4D-Printed Elution-Peak-Guided Dual-Responsive Monolithic Packing for the Solid-Phase Extraction of Metal Ions.

Four-dimensional printing (4DP) technologies are revolutionizing the fabrication of stimuli-responsive devices. To advance the analytical performance of conventional solid-phase extraction (SPE) devices using 4DP technology, in this study, we employed N-isopropylacrylamide (NIPAM)-incorporated photocurable resins and digital light processing three-dimensional printing to fabricate an SPE column with a [H+]/temperature dual-responsive monolithic packing stacked as interlacing cuboids to extract Mn, Co, Ni, Cu, Zn, Cd, and Pb ions. When these metal ions were eluted using 0.5% HNO3 solution as the eluent at a temperature below the lower critical solution temperature of polyNIPAM, the monolithic packing swelled owing to its hydrophilic/hydrophobic transition and electrostatic repulsion among the protonated units of polyNIPAM. These effects resulted in smaller interstitial volumes among these interlacing cuboids and improvements in the elution peak profiles of the metal ions, which, in turn, demonstrated the reduced method detection limits (MDLs; range, 0.2-7.2 ng L-1) during analysis using inductively coupled plasma mass spectrometry. We studied the effects of optimizing the elution peak profiles of the metal ions on the analytical performance of this method and validated its reliability and applicability by analyzing the metal ions in reference materials (CASS-4, SLRS-5, 1643f, and Seronorm Trace Elements Urine L-2) and performing spike analyses of seawater, groundwater, river water, and human urine samples. Our results suggest that this 4D-printed elution-peak-guided dual-responsive monolithic packing enables lower MDLs when packed in an SPE column to facilitate the analyses of the metal ions in complex real samples.

TiO2 nanoparticle-Coated 3D-Printed porous monoliths enabling highly sensitive speciation of inorganic Cr, As, and Se.

Post-printing functionalization can enhance the functionality and applicability of analytical devices manufactured using three-dimensional printing (3DP) technologies. In this study we developed a post-printing foaming-assisted coating scheme-through respective treatments with a formic acid (30%, v/v) solution and a sodium bicarbonate (0.5%, w/v) solution incorporating titanium dioxide nanoparticles (TiO2 NPs; 1.0%, w/v)-for in situ fabrication of TiO2 NP-coated porous polyamide monoliths in 3D-printed solid phase extraction columns, thereby enhancing the extraction efficiencies of Cr(III), Cr(VI), As(III), As(V), Se(IV), and Se(VI) for speciation of inorganic Cr, As, and Se species in high-salt-content samples when using inductively coupled plasma mass spectrometry. After optimizing the experimental conditions, the 3D-printed solid phase extraction columns with the TiO2 NP-coated porous monoliths extracted these species with 5.0- to 21.9-fold enhancements, relative to those obtained with the uncoated monolith, with absolute extraction efficiencies ranging from 84.5 to 98.3% and method detection limits ranging from 0.7 to 32.3 ng L-1. We validated the reliability of this multi-elemental speciation method through determination of these species in four reference materials [CASS-4 (nearshore seawater), SLRS-5 (river water), 1643f (fresh water), and Seronorm Trace Elements Urine L-2 (human urine); relative errors between certified and measured concentrations: 5.6 to +4.0%] and spike analyses of seawater, river water, agriculture waste, and human urine samples (spike recoveries: 96-104%; relative standard deviations of these measured concentrations all below 4.3%). Our results demonstrate that post-printing functionalization has great potential for future applicability in 3DP-enabling analytical methods.

4D-printed needle panel meters coupled with enzymatic derivatization for reading urea and glucose concentrations in biological samples.

On-site analytical techniques continue being developed with advances in modern technology. To demonstrate the applicability of four-dimensional printing (4DP) technologies in the direct fabrication of stimuli-responsive analytical devices for on-site determination of urea and glucose, we used digital light processing three-dimensional printing (3DP) and 2-carboxyethyl acrylate (CEA)-incorporated photocurable resins to fabricate all-in-one needle panel meters. When adding a sample having a value of pH above the pKa of CEA (ca. 4.6-5.0) into the fabricated needle panel meter, the [H+]-responsive layer of the needle, printed using the CEA-incorporated photocurable resins, swelled as a result of electrostatic repulsion among the dissociated carboxyl groups of the copolymer, leading to [H+]-dependent bending of the needle. When coupled with a derivatization reaction (urease-mediated hydrolysis of urea to decrease [H+]; glucose oxidase-mediated oxidization of glucose to increase [H+]), the bending of the needle allowed reliable quantification of urea or glucose when referencing pre-calibrated concentration scales. After method optimization, the method's detection limits for urea and glucose were 4.9 and 7.0 µM, respectively, within a working concentration range from 0.1 to 10 mM. We verified the reliability of this analytical method by determining the concentrations of urea and glucose in samples of human urine, fetal bovine serum, and rat plasma with spike analyses and comparing the results with those obtained using commercial assay kits. Our results confirm that 4DP technologies can allow the direct fabrication of stimuli-responsive devices for quantitative chemical analysis, and that they can advance the development and applicability of 3DP-enabling analytical methods.

Tuning the fabrication of knotted reactors via 3D printing techniques and materials.

Although three-dimensional (3D) printing technologies can customize a diverse range of devices, cross-3D printing technique/material comparisons aimed at optimizing the fabrication of analytical devices have been rare. In this study, we evaluated the surface features of the channels in knotted reactors (KRs) fabricated using fused deposition modeling (FDM) 3D printing [with poly(lactic acid) (PLA), polyamide, and acrylonitrile butadiene styrene filaments], and digital light processing and stereolithography 3D printing with photocurable resins. Also, their ability to retain Mn, Co, Ni, Cu, Zn, Cd, and Pb ions was evaluated to achieve the maximal sensitivities of these metal ions. After optimizing the techniques and materials for 3D printing of the KRs, the retention conditions, and the automatic analytical system, we observed good correlations (R > 0.9793) for the three 3D printing techniques in terms of the surface roughnesses of their channel sidewalls with respect to the signal intensities of their retained metal ions. The FDM 3D-printed PLA KR provided the best analytical performance, with the retention efficiencies of the tested metal ions all being greater than 73.9% and with the detection limits of the method ranging from 0.1 to 5.6 ng L-1. We used this analytical method to perform analyses of the tested metal ions in several reference materials (CASS-4, SLEW-3, 1643f, and 2670a). Spike analyses of complicated real samples verified the reliability and applicability of this analytical method, highlighting the possibility of tuning 3D printing techniques and materials to optimize the fabrication of mission-oriented analytical devices.

Post-administration labeling with Palladium(II) ions enables ICP-MS-based determination of the biodistribution of carbonized nanogels.

Carbonized nanogels (CNGs) are carbon-based nanomaterials possessing excellent antibacterial and antiviral activities for treating infectious diseases. Thus, investigations of the biodistribution of CNGs are crucial in ensuring their biosafety for in vivo applications. In this study, we combined a labeling scheme, employing tetrachloropalladate (PdCl42-) ions to selectively label the administered CNGs in solubilized tissue samples, and an automatic sample pretreatment scheme, using a knotted reactor to effectively separate the PdCl42--labeled CNGs from the free PdCl42- ions and the tissue matrices, to enable reliable and interference-free quantification of CNGs through measuring the signal intensities of Pd using inductively coupled plasma mass spectrometry (ICP-MS). After optimizing the labeling conditions and the separation scheme, we observed that the PdCl42- ions bound strongly to the CNGs (dissociation constant: 23.0 nM), with the method's detection limits reaching 1.6 fg L-1 and 0.9 µg L-1 within working ranges from 10-4 to 1 µg L-1 and from 1 to 1000 µg L-1, respectively. We verified the reliability and applicability of this analytical method through spike analyses of solubilized rat liver, spleen, kidney, lung, brain, and blood samples (recoveries ranging from 96 to 102%) and through analyses of these rat organ and tissue samples after giving rats an intravenous dose of CNGs (2.5 mg kg-1 body weight). The biodistribution data indicated that these administered CNGs deposited mainly in the liver, lung, and spleen at 10 min and 1 h post-administration. Our study revealed that this post-administration labeling scheme coupled with ICP-MS allows accurate determination of the biodistribution of carbonized nanomaterials.

4D-printed pH sensing claw.

As an example of extending the functionality of analytical devices manufactured using four-dimensional printing (4DP), in this study we employed acrylonitrile butadiene styrene (ABS) thermoplastic filaments, poly(4-vinylpyridine) (P4VP)-incorporated ABS filaments, and multi-material fused deposition modeling three-dimensional printing (3DP) to fabricate a pH measurement device that underwent pH-dependent geometric changes. Upon immersion in a solution having a pH close to the value of pKa of P4VP (ca. 5.0), electrostatic repulsion among the protonated units of P4VP resulted in swelling only of the part printed using the P4VP-incorporated ABS filaments, leading to lifting of the whole device along the z-axis (ΔH) in a pH-dependent manner. After optimizing the device's design and fabrication, this 4D-printed pH sensing claw exhibited linearity between the value of ΔH and values of pH in the range from 5.0 to 8.6. We used this 4D-printed pH sensing claw to perform pH analyses of complicated real samples, verifying its analytical reliability for non-electrochemical and non-optical pH measurement and highlighting the capability of 4DP technologies in the direct fabrication of stimuli-responsive sensing devices. We envision that 4DP technologies will prompt the manufacture of smart sensing devices through the printing of stimuli-responsive materials, thereby diversifying the development of 3DP-enabling analytical chemistry.

Solution Foaming-Treated 3D-Printed monolithic packing for enhanced solid phase extraction of trace metals.

Post-printing treatment is a promising means of enhancing the performance of devices manufactured using conventional three-dimensional printing (3DP) technologies. In this study we developed a post-printing solution foaming process-involving respective treatment with formic acid (60%, v/v) and sodium bicarbonate (5%, w/v) solutions to generate CO2 as a foaming agent-to increase the surface roughness and porosity of the polyamide 6 (PA6) monolithic packing in a multimaterial fused deposition modeling 3D-printed solid phase extraction (SPE) column, thereby enhancing the extraction of Mn, Co, Ni, Cu, Zn, Cd, and Pb ions from complicated real samples prior to their determination using inductively coupled plasma mass spectrometry. After optimizing the column fabrication process, the solution foaming treatment process, the extraction conditions, and the automatic analytical system, the 3D-printed SPE column incorporating the solution foaming-treated PA6 monolithic packing extracted these metal ions with 18.9- to 42.0-fold enhancements, relative to those of the as-printed column, with absolute extraction efficiencies all greater than 94.3% and method detection limits ranging from 0.2 to 7.7 ng L-1. We verified the reliability and applicability of this method through analyses of the tested metal ions in several reference materials (CASS-4, SLEW-3, 1643f, and 2670a) and spike analyses of seawater, river water, ground water, and urine samples. We conclude that post-printing treatment can dramatically improve the performance of 3D-printed analytical devices.

Identified Seaweed Compound Diphenylmethane Serves as an Efflux Pump Inhibitor in Drug-Resistant Escherichia coli.

Drug efflux pumps are one of the major elements used by antibiotic-resistant bacteria. Efflux pump inhibitors (EPIs) are potential therapeutic agents for adjunctive therapy, which can restore the activity of antibiotics that are no longer effective against pathogens. This study evaluated the seaweed compound diphenylmethane (DPM) for its EPI activity. The IC50 and modulation results showed that DPM has no antibacterial activity but can potentiate the activity of antibiotics against drug-resistant E. coli. Time-kill studies reported that a combination of DPM and erythromycin exhibited greater inhibitory activity against drug-resistant Escherichia coli. Dye accumulation and dye efflux studies using Hoechst 33342 and ethidium bromide showed that the addition of DPM significantly increased dye accumulation and reduced dye efflux in drug-resistant E. coli, suggesting its interference with dye translocation by an efflux pump. Using MALDI-TOF, it was observed that the addition of DPM could continuously reduce antibiotic efflux in drug-resistant E. coli. Additionally, DPM did not seem to damage the E. coli membranes, and the cell toxicity test showed that it features mild human-cell toxicity. In conclusion, these findings showed that DPM could serve as a potential EPI for drug-resistant E. coli.

4D-Printed Temperature-Controlled Flow-Actuated Solid-Phase Extraction Devices.

Four-dimensional printing (4DP) technologies can extend the functionality and applicability of manufactured analytical devices through employing stimuli-responsive materials. In this study, we used a photocurable resin of stimuli-responsive shape-memory polymers and digital light processing three-dimensional printing (3DP) to fabricate a smart sample pretreatment device featuring a solid-phase extraction (SPE) column and a temperature-controlled flow-actuated valve. Through manipulation of the temperatures and flow rates of the sample, eluent, and rinsing streams, we used this 4D-printed SPE device to extract Mn, Co, Ni, Cu, Zn, Cd, and Pb ions from high-salt content samples and remove the sample matrix prior to their determination by inductively coupled plasma mass spectrometry. After optimizing the valve design and operation and the analytical scheme, this device displayed competitive analytical performance-the method detection limits (MDLs) ranged from 0.7 to 22.1 ng L-1 for these metal ions (the MDLs ranged from 0.5 to 18.8 ng L-1 when validating the same printed SPE column using an online automatic system equipped with electric switching valves). Furthermore, we performed analyses of these metal ions in three reference materials (CASS-4, 1643f, and 2670a) and spike analyses of collected samples (seawater, ground water, river water, and human urine) to confirm the reliability and applicability of this analytical method. For the first time, 4DP has been used to fabricate a multi-functional, stimuli-responsive sample pretreatment device displaying analytical performance equal to that of a commercial apparatus. This novel approach builds upon the functionality and diversity of 3DP-enabling devices with the goal of developing more efficient analytical schemes.

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.

Review of 3D-Printed functionalized devices for chemical and biochemical analysis.

Recent developments in three-dimensional printing (3DP) have attracted the attention of analytical scientists interested in fabricating 3D devices having promising geometric functions to achieve desirable analytical performance. To break through the barrier of limited availability of 3DP materials and to extend the chemical reactivity and functionalities of devices manufactured using conventional 3DP, new approaches are being developed for the functionalization of 3D-printed devices for chemical and biochemical analysis. This Review discusses recent advances in the chemical functionalization schemes used in the main 3DP technologies, including (i) post-printing modification and surface immobilization of reactive substances on printed materials, (ii) pre-printing incorporation of reactive substances into raw printing materials, and (iii) combinations of both strategies, and their effects on the selectivity and/or sensitivity of related analytical methods. In addition, the state of the art of 3D-printed functionalized analytical devices for enzymatic derivatization and sensing, electrochemical sensing, and sample pretreatment applications are also reviewed, highlighting the importance of introducing new functional and functionalized materials to facilitate future 3DP-enabled manufacturing of multifunctional analytical devices.

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.

3D-Printed Column with Porous Monolithic Packing for Online Solid-Phase Extraction of Multiple Trace Metals in Environmental Water Samples.

In this study, we used a multimaterial three-dimensional printing (3DP) technology and porous composite filaments (Lay-Fomm, Gel-Lay, and Lay-Felt) to fabricate solid phase extraction (SPE) columns for the enhanced extraction of multiple metal ions. When employed as sample pretreatment devices in an automatic flow injection analysis/inductively coupled plasma mass spectrometry (ICP-MS) system, these 3D-printed SPE columns performed the near-complete extractions of Mn, Co, Ni, Cu, Zn, Cd, and Pb ions from natural water samples prior to ICP-MS determination. After optimizing the column fabrication, the extraction conditions, and the automatic analysis system, the column packed with the porous composite Lay-Fomm 40 was found to provide the highest extraction performance-the extraction efficiencies of the listed metal ions were all greater than 99.2%, and the detection limits of the method ranged from 0.3 to 6.7 ng L-1. The detection of these metal ions in several reference materials (CASS-4, SLEW-3, 1640a, and 1643f) validated the reliability of this method; spike analyses of collected water samples (groundwater, river water, and seawater) demonstrated the applicability of the method. The nature of the printing materials enhanced the analytical performance of 3D-printed sample pretreatment devices. Such approaches will be useful to diversify the range of sample preparation schemes and analytical methods enabled by 3DP technologies.

Injectable DNA-architected nanoraspberry depot-mediated on-demand programmable refilling and release drug delivery.

Drug delivery depots boosting a local concentration of therapeutic agents have received great attention in clinical applications due to their low occurrence of side effects and high therapeutic efficacy. However, once the payload is exhausted, the local drug concentration will be lower than the therapeutic window. To address this issue, an injectable double-strand deoxyribonucleic acid (DNA)-architected nanoraspberry depot (DNR-depot) was developed that can refill doxorubicin (Dox, an anticancer drug) from the blood and remotely control drug release on demand. The large porous surface on a uniform nanoraspberry (NR) filled covalently with DNA serves as a Dox sponge-like refilling reservoir, and the NR serves as a magnetic electrical absorber. Via the strong affinity between Dox and DNA molecules, the refilling process of Dox can be achieved on DNR-depot both in vitro and in vivo. Upon high-frequency magnetic field (HFMF) treatment, the remotely triggered release of Dox is actuated by the dissociation of Dox and DNA molecules, facilitating an approximately 800% improvement in drug concentration at the tumor site compared to free Dox injection alone. Furthermore, the cycles of refilling and release can be carried out more than 3 times in vivo within 21 days. The combination of refilling and HFMF-programmable Dox release in tumors via DNR-depot can effectively inhibit tumor growth for 30 days.

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.

3D-printed CuO nanoparticle-functionalized flow reactor enables online fluorometric monitoring of glucose.

An online flow reactor was fabricated by using a fused deposition modeling three-dimensional printing (3DP) technology along with thermoplastic poly(lactic acid) filaments incorporating copper oxide nanoparticles (CuO NPs). In the presence of glucose, the flow reactor displays multi-catalytic activities because accelerates the oxidation of 2',7'-dichlorodihydrofluorescein to form fluorescein which displays green fluorescence under 480 nm excitation (emission wavelength: 530 nm). The CuO NPs exert two functions to mediate electron transfer at a basic reaction condition, viz. direct oxidation of glucose to generate reactive oxygen species (ROS), and prompting the ROS to oxidize 2',7'-dichlorofluorescin diacetate. The flow reactor coupled to a microdialysis sampler and a fluorometer was applied for online fluorometric monitoring of brain extracellular glucose levels in living rats based on scanning of time-resolved fluorescence intensities. After optimization of (a) the manufacture of the flow reactor, (b) the reaction conditions (pH 10; 50 °C), and (c) the online analytical system, the detection limit of the method (when using 10-µL samples of microdialysate) is as low as 6.1 µM (linear range: 0.05-5 mM) with a sampling frequency of 7.5 h-1. To illustrate the method's applicability, analyses of spiked off-line-collected rat brain microdialysates were conducted. In addition, rat brain extracellular glucose levels were monitored in-vivo and online upon neuronal depolarization triggered by perfusing a high-K+ medium. The results demonstrate that functionalizing raw 3DP materials with appropriate nanomaterials can simplify the manufacturing of analytical devices and related analytical procedures. This will extend the diversity and adaptability of current 3DP-enabling analytical strategies. Graphical abstract Schematic presentation of an online flow reactor fabricated using a fused deposition modeling 3D printer along with poly(lactic acid) (PLA) filaments incorporating CuO NPs. The manufactured flow reactor displays multi-catalytic activities and simplifies online fluorometric monitoring of living rat brain extracellular glucose.

Online profiling of living rat brain extracellular pH using a pH-Dependent solid phase extraction scheme coupled with microdialysis sampling and inductively coupled plasma mass spectrometry.

In this study, a novel analytical method was developed for online profiling of living rat brain extracellular pH. It involved microdialysis (MD) sampling, introduction of metal ions (e.g., Mn, Co, Ni, Cd) as acid/base indicators, and a pH-dependent solid phase extraction (SPE) based on polymer-metal ion interactions as a sample pretreatment scheme prior to analysis through inductively coupled plasma mass spectrometry (ICP-MS). With a 10-µL microdialysate, optimization of the system provided a working pH range from 5.8 to 8.2 and allowed differentiation of tiny changes in pH, down to a resolution of 0.015 pH units. Standard deviations of measured pH for 6 h of continuous measurement were below 0.05, which was sufficient for evaluating the homeostatic status and the dynamic fluctuations in living rat brain extracellular pH. The method's applicability was verified through measurement of the basal extracellular pH in living rat brains and through monitoring of its changes in response to perfusion of a high-K+ medium. By applying metal ions as acid/base indicators and coupling a pH-dependent SPE scheme with MD sampling and ICP-MS, this method presents an alternative strategy for reliable online profiling of the living rat brain extracellular pH.

One-step three-dimensional printing of enzyme/substrate-incorporated devices for glucose testing.

To substantially simplify the fabrication of analytical devices for rapid screening tests, in this study we employed multi-material fused deposition modeling-type three-dimensional printing (3DP) and two functionalized thermoplastic filaments-acrylonitrile butadiene styrene (ABS) incorporating peroxidase-mimicking iron oxide (Fe3O4) nanoparticles and polyvinyl alcohol (PVA) infiltrated with the chromogenic substrate o-phenylenediamine (OPD)-for the one-step manufacture of enzyme/substrate-incorporated multi-well plates. Upon contact with samples, these fabricated devices (i) released the chromogenic substrate OPD into the solution, (ii) efficiently catalyzed the oxidation of OPD mediated by the peroxidase substrate H2O2, (iii) enabled assays of those substances availably oxidized by their specific oxidases to generate H2O2, and (iv) facilitated colorimetric observation by the naked eye or through absorbance measurements after loading into a microplate reader. With glucose oxidase immobilized in each well, samples appropriately diluted could be directly loaded for derivatizing and analyzing glucose without adding any other reagents. After assay optimization, the limits of detection reached as low as 2.8 µM for H2O2 and 5.0 µM for glucose; the method's applicability was illustrated in terms of determining glucose concentrations in urine, serum, and plasma samples. These 3D-printed peroxidase mimic/chromogenic substrate-incorporated multi-well plates appear to be highly suitable for rapid and high-throughput screening of glucose in clinical samples. We demonstrate that adequate functionalization of raw materials for 3DP can contribute to the development of novel multifunctional devices with many potential practical applications.

A Highly Stable Framework of Crystalline Zinc Phosphite with Selective Removal, Recovery, and Turn-On Sensing Abilities for Mercury Cations in Aqueous Solutions.

A highly stable framework of organic-inorganic hybrid zinc phosphite (NTOU-4) and its cobalt analogue (NTOU-4a) were synthesized under the hydro(solvo)thermal conditions and structurally characterized by single-crystal X-ray diffraction. Their frameworks consisted of inorganic metallophosphite chains, in which the metal atoms were interlinked through 1H-1,2,4-triazole-3,5-diamine and 1,4-benzenedicarboxylate linkers to form new crystalline materials. It is extremely difficult to achieve the consolidation of three distinct coordinations of metal-carboxylate, metal-triazolate, and metal-phosphite bonds into one crystal, resulting in the synthesis of the first mixed-ligand terephthalate-metallophosphite solids in the absence of organic molecules as templates or space-filling counters in their structures. Interestingly, the zinc compound not only exhibits high thermal stability (up to 400 °C in air) and chemical resistance to seawater, aqueous solutions (pH 3-11), and organic solvents at boiling conditions, but also shows selective removal, recovery, and "turn-on" sensing abilities of toxic mercury ions in aqueous solutions. Furthermore, the synthesis, characterization, and the difference of the framework stabilities between isostructural zinc and cobalt compounds are also reported.

3D-printed, TiO2 NP-incorporated minicolumn coupled with ICP-MS for speciation of inorganic arsenic and selenium in high-salt-content samples.

To extend the applicability of solid phase extraction devices manufactured using 3D printing technologies, a stereolithographic 3D printer and resins incorporating titanium dioxide nanoparticles (TiO2 NPs) were employed to fabricate a demountable minicolumn with TiO2 NP-incorporated packing as a sample pretreatment device for the selective extraction of inorganic As and Se species from high-salt-content samples, and to facilitate their analyses when coupled to an inductively coupled plasma mass spectrometer. After optimization, the automatic system enabled highly sensitive determinations of As and Se species with detection limits as low as 0.004-0.033 µg L-1 for As and 0.061-0.128 µg L-1 for Se. Reliability was confirmed through analyses of the reference materials 1643f, SLEW-3, CASS-4, and 2670a, as well as spike analyses of samples of water and human urine. These 3D-printed minicolumns appear to be very useful for multi-elemental speciation of these elements from high-salt-content samples. Thus, the incorporation of active nanomaterials into raw printing resins can enable 3D printing technologies-not only to fabricate functionalized devices for diverse sample pretreatment applications but also to encourage the future development of multifunctional devices for analytical science. Graphical abstract Schematic presentation of a demountable minicolumn fabricated using a stereolithographic 3D printer and the resins incorporating with TiO2 NPs. They were used to selectively extract As and Se species through controlling the sample acidities.