Facile synthesis of Gd/Ru-doped fluorescent carbon dots for fluorescent/MR bimodal imaging and tumor therapy.

Functional metal doping endows fluorescent carbon dots with richer physical and chemical properties, greatly expanding their potential in the biomedical field. Nonetheless, fabricating carbon dots with integrated functionality for diagnostic and therapeutic modalities remains challenging. Herein, we develop a simple strategy to prepare Gd/Ru bimetallic doped fluorescent carbon dots (Gd/Ru-CDs) via a one-step microwave-assisted method with Ru(dcbpy)3Cl2, citric acid, polyethyleneimine, and GdCl3 as precursors. Multiple techniques were employed to characterize the morphology and properties of the obtained carbon dots. The Gd/Ru-CDs are high mono-dispersity, uniform spherical nanoparticles with an average diameter of 4.2 nm. Moreover, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) confirmed the composition and surface properties of the carbon dots. In particular, the successful doping of Gd/Ru enables the carbon dots not only show considerable magnetic resonance imaging (MRI) performance but also obtain better fluorescence (FL) properties, especially in the red emission area. More impressively, it has low cytotoxicity, excellent biocompatibility, and efficient reactive oxygen species (ROS) generation ability, making it an effective imaging-guided tumor treatment reagent. In vivo experiments have revealed that Gd/Ru-CDs can achieve light-induced tumor suppression and non-invasive fluorescence/magnetic resonance bimodal imaging reagents to monitor the treatment process of mouse tumor models. Thus, this simple and efficient carbon dot manufacturing strategy by doping functional metals has expanded avenues for the development and application of multifunctional all-in-one theranostics.

MRI-guided cell membrane-camouflaged bimetallic coordination nanoplatform for combined tumor phototherapy.

Nanotechnology for tumor diagnosis and optical therapy has attracted widespread interest due to its low toxicity and convenience but is severely limited due to uncontrollable tumor targeting. In this work, homologous cancer cell membrane-camouflaged multifunctional hybrid metal coordination nanoparticles (DRu/Gd@CM) were prepared for MRI-guided photodynamic therapy (PDT) and photothermal therapy (PTT) of tumors. Bimetallic coordination nanoparticles are composed of three functional modules: dopamine, Ru(dcbpy)3Cl2 and GdCl3, which are connected through 1,4-Bis[(1H-imidazole-1-yl)methyl]benzene (BIX). Their morphology can be easily controlled by adjusting the ratio of precursors. Optimistically, the intrinsic properties of the precursors, including the photothermal properties of polydopamine (PDA), the magnetic resonance (MR) response of Gd3+, and the singlet oxygen generation of Ru(dcbpy)3Cl2, are well preserved in the hybrid metal nanoparticles. Furthermore, the targeting of homologous cancer cell membranes enables these coordinated nanoparticles to precisely target tumor cells. The MR imaging capabilities and the combination of PDT and PTT were demonstrated in in vitro experiments. In addition, in vivo experiments indicated that the nanoplatform showed excellent tumor accumulation and therapeutic effects on mice with subcutaneous tumors, and could effectively eliminate tumors within 14 days. Therefore, it expanded the new horizon for the preparation of modular nanoplatform and imaging-guided optical therapy of tumors.

Exponential Amplification-Induced Activation of CRISPR/Cas9 for Sensitive Detection of Exosomal miRNA.

As an important component of highly heterogeneous exosomes, exosomal microRNAs (miRNAs) have great potential as noninvasive biomarkers for cancer diagnosis. Therefore, a sensitive and simple sensor is the key for its clinical application. Herein, we designed an exponential amplification reaction (EXPAR) to induce the reactivation of the CRISPR-associated protein 9/small guide RNA (Cas9/sgRNA) complex, thus achieving sensitive and visual exosomal miRNAs-21 (miR-21) fluorescence sensing. In this design, we inactivated the sgRNA by hybridizing sgRNA and blocker DNA. Then, we used a trigger DNA to hybridize with miR-21 and produced a lot of activated DNA by EXPAR. Those activated DNA further hybridized with blocker DNA and released the free sgRNA to form the activated Cas9/sgRNA complex. Based on the quick cleavage of activated Cas9/sgRNA complex, the reporter DNA labeled by SYBR Green I was released from the surface of the magnetic nanoparticles (MNPs) into the supernatant, and thus was used to sensitively quantify the miRNAs concentration with a limit of detection of 3 × 103 particles/mL. In addition, this fluorescence sensor has also been successfully employed to distinguish healthy people and cancer patients by naked-eye observation of the fluorescence, thus demonstrating its great potential for accurate and point-of-care cancer diagnosis.

Biochemotaxis-Oriented Engineering Bacteria Expressing GLP-1 Enhance Diabetes Therapy by Regulating the Balance of Immune.

Glucagon like peptide-1 (GLP-1) is an effective hypoglycemic drug that can repair the pancreas ß cells and promote insulin secretion. However, GLP-1 has poor stability and lacks of target ability, which makes it difficult to reach the site of action to exert its efficacy. Here, GLP-1-expressing plasmids are introduced into the Escherichia coli Nissle 1917 (EcN) and a lipid membrane is formed through simple self-assembly on its surface, resulting in an oral delivery system (LEG) capable of resisting the harsh environment of the gastrointestinal tract. The system utilizes the chemotactic properties of probiotics to achieve efficient enrichment at the pancreatic site, and protects islet ß cells from destruction by regulating the balance of immune cells. More interestingly, LEG not only continuously produces GLP-1 to restore pancreatic islet ß cell function and secrete insulin to control blood sugar levels, but also regulates the intestinal flora and increases the richness and diversity of probiotics. In mice diabetes models, oral administration of LEG only once every other day has good biosafety and compliance, and achieves long-term control of blood glucose. Therefore, this strategy not only provides an oral delivery platform for pancreatic targeting, but also opens up new avenues for reversing diabetes.

A facile strategy for the large-scale preparation of starch-based AIE luminescent nanoaggregates via host-guest interactions and their versatile applications.

Luminescent nanomaterials with outstanding optical properties have attracted growing interest due to their widespread applications. However, large-scale fabrication of luminescent nanomaterials with desired properties through a simple and economical process remains challenging. As a renewable natural resource, starch is non-toxic, easily accessible, and inexpensive, making it a popular choice for uses in various biomedical fields. In this work, we present a facile assembly strategy for the fabrication of starch-based luminescent nanoaggregates using starch as the host material and aggregation-induced emission luminogens (AIEgens) as guest molecules. By employing simple procedures under mild conditions, highly luminescent nanoparticles with small sizes, high water dispersibility, and low cytotoxicity are prepared on a large scale. The resulting nano-assemblies demonstrate significantly enhanced fluorescence intensities, reduced susceptibility to photobleaching and low cytotoxicity. These fluorescent supramolecular aggregates can be employed in various application fields, including the fabrication of fluorescent hydrogels, fingerprint detection, cell imaging and in vivo lymphatic system imaging. The methodology developed in this work has immense potential to greatly promote the production of high-quality nanoparticles on the industrial scale, offering a cost-effective solution that can meet the needs of various applications and pave the way for wider implementation of nanotechnology.

Visualizing hypoxic modulation of beta cell secretions via a sensor augmented oxygen gradient.

One distinct advantage of microfluidic-based cell assays is their scalability for multiple concentrations or gradients. Microfluidic scaling can be extremely powerful when combining multiple parameters and modalities. Moreover, in situ stimulation and detection eliminates variability between individual bioassays. However, conventional microfluidics must combat diffusion, which limits the spatial distance and time for molecules traveling through microchannels. Here, we leveraged a multilayered microfluidic approach to integrate a novel oxygen gradient (0-20%) with an enhanced hydrogel sensor to study pancreatic beta cells. This enabled our microfluidics to achieve spatiotemporal detection that is difficult to achieve with traditional microfluidics. Using this device, we demonstrated the in situ detection of calcium, insulin, and ATP (adenosine triphosphate) in response to glucose and oxygen stimulation. Specifically, insulin was quantified at levels as low as 25 pg/mL using our imaging technique. Furthermore, by analyzing the spatial detection data dynamically over time, we uncovered a new relationship between oxygen and beta cell oscillations. We observed an optimum oxygen level between 10 and 12%, which is neither hypoxic nor normoxic in the conventional cell culture sense. These results provide evidence to support the current islet oscillator model. In future applications, this spatial microfluidic technique can be adapted for discrete protein detection in a robust platform to study numerous oxygen-dependent tissue dysfunctions.

Homologous cancer cell membrane-camouflaged nanoparticles target drug delivery and enhance the chemotherapy efficacy of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a common digestive tract malignancy that seriously threatens human life and health. Early HCC may be treated by intervention, surgery, and internal radiotherapy, while the choice for late HCC is primarily chemotherapy to prolong patient survival. Lenvatinib (LT) is a Food and Drug Administration (FDA)-approved frontline drug for the treatment of advanced liver cancer and has achieved excellent clinical efficacy. However, its poor solubility and severe side effects cannot be ignored. In this study, a bionic nanodrug delivery platform was successfully constructed. The platform consists of a core of Lenvatinib wrapped with a pH-sensitive polymer, namely, poly(ß-amino ester)-polyethylene glycol-amine (PAE-PEG-NH2), and a shell formed by a cancer cell membrane (CCM). The prepared nanodrugs have high drug loading capacity, long-term stability, good biocompatibility, and a long retention time. In addition, the targeting effect of tumor cell membranes and the pH-responsive characteristics of the polymer materials enable them to precisely target tumor cells and achieve responsive release in the tumor microenvironment, which makes them suitable for effective drug delivery. In vivo experiments revealed that the nanodrug showed superior tumor accumulation and therapeutic effects in subcutaneous tumor mice model and could effectively eliminate tumors within 21 days. As a result, it opens up a new way to reduce side effects and improve the specific therapeutic effect of first-line clinical medications to treat tumors.

MRI-guided dual-responsive anti-tumor nanostructures for synergistic chemo-photothermal therapy and chemodynamic therapy.

Image-guided stimulus-responsive theranostics are beneficial for identifying malignant lesions and integrating multiple cell-killing mechanisms to enhance tumor cell clearance. Herein, an intelligent dual-responsive nanostructure (HSPMH-DOX) was developed for magnetic resonance imaging (MRI)-guided synergistic chemo-photothermal therapy (PTT) and chemodynamic therapy (CDT). The core-shell nanostructure was synthesized by layering polydopamine (PDA), manganese oxide (MnO2), and hyaluronic acid (HA) onto drug-loaded hollow mesoporous silica nanoparticles (HS). The constructed nanoagent has both endogenous and external dual responses. The tumor microenvironment (pH/GSH) can trigger the degradation of gatekeeper (MnO2 and PDA), resulting in the release of anti-tumor drugs, whereas external near-infrared light irradiation can accelerate the degradation process and generate local overheating, resulting in PTT. Notably, MnO2 can not only consume intracellular GSH to enhance CDT but also release Mn2+ for precise localization of tumor tissues using MRI. Both in vitro and in vivo experiments showed that the prepared dual-response nanoagent satisfied biocompatibility, targeting, and the great efficiency of MRI-guided combined therapy. In animal models, combining chemo-PTT and CDT can eradicate tumors in less than two weeks. This work could pave the way for a wide range of stimulus-responsive synergistic theranostic applications, including MRI, chemo-photothermal therapy, and chemodynmic therapy. STATEMENT OF SIGNIFICANCE: Low bioavailability and severe side effects remain the major limitations of conventional cancer chemotherapy. Image-guided combination therapy can alleviate these problems and improve tumor-specific therapy. In the present study, the anticancer drug doxorubicin was encapsulated in a core-shell hollow mesoporous silica nanostructure (HSPMH-DOX), enabling MRI-guided targeted release under both endogenous and external dual stimuli. Moreover, the photothermal and nanoenzymatic effects of nanomedicine can cause local overheating in the tumor and amplify the intracellular CDT effect, accelerating tumor eradication. Systematic evaluations in vitro and in vivo confirmed that nanomedicine enables highly effective MRI-guided synergistic chemo-photothermal and chemodynamic therapy. This work offers a promising therapeutic strategy for precise anti-tumor applications.

CRISPR/Cas9 mediated triple signal amplification platform for high selective and sensitive detection of single base mutations.

Single base mutations detection is crucial for the diagnosis and treatment of cancer. However, the current methods with poor selectivity and sensitivity required large instruments, which are difficult to meet clinical demands. Herein, we develop a CRISPR/Cas9 based visual colorimetric platform to specifically detect all single base mutations. In this strategy, the Recombinase Polymerase Amplification (RPA) was firstly used to amplify the target, and introduced the PAM site in the target DNA sequence by designing the point mutation primer, thus achieving detection for all single base mutations by the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated specific recognition. With the help of CRISPR/Cas9 system, those RPA products can release single strand DNA to hybridize with the padlock probe and trigger rolling circle amplification (RCA). Based on the magnetic separation, HRP-gold nanoparticles complex (hGNPs) and biotin modified probe (Bio-probe) were further used to achieve enhanced visual variations assay by hybridizing with RCA products. Benefiting from the RPA assisted triple signal amplification, this method not only showed enhanced sensitivity with a limit of detection (LOD) as low as 0.2 fM and 0.01% of KRAS-G12D mutation percentage, but the specificity against KRAS-G12D mutation also be synergistically enhanced by combining the CRISPR/Cas9-mediated specific recognition with the specific T4 ligation reaction of RCA system. Furthermore, this system has been successfully used to visually detect genome in serum, suggesting its great potential for point-of-care diagnosis in clinical.

Correction: Rapid and sensitive leukemia-derived exosome quantification via nicking endonuclease-assisted target recycling.

Correction for 'Rapid and sensitive leukemia-derived exosome quantification via nicking endonuclease-assisted target recycling' by Mengyang Zhou et al., Anal. Methods, 2021, 13, 4001-4007, https://doi.org/10.1039/D1AY00854D.

A Cancer Cell Membrane-Derived Biomimetic Nanocarrier for Synergistic Photothermal/Gene Therapy by Efficient Delivery of CRISPR/Cas9 and Gold Nanorods.

Bimodal synergistic therapy produces superadditive effect for enhanced therapeutic efficacy. However, how to efficiently and simultaneously deliver several kinds of therapeutic agents is still challenging. A cancer cell membrane-derived nanocarrier (mCas9-sGNRs) is proposed for synergistic photothermal/gene therapy (PTT/GT) by efficient delivery of clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) and gold nanorods (GNRs). In this approach, Cas9 proteins can be efficiently loaded inside the cell membranes (mCas9) by electrostatic interactions. Similarly, single-guide RNAs, which target survivin, can be loaded onto GNRs (sGNRs) through electrostatic interactions and encapsulated by mCas9. As a result, the nanodelivery systems present advantages in biocompatibility, homologous targeting capacity and loading efficiency of cargoes. In addition, significant antitumor effects is achieved by gene editing of survivin which induces anticancer activity and reduces heat tolerance of cancer cells caused by GNRs mediated PTT due to the downregulation of HSP70. These results indicate the nanotherapeutic platform leads to enhanced PTT/GT efficacy. Therefore, this work not only provides a general strategy to construct a versatile nanoplatform for loading and target delivery of several therapeutic cargos but will also be valuable for PTT/GT and other bimodal synergistic therapy.

Peptide-Grafted Microspheres for Mesenchymal Stem Cell Sorting and Expansion by Selective Adhesion.

Mesenchymal stem cells (MSCs) have considerable value in regenerative medicine because of their unique properties such as pluripotency, self-renewal ability, and low immunogenicity. Isolation and purification are prerequisites for various biomedical applications of MSCs, and traditional sorting methods are often expensive, complicated, and difficult to apply on a large scale. In addition to purification, the requirement for expansion of cells also limits the further application of MSCs. The purpose of this study was to develop a unique magnetic sorting microsphere to obtain relatively pure and high-yield MSCs in an economical and effective way, that can also be used for the expansion of MSCs. Poly (ethylene glycol) (PEG)-based anti-adhesive treatment of the prepared oleic acid grafted Fe3O4-poly (lactic-co-glycolic acid) magnetic microspheres was performed, and then E7 peptide was covalently grafted onto the treated microspheres. Upon a series of characterization, the magnetic microspheres were of uniform size, and cells were unable to adhere to the PEG-treated surface. E7 grafting significantly improved cell adhesion and proliferation. The results obtained from separate culture of various cell types as well as static or dynamic co-culture showed that selective adhesion of MSCs was observed on the magnetic sorting microspheres. Furthermore, the cells expanded on the microspheres maintained their phenotype and typical differentiation potentials. The magnetic properties of the microspheres enabled sampling, distribution, and transfer of cells without the usage of trypsin digestion. And it facilitated the separation of cells and microspheres for harvesting of MSCs after digestion. These findings have promising prospects for MSC research and clinical applications.

Synergistically Promoting Bone Regeneration by Icariin-Incorporated Porous Microcarriers and Decellularized Extracellular Matrix Derived From Bone Marrow Mesenchymal Stem Cells.

Multifunctionality has becoming essential for bone tissue engineering materials, such as drug release. In this study, icariin (ICA)-incorporated poly(glycolide-co-caprolactone) (PGCL) porous microcarriers were fabricated and then coated with decellularized extracellular matrix (dECM) which was derived from bone marrow mesenchymal stem cells (BMSC). The porous structure was generated due to the soluble gelatin within the microcarriers. The initial released ICA in microcarriers regulated osteogenic ECM production by BMSCs during ECM formation. The dECM could further synergistically enhance the migration and osteogenic differentiation of BMSCs together with ICA as indicated by the transwell migration assay, ALP and ARS staining, as well as gene and protein expression. Furthermore, in vivo results also showed that dECM and ICA exhibited excellent synergistic effects in repairing rat calvarial defects. These findings suggest that the porous microcarriers loaded with ICA and dECM coatings have great potential in the field of bone tissue engineering.

Rolling circle amplification assisted dual signal amplification colorimetric biosensor for ultrasensitive detection of leukemia-derived exosomes.

Tumor-derived exosomes as a liquid biopsy marker hold great promising for the accurate tumor diagnosis. However, the visual exosomes detection method with high sensitivity and convenience is still a challenge and highly valuable in the clinical application. Herein, we fabricated a colorimetric biosensor that could visually detect leukemia-derived exosomes, and dual amplified the signal based on the rolling circle amplification (RCA) assisted platform. To avoid the interference of components in serum, trigger-aptamer complex was firstly modified on the magnetic beads (MBs) to recognize exosomes, and then release trigger probe to initiate RCA reaction. Therefore, the trigger probe could produce long repeated sequences and hybridized with numerous signal probe. After that, GNPs-HRP (HRP modified gold nanoparticles) bound with signal probe and induced dramatic color change of TMB to achieve the sensing of exosomes. Benefiting from the RCA assisted dual signal amplification, the presented method showed a limit of detection as low as 100 particles/µL. Moreover, this method exhibited good specificity to distinguish healthy and leukemia patients, suggesting its great potential for clinical diagnosis.

Influence of sample volume on nitrate N and O isotope ratio analyses with the denitrifier method.

RATIONALE: Analyses of the isotope ratios of nitrogen (15 N/14 N) and oxygen (18 O/16 O) in nitrate (NO3 - ) with the denitrifier method require relatively high sample volumes at low concentrations (≤1 µM) to afford sufficient analyte for mass spectrometry, resulting in isotopic offsets compared to more concentrated samples of the same isotopic composition. METHODS: To uncover the origins of isotopic offsets, we analyzed the N and O isotope ratios of NO3 - reference materials spanning concentrations of 0.5-20 µM. We substantiated the incidence of volume-dependent isotopic offsets, then investigated whether they resulted from (a) incomplete sample recovery during N2 O sparging, (b) blanks - bacterial, atmospheric, or in reference material solutions - and (c) oxygen atom exchange with water during the bacterial conversion of NO3 - to N2 O. RESULTS: Larger sample volumes resulted in modest offsets in δ15 N, but substantial offsets in δ18 O. N2 O recovery from sparging was less complete at higher volumes, resulting in decreases in δ15 N and δ18 O due to associated isotope fractionation. Blanks increased detectably with volume, whereas oxygen atom exchange with water remained constant within batch analyses, being sensitive to neither sample volume nor salinity. The sizeable offsets in δ18 O with volume are only partially explained by the factors considered in our analysis. CONCLUSIONS: Our observations argue for bracketing of NO3 - samples with reference materials that emulate sample volumes (concentrations) to achieve improved measurement accuracy and foster inter-comparability.

Resveratrol-Loaded TPGS-Resveratrol-Solid Lipid Nanoparticles for Multidrug-Resistant Therapy of Breast Cancer: In Vivo and In Vitro Study.

Multidrug resistance (MDR) is a serious problem during cancer therapy. The purpose of the present study was to formulate D-α-Tocopheryl polyethylene glycol 1000 succinate-resveratrol-solid lipid nanoparticles (TPGS-Res-SLNs) to improve its therapeutic efficacy against breast cancer. In this study, the solvent injection method was used to prepare the TPGS-Res-SLNs. It was found that the TPGS-Res-SLNs exhibited zeta potential and drug-loading of -25.6 ± 1.3 mV and 32.4 ± 2.6%, respectively. Therefore, it was evident that the TPGS-Res-SLNs can increase cellular uptake of chemotherapeutic drugs, induce mitochondrial dysfunction, and augment tumor treatment efficiency by inducing apoptosis. Moreover, it was found that SKBR3/PR cells treated with TPGS-Res-SLNs exhibited significant inhibition of cell migration and invasion, as compared with free resveratrol. In addition, results from in vivo SKBR3/PR xenograft tumor models revealed that TPGS-Res-SLNs has better efficacy in promoting apoptosis of tumor cells owing to high therapeutic outcomes on tumors when compared with the efficacy of free resveratrol. In conclusion, the findings of the present study indicate significant potential for use of TPGS-Res-SLNs as an efficient drug delivery vehicle to overcome drug resistance in breast cancer therapy.

Rapid and sensitive leukemia-derived exosome quantification via nicking endonuclease-assisted target recycling.

Exosomes as fluid biomarkers hold great promise for noninvasive cancer diagnosis. However, a method for the rapid and convenient detection of exosomes is still a challenge because current analysis processes involve multiple steps and yield low sensitivity. Here, we developed a wash-free fluorescent biosensor for the rapid and sensitive quantification of exosomes by combining aptamer and nicking endonuclease (Nb·BbvCI). In this system, an aptamer-trigger complex was used as the recognition element; the trigger probe could be released, and it hybridized with gold nanoparticles (GNPs)-DNA-FAM conjugates, thereby resulting in Nb·BbvCI-assisted target recycling. As a result, our method allowed the quantification of exosomes with lower analysis time by using a cocktail containing an aptamer-trigger complex, Nb·BbvCI, and GNPs-DNA-FAM. A high sensitivity with a limit of detection (LOD) of 1.0 × 104 particles per µL could be achieved. Besides, this biosensor exhibited potential application for the quantification of exosomes in human plasma, facilitating the development of exosome-based noninvasive cancer diagnosis.

Wearable Strain Sensors Based on a Porous Polydimethylsiloxane Hybrid with Carbon Nanotubes and Graphene.

High-performance flexible strain sensors are urgently needed with the rapid development of wearable intelligent electronics. Here, a bifiller of carbon nanotubes (CNTs) and graphene (GR) for filling flexible porous polydimethylsiloxane (CNT-GR/PDMS) nanocomposites is designed and prepared for strain-sensing applications. The typical microporous structure was successfully constructed using the Soxhlet extraction technique, and the connected CNTs and GR constructed a perfect three-dimensional conductive network in the porous skeleton. As a result, the stretchability and sensitivity of the CNT-GR/PDMS-based strain sensors were well regulated based on the porous structure and the typical synergistic conductive network. Based on the destruction effect of the brittle synergistic conductive network located in the outer and inner layers of the cell skeleton and the contact effect between adjacent cells in different strain ranges, the prepared CNTs-GR/PDMS-based strain sensor exhibited superior gauge factors of 182.5, 45.6, 70.2, and 186.5 in the 0-3, 3-57, 57-90, and 90-120% strain regions, respectively. In addition, this material also exhibited an ultralow detection limit (0.5% strain), a fast response time (60 ms), good stability and durability (10,000 cycles), and frequency-/strain-dependent sensing performances, making it active for the detection of various external environments. Finally, the prepared porous CNTs-GR/PDMS-based strain sensor was attached to the skin to detect various human motions, such as wrist bending, finger bending, elbow bending, and knee bending, thereby demonstrating wide application prospects in smart wearable devices.

Novel 3D Pd-Cu(OH)2/CF cathode for rapid reduction of nitrate-N and simultaneous total nitrogen removal from wastewater.

Removal of NO3- is a challenging problem in wastewater treatment. Electrocatalysis shows a great potential to remove NO3- but selectively converting NO3- to N2 is facing a low efficiency. Here, a novel 3D Pd-Cu(OH)2/CF cathode based electrocatalytic (EC) system was proposed that can rapidly and selectively convert NO3- to NH4+, and further convert to N2 simultaneously. The special designs for the system include: Cu(OH)2 nanowires were firstly grown on copper foam (CF) with excellent conductivity that features high specific surface area in enhancing NO3- absorption and conversion to NO2-. Then, palladium (Pd) with a superior photons activation capacity was doped on the Cu(OH)2 nanowires to promote the reduction of NO2- to NH4+. Then NH4+ was quickly oxidized into N2 by active chlorine. Finally, total nitrogen (TN) could easily be removed completely via above exhaustive cycle reactions. The 3D Pd-Cu(OH)2/CF cathode exhibits a 98.8 % conversion of NO3- to NH4+ in 45 min with the reported highest removal rate of 0.017 cm-2 min-1, which is 19.4 times higher than that of CF. The converted NH4+ was finally exhaustively oxidized to N2 with a 98.7 % of TN removal in 60 min.

Efficient urine removal, simultaneous elimination of emerging contaminants, and control of toxic chlorate in a photoelectrocatalytic-chlorine system.

Urine, which is an important waste biomass resource, is the main source of nitrogen in sewage and contains large quantities of emerging contaminants (ECs). In this study, we propose a new method to efficiently remove urine, simultaneously eliminate ECs, and control the generation of toxic chlorate during urine treatment using a photoelectrocatalytic-chlorine (PEC-Cl) system. A type-II heterojunction of WO3/BiVO4 was used as a photoanode to generate chlorine radicals (Cl•) by decreasing the oxidation potential of WO3 valence band for the highly selective conversion of urine to N2 and the simultaneous degradation of ECs in an efficient manner. The method presented surprising results. It was observed that the amount of toxic chlorate was significantly inhibited by circumventing the over-oxidation of Cl- by holes or hydroxyl radicals (•OH). Moreover, the removal of urea nitrogen reached 97% within 90 min, while the degradation rate of trimethoprim in urine was above 98.6% within 60 min, which was eight times more than that in the PEC system (12.1%). Compared to the bare WO3 photoanode, the toxic chlorate and nitrate generated by the WO3/BiVO4 heterojunction photoanode decreased by 61% and 44%, respectively. Thus, this study provides a safe, efficient, and environmentally-friendly approach for the disposal of urine.