for preconcentration but also as a catalyst for photocatalyst-assisted VG. Under optimum operation conditions, the developed method was validated by analyzing the certified reference material (CRM) Seronorm™ Trace Elements Urine L-2 (freeze-dried human urine). Based on the obtained results, the dramatic reduction of "hands-on" manipulation and the elimination of hazardous materials (e.g., sodium borohydride (NaBH4) and stannous chloride (SnCl2)) from the process enabled a simple and ultraclean procedure with an extremely low detection limit of 0.75 ng L-1 for Hg2+ in urine samples. To the best of our knowledge, this is the first study to report the direct exploitation of a nano-TiO2-coated microfluidic device for online sample preconcentration and on-site VG prior to ICP-MS measurement.

Characterization and composition of heavy metals and persistent organic pollutants in water and estuarine sediments from Gao-ping River, Taiwan.

The objective of this study was to determine the concentrations and possible sources of heavy metals and persistent organic pollutants (POPs) in water and estuarine sediments from Gao-ping River in order to evaluate the environmental quality of aquatic system in southern Taiwan. High concentrations of heavy metals including Cr, Zn, Ni, Cu and As, ranging from 10.7 to 180 mg/kg-dry weight (dw), were detected in sediments from Gao-ping River. When normalized to the principal component analysis (PCA), swinery and electroplating wastewaters were found to be the most important pollution sources for heavy metals. Of various organochlorine pesticide (OCP) residues detected, aldrin and total-hexachlorocyclohexane (HCH) were frequently found in sediments. The total concentrations of OCPs were in the range 0.47-47.4 ng/g-dw. Also, the total-HCH, total-cyclodiene, and total-dichlorodiphenyltrichloroethane (DDT) were in the range 0.37-36.3, 0.21-19.0, and 0.44-1.88 ng/g-dw, respectively. The polychlorinated biphenyl (PCB) concentrations in sediments from Gao-ping River ranged between 0.37 and 5.89 ng/g-dw. The PCB concentrations are positively correlated to the organic contents of the sediment particles. alpha-HCH was found to be the dominant compound of HCH in the sediments, showing that long-range transport may be the possible source for the contamination of HCH in sediments from Gao-ping River. In summary, trace amounts of POPs in estuarine sediments from Gao-ping River were detected, showing that there still exist a wide variety of POP residues in the river sediments in Taiwan. These POP residues may be mainly from long-range transport and weathered agricultural soils, while heavy metal contamination is primarily from the swinery and industrial wastewaters.

Using on-line solid phase extraction for in vivo speciation of diffusible ferrous and ferric iron in living rat brain extracellular fluid.

Exploration of brain extracellular non-protein-bound/diffusible iron species remains a critically important issue in investigations of free radical biology and neurodegenerative diseases. In this study, a facile sample pretreatment scheme, involving poly(vinyl chloride)-metal ion interactions as a selective extraction procedure, was optimized in conjunction with microdialysis (MD) sampling and inductively coupled plasma mass spectrometry (ICP-MS) in cool-plasma mode for in vivo online monitoring of rat brain extracellular Fe(II) and Fe(III) species. Optimization of the system provided detection limits in the range 0.9-6.9 µg Fe L-1, based on a 12-µL microdialysate, for the tested iron species; relative standard deviations of the signal intensities during 7.8 h of continuous measurement were less than 9.4%-sufficient to determine the basal concentrations of rat brain extracellular Fe(II) and Fe(III) species and to describe their dynamic actions. The method's applicability was verified through (i) spike analyses of offline-collected rat brain microdialysates, (ii) determination of the basal Fe(II) and Fe(III) concentrations of living rat brain extracellular fluids, and (iii) monitoring of the dynamic changes in the Fe(II) and Fe(III) concentrations in response to perfusion of a high-K+ medium. This proposed sample pretreatment scheme, based on polymer-metal ion interactions and hyphenation to an MD sampling device and an ICP-MS system, appears to have great practicality for the online monitoring of rat brain extracellular diffusible iron species.

Albumin-Gold Nanorod Nanoplatform for Cell-Mediated Tumoritropic Delivery with Homogenous ChemoDrug Distribution and Enhanced Retention Ability.

Recently, living cells with tumor-homing properties have provided an exciting opportunity to achieve optimal delivery of nanotherapeutic agents. However, premature payload leakage may impair the host cells, often leading to inadequate in vivo investigations or therapeutic efficacy. Therefore, a nanoplatform that provides a high drug-loading capacity and the precise control of drug release is required. In the present study, a robust one-step synthesis of a doxorubicin (DOX)-loaded gold nanorod/albumin core-shell nanoplatform (NR@DOX:SA) was designed for effective macrophage-mediated delivery to demonstrate how nanoparticle-loaded macrophages improve photothermal/chemodrug distribution and retention ability to achieve enhanced antitumor effects. The serum albumin shell of these nanoagents served as a drug reservoir to delay the intracellular DOX release and drug-related toxicity that impairs the host cell carriers. Near-infrared laser irradiation enabled on-demand payload release to destroy neighboring tumor cells. A series of in vivo quantitative analyses demonstrated that the nanoengineered macrophages delivered the nanodrugs through tumor-tropic migration to tumor tissues, resulting in the twice homogenous and efficient photothermal activations of drug release to treat prostate cancer. By contrast, localized pristine NR@DOX:SAs exhibit limited photothermal drug delivery that further reduces their retention ability and therapeutic efficacy after second combinational treatment, leading to a failure of cancer therapy. Moreover, the resultant unhealable wounds impair quality of life. Free DOX has rapid clearance and therefore exhibits limited antitumor effects. Our findings suggest that in comparison with pristine nanoparticles or free DOX, the nanoengineered macrophages effectively demonstrate the importance and effect of homogeneous drug distribution and retention ability in cancer therapy.

Sequential enzymatic derivatization coupled with online microdialysis sampling for simultaneous profiling of mouse tumor extracellular hydrogen peroxide, lactate, and glucose.

Probing tumor extracellular metabolites is a vitally important issue in current cancer biology. In this study an analytical system was constructed for the in vivo monitoring of mouse tumor extracellular hydrogen peroxide (H2O2), lactate, and glucose by means of microdialysis (MD) sampling and fluorescence determination in conjunction with a smart sequential enzymatic derivatization scheme-involving a loading sequence of fluorogenic reagent/horseradish peroxidase, microdialysate, lactate oxidase, pyruvate, and glucose oxidase-for step-by-step determination of sampled H2O2, lactate, and glucose in mouse tumor microdialysate. After optimization of the overall experimental parameters, the system's detection limit reached as low as 0.002 mM for H2O2, 0.058 mM for lactate, and 0.055 mM for glucose, based on 3 µL of microdialysate, suggesting great potential for determining tumor extracellular concentrations of lactate and glucose. Spike analyses of offline-collected mouse tumor microdialysate and monitoring of the basal concentrations of mouse tumor extracellular H2O2, lactate, and glucose, as well as those after imparting metabolic disturbance through intra-tumor administration of a glucose solution through a prior-implanted cannula, were conducted to demonstrate the system's applicability. Our results evidently indicate that hyphenation of an MD sampling device with an optimized sequential enzymatic derivatization scheme and a fluorescence spectrometer can be used successfully for multi-analyte monitoring of tumor extracellular metabolites in living animals.

Three-dimensional printed knotted reactors enabling highly sensitive differentiation of silver nanoparticles and ions in aqueous environmental samples.

Whether silver nanoparticles (AgNPs) persist or release silver ions (Ag(+)) when discharged into a natural environment has remained an unresolved issue. In this study, we employed a low-cost stereolithographic three-dimensional printing (3DP) technology to fabricate the angle-defined knotted reactors (KRs) to construct a simple differentiation scheme for quantitative assessment of Ag(+) ions and AgNPs in municipal wastewater samples. We chose xanthan/phosphate-buffered saline as a dispersion medium for in situ stabilization of the two silver species, while also facilitating their extraction from complicated wastewater matrices. After method optimization, we measured extraction efficiencies of 54.5 and 32.3% for retaining Ag(+) ions and AgNPs, respectively, in the printed KR (768-turn), with detection limits (DLs) of 0.86 and 0.52 ng L(-1) when determining Ag(+) ions and AgNPs, respectively (sample run at pH 11 without a rinse solution), and 0.86 ng L(-1) when determining Ag(+) ions alone (sample run at pH 12 with a 1.5-mL rinse solution). The proposed scheme is tolerant of the wastewater matrix and provides more reliable differentiation between Ag(+)/AgNPs than does a conventional filtration method. The concept and applicability of adopting 3DP technology to renew traditional KR devices were evidently proven by means of these significantly improved analytical performance. Our analytical data suggested that the concentrations of Ag(+) ions and AgNPs in the tested industrial wastewater sample were both higher than those in domestic wastewater, implying that industrial activity might be a main source of environmental silver species, rather than domestic discharge from AgNP-containing products.